SustainAqua Handbook En

Sixth Framework Programme Integrated approach for a sustainable and healthy freshwater aquaculture

Project N°: COLL-CT-2006-030384

A handbook for

Sustainableaquaculture

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CONTENTS

Preface 3

1. SustainAqua – An Introduction 4

2. Sustainability in aquaculture 6

3. Technology and production of main freshwater aquaculture types in Europe 11

3.1. Pond fish farming 11

3.2. Flow-through aquaculture systems 12

3.3. Recirculation Aquaculture Systems 12

3.4. Cage cultures in freshwater lakes and rivers 13

4. Regulatory framework and governance in European freshwater aquaculture 14

4.1. Common Fisheries Policy (CFP) and related documents 15

4.2. Environmental policies with major impact on aquaculture development 18

5. Product quality and diversification – Market opportunities for aquaculture farmers for their fish products and by-products 20

5.1. Product quality – the Polish case 20

5.2. Wetland crops for the bioenergy industry – the Hungarian case 21

5.3. Hydro-culture plants and tropical fruits for the cosmetic industry – the Swiss case 22

6. Water treatment of intensive aquaculture systems through wetlands and extensive fish ponds – Case study in Hungary 24

6.1. Constructed wetlands as a sustainable method to treat aquaculture effluents and produce valuable crops (African Catfish Site) 24

6.2. From a case study to a fish farm: How to treat the effluents of a catfish farm? 29

6.3. Combination of intensive and extensive aquaculture for the sustainable utilisation of water and nutrients (Intensive-Extensive Site) 33

6.4. From a case study to a fish farm: Design of a theoretical combined system 38

7. Improved natural production in extensive fish ponds – Case study in Poland 41

7.1. New species and methods in pond fish culture: Module POLYCULTURE 41

7.2. Practical recommendations and conclusions for stocking paddlefish in pond polyculture 47

7.3. Using agricultural waste nutrients in pond fish culture: Module CASCADE in Poland 50

7.4. From a case study to a fish farm: Designing a cascading module 55

8. New methods in trout farming to reduce the farm effluents – Case study from Denmark 58

8.1. Introduction – General description of the case study 58

8.2. Feed and feeding - Environmental impact from model trout farms 60

8.3. Energy consumption on model trout farms 62

8.4. Cultivation of pond plants in the lagoons of model farms 65

8.5. Cultivation of alternative Fish Species in the lagoons of model farms 66

8.6. Summary – Success factors and constraints 67

8.7. From a case study to a fish farm: How to manage a model trout farm producing 500 t fish per year (Ejstrupholm Model Trout Farm) 68

9. Tilapia farming using Recirculating Aquaculture Systems (RAS) - Case study in the Netherlands 70

9.1. Module - Manure Denitrifying Reactor (MDR) 70

9.2. From a case study to a fish farm: Integration of a denitrifying USB-MDR in a 100 MT tilapia RAS 74

9.3. Module – Periphyton Turf Scrubber (PTS) 92

9.4. From a case study to a fish farm: How to manage a model fish pond producing 5 metric tonnes fish per year with the PTS module 93

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10. Tropical polyculture production with the integrated “Tropenhaus” concept – Case study in Switzerland 95

10.1. Introduction – General concept of the Tropenhaus in Switzerland 95

10.2. Integration of crustaceans in tilapia production and fish feed from tropical plants 96

10.3. Warm water aquaponic filter in a "tropical" polyculture system 98

10.4. From a case study to a fish farm: The design of a warm water aquaponic filter system in the “Tropenhaus Wolhusen” 101

References and recommendations for further readings 105

Authors of the handbook 109

Acknowledgements 110

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Preface

All over the world, aquaculture is developing rapidly, due to the combination of a strong increasing demand for seafood products and depleted fish stocks in the world's oceans. To avoid the same mistakes of the European agricultural and fisheries sector, aquaculture farmers need to address simultaneously the equally and mutually important considerations of environmentally sound, economically viable and socially acceptable development – that is the principles of sustainability – for the healthy development of the sector. Ultimately, each aquaculture farmer, irrespective of whether farming fish in RAS or ponds, has to face the same issues: how to utilise feed nutrients more efficiently to save feeding costs, achieve higher production and have less nutrients in the effluent? How to improve wastewater treatment and decrease its discharges, in order to reduce water pollution charges, due to the authorities? How to meet all legal requirements and restrictions, demonstrate to consumers that the cultured products are of the highest quality, that they are produced in environmentally friendly systems whilst providing sufficient income to make a living for the farmer and ensure the jobs of employees? The EU project SustainAqua aimed to answer several of these questions. With the overall aim to make the European freshwater aquaculture industry more sustainable by improving production methods, research potential market applications and increase product quality, SustainAqua undertook five different case studies in Europe representative of the most relevant freshwater aquaculture systems and fish species. Various practical techniques were tested, on how to strengthen the diverse aquaculture farms in Europe in a sustainable way, from extensive and semi-intensive pond systems, which predominate in Central and Eastern Europe, to intensive recirculation aquaculture systems (RAS) as they are practiced in North-Western Europe. The main findings are described here in this SustainAqua handbook. As a starting point, we discuss 'sustainability' and what this implies for aquaculture. We present the indicators for sustainability that have been developed for evaluating the different SustainAqua case studies. The different technologies in the sector – pond fish farming, flow-through and RAS – are briefly introduced to classify the subsequent sections satisfactorily. As we all know, the work of fish farmers and the future development of their farms are heavily influenced by the various national and European regulations which are applied to the sector. Therefore, an introduction to the European regulatory framework is given. A very important criterion for maintaining competitiveness on the market is excellence and proven fish quality and the innovative utilisation of aquacultural by-products. One chapter in the handbook presents the impact of different cultural systems on product quality and potential market applications for aquaculture by-products. The core of this handbook consists of a description of the different modules researched in the five SustainAqua case studies. The traditionally cultivated pond areas of Central Europe are represented by the Hungarian and Polish case studies. In Hungary, water treatment of intensive flow-through fish production is improved through constructed wetlands, deployed as biofilters. In addition, the advantages of combining intensive and extensive aquaculture for the efficient use of water and nutrients are presented. The Polish case study integrates aquaculture with the requirements of a modern agricultural farm in a ‘cascading’ pond system by utilising animal manure to produce plankton as feed for carp polyculture. The general decrease in demand for carp in Eastern Europe is addressed by introducing paddlefish as a new species into polyculture to diversify species production, efficiently use nutrients and to increase the profitability of carp farms’. In Denmark and the Netherlands, techniques for application in outdoor and indoor recirculation systems were tested. Whilst in Denmark, rainbow trout was studied at so-called model farms with the aim to optimise feeding management and to reduce the environmental impact and energy costs. The Dutch case study looked at intensive tilapia production in RAS, using two different modules with a Manure Denitrifying Reactor and Periphyton Turf Scrubber to reduce water use, energy consumption and the emission of nutrients. As a unique case in Europe, the Swiss case study rounds off this project through rearing tilapia and tropical fruits in a polyculture greenhouse system, using available waste heat, in order to prove that ‘waste’ can be used as a multifunctional resource to produce economically and ecologically viable fish and co-products. To make our scientific results transferable to farmers, the chapter "From a case study to a fish farm" presents on-hand-information for implementing the modules, preceded by a general description, its principles, the assessment of SustainAqua indicators, the factors contributing towards both success and constraints as well as major benefits of sustainable aquaculture systems. Freshwater aquaculture in Europe expects challenging times and looks forward to a bright future, so long as we continue to combine our forces, both as researchers to further develop systems and the industry to implement technologies for a sustainable aquaculture, and towards a sustainable European community. Dipl. Ing. Alexandra Oberdieck Prof. Dr. Johan Verreth Bremerhaven, Germany, June 2009 Wageningen, Netherlands, June 2009 Coordinator SustainAqua Scientific Manager SustainAqua

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1. SustainAqua – An Introduction

European freshwater fish farmers are fighting a battle on two fronts: On the one hand, with the spread of globalisation they are increasingly forced to compete with producers from countries with far lower costs of production. On the other hand, they have to conform to the stringent demands of European and national legislation with regard to product quality, environment and health. In addition, there are legal restrictions on the discharge of effluents, water extraction, the use of chemicals and genetic modification. The success of Europe’s freshwater aquaculture sector depends, to a great extent, on farmers’ abilities to face these challenges.

Concept of SustainAqua

SustainAqua is a three-year collective research project, co-funded by the European Union under the Sixth Framework Programme with the overall aim to make the European freshwater aquaculture industry more sustainable and thereby to help farmers to become globally more competitive. The overall objective of the project is to expand the knowledge base of European freshwater aquaculture farmers by training them to:

• Improve production methods, process efficiency and profitability

• Research potential market applications of different aquaculture by-products for alternative industries, such as the energy and cosmetics industry

• Increase product quality (taste, nutritional value) as marketing tools to boost consumer acceptance of farmed freshwater fish and thus, to improve the industry’s image.

The project will present a variety of technological possibilities and information on how to upgrade different conventional aquaculture systems. The new technologies are expected to have significantly lower construction, maintenance and running costs than conventional systems particularly in the case of wastewater treatment.

Case studies – applied research

In order to meet the general objectives, the consortium accomplishes five different case studies from Hungary, Poland, the Netherlands, Denmark and Switzerland. Each site represents one of Europe’s most relevant freshwater aquaculture types and fish species with trout, carp, tilapia and catfish. Each case study develops and researches different options for optimisation of production processes, quality improvement, and product diversification. In detail, the project consortium will research:

• Different techniques for optimising the nutrient, water and energy management by o Reducing energy costs by increasing energy efficiency; o Reducing wastewater treatment costs by decreasing wastewater volume and waste discharge; o Reducing costs for fish feed by higher nutrient utilisation efficiency; o Reducing labour costs per produced product;

• Taste and nutritional value of fish produced in different production systems, • Compounds and the economic value of different potential aquaculture by-products, The consortium intends to transfer the highly effective nutrient management principles of natural systems into competitive aquaculture systems. One example is efficient nutrient management: Alongside fish production, organic material will be exploited as far as possible for the production of marketable products like macroinvertebrates, algae or plants for different industrial applications. This optimised nutrient chain reduces waste, avoids the implementation of expensive wastewater treatment and filter technologies and reduces costs. These principles are tested in different extensive, semi-intensive and intensive aquaculture systems. In addition, as "health" and "taste" are important consumer demands, the consortium investigates by professional sensory and analytical tests whether the foreseen optimisation steps will have a positive influence on the quality of the fish products.

Short introduction to the five case studies

The Hungarian case study looks at African and European catfish produced in tanks and in-pond cages as well as at effluent-water treatment in serially-connected ponds, producing different carp species and wetlands crops such as willow and reed. These are produced as by-products, whilst also acting as cost effective and efficient biological wastewater treatment systems. In addition, their potential as a renewable resource for the bioenergy industry is being researched. In Switzerland tilapia is being reared in a hydro-culture system with tropical fruits, such as banana, mango and guava, as co-products. The rearing system “Tropenhaus Ruswil” is a 1 500 m² polyculture greenhouse type system which uses waste heat from a natural gas densification plant as its energy source. The case

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study aims to prove that “waste” can be used as a multifunctional resource in a polyculture system to produce economically and ecologically viable fish and co-products. In the Polish case study, carp is reared in two modules. One goal is to produce feed from recycled wastewater using a “cascading” pond system where organic agricultural waste is used to farm fish and plant biomass. This allows fish to be produced without using external feed sources. In addition, new species were introduced into the traditional polyculture setup to increase product diversity of pond farms and to improve carp farms’ profitability. The Netherlands case study looks at intensive tilapia production in recirculating aquaculture systems (RAS) using two different experiments with a Manure Denitrifying Reactor (MDR) and Periphyton Turf Scrubber (algae and biomass were able to recover pollutants from water). The aim is to reduce water use to less than 25 litres/kg of feed, to reduce energy consumption and the emission of dissolved and particulate nitrogen, phosphorus, carbon dioxide and organic matter. In Denmark rainbow trout production is being studied at eight model farms, with the aim to optimise feeding and farm management and to reduce the environmental impact and energy costs. The model farms combine technologies from intensive recirculating fish farms with effluent treatment in constructed wetlands to achieve substantial increases in fish production while reducing or even eliminating the environmental impact.

Importance of Sustainability

The sustainability of aquaculture is crucial if the industry is not to go the way of the fisheries sector. About 75 percent of the world's most valuable marine fish stocks are either fished to the limits or over-fished. At the same time world fish consumption has increased from 45 million tonnes in 1973 to more than 130 million in 2000 and the FAO estimates an additional 40 million tonnes of seafood will be required by 2030, just to maintain current levels of consumption. In order to serve this increasing demand in the long run, sustainable alternatives have to be strengthened. The most promising of these is the aquaculture industry. With a growth rate of 8% per year since the 1980’s, aquaculture is probably the fastest growing food-production industry, that today accounts for almost half the fish consumed globally, up from 9% in 1980.

Knowledge transfer

The SustainAqua project with its different AQUA+ modules provides different practical techniques and broad information on how to upgrade the different conventional aquaculture systems to improve production process profitability, environmental performance, product quality, and to diversify the product range. These options will help aquaculture farmers to comply with current and upcoming European and national legislation, and to meet future sustainable quality standards and Codes of Conducts – an important tool for the farmers’ advertising strategies. Most of the AQUA+ modules have more than one simultaneous function, as for instance wastewater treatment, effective nutrient management and the production of economically efficient by-products. With the diversification of their products farmers will be more flexible and their enterprises less susceptible to market fluctuations. The generated know-how from the case studies will be promoted via 22 training seminars for aquaculture farmers in Austria, Denmark, Germany, Hungary, Poland, Sweden, Spain, and Turkey and two e-learning seminars between May and July 2009. The training and information activities include this training handbook, the SustainAqua-wiki and an E-learning platform summarising benefits, risks and costs, success criteria as well as technical information on the different research modules. Eight national contact points coordinated by the responsible aquaculture associations will serve as individual advisory platforms for aquaculture farmers even after the duration of the project, giving farmers ready access to the knowledge generated by the project. With the help of these tools, farmers will be encouraged to restructure part or all of their production to make it more sustainable, efficient, and with long-term economic and environmental benefits.

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2. Sustainability in aquaculture

The term "sustainability" or also "sustainable development", often used as nothing more than a catch-phrase, has much more to offer. It is a concept to guarantee a liveable environment for all people in the long term, encompassing at least three fundamental components of sustainable development: preservation of a functional environment, economic welfare and social equity. Accordingly, also in the field of aquaculture, aiming for sustainability requires not only the achievement of environmental objectives, but also to provide clear economic advantages for aquaculture farmers in the long term. However, the term "sustainability" is often diluted and weakened, being used by politicians, entrepreneurs and the public, in a general way on numerous occasions, very often in a superficial or misleading way and with an incorrect definition, just to exploit the positive connotations of the term (as was the case with the terms "bio" or "eco" in the 1990's). The following text will describe the context in which the SustainAqua project was developed and carried out, through first providing a short insight into the background and original definition of the term "sustainability", then introducing the topic of "sustainability and aquaculture" followed by its application in SustainAqua.

Introduction – Background to "sustainability"

One important origin of the concept of "sustainability" or "sustainable development" is found in the report "Our Common Future", more commonly known as the Brundtland Report. Its key statement is that sustainable development 'meets the needs of the present without compromising the ability of future generations to meet their own needs'. Such sustainable development (in agriculture, forestry, fisheries sectors) conserves land, water, plant, and animal resources, is environmentally non-degrading, technically appropriate, economically viable, and socially acceptable. Sustainable development is based on long-term considerations, being an integrative, not a sectoral approach. The term is usually presented in three dimensions: ecological, economic and social sustainability. Each dimension is of equal importance and and each influence each other in an interdependent way. They cannot be separated. First, this model of the three dimensions with their equal importance was considered to improve the standing of environmental concerns. However, since then, thinking on the dependency of each dimension on another, it has been criticised for not adequately highlighting that economy and society fundamentally rely on the natural world and resources (see figure 1).

Figure 1: Framework of sustainability

However, at the beginning of the 21. century, it must be clearly stated that a better integration of these three objectives is needed to achieve sustainable development. The current focus is primarily on the economy, often neglecting social and environmental aims. It is therefore of great importance to balance the three pillars of sustainability by applying a higher focus on environmental and social sustainability to compensate for the current overweighting of the economy. Certainly, in this process the Rio Declaration on Environment and Development must be considered, indicating that environmental protection shall constitute an integral part of the overall development process and cannot be considered in isolation from it. Whilst it is acknowledged that no activity in industry, agriculture or aquaculture will take place if it is not economically profitable, it is the task of politics and society to find ways to equally achieve all three objectives of sustainability. An important tool to achieve this criterion – "sustainability" – correspondingly in all three dimensions, is to research and apply innovative or optimised technologies. In the area of freshwater aquaculture, this was exactly the objective of SustainAqua.


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Figure 2: Three levels of system limits for which sustainability is defined in SustainAqua

Sustainability and aquaculture

Aquaculture, as with all other food production and also industrial practices, is facing the challenge of sustainable development. Aquaculture has grown exponentially over the last 50 years from the production of less than 1 million tonnes of product in the 1950s to 51.7 million tonnes in 2006. Whereas capture fishery production is static and has even been decreasing for years, aquaculture continues to grow more rapidly than any other animal food-producing sector. Aquaculture will continue to play a large and increasing part in the world's fish production to meet the globally rising demand for fishery products. It is therefore essential to continuously pursue methods and means to make production practices in aquaculture more sustainable, efficient and cost-effective by, for instance, improving human capacity, resource use and environmental management. SustainAqua can be understood particularly in this context: SustainAqua firstly researches concrete solutions as technical and methodological tools and secondly offers diverse training activities to inform aquaculture farmers on the complex results of the project to achieve a more sustainable aquaculture in Europe. It is, however, essential, that various initiatives on a national, European and also global level develop and permanently update codes of conduct, sustainability indicator and certification systems, etc. in order to achieve a common and accepted understanding of sustainability in aquaculture among all stakeholders and how to achieve these goals in practice. To name just a few existing instruments:

• FAO "Code of conduct for responsible fisheries" (1995)

• FEAP "Code of conduct for European Aquaculture" (2000); currently being reviewed

• EVAD “Guide to the co-construction of sustainable development indicators in aquaculture” (2008)

• Agreement of Global Aquaculture Alliance (GAA) and GLOBALGAP to develop and harmonise certification systems for the aquaculture sector world-wide (2009)

Under the EU project CONSENSUS (2005-2008), for instance, a "Multi-stakeholder involvement towards protocols for sustainable aquaculture in Europe", developed a set of sustainability indicators as a starting point for a certification system for sustainable aquaculture and for a benchmarking process that is based on low environmental impact, high competitiveness and ethical responsibility with regard to biodiversity and animal welfare. All major organisations and associations within aquaculture production were involved. SustainAqua "completed" CONSENSUS through investigating several technological improvements to make different European freshwater aquaculture systems more sustainable (see chapter 1). Therefore, the description of sustainability that is presented here aims, primarily, to give a clear direction for the research carried out within SustainAqua in order to develop methods and technologies for more sustainable aquaculture production in Europe. In this way, SustainAqua anticipates future legislation and labels, that are currently still under discussion, and provides guidelines and technical solutions on more sustainable aquaculture practices.

Limits of the system

To keep the practice of "sustainability and aquaculture" manageable and practicable, it is important to define the limits of the system for which sustainability is defined. For SustainAqua, three levels of system limits can be differentiated, visualised in three concentric circles in figure 2: 1. "Farm level": includes the factors that can be

directly influenced by the farmer, for instance water quality, nutrient and energy management, fish health, etc.

2. "Second level": addresses the factors directly linked to the farm processes for which the farmer does not have direct influence, but on which he could potentially have an influence if he/she wanted or needed to. For instance: fish feed quality, how fish feed is composed/ processed, distance of transportation for the feed, the kind of energy the farmers uses (renewable or non-renewable), markets for the products (distant markets – requiring long transport distance, local markets – requiring short transport distance), etc. The farmer might also "transfer" some factors of the second level into the "farm level", e.g. by producing fish feed on the farm, using energy produced on the farm or by selling the products directly from the farm.

The first two circles are the most relevant for the SustainAqua project. 3. The "Third level": contains factors that are indirectly linked to the farm processes but which can normally

not be influenced by the farmer. These are factors like sustainability of the packaging material (production, material, etc.), the type of fuel for the transportation of the fish, etc.


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SustainAqua focuses on the farming process itself ("farm level"). The most relevant factors from the second circle are also considered, for instance fish feed production, energy production, energy for water supply of a certain quality, transportation energy, and potential markets. For completeness, the "regulative level" needs to be taken into account as well, such as EU, national or regional regulations, norms, etc. They affect all levels in different ways, but cannot be influenced by the farmer directly. In SustainAqua only those regulations are taken into account, which are directly relevant for the first and the second circles.

Sustainability indicators and certification

The limited availability of natural resources coupled with increasing energy prices emphasise the need to move forward in aquaculture to become more sustainable. The aquaculture industry is already working on this demanding task, but there is still a long way to go. Compared to other animal production systems, aquaculture is put under special pressure to become more sustainable, because of their use of important natural resources, such as freshwater, wetlands, coastal areas and also the wild catch of fish for fish feed production or stock recruitment. The sustainability of an activity and its measurement is not a static topic as, by definition, it incorporates economic, environmental and social considerations (see Figure 3). Each approach to sustainability as well as being based on indisputable facts contains some level of attached societal values and value judgements, which may be under discussion or may change over time. This means it is not always possible to decide unambiguously whether a process is sustainable or not. Often there are transitions between non-sustainable to sustainable processes.

Figure 3: Sustainable freshwater aquaculture combines ecological, economical and social aspects

The different Codes of conducts and criteria systems mentioned earlier aim to resolve this issue of how to achieve sustainability and are intended to support a sustainable cultivation of aquaculture products. But up until now there have been no complete and practicable European criteria, indicators, and related labelling systems which are really able to certify the sustainability status of a fish product. The SustainAqua project intents to contribute to the development of criteria which are currently being developed by various initiatives (see above). As mentioned before, SustainAqua does not intend to compete with indicator systems that were already developed in a broad stakeholder-oriented approach, e.g. by CONSENSUS. The selected criteria presented below are focused on the five SustainAqua case studies and shall provide a clear direction on how sustainability could be increased in such aquaculture farms. They are primarily designed to give a measurable orientation to the transferability and practicability of the research carried out in the five SustainAqua case studies in order to develop applicable methods and technologies for more sustainable aquaculture production in Europe. It is not the task of SustainAqua to judge, if a certain freshwater aquaculture farm is sustainable or not, but to provide an unambiguous direction, on what can be done in a case study or at a specific farm to improve sustainability.

SustainAqua Sustainability Indicators

The SustainAqua consortium developed 28 indicators at the beginning of the project for the three dimensions of environmental, economic and social sustainability. However, as SustainAqua could not cover all possible areas of researching and improving sustainability on an aquaculture farm, the final number of indicators was filtered down to eight which are then applied to the five case studies of the project, as can be seen in Table 1. The eight indicators were selected upon the basis of the following four criteria:


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• Action relevant: The indicator is sensitive to changes of management according to the objective and is useful to measure whether the actor works towards the objective or not.

• Plausible: The indicator is understandable for the actor.

• Measureable: It is possible to measure the indicator.

• Feasible: It will be possible to measure and record this indicator within the foreseen resources (budget, time) of the project

Environmental dimension

Specific objective/ criterion Indicator Unit

Ene

rgy

Energy efficiency: To reduce the necessary energy input as far as possible

Energy input per produced output (fish, biomass)

kWh/ kWh output (differentiated for each product)

Wat

er

Input: To reduce the amount of freshwater input from outside the system (re-use water as far as possible)

Water supply per produced product (fish, biomass) l/kg product

Output: To reduce the amount of wastewater discharge (for quality aspects see Nutrients/ Output)

Outflow per produced product (fish, biomass) -excluding evapotranspiration and seepage, but including precipitation

l/kg product

Nut

rient

s

Utilisation efficiency: To use the nutrient input as effectively as possible (to produce from a certain unit of nutrient input as many marketable products at as high a quality as possible)

Nutrient retention efficiency (NRE) - nutrient retention in produced product per kg nutrient input to the system as a whole (fish, biomass)

kg nutrient (N, P, COD) retained in product/kg nutrient input [%] (TOD calculated from COD and N)

Output (see also water): To reduce the amount of wastewater discharge (nutrient, minerals and organic material losses)

Amount of nutrients/ wastewater quality

N, P, COD, electrical conductivity discharged per kg product produced

Nutrient re-use to produce valuable secondary products within the fish farm

Nutrient retention of reused N/P for valuable secondary products

kg nutrient retention in the secondary products per kg nutrient input to the system as a whole [%]

Economical dimension

Specific objective/ criterion Indicator Unit

Pro

duct

ion

cost

s

To increase productivity per unit of labour required working time per produced product at commercial farm level (model-based assumption)

h/kg product

Buf

ferin

g m

arke

t flu

ctua

tions

Improving product safety/ fish health: To reduce disease outbreaks Treatments/ production cycle treatments/ production cycle

Table 1: Sustainability indicators for the 5 SustainAqua case studies

In the case-study chapters frequent reference will be made to these indicators as they establish the basis for evaluating the research in the five case studies of SustainAqua and for transferring the results for practical application. The remaining 20 indicators have neither been measured nor evaluated in detail, as their assessment was beyond the scope of this project. Among them were indicators such as "Water and Climate: To support local climate stabilisation by increasing evapotranspiration through increasing the amount of constructed wetlands/ open water" or all indicators found for the social dimension, such as "To support the development of additional jobs" or "To support rural development". More details on this issue can be found in the SustainAqua wiki on http://wiki.sustainaqua.org.

Application of sustainable principles to aquaculture

In the following paragraphs, the principles of each sustainability area will be introduced in detail. In addition, general suggestions are made on how to make an aquaculture system more sustainable by considering these principles. Practical examples of these potential application of principles can be seen in the different SustainAqua case studies presented in this handbook.

Improving ecological sustainability

Water, nutrients, the area used for the farm, and energy are the most important topics related to the ecological sustainability of aquaculture farms. Regarding water, both the amount needed and the quality are important aspects. Freshwater may be obtained from surface sources, such as lakes or rivers, or from the


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ground (aquifers) by the use of wells. One important goal in all systems is to reduce the amount of freshwater needed to relieve the natural ecosystems. An equally essential objective is (as in most cases the outflow of an aquaculture contains a lot of nutrients which may eutrophicate the natural systems), to reduce the amount of wastewater and to optimise the effluent treatment. The best management practice naturally depends on the type of aquaculture. Traditional carp ponds, for example, need water only for replacing the evaporation and seepage; the outflow is limited to the harvest. Recirculation aquaculture systems, like the Danish model trout farms, are another example of how to substantially reduce the amount of water needed. In the latter case, they use for instance plant lagoons to retain the nutrients of the outflow. An efficient use of the required nutrients is also essential for environmental sustainability. Reducing feed losses by an advanced feeding regime and the selection of appropriate feeds is the first step. The additional use of the remaining nutrients is again a site-specific task. The use of periphyton, as in the Hungarian case study, is one possibility. The use of different fish species in the same ponds, a polyculture, may raise the nutrient efficiency because of the different ecological niches of the fish species, which are used e.g. in the Polish case study. However, it should be considered in this case, to avoid the use of alien and exotic species. If sufficient area is available, renewable resources like reed or willow (one example is the Hungarian case study), or garden plants, as in the Danish case study, are further examples of how to increase nutrient utilisation efficiency. The origin of the feed used is a further task to contribute to ecological sustainability, for instance to use fishmeal produced from by-catch originating from sustainable fisheries (e.g. MSC certified). Sustainability with regard to the area used for the aquaculture farm depends greatly on the local circumstances. In general, the need to produce renewable resources in addition to food puts more pressure on the land use. The decreased land used per unit of fish produced in some recirculation aquaculture systems can offer a contribution. On the other hand, the pond area of the aquaculture farm can also contribute to local climate stabilisation by increased evapotranspiration. Ponds can also provide excellent ecologically valuable areas. Regarding the use of energy, this is a particularly major topic in recirculation aquaculture systems, as in the case of the Netherlands (see chapter ‘Netherlands'). Also in other aquaculture systems, it is possible and important to reduce the amount of energy by increasing the energy efficiency, e.g. through the use of more efficient pumps. With regard to energy use, the aim is to produce at least the same amount of fish with less energy or more fish with the same amount of energy.

Improving economical sustainability

An aquaculture is economically sustainable and viable, if the farm is profitable, the farm revenue is reliable and the farm system and products are accepted by the consumer. In many cases, improving environmental sustainability can be connected to the optimisation of economic sustainability. For instance, a more efficient use of feed and nutrients or the reduction of the use of freshwater is not only positive for the environment, it can also reduce costs. Depending on national laws, reducing wastewater contributes also to the lowering of production costs. The same is true for all energy dependent processes. A more local or regional distribution of products will decrease the transport costs, which are partly energy costs. The diversification of the aquaculture can buffer market fluctuations. Polyculture or the additional production of renewable resources, garden plants or fish fry are examples applied in the SustainAqua case studies. Production of traceable high quality products can both increase realised prices and consumer confidence. Last, but not least, fully endorsing sustainability (and not just adopting under duress as an necessary chore) can be a valuable argument to increase consumer acceptance. However, all these aspects need to be evaluated very individually, because the availability of all resources needed for an aquaculture (water, land, nutrients, energy) vary greatly between the different European countries and regions. In the vicinity of a big city, for instance, a highly intensive recirculation system might be very much sustainable, especially if it can be heated by waste heat; whereas in rural areas, as is the case in many areas of Hungary, it might be economically much more sustainable to run a large extensive carp pond, as land and water is relatively cheap and available.

Improving social sustainability

The issue of social sustainability is also very complex. It includes employment opportunities in the sector, the conditions of employment on the aquaculture farm (hygiene, safety, training), but also the general public in connection with e.g. recreation, health and nutritional issues. Important aspects are also the attractiveness of aquaculture to the younger generation or in which way an aquaculture system preserves culture and traditions, for example with pond fish farming in Eastern Europe. Social sustainability was not a primary focus of SustainAqua, which concentrated more on technical solutions to directly increase economic and environmental sustainability, but which, nonetheless, if achieved support social sustainability (securing jobs, ensuring functional environment for recreation, contributing to high-quality and healthy nutrition, etc.).

SUSTAINAQUA HANDBOOK Freshwater aquaculture types

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3. Technology and production of main freshwater aquaculture types in Europe

There are many possible ways to classify and describe the very diverse freshwater aquaculture production types. But from a sustainability point of view, the production methods can be the most reasonable basis for a classification system. Whilst, there are many overlaps and transitions amongst freshwater fish production systems, the following basic methods can be distinguished:

• Pond fish farming

• Flow-through systems

• Recirculation Aquaculture Systems

• Cage cultures

3.1. Pond fish farming

Production of freshwater fish in artificial ponds is often considered as the oldest fish farming activity in Europe, dating back to medieval times. Ponds were built in areas where water supply was available and the soil was not suitable for agriculture. The wetlands of Central and Eastern Europe are good examples of this. The total European production from pond farming is approximately 475 000 tonnes per annum. About half of this production is cyprinid fish, such as common carp, silver carp and bighead carp. The main producer countries are the Russian Federation, Poland, the Czech Republic, Germany, Ukraine and Hungary. Typical fish ponds are earthen enclosures in which the fish live in a natural-like environment, feeding on the natural food growing in the pond itself from sunlight and nutrients available in the pond water. In order to reach higher yields, farmers today introduce nutrients (organic manure) and additional food (grain). This is accompanied by the stocking of fingerlings. Fish pond production, however, remains ‘extensive’ or ‘semi-intensive’ (with supplementary feeding) in most countries, where semi-static freshwater systems play an important role in aquaculture. Chemicals and therapeutics are not usually used in such ponds. Chemicals and therapeutics are not usually used in such ponds. Hence, the main environmental issue is the use of organic fertilisers, which may cause eutrophication in the surrounding natural waters. The use of organic fertilisers is regulated at national levels. Extensive fish ponds are usually surrounded by reed belts and natural vegetation, thus providing important habitats for flora and fauna. They play a growing role in rural tourism. Many pond fish farms have been turned into multifunctional fish farms, where various other services are provided for recreation, maintenance of biodiversity and improved of water management.

Pond fish farm in Hungary (Photo: HAKI)


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3.2. Flow-through aquaculture systems

In traditional flow-through aquaculture systems, water passes through the culture system only once and is then discharged back to the aquatic environment. The flow of water through the culture system supplies oxygen to the fish and carries dissolved and suspended wastes out of the system. The most widely-practiced form of flow-through aquaculture in Europe is trout farming. Water is taken from the river, circulated through the farm and treated before being released downstream. All water in the farm is renewed at least once per day. Where more than one farm exists on the same river, it is in everyone’s interests that the quality of the outflowing water from one farm is good, as this then becomes the inflowing water for the next farm. Trout production is spread throughout Europe and fresh trout can be bought everywhere. Because of its growth requirements and production performance, rainbow trout (Oncorhynchus mykiss) largely dominates European trout production (approximately 95% of the total production). Most of the EU member states have trout farms near to rivers, and use concrete basins or ponds. Some lake cages are also in use. Approximately 220 000 tonnes of portion size trout are produced and marketed within Europe each year, 85% are produced in the EU where the main producers are Italy and France, followed by Denmark, Germany and Spain. The only big producer of portion trout outside the EU is Turkey. After many years of slow but steady increase, in the period 2000-2005 the production of portion trout fell slightly (approximately minus 0.6% per year), but prices remained good. Other water sources include spring water or drilled and pumped ground water. In some countries, heated industrial water sources (such as electricity generating plants) are also used to produce fish in flow-through systems. Geothermal water also provides naturally warmed water, thus allowing the farming of new fresh water species (especially African catfish, eel, sturgeon, perch and tilapia).

Traditional trout farm in Denmark (Photo: DTU-Aqua)

3.3. Recirculation Aquaculture Systems

Recirculation Aquaculture Systems (RAS) are land-based systems in which water is re-used after mechanical and biological treatment so as to reduce the need for water and energy and the discharge of nutrients to the environment. These systems present several advantages, such as: water saving, a rigorous control of water quality, low environmental impacts, high biosecurity levels and an easier control of waste production as compared to other production systems. The main disadvantages are high capital costs, high operational costs, requirements for very careful management (and thus highly skilled labour forces) and difficulties in treating disease. RAS is still a small fraction of Europe’s aquaculture production and is most significant in the Netherlands and Denmark. The main freshwater species produced in RAS are catfish and eel but other species are already being produced using this type of technology. The eel production in the EU was around 11 000 tonnes/year up to 2001, and then it dropped to approximately 8 500 tonnes/year from 2002 and has stabilised overall since. However, this figure hides major shifts among the main producers;


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Italian production (once the biggest EU producer) is on a constant downward trend since the late 1990's, and Danish production has also declined since 2001. These losses have been partially compensated by some increase in Dutch production. However, because of the uncertain supply of young eels, some eel farmers have switched production to other species or simply abandoned the sector.

Intensive Tilapia production in RAS (Photo: Fishion Aquaculture B.V.)

3.4. Cage cultures in freshwater lakes and rivers

Well designed and carefully managed cage cultures also provide limited but important possibilities for freshwater aquaculture. In certain water bodies, extensive or intensive production of fish in cages can be in line with the sustainable use of natural resources. For instance, Arctic charr (Salvelinus alpinus) farming is at present a small but successful business in Sweden and is expected to increase considerably over the coming years. These farms are located in the mainly unexploited regulated lakes and waterpower reservoirs along the dammed rivers in the northern parts of the country. These waters were naturally poor in nutrients, but, following water regulation, have been further nutrient depleted to what are now almost sterile conditions. Farming fish in these waters would represent a restoration action as the increased amount of nutrients would serve to bring the aquatic environment closer to the natural state. It requires an annual production of at least 5 000 tonnes Arctic charr to increase the present level of phosphorus of 3 µg/l to an estimated 'original level' of 10 µg/l in these lakes.

SUSTAINAQUA HANDBOOK Regulatory framework

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4. Regulatory framework and governance in European freshwater aquaculture

It is a well-known fact that aquaculture is one of the most regulated industries in the European Union. Fish production using the very limited natural resources of coast-lines and freshwater bodies remains at the forefront of public interest. It is of little surprise, therefore, that all interested parties, such as EU and national governmental bodies, non-governmental organisations and the industry itself want to control the aquaculture industry. On the other hand, this attention has led to a large amount of regulations, documents and other communications, which it is very difficult for farmers (who just want to produce healthy fish without destroying their natural resources), to review themselves. In the SustainAqua project case studies were carried out to support freshwater fish farmers in how they can develop their businesses, whilst at the same time conserve their most precious resource: the clean freshwater. The aim of this chapter is to provide an overview for farmers about the most important freshwater aquaculture related documents from the EU, NGO's and other organisations. More detail is provided on this topic in on the free internet based SustainAqua Wiki (http://wiki.sustainaqua.org). In the EU member states it is evident that the different Community legal instruments have the largest impact on aquaculture regulation. An excellent definition of different types of legislative documents was prepared by the Federation of European Aquaculture Producers (source: www.profetpolicy.info): Green Paper: Green Papers are documents published by the European Commission to stimulate discussion on given topics at the European level. They invite the relevant parties (bodies or individuals) to participate in a consultative process and debate on the basis of the proposals they put forward. Green Papers may give rise to legislative developments that are then outlined in White Papers. White Paper: Commission White Papers are documents containing proposals for Community action in a specific area. In some cases they follow a Green Paper published to launch a consultation process at the European level. When a White Paper is favourably received by the Council, it can lead to an action programme for the Union in the area concerned. COM documents: covering proposed legislation and other Commission communications to the Council and/or the other institutions, and their preparatory papers; SEC documents: representing internal documents associated with the decision-making process and the general operation of Commission departments; Decision: An EU decision is binding on the persons, companies or Member States mentioned in the decision. It is not generally binding, as is the case with a regulation. Directive: Directives are to be transferred into national law through the member states' parliaments and governments. Over the years, the EU Court has proclaimed many directives to be directly applicable and even declared that countries are liable to pay compensation if they have not implemented a directive in time. Directives are normally transformed into national laws by the national parliaments or most often by the governments through delegated acts. Recommendation: A non-binding decision, which only urges Member States to comply. A Member State cannot be fined for the breach of recommendations. Regulation: An EU decision that directly binds all Member States and citizens in the whole of the EU. Whereas directives need to be "transformed" into national law, regulations are directly applicable. It is therefore forbidden to change EU regulations when putting them into national laws. Resolution: A resolution is a non-binding statement, which defines objectives and makes political declarations. The European Council's resolutions set out the direction of future policy initiatives. Resolutions may be used by the EU Court to interpret laws. They may be referred to as a form of "soft law". Treaty:

1. A formal agreement between two or more states in reference to peace, alliance, commerce, or other international relations.

2. The formal document embodying such an international agreement. These are the tools supporting the implementation of the EU policies which are first "pillars" of the EU. There are many common policies influencing the freshwater aquaculture, but probably the most important are:

• Common Fisheries Policy

• Policies on environmental issues, primarily water policies


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4.1. Common Fisheries Policy (CFP) and related documents

The Common Fisheries Policy (CFP) is the European Union's instrument for the management of fisheries and aquaculture. It was created to manage a common resource and to meet the obligation set in the original Treaties of the then European Community. The Common Fisheries Policy shall ensure exploitation of living aquatic resources that provides sustainable economic, environmental and social conditions. For this purpose, the Community shall apply the precautionary approach in taking measures designed to protect and conserve living aquatic resources, to provide for their sustainable exploitation and to minimise the impact of fishing activities on marine eco-systems. However, its main aim is a progressive implementation of an eco-system-based approach to fisheries management. It also contributes to an economically viable and competitive aquaculture industry, as well as taking into account the interests of consumers. Common measures are agreed in the following main areas:

• Conservation and limitation of the environmental impact of fishing - to protect fish resources by regulating the amount of fish taken from the sea, by allowing young fish to reproduce, and by ensuring that measures are respected.

• Structures and fleet management - to help the fishing and aquaculture industries adapt their equipment and organisations to the constraints imposed by scarce resources and the market; measures aimed at creating a balance between fishing effort and available fish resources are also in place;

• Markets - to maintain a common organisation of the market in fish products and to match supply and demand for the benefit of both producers and consumers;

• Relations with the wider world - to set up fisheries partnerships agreements and to negotiate at the international level within regional and international fisheries organisations for common conservation measures in deep-sea fisheries.

Since 2007 the implementation of the CFP is parallel with the Integrated Maritime Policy of the European Union. The name of the responsible Directorate General became Directorate-General for Maritime Affairs and Fisheries (DG MARE). However, the main focus of the CFP is the extractive fisheries on the seas. Aquaculture has gained an important role only in the last few years. The aquaculture related issues have now became an important part of the above-mentioned common activity areas. As the main executive body of the CFP, in 2002, the Directorate-General for Maritime Affairs and Fisheries prepared a COM document about the a strategy for the sustainable development of European aquaculture (COM(2002) 511). In 2007, DG MARE started a mutual discussion with the aquaculture industry to update this strategy. This new strategy document COM(2009) 162 just has been published in April 2009 and is available in all national languages of the EU.

4.1.1. The Commission strategy for a sustainable development of the European aquaculture industry

The Commission strategy for a sustainable development of the European aquaculture industry aims at:

• Creating long term secure employment, in particular in fishing-dependent areas;

• Assuring the availability to consumers of products that are healthy, safe and of good quality, as well as promoting high animal health and welfare standards;

• Ensuring an environmentally sound industry. The strategy says, that it is important to reduce the negative environmental impacts of aquaculture by developing a set of norms and/or voluntary agreements which prevent environment degradation. Conversely, the positive contribution of certain aquaculture developments to the environment must be recognised and encouraged, including through public financial incentives. Regarding the conflicts between aquaculture and environment the strategy identified the following areas:

• Mitigate the impact of wastes

• Manage the demand for wild fish for on-growing as stock for aquaculture

• Develop instruments to tackle the impact of escapees, alien species and GMO's

• Integrated pollution prevention and control

• Specific criteria and guidelines for aquaculture Environmental Impact Assessments

• Recognise and strengthen the positive impact of extensive culture and re-stocking

• Find solutions for the predation of protected wild species


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Generally, the vision and objectives of the 2002 strategy are fully supported and are considered to be still valid, but several arguments are put forward to justify the need for a revision. The commission started a consultation process in 2007 to update this aquaculture strategy. The just recently published, updated strategy points out new goals and underlines the importance of the following elements: 1. Environmentally friendly aquaculture growth: The EU is committed to a high level of environmental

protection. Community legislation is based on the precautionary principle. Technologies for cleaning water by removing wastes and contaminants are available and the further development of new technologies to decrease effluent is likely to be significant in the coming years. Compliance with EC water legislation is also crucial to ensuring the water quality needed to produce quality and safe food.

2. Animal domestication: Optimal husbandry conditions, good health and adequate feed well suited to the physiological needs of the farmed aquatic animals are essential for optimal growth and production. Guaranteeing the welfare of farmed fish also contributes to a better image for the aquaculture industry.

3. Equal competitor in terms of space: The increasing competition with agriculture, industry and tourism for space represents a major challenge for further development or even maintaining of freshwater fish farming and aquaculture production in coastal areas. Area choice is crucial and spatial planning has a key role to play in providing guidance and reliable data for the location of an economic activity.

4. Reducing the administrative burden: Reducing the administrative burden, especially for Small and Medium Enterprises is essential to promote development.

5. Enabling the aquaculture business to cope with market demands: The EU aquaculture industry should be able to answer to consumer demands, be adaptable to changing market requirements and be capable of interacting on an equal footing with the other actors of the marketing chain. Accordingly, the needs of the aquaculture sector shall be assessed and addressed, in particular regarding producer organisations, consumer information and marketing instruments such as labelling of aquatic food products, in the framework of the future reform of the market policy for fisheries and aquaculture products.

4.1.2. European Fisheries Fund

Until 2006 the main financial tool supporting the achievement of the Common Fisheries Policy was the Financial Instrument for Fisheries Guidance (FIFG). For the EU financial planning period 2007-2013 a new financial tool will be used, the European Fisheries Fund (EFF). Funds are granted in priority to micro and small enterprises operating in the aquaculture, processing and marketing sectors, but it is also possible to support medium and some large enterprises. In addition new compensation could be granted for fish farmers whose businesses are located in the NATURA 2000 protected areas. Support for inland fisheries, producer organisations and the purchase of some fishing equipment by young fishermen will also be possible. The EFF will run for seven years, with a total budget of around € 3.8 billion. Funding will be available for all sectors of the industry – sea and inland fisheries, aquaculture businesses, producer organisations, and the processing and marketing sectors - as well as for fisheries areas. It will be up to Member States to decide how they allocate funds between the different priorities set, but they have to prepare a National Strategic Plan (NSP) as a base of the Operational Program. A NSP should contain the following elements:

• General description of the sector

• Swot analysis of the sector and its development

• Objectives and priorities of the Member States vis à vis sustainability

• Development of fisheries and aquaculture with regard to the CFP

• Indication of resources to be mobilised to carry out the national strategy

• Procedure for the development, implementation and monitoring of the NSP

Financial support for aquaculture farmers

Of course, the strategies and the planned measures have to harmonise with the council regulation of European Fisheries Fund. This document identifies 5 Priority Axis as follows: 1. Measures for the adaptation of the Community fishing fleet 2. Aquaculture, inland fishing, processing and marketing of fishery and aquaculture products 3. Measures of common interest 4. Sustainable development of fisheries areas 5. Technical assistance For fish farmers working in a freshwater environment the most important measures are detailed within the Axes 2 and 3.


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Axis 2 - Aquaculture, inland fishing, processing and marketing of fishery and aquaculture products

Within the Axis 2, the following measures are eligible for funding the aquaculture sector: Productive investments in aquaculture: The EFF may support investments in the construction, extension, equipment and modernisation of production installations, in particular with a view to improving working conditions, hygiene, human or animal health and product quality, reducing negative impact or enhancing positive effects on the environment. Investments shall contribute to one or more of the following objectives: a. Diversification towards new species and production of species with good market prospects; b. Implementation of aquaculture methods substantially reducing negative impact or enhancing positive

effects on the environment when compared with normal practice in the aquaculture sector; c. Support for traditional aquaculture activities important for preserving and developing both the economic

and social fabric and the environment; d. Support for the purchase of equipment aimed at protecting the farms from wild predators; e. Improvement of the working and safety conditions of aquaculture workers. Aqua-environmental measures: The EFF may support granting compensation for the use of aquaculture production methods in helping to protect and improve the environment and to conserve nature. For example, forms of aquaculture comprising protection and enhancement of the environment, natural resources, genetic diversity, and management of the landscape can get support within this measure. For the support provided, the environmental benefits of such commitments must be demonstrated by a prior assessment conducted by designated competent bodies. In order to receive compensation under this Article, beneficiaries of compensation must commit themselves for a minimum of five years to aqua-environmental requirements, which go beyond the mere application of normal good aquaculture practice. The Commission also wants to encourage fish farmers to participate in the Community eco-management and audit scheme (EC No 761/2001) allowing voluntary participation by organisations in a Community eco-management and audit scheme (EMAS). Public health measures: These measures concern mainly the mollusc farmers, protecting them against the economic impacts of harmful algal blooms. Animal health measures: The EFF may contribute to the financing of the control and eradication of diseases in aquaculture (Council Decision 90/424/EEC, 26 June 1990 on expenditure in the veterinary field). There are some other measures within Axis 2 which do not affect directly the freshwater aquaculture farmers, however in some cases they can be of interest, too. Inland fishing: Eligible measures for aid include:

• Aid for inland fishing and fishing on ice, according to similar provisions as in the current FIFG

• Aid for the reassignment of inland vessels outside fishing

• Temporary cessation foreseen in a Community legal act Processing and Marketing: Eligible measures for aid include:

• Improve working, health, hygiene conditions and product quality

• Reduce negative impacts on the environment

• Improve the use of little used species, by-products and waste

• Apply new technologies, develop innovative production methods

• Marketing of products (mainly originating from local landings and aquaculture)

• Lifelong learning

Axis 3 - Measures of common interest

Within Axis 3, the EFF may support measures of common interest which cannot be normally supported by the private sector and which help to meet the objectives of the Common Fisheries Policy. The promoters of these measures can be private operators, organisations acting on behalf of producers or recognised organisations, provided that their actions are of common interest. Eligible measures are:

• Collective actions

• Protection and development of aquatic fauna and flora

• Fishing ports, shelters and landing sites

• Development of new markets and promotion campaigns

• Pilot projects carried out by an economic operator, a recognised trade association or any other competent body designated for that purpose by the Member State, in partnership with a scientific or


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technical body

• Modification of fishing vessels with a view to reassignment Aquaculture related collective actions can be for example:

• Improvement of working conditions and safety

• Transparency of markets

• Improvement of quality and food safety

• Development, restructuring or improvement of aquaculture sites

• Development of new training methods

• Promotion of partnership between scientists and operators

• Promotion of equal opportunities

• Creation and restructuring of Producers Organisations and implementation of their plans

• Feasibility studies related to the promotion of partnerships with third countries

4.2. Environmental policies with major impact on aquaculture development

An EU environment policy is nothing new. The current environment action programme, which will take the EU through to 2012, is the sixth in the series. It builds on 30 years of activity which has already delivered a range of benefits — including much cleaner air and water, expansion of protected natural habitats, better management of wastes, better upfront consideration of the environmental implications of planning decisions, and more environmentally friendly products. However, huge challenges remain. The sixth environment action programme identifies four priorities:

• Climate change

• Nature and biodiversity

• Environment and health, and quality of life

• Natural resources and waste From the point of view of an aquaculture farmer, the actions in the field of nature conservation and the protection of natural resources (like water) are the most important.

4.2.1. Nature conservation policy: Habitat and Bird Directive, Natura 2000

EU Nature conservation policy is based on two main pieces of legislation - the Birds directive and the Habitats directive. Its priorities are to create the European ecological network (of special areas of conservation), called NATURA 2000, and to integrate nature protection requirements into other EU policies such as agriculture, regional development and transport. It is part of Europe’s response to conserve global biodiversity in line with international obligations under the Biodiversity Convention. The aim of the Natura 2000 Network is to protect and manage vulnerable species and habitats across their natural range within Europe, irrespective of national or political boundaries. It is composed of Special Areas of Conservation (SACs) designated for one or more of the 231 threatened habitat types and 900 species listed in the annexes to the Habitats Directive. It also includes Special Protection Areas (SPAs) classified under the Birds Directive for around 200 endangered bird species and wetlands of international importance. Natura 2000 is not merely a system of strict nature reserves where all human activities are systematically excluded. It adopts a different approach – it recognises that man is an integral part of nature and the two work best in partnership with one another. Indeed, many sites in Natura 2000 are valuable precisely because of the way they have been managed up to now and it will be important to ensure that these sorts of activities (such as extensive farming) can continue into the future. By actively associating different land-users in the management of Natura 2000 sites it is possible to ensure that vulnerable semi-natural habitats and species, which are dependent upon positive management, are maintained. The recent reform of the Common Agricultural Policy has decoupled payments from production and replaced it with a single farm payment that is based on good agricultural and environmental condition. Natura 2000 also was incorporated into the Common Fisheries Policy and fish farmers will be supported and required to meet with site management requirements of Natura 2000. The Directive requires that within Natura 2000 sites damaging activities are avoided that could significantly disturb the species or deteriorate the habitats for which the site is designated. It says that positive measures should be taken, where necessary, to maintain and restore these habitats and species to a 'favourable conservation status’ in their natural range. It is up to the Member States to decide, how they can achieve the site conservation.


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4.2.2. Water Framework Directive and freshwater aquaculture

On 23 October 2000, the "Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for the Community action in the field of water policy" or, in short, the EU Water Framework Directive (WFD) was finally adopted. The Water Framework Directive expands the scope of water protection to all waters and sets clear objectives that a “good status” must be achieved for all European waters by 2015 and that water use be sustainable throughout Europe. This new overarching system is quite timely as Europe’s water resources are facing increasing pressures. The implementation of the Water Framework Directive raises a number of shared technical challenges for the Member States, the Commission, the Candidate and EEA Countries as well as stakeholders and NGOs. In addition, many of the European river basins are international, crossing administrative and territorial borders and therefore a common understanding and approach is crucial to the successful and effective implementation of the Directive. The Commission presented a Proposal for a Water Framework Directive with the following key aims:

• Expanding the scope of water protection to all waters, surface waters and groundwater

• Achieving "good status" for all waters by a set deadline

• Water management based on river basins

• A "Combined approach" of emission limit values and quality standards

• Setting the prices right

• Getting the citizen involved more closely

• Streamlining legislation The best model for a single system of water management is management by river basin - the natural geographical and hydrological unit - instead of according to administrative or political boundaries. Initiatives taken forward by the States concerned for the Maas, Schelde or Rhine river basins have served as positive examples of this approach, with their cooperation and joint objective-setting across Member State borders, or in the case of the Rhine even beyond the EU territory. While several Member States already take a river basin approach, this is at present not the case everywhere. For each river basin district - some of which will traverse national frontiers - a "river basin management plan" will need to be established and updated every six years, and this will provide the context for the co-ordination requirements identified above. In order to address the challenges in a co-operative and coordinated way, the Member States, Norway and the Commission agreed on a Common Implementation Strategy (CIS) for the Water Framework Directive only five months after the entry into force of the Directive. The CIS is regularly updated by Member States and for the period 2007-2009 the following priorities were considered the most important by the Water Directors: “WFD and Agriculture”, “WFD and Hydromorphology”, “environmental objectives, exemptions and related economic issues”, “water scarcity and drought” and “biological and chemical monitoring”. Furthermore, an activity on climate change is certainly envisaged, which will focus on the options and opportunities provided for by the EU-Water Policy framework for adapting to the impacts of climate change. The activity therefore will have to closely cooperate with other CIS activities with a view to linking and co-ordinating work related to climate change. The environmental objectives are defined in Article 4 - the core article - of the Water Framework Directive (WFD). The aim is long-term sustainable water management based on a high level of protection of the aquatic environment. Article 4.1 defines the WFD general objective to be achieved in all surface and groundwater bodies, i.e. good status by 2015, and introduces the principle of preventing any further deterioration of status. There follows a number of exemptions to the general objectives that allow for less stringent objectives, extension of the deadline beyond 2015, or the implementation of new projects, provided a set of conditions are fulfilled. The intercalibration exercise is a key element in making the general environmental objective operational in a harmonised way throughout the EU. The WFD classification scheme for water quality includes five status categories: high, good, moderate, poor and bad. The general objective of the WFD is to achieve ‘good status’ for all surface waters by 2015. ‘Good status’ means both ‘good ecological status’ and ‘good chemical status’. Guidance documents and technical reports have been produced to assist stakeholders to implement the WFD. Guidance Documents and are intended to provide an overall methodological approach, but these will need to be tailored to the specific circumstances of each EU Member State. All these documents and others produced by the Common Implementation Strategy process can be found on the WFD CIRCA library (http://ec.europa.eu/environment/water/water-framework/iep/index_en.htm).

SUSTAINAQUA HANDBOOK Market opportunities

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5. Product quality and diversification – Market opportunities for aquaculture farmers for their fish products and by-products

A very important criterion for standing up to increasing competition on the fish market is excellence of product quality related to flesh quality and consumers’ preferences. Consumers are becoming more concerned about how fish is produced or which type of feed ingredients are used. EU regulations and authorities are increasing their focus on food safety and traceability of the production from 'egg to plate'. Because of their own trading interests and to meet consumer needs, whilst at the same time fulfilling regulatory requirements, most supermarket chains have introduced very strict rules on fishery products. To sell fish through this important retail market channel the products have to meet extremely high quality standards. On the other hand, the changing economic and social environment create new markets for freshwater aquaculture by-products and fish farmers have to find innovative ways to utilise aquaculture by-products more efficiently. By accessing alternative and fast growing markets parallel to the main market of high quality fish products, European aquaculture farmers could increase their economic sustainability and improve their competitiveness within the international aquaculture market, especially in the face of low-cost imports from Asia. One of the major goals of SustainAqua was therefore to analyse the influence of different rearing systems and feeding patterns on the quality of fish and to research potential market applications of different aquaculture by-products to attain new markets. In the Polish case study, the impact of three different pond culture systems and feed regimes on the quality of common carp was assessed. In the case studies of Switzerland and Hungary, the market potential of by-products for the booming cosmetic and energy industries was analysed: hydro-culture plants and tropical fruits of the 'Tropenhaus' in Switzerland and various wetland crops in the Hungarian case.

5.1. Product quality – the Polish case

The term 'fish quality' is a complex set of characteristics influenced by numerous factors. It includes: external appearance (e.g. colours), nutritional value (composition of the edible part – e.g. fatty acids, fat), organoleptic characteristics (taste, flavour, odour, texture), freshness, and safety (inclusion of toxic constituents, heavy metals, chemicals used in aquaculture practices and their metabolites, human pathogens). In the framework of SustainAqua, the main aim was to find out the influences of different fish feeding and cultivation systems on the quality and taste of carp, with the help of consumer tests, sensory profiling with expert panels, and chemical analyses of protein, fat and fatty acids. The following questions were analysed:

• Is there a difference in taste and quality if carp is reared in polyculture or monoculture systems (different food spectrum and utilisation efficiency available)?

• Is there a difference in taste and quality if carp is fed on grain (maize and wheat) or with natural food? The research focused on common carp (Cyprinus carpio), the main species cultured in Poland. The following fish samples were analysed: 1. Common carp bred in traditional monoculture - fed with grain 2. Common carp bred in traditional polyculture - fed on natural food 3. Common carp bred in monoculture - fed on natural food In addition, bighead carp (Hypophthalmichthys nobilis) was analysed, also from a polyculture system with natural feeding, to prove its high quality and taste and attain a higher market acceptance. Currently, several prejudices among consumers exist with regard to an inferior taste of this species, resulting in low prices (ca. 1€/kg). Results show that carp with natural feeding had much lower fat contents than their grain-fed counterparts. Significant differences are apparent in their fatty acid content and composition. Carp with natural feeding regimes had higher proportions of the n-3 and n-6 polyunsaturated fatty acids (PUFA) which are considered to have positive effects on human health. Also in regard to consumer acceptance, carp with natural feeding was rated much higher, due to its fresh, neutral and not too acerb smell and its tender, not mouldy taste. No significant differences between carp from monoculture or polyculture systems was detected in any analysis. It can be concluded that the feeding system has a higher impact on the sensory and chemical qualities than the culturing system. The main factor that controls fat content, fatty acid composition and organoleptic characteristics is the diet. Whether carp is bred in monoculture or polyculture systems seems not to have a strong influence on the (taste) quality of the fish.


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In addition, concerning the marketing of bighead carp (Hypophthalmichthys nobilis), results of this study show a positive correlation in terms of both sensory quality/ consumer acceptance and chemical composition, reaching the same values as common carp.

5.2. Wetland crops for the bioenergy industry – the Hungarian case

The potential for biomass production for the booming bioenergy sector is massive. Lignocellulosic by-products of aquacultural activities offer huge possibilities for the production of fuel ethanol, heat or electricity. The combination of aquaculture, wastewater treatment and bioenergy production is an innovative approach in the European Union. It could serve two purposes with enormous advantages at the same time: 1. Aquaculture farmers profit in two ways simultaneously: The farmer saves costs for wastewater treatment

and sells a new product for additional income. 2. To meet the emerging massive demands on biomass in the EU, all potential areas for cultivating biomass

must be used, including aquaculture sites.

Willow after planting in water covered wetland unit (Photo: AKVAPARK)

Potentials

Within the framework of SustainAqua, common reed (Phragmites australis), cattail (Typha latifolia/ angustifolia), giant reed (Arundo donax) and willow (Salix viminalis) were specifically analysed for their contents for potential use as biomass for energy purposes, e.g. for the production of woodchips or pellets for heat and electricity generation or for the production of cellulosic bioethanol as biofuel for transport (see Table 2).

Water content - Critical factor determining the amount of heat obtained through combustion - The higher the water content in the fuel, the lower the energy content

Fuel value - Amount of energy released in form of heat when 1 kg of plant (biomass) is burned

Cell wall poly-saccharides

- Plant cell walls contain mainly three different polymer types: cellulose, hemicellulose and lignin. - Cellulose and hemicellulose contain long chains of sugars that can be converted to fuels for transport such as bioethanol. - To know the share of the single sugars (polysaccharides) is important to evaluate the initial potential of crops for biofuel production

Table 2: SustainAqua analyses to determine bioenergy potential of wetland crops


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Results of these analyses prove the clear potentials for bioenergy applications. The figures for cell wall polysaccharides show the opportunities for cellulosic bioethanol production of these crops, especially of Arundo donax and Phragmites australis. The heating value showed promising figures especially for cattail. Other international experiments demonstrate the great potential for all four tested wetland crops. However, it needs to be considered that on an aquaculture farm the primary goal of a wetland crop plantation is the treatment of wastewater from the aquaculture activities. Whilst it is a target to use this produced biomass as co-product for bioenergy production the wastewater treatment will always be the priority of the wetland crop plantation, not the bioenergy production. This may result in the following limiting factors that are detrimental to efficient and cost-effective bioenergy production: 3. The site of the wetland crops may not provide optimal growing conditions for bioenergy production. 4. Harvesting time is important for optimal combustion quality (best in spring). 5. Harvesting cycles of 2 or 3 years could be more appropriate. It needs to be closely investigated in which way the water treatment and energy crop production can be combined as efficiently as possible in order to find optimal conditions to achieve both goals.

Market opportunities

Conditions are currently very favourable for the development of biomass for energy production. The ambitious goals of the EU to increase the share of bioenergy in the European energy mix will create a tremendous demand for biomass resources in the coming decade. It is also a unique chance for aquaculture farmers to earn a valuable additional income by utilising biomass by-products from their aquaculture farm to provide the booming bioenergy industry with the urgently needed biomass. Willow (Salix viminalis) is already used for the production of wood chips for heat and electricity generation, e.g. in so-called Short Rotation Coppice (SRC) plantations. SRC indicate useful information on the design of wetland crop areas for aquaculture application. To profitably market, the area should be a minimum of 1 ha, be accessible for machines for harvest and produce at least 8-11 t dry mass per ha per year. Regarding the three herbaceous plants of the Hungarian case study, common reed, cattail and giant reed, this sector is currently just beginning to develop and take off. Improvements, though, are expected to occur in the near future. Therefore, while the techno-economic developments for a working biomass-bioenergy market across Europe are establishing and should be achieved in the coming 3-5 years, this time should be used to optimise the conditions for biomass production in connection with aquaculture activities while not neglecting the primary goal of the wetland crops, the wastewater treatment and nutrient retention.

5.3. Hydro-culture plants and tropical fruits for the cosmetic industry – the Swiss case

Hydro-culture plants and tropical fruits have great potential to be used as renewable primary products in the cosmetic industry. The opportunity for such aquaculture co-products lies in the selling of the “local origin” and environmental friendly image of the product. The holistic concept could be the unique selling point for such products. Especially SMEs could be particularly interested in jointly developing new products, such as a papaya or guava crème.

Potentials

Within the framework of SustainAqua, duckweed (Lemna sp.),(which could also be a significant by-product of the Hungarian wetland water treatment system or the Polish cascading system), water hyacinth (Eichhornia crassipes), guava (Psidium sp.), and papaya (Carica papaya) were analysed. For the tropical fruits, analyses focused on low- and middle quality fruits which cannot be sold to the fruit markets as first class product. As it was not possible to search for new ingredients or analyse the entire chemical composition of all selected plants, the most promising known ingredients were assessed for their concentration (see Table 3):

Pectin

- Duckweed is rich in a Lemna-specific pectin (apiogalactoronan/ lemnan) - Extraordinary characteristics compared to ordinary pectin (from apples) - Could be used for treating symptoms of skin aging and skin inflammation

Carotenoids, lycopene

- Guava and papaya are both rich in bioactive substances - ß-carotene and lycopene are known for positive impact on human health

Polyphenols

- Guava has antioxidant properties attributed to its polyphenols content - Water hyacinth, with its polyphenols content, can protect skin against harmful effects of heavy metals and improve cell respiration. - Water hyacinth could also be suitable for phytoremediation as it is able to take up metals and toxic materials from wastewater for its metabolic use.

Table 3: SustainAqua analyses to determine industrial potential of hydro-culture plants and tropical fruits


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Results of these analyses show that the aquaculture co-products from the 'Tropenhaus' case study did not contain a higher concentration of a known active substance compared to other plants. However, an added value in the utilisation of aquaculture co-products in the cosmetic sector could be the holistic and organic approach of, for instance, the 'Tropenhaus' production or other sustainable aquaculture farms. Such a unique selling point could be beneficial for certain branches of the industry, in particular small or medium enterprises.

Market opportunities

Current developments in the cosmetics, in particular the natural cosmetics market, are quite favourable for the utilisation of aquaculture by-products:

• Rapid market growth of up to 20% in the natural cosmetics branch

Global sales of organic cosmetics are soaring with revenues approaching € 5 bn in 2006. Europe is a major engine of growth with growth rates of over 20% to reach € 1,1 bn of sales. Germany, followed by Austria and Switzerland, is by a long stretch the leading country in this market segment, achieving € 650 mill. in sales in 2006. The market share of the overall cosmetic market is forecast to grow from currently 6% to 10% by 2012. However, French markets are the fastest growing, with growth rates of 40% in 2005.

• Domination of highly innovative SME's

In Europe, the supply-side is highly fragmented and dominated by small- and medium-sized companies with over 400 SMEs producing natural cosmetics.

• High rate of new product development (NPD); NPD is key feature

The cosmetics industry is characterised by innovation and a high rate of product development. Innovation is essential to improve performance, safety and the environmental impact of products. Companies are experimenting with natural ingredients moving away from synthetic chemicals.

• Product positioning: Successful marketing comes from clear differentiation from competing products

A critical success factor for natural cosmetics is product positioning. Market winners are the companies that can successfully differentiate their products from their competitors, both natural and conventional.

SUSTAINAQUA HANDBOOK Case study in Hungary

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6. Water treatment of intensive aquaculture systems through wetlands and extensive fish ponds – Case study in Hungary

6.1. Constructed wetlands as a sustainable method to treat aquaculture effluents and produce valuable crops (African Catfish Site)

6.1.1. Introduction – General description of the innovation

Obtaining and maintaining good water quality in natural water bodies is a highlighted objective of European and national legal regulation and NGO's because the quality and quantity of freshwater resources is one of the key factors of healthy human life. Discharged effluents cause eutrophication and deterioration of natural recipient ecosystems. Furthermore, the water loading fee is a significant incurring charge in Hungary. These arguments force the producers to find efficacious and cost-effective treatment methods. In the last decades constructed wetlands have been rediscovered as an effective method for waste water treatment. In wetland ecosystems the pollutant load is reduced by natural processes using water-purifying plants. The discharged suspended solids are settled and converted into soluble nutrients which are utilised through the organisms of wetlands. , With the combination of different wetland types, like a stabilisation pond, fishpond and macrophyte pond, the nutrient removal efficiency can be enhanced. Furthermore, by the integration of valuable fish and plant species, these nutrients can be converted into marketable by-products. By stocking fish into one pond a certain proportion of discharged nutrients is captured in fish flesh and the necessary dissolved oxygen level ensures adequate conditions for aerobic processes. In the macrophyte pond, several macrophytes tolerating the applied water level assimilate a considerable quantity of nutrients for biomass production, which can be suitable for bioenergy production.

6.1.2. Principles of the case study

The African Catfish Site (ACS) is located at the Experimental Pond System of the Research Institute for Fisheries, Aquaculture and Irrigation (HAKI) in Szarvas, Hungary. The pilot-scale 1.1 ha (Subsystem ‘A’) and 0.4 ha (Subsystem ‘B’) wetland systems were constructed to treat effluent water of an intensive flow-through African catfish farm. The wetland subsystems were constructed by the combination of a stabilisation pond, a fishpond and macrophyte pond units. The ponds were filled with stored freshwater originating from the nearby oxbow lake of River Körös at the beginning of the operation period (May in 2007, February in 2008). The effluent from the African catfish farm was channelled into the aerated stabilisation pond, where a paddle wheel aerator was operated and supplemental river water was added. The water from the stabilisation pond was introduced into the fishpond unit, where a certain proportion of the nutrients was retained in fish biomass. The effluent from the fishpond unit was channelled into four surface-flow constructed wetlands planted with different energy plants: common reed (Phragmites australis), cattail (Typha latifolia and T. angustifolia), willow (Salix viminalis), giant reed (Arundo donax) and salt-cedar (Tamarix tetrandra) (see also Table 4). The scheme of this module is shown in Figure 4.

A_PH 2288m2

A_TY 2728m2

B_SA 683 m2

B_AR 683 m2

Subsystem ’A’ Subsystem ’B’

B_SAi 683 m2

B_TAi 683 m2

A_SP 3072 m2

A_FP 3072 m2

B_SP 1387 m2

B_FP 1380 m2

Stabilisation pond Fishpond Macrophyte pond Irrigated area

Flow-through African catfish

farm

Figure 4: Schematic picture of the ACS case study design


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Two additional irrigated fields were connected to the Subsystem ‘B’ in 2008, where the water level was maintained under the surface and the sodium remediation capacity of energy willow and salt-cedar was examined. The following principles were applied: � Retention time: Calculated hydraulic retention time was 18 days in each wetland unit. � Water depth: The average water depth in the stabilisation and fishponds was 1.2 m, and 0.5 m in the

macrophyte ponds. � Fish stock: Fish were stocked in polyculture at a stocking density of 900 kg/ha: 35% common carp

(Cyprinus carpio), 60% silver carp (Hypophthalmichthys molitrix) and 5% grass carp (Ctenopharyngodon idella) in April and May. This fish stocking composition was chosen to achieve the water treatment goals and to utilise the different natural food sources as effectively as possible.

� Feeding: There was no artificial feeding applied in the fishponds. � Harvest: The fishponds were harvested in November, the water was drained and the bottom kept dry in

winter (from November till February)

Unit Area Water depth Species Comments

A_SP 3 072 m2 1.2 m Duckweed (Lemna sp.) Regularly removed

A_FP 3 072 m2 1.2 m Carp polyculture Stocked in April Harvested in November

A_PH 2 288 m2 0.5 m Common reed (Phragmites australis), duckweed Harvested in November

A_TY 2 728 m2 0.5 m Cattail (Typha latifolia, T. angustifolia) Harvested in November

B_SP 1 387 m2 1.2 m Duckweed (Lemna sp.) Regularly removed

B_FP 1 380 m2 1.2 m Carp polyculture Stocked in April Harvested in November

B_SA 683 m2 0.5 m Willow (Salix viminalis), cattail (Typha sp.)

Planted in 2006, insufficient growth of willow, cattail invasion

B_AR 683 m2 0.5 m Giant reed (Arundo donax), cattail (Typha sp.)

Planted in 2006, insufficient growth of giant reed, cattail invasion

B_SAi 683 m2 not applicable Willow (Salix viminalis) Planted in 2007, irrigated with outflow water from the fishpond (B_FP)

B_TAi 683 m2 not applicable Salt-cedar (Tamarix tetrandra) Planted in 2007, irrigated with outflow water from the fishpond (B_FP)

Table 4: Main features of the experimental units

6.1.3. Assessment of selected SustainAqua sustainability indicators

Water input and output

Input water was introduced into the experimental system from two sources:

• African catfish farm effluent to be treated and

• Freshwater from the River Körös to fill up ponds and supply oxygen and algae to the stabilisation ponds during the operation.

The ponds were filled up initially with freshwater from the nearby branch of River Körös. The majority of the river water was used at the filling up stage (13 829 m3 in 2007; 11 173 m3 in 2008); another 10 037 m3 in 2007 and 17 089 m3 in 2008 was added during the operation to the stabilisation ponds. The daily water consumption was, on average 65.6 m3 and 69.5 m3 in 2007 and 2008, respectively. The theoretical daily volume was calculated because refreshing water input was not supplied routinely, only in the case of an unfavourable oxygen regime. The specific refreshing water consumption was computed for the treatment system and it was found that for 1 m3 aquaculture effluent treatment 0.159-0.274 m3 river water was used during the operation and altogether (including the initial filling up) 0.279-0.453 m3 was applied. The water output was controlled at the outflow gate of the macrophyte ponds. During the retention time the inlet water volume decreased by the evaporation, evapotranspiration and seepage lost. Thus, the output water volume was lower by 55-57% than the total input water volume.


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Nutrient utilisation efficiency

The total nitrogen output was found to be 162 kg during the operational period in 2007, which corresponded to 1.05 kg/day discharge of the whole treatment system. In the output water less than 10% of the nitrogen level was detected compared with the input water sources. The total phosphorus output was 44.9 kg and the daily discharge was 0.29 kg, in the output water 27% of the input phosphorus amount was found. The carbon content of the water samples was calculated as half of the volatile suspended solids amount: the total carbon output was 3 262 kg during the operation corresponding to 21.1 kg daily output. In the output water, less than 8% of the total organic carbon input was detected (Table 5).

N P C

Unit Input Output Removal Input Output Removal Input Output Removal

kg kg % kg kg % kg kg %

A_ST 1 167 722 38.1 117 95.1 18.7 1 930 1 307 32.2

A_FI 722 404 27.2 (44.0) 95.1 69.0 22.3 (27.4) 1 307 1 022 14.8 (21.9)

A_PH 207 77.4 11.1 (62.6) 35.6 20.5 12.9 (42.4) 526 325 10.4 (38.2)

A_TY 196 46.5 12.8 (76.3) 33.4 15.1 15.6 (54.8) 495 279 11.2 (43.6)

A_Total 1 167 124 89.4 117 35.6 69.6 1 930 605 68.7

B_ST 512 235 54.1 50.0 31.9 36.2 813 561 31.0

B_FI 235 114 23.6 (51.5) 31.9 18.8 26.1 (41.0) 561 374 23.0 (33.4)

B_SA 56.4 21.1 6.90 (62.6) 9.30 5.13 8.36 (44.9) 188 108 9.82 (42.5)

B_AR 58.1 17.0 8.03 (70.8) 9.55 4.13 10.8 (56.7) 186 79.4 13.1 (57.3)

B_Total 512 38.1 92.6 50.0 9.26 81.5 813 187 77.0

Total 1 679 162 90.3 167 44.9 73.1 2 743 792 71.1

Table 5: Nutrient input, output and the nutrient removal of the pond units in ACS in 2007 (in brackets: removal calculated for the pond input)

N P C

Unit Input Output Removal Input Output Removal Input Output Removal

kg kg % kg kg % kg Kg %

A_ST 1 352 865 36.0 152 95.9 37.0 2 646 1 304 50.7

A_FI 865 376 36.1 (56.5) 95.9 48.0 31.5 (49.9) 1 304 1 143 6.07 (12.3)

A_PH 184 41.9 10.5 (77.3) 23.7 15.5 5.36 (34.4) 562 161 15.2 (71.4)

A_TY 198 37.1 11.9 (81.2) 23.3 14.7 5.66 (36.9) 522 166 13.4 (68.1)

A_Total 1 352 79.0 94.2 152 30.2 80.1 2 646 327 87.6

B_ST 717 361 49.6 78.9 40.4 48.7 1 351 554 59.0

B_FI 361 184 24.7 (49.0) 40.4 19.3 26.7 (52.2) 554 503 3.78 (9.22)

B_SA 88.3 17.3 9.90 (80.4) 9.21 2.96 7.93 (67.9) 238 68.3 12.5 (71.3)

B_AR 99.0 19.5 11.1 (80.3) 9.78 3.97 7.36 (59.4) 257 80.1 13.1 (68.8)

B_Total 717 36.8 94.9 78.9 6.93 91.2 1 351 148 89.0

Total 2 069 116 94.4 231 37.1 83.9 3 997 475 88.1

Table 6: Nutrient input, output and the nutrient removal of the pond units in ACS in 2008 (in brackets: removal calculated for the pond input)

The total nitrogen output amounted to 116 kg during the operational period in 2008, which corresponded to 0.48 kg/day discharge from the whole treatment system. In the output water less than 6% of the nitrogen amount was detected as compared with the input water sources. The total phosphorus output was 37.1 kg and the daily discharge was 0.15 kg, in the output water 16% of the input phosphorus amount was found. The total organic carbon output was 4 812 kg during the operation corresponding to 19.7 kg daily output. In the output water, less than 5% of the total organic carbon input was detected (Table 6). The nitrogen and phosphorus output was considerable lower in 2008 than in 2007, especially regarding the daily outputs which were nearly 50% less in 2008. The organic carbon output, according to the daily amounts, was found to be similar in both years.


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Nutrient Unit 2007 2008

N P C N P C

Input kg 1 679 167 2 743 2 069 231 3 997

Output

Water % 9.7 27 29 5.6 16 4.3

Water at harvest % 10 17 20 5.9 9.2 7.5

Fish % 1.0 1.8 3.5 0.99 1.7 2.3

Plants % 4.0 9.2 n.c.* 3.7 8.5 n.c.* *not calculated

Table 7: Nutrient outputs and nutrient retention in secondary products

A part of the nutrients in the ACS module was taken up by fish and energy plants as valuable by-products. A similar proportion of the input nutrients was converted into fish and plant biomass in both years: 1.0%, 1.8%, and 2.3-3.5% of nitrogen, phosphorus and organic carbon were retained in the harvested fish, respectively., 3.7-4.0% nitrogen and 8.5-9.2% phosphorus were absorbed by energy plants from the input of nutrient amounts (Table 7).

Energy efficiency

During the operation of the ACS experimental system, electrical energy was used to pump effluent into stabilisation ponds (one pump with a power of 3.1 kW) to mix and aerate pond water by aerators (2 pcs with a power of 0.75 kW). The energy consumption of electrical pumps and aerators was 16 221 kWh and 16 997 kWh in 2007 and 2008, respectively. In the case where the effluent inflow to the treatment system can be solved by gravity, the energy consumption needed for pumping can be eliminated. The specific energy consumption calculated for the treated aquaculture effluent volume was 0.257 kWh/m3 in 2007 and 0.273 kWh/m3 in 2008, respectively. Approximately 48 l fuel, i.e. 487 kWh was used for the harvest and transport of the biomass. The total fuel value of the harvested biomass was 81 728 MJ corresponding to 22 702 kWh in 2007 and 359 207 MJ equal to 99 780 kWh in 2008. Calculating the energy budget of the experimental system 6 000 kWh more energy was produced than consumed during the operation period in 2007 and 82 296 kWh more energy was gained in 2008 (Table 8).

2007 2008

kWh MJ kWh MJ

Electric energy consumption 16 221 58 396 16 997 61 189

Effluent pumping 10 714 38 570 9 077 32 677

Aeration 5 508 19 829 7,920 28 512

Fuel consumption 487 1 754 487 1 754

Effective fuel value of plants 22 702 81 728 99 780 359 207

Balance 5 994 21 578 82 296 296 263

Table 8: The energy budget of the ACS

In the effluent treatment system energy crops were cultivated as valuable by-products, since by utilising them as fuel a considerable renewable energy source is produced. The plants were harvested in the macrophyte ponds in December 2007, the total biomass weight was 8 320 kg. The produced macrophyte biomass was estimated to be 40 900 kg in 2008. The cattail showed the highest growing rate and the lowest rate was recorded for the willow plantation. In giant reed and willow ponds, a strong spontaneous cattail growth occurred suppressing the development of planted species. Common reed had the highest fuel values with an average of 11 372 J/g. Willow had a value of 9 699 J/g. Cattail and giant reed showed comparatively low fuel values of 9 214 J/g and 8 611 J/g respectively. Within the seasons of autumn, winter and spring, the heating value nearly doubled for reed and increased by 45% for cattail, while the water content decreased. These results indicate that between March and April is the best time in the year for the harvesting the wetland crops, to gain the highest heating value, as the water content is the lowest at that period and accordingly the calorific value is comparatively high.

Productivity of labour

Plant stocking, daily operation activities, plant harvest and fish harvest required approximately 64, 176, 216 and 32 man-hours, respectively. Thus, the total labour input during the treatment process was 488 h, or 0.00778 man-hours/m3 effluent water were used for the treatment in ACS.


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6.1.4. Success factors and constraints

The African Catfish Site provided significant positive environmental and economical results:

• Nutrient reuse and retention: The application of the examined treatment system decreased the amount of discharged nutrients of the intensive aquaculture by 1 300 kg N/ha, 130 kg P/ha and 7 500 kg COD/ha throughout the whole operation period from February to November in 2008

• Fish production: In the fishponds on average 1 458 kg/ha fish biomass was produced on natural food

• Biomass production: 40 900 kg plant biomass was produced as potential renewable energy source. This biomass could offset the burning of fossil gas, the savings of CO2 emission would be 11 250 kg annually

• Positive energy budget: During the operation of the constructed wetland system less energy was consumed than produced in form of plant biomass

• The removal of nutrients from the effluent water leads to the reduction of the water loading fee and helps avoid environmental fines

• Lower costs than the industrial waste water treatment technologies

• Production of marketable by-products generates additional income However, the application of the treatment method raised some constraints:

• The climatic conditions in Central and Eastern Europe limit the continuous operation of constructed wetlands under the same loading level in winter. At low temperature (under 15 ºC), it is recommended to reduce the effluent load by decreasing the concentration (filtering the suspended solids) or volume of used water (storage).

• The surface-flow (with continuous water supply) in the wetlands assured advantageous conditions for reed and cattail. However, the open water surface and the relatively thin soil layer were not optimal for the growth of willow and giant reed. Wet soils with a deep fertile layer provide favourable growing conditions for these species.

• The construction and successful operation require detailed planning and continuous control of the water quality in the units and the dissolved oxygen level in fishponds, because overloading the system may cause serious disturbances to the natural equilibrium in ponds functioning as constructed ecosystems.

6.1.5. Benefits of implementation

Environmental legislation forces aquaculture producers to minimise their nutrient and pollutant discharge and use sustainable purification methods. The combined wetland system provides an adequate treatment method that is able to meet the environmental standards. Its construction and operation costs are lower than those of artificial purification technologies. Calculating on the basis of average water quality parameters from the experiments, it would lead to 34,500 € (9.7 million HUF) reduction in the water loading fee costs of the African catfish farm. It could generate an additional income of 15,000 € (4.2 million HUF) from cattail and fish production, while the total costs of operation would be under 17,000 € (4.6 million HUF). The fishpond units are suitable for additional fish production, for example, the culture of ornamental fish or species utilising natural food resources, potentially providing profitable opportunities to utilise otherwise wasted nutrients. Natural treatment methods require a low amount of non-renewable energy, however these are land intensive systems. Based on the results of the experimental years and taking into consideration climatic and economical considerations a wetland system of 12 ha area would be able to treat 100% of the effluent water from a flow-through African catfish farm with a capacity of 300 t fish/year.


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6.2. From a case study to a fish farm: How to treat the effluents of a catfish farm?

6.2.1. Description of the intensive fish farm

The results of the ACS case study are extrapolated to an existing flow-through fish farm with a total production capacity of 300 tonnes annually. African catfish (Clarias gariepinus) is produced intensively in outdoor tanks in geothermal water at the farm. The total water volume of the tanks is 1 200 m3 on an area of 3 690 m2. The average feed conversion ratio for market-sized fish is 1.2 kg feed/kg fish. Thus, while culturing 1 t African catfish, 24 kg nitrogen (N) and 3.9 kg phosphorus (P) are converted into fish biomass; and 52 kg N and 9.8 kg P are discharged with the effluent water. The used water is channelled into an oxbow lake where the discharged effluents cause eutrophication and deterioration of the natural ecosystem. Furthermore, according to the recent environmental legislation, a water loading fee is charged on the basis of the net output nutrient mass, and the producers are under an obligation to apply a sustainable treatment technology.

6.2.2. Treatment mechanism of wetlands

In wetland ecosystems, the pollutant content is diminished by natural processes. Constructed wetlands are sustainable technologies since:

• They are effective in pollutant removal;

• Minimal amounts of fossil energy and chemicals are necessary;

• Construction costs are lower, and operational and maintenance costs considerably lower than those of artificial treatment systems;

• They fit well into the natural environment and their notable aesthetic value results in higher acceptance by society;

• Creation of wetland habitats helps in preserving rare wetland species and contributes to biodiversity. With the combination of different wetland types, like the stabilisation pond, fishpond and macrophyte pond, the nutrient removal efficiency can be enhanced; furthermore, by the integration of saleable species, the nutrients are converted into marketable by-products. When applying surface-flow wetlands, consideration of the following factors is essential:

• The land availability is significant,

• The climatic conditions influence the treatment efficiency.

6.2.3. Planning parameters

Effluent water characteristics

The effluent water of the African catfish farm is characterised by a high total dissolved solids content originating from the used geothermal water, and by high chemical oxygen demand (COD). The total nitrogen is composed of approximately 60% total ammonium N (TAN) and 40% organic nitrogen, other N forms were found in negligible amounts. The total phosphorus contained nearly 50% orthophosphate P, while the volatile suspended solids represented 90% of the total suspended solids. On the basis of average concentrations, the annual total nitrogen output equalled 13 t, the phosphorus mass amounted to 1.3 t, and 87 t COD was discharged annually (Table 9).

Parameter CEffluent STD Load

mg/l kg/day

Total dissolved solids 714 62.5 857

Chemical oxygen demand 200 89.0 239

Ammonium N 18.7 5.84 22.4

Total organic N 11.6 11.8 13.9

Total N 29.7 11.4 35.6

Orthophosphate P 1.37 1.07 1.64

Total P 2.90 0.92 3.48

Volatile suspended solids 114 57.6 137

Table 9: Average values of the water chemistry parameters and the calculated daily load of the effluent water (n=38) (STD: standard deviation)


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Nutrient retention

Based on the data of a temperature-dependent loading experiment in 2008, the retention capacities were calculated for 5 ºC intervals. The N removal showed the highest sensitivity, and the COD removal also improved when the water temperature increased. The P retention and VSS removal were more efficient only in the highest temperature range (Table 10). During the planning of the system, the lowest removal efficiency should be considered, and it is recommended that the sizing of the area of different wetland types is undertaken with parallel pond units, which can be attached or detached depending on demand.

Water temperature interval N removal P removal VSS removal COD removal

kg/ha/day

10-15 ºC 2.96 0.36 19.48 18.99

15-20 ºC 5.71 0.37 18.68 30.92

20-25 ºC 7.41 0.75 37.66 44.46

Table 10: The specific removal of the constructed wetland system at different temperature intervals

The possibility of adding refreshing water during the operation, especially in case of stabilisation of fishponds, is an important principle of the treatment process. The supply and drainage channel system of the ponds has to be planned and constructed so as to make possible the independent filling-up and draining of the units when it is necessary.

Fish stocking

In the fish ponds, carp polyculture was chosen in order to utilise a certain amount of wasted nutrients directly by fish or through the food web of ponds. Common carp, as a bottom feeder, stirs up the sediment, whereby the nutrients and organic matter enter the water column, enhancing the primary production and increasing the available food pool for filter feeders. Silver carp tolerates higher densities and can consume a large part of the phytoplankton and zooplankton. It was observed that silver carp can filter the feed remnants from the intensive farm effluent. Grass carp, as a macrophyte feeder, was stocked to control the duckweed growth in the ponds. In an eutrophic/hypertrophic pond, the duckweed species grow spontaneously and in small ponds, could cover the whole pond surface interfering with the primary production of algae. Furthermore, stocking juvenile common carp can prevent abundant zooplankton growth. Various stocking densities were tested in the course of the experiments. The best net yields for both common carp and silver carp were found at a total stocking density of 1 000 kg/ha and stocking composition of 35%:50%:15% (completed with grass carp). The individual stocking weight, i.e. the age of stocked fish, also influences the yields since 1-year-old fish is expected to grow more intensively than larger-sized fish; however, 2-year-old common carp is able to resuspend the sediment more efficiently.

6.2.4. Critical factors of the operation

Climatic conditions: Natural water treatment systems function adequately at water temperatures of 15-30 ºC, i.e. from April to October in Central and Eastern Europe. However, fish production farms operate continuously all year round. In winter, a reduced nutrient (especially nitrogen), removal is characteristic to surface-flow constructed wetlands. Therefore, the loadability decreases at lower temperatures and a larger area is needed for the required nutrient removal. Mechanical filtration could also decrease the nutrient load of dissolved compounds. Fish stocks: In pond ecosystems, stocked species and naturally occurring organisms require adequate management measures. Fish are sensitive to low oxygen levels (<1.5-2.0 mg/l) and increased unionised ammonia concentration (>0.3-0.4 mg/l). When solar radiation is permanently hindered by cloudy, rainy weather, photosynthetic O2 production can be reduced, and thus, the dissolved O2 concentration decreases in water. Higher ammonia levels can be caused by overloading the ponds, especially at lower temperatures and when the activity of nitrifying bacteria is suppressed. Below the desired dissolved O2 level, supplementation of the deficit has to be achieved by aeration or refreshing water supply. Aeration and refreshing water addition also helps in the reduction of unionised ammonia. Regular (daily) monitoring of O2 and ammonia concentrations and considering weather conditions can prevent fatal water quality deterioration. Planktonic booms: At the beginning of the vegetation period, abundant zooplankton growth can occur in ponds. Filtering the suspended solids and phytoplankton, a considerable biomass is produced; however, the gradations of zooplankton lower the oxygen concentration of water. To prevent unfavourable zooplankton reproduction, the removal of its biomass can be solved by stocking juvenile fish or by filtration. No cyanobacterial blooms were observed in the treatment units.


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Duckweed: In stagnant waters, different duckweed species can appear and at optimal conditions, reproduce abundantly. Covering the pond surface, the duckweed hampers phytoplankton growth and activity, which results in anaerobic conditions in the water column. Since aerobic processes are preferred in treatment systems, the removal of duckweed is recommended from all pond units. The best solution for duckweed control in fishponds is the stocking of grass carp, that can consume duckweed, and thus, it is transferred into fish biomass. In macrophyte ponds, the manual removal of duckweed is also recommended to increase the ratio of open water surface. Accumulation: Moderate sludge accumulation was observed at the inflow of aquaculture effluents in the stabilisation ponds and after longer operation (15-20 years), the removal of the accumulated sludge may be necessary.

6.2.5. Design of the suggested wetland system

On the basis of the existing results and the calculated daily load discharged from a fish farm with a 300 t/year capacity, a 12 ha wetland system is recommended. The size and structure of the system is designed in order to assure the treatment safety in winter and to improve the outflow water quality. The construction of parallel pond units can increase the flexibility of the system since a larger area could be necessary in winter than in summer to meet discharge limits (see Figure 5). Studying the share of different wetland types in nutrient removal, the recommended proportion for the stabilisation pond: fishpond: macrophyte pond combination is 3.5:2:1. Thus, the suggested wetland system consists of:

• Three stabilisation ponds of 2.2 ha,

• One fishpond of 3.7 ha and

• One macrophyte pond of 1.8 ha. Stocking carp in polyculture is recommended in the fishponds unit. The advisable stocking rate for fish is 35%:50%:15% common carp (2y): silver carp (1y): grass carp at 1 000 kg/ha density and 50-300 g individual weight. Other carp species, e.g. ornamental fish, can also be stocked at a similar stocking density. At the beginning of the operation, ponds are filled with river water (i.e. not polluted surface or groundwater). Using parallel stabilisation ponds, the draining and filling-up can be managed alternatively. According to our assumption, one stabilisation pond will not be in operation during warm months (from April till September), the filling-up in this unit can start before or parallel with the draining and filling-up of other stabilisation units. During the draining and filling-up of certain stabilisation ponds, the treatment can run in the already filled pond. The fish pond is harvested at the end of October or beginning of November. After harvesting, the water inlet from the stabilisation ponds can be continued. It is recommended to harvest macrophytes in early spring, in March, when the water content of above-ground plant parts is the lowest. It is reasonable to keep the water level reduced in macrophyte ponds during harvest. It is supposed that during one year the proposed wetland would remove

• Around 1 000-1 100 kg phosphorus,

• 7 000-8 000 kg inorganic nitrogen, and

• 70 000-80 000 kg COD from the effluent water. Calculating on the basis of the average water quality parameters from the experiments, it would lead to 34 543 € reduction in the water loading fees for the African catfish farms. Additional earnings would originate from the fish production in the fishpond, and cattail (biofuel) production in the macrophyte pond. According to our calculation the investment’s payback period is 8 years, while the investment net present value (discount rate: 5%) amounts to 102 175 € after 15 years of operation. Further calculations are listed in the table below. In the Cost Benefit Analysis (CBA), it is assumed that the energy and fuel prices and the market price of cattail would increase by 6 % annually. The inflation of wages is set in the model to 3 %, while the increase in fish and fingerling prices is calculated to 2 % annually.

Stabilisation pond

2.2 ha depth 1.2 m

Stabilisation pond

2.2 ha depth 1.2 m

Stabilisation pond

2.2 ha depth 1.2 m

Fishpond

3.7 ha depth 1.2 m

Macrophyte pond 1.8 ha

depth 0.5 m

AC farm

Figure 5: Suggested structure of the wetland treatment system for a 300 t/year capacity African catfish (AC) farm


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2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024

Investment costs (land, ponds, pumps, aerators) 228 571 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Cost of fish juveniles 0 4 029 4 109 4 191 4 275 4 361 4 448 4 537 4 628 4 720 4 815 4 911 5 009 5 109 5 211 5 316

Fuel costs (250 litres/year) 89 268 284 301 319 338 358 380 403 427 453 480 508 539 571 606 Cost of electricity (35,040 kWh/ year) 0 4 505 4 775 5 062 5 366 5 688 6 029 6 391 6 774 7 181 7 611 8 068 8 552 9 065 9 609 10 186

Labour costs (2,800 hour/year) 1 429 7 500 7 725 7 957 8 195 8 441 8 695 8 955 9 224 9 501 9 786 10 079 10 382 10 693 11 014 11 344 Revenue from cattail (2.9 EUR/GJ) 0 3 082 3 267 3 463 3 671 3 891 4 125 4 372 4 634 4 912 5 207 5 520 5 851 6 202 6 574 6 968

Revenue from fish production 0 11 986 12 225 12 470 12 719 12 974 13 233 13 498 13 768 14 043 14 324 14 611 14 903 15 201 15 505 15 815

Avoided water discharge fees 0 34 543 34 543 34 543 34 543 34 543 34 543 34 543 34 543 34 543 34 543 34 543 34 543 34 543 34 543 34 543

Profit -230 089 33 309 33 142 32 965 32 778 32 580 32 371 32 150 31 917 31 670 31 410 31 135 30 845 30 539 30 216 29 875

Discounted profit (r=5%) -230 089 31 723 30 061 28 476 26 966 25 527 24 156 22 848 21 602 20 415 19 283 18 204 17 176 16 195 15 261 14 370

Net present value -230 089 -198 366 -168 306 -139 829 -112 863 -87 336 -63 180 -40 332 -18 729 1 686 20 969 39 173 56 348 72 544 87 805

102 175

Table 11: CBA of the proposed 12-hectare wetland system (thousands HUF, 1 EURO=275 HUF)


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6.3. Combination of intensive and extensive aquaculture for the sustainable utilisation of water and nutrients (Intensive-Extensive Site)

6.3.1. Introduction – General description of the innovation

During the development of environmental friendly fish production technologies it seems to be the obvious solution that intensive aquaculture is integrated within fishpond systems. The principle of this method is to treat the effluent water enriched with organic and inorganic nutrients of intensive fish ponds in an extensive pond. There, a part of the nutrients is utilised through various biological production processes and the other part is fixed in the pond sediment. The water treated or purified is recycled to the intensive fishponds. The application of the combined production system contributes to the ecological sustainability and production of marketable fish. Periphyton based aquaculture is a technology for increasing natural food production in the pond and its utilisation for fish production. The better utilisation of nutrients in aquacultural systems aims at decreasing the nutrient discharge into natural waters. Aquaculture production is higher in ponds, which are provided with periphyton substrates than in ponds without. The new primary production and benthic secondary production of the attached communities fostered by the artificial substrate supports a new food web, part of which ends up as fish biomass. Grazing on a two-dimensional layer of periphyton is mechanically more efficient than filtering algae from a three-dimensional planktonic environment. If pond algae could be grown on substrates, more fish species would be able to harvest them, resulting in a more efficient utilisation of primary production. The application of periphyton in an extensive pond built for wastewater treatment can improve the purification capacity of ponds as well. The overall objective of the “Intensive-Extensive Site” (IES) case study is to help the traditional carp farmers to use their water more efficiently by producing valuable species in their reservoir or extensively used ponds in order to diversify their production and increase the economical performance of fish production. The principle of the research on IES was based on a linkage of intensive and extensive aquaculture production methods and different species that occupy different niches in the food web into one single integrated system, so that wasted nutrients could be recycled. This results in a higher nutrient utilisation efficiency and reduced environmental emissions; at the same time the production per unit of water intake increases. The purpose of the task was to develop a new method for predatory fish production in pond systems and to increase the nutrient utilisation of fish production. The goals of the IES innovation were to: 1. Increase production capacity; 2. Diversify the cultured species and 3. Recycle the nutrients within the production system. With these objectives the research work focused on:

• Evaluating the potential of nutrient reusing in combined aquaculture systems

• Investigating different biotechnological elements (e.g. periphyton application, mussel stocking) on the additional fish production and the water quality

• Evaluating the nutrient budget of the experimental system

6.3.2. Principles of the module

The experiments of IES were carried out in three ponds (area 310 m2, depth 1 m each). These ponds served as extensive units, where a cage was placed as an intensive unit (volume 10 m3) in each pond (Figure 6). The ponds were filled up with natural water from a river before a week of fish stocking. The water level was maintained by supplying river water regularly. A paddlewheel aerator (0.5 kW) was installed in the pond to provide sufficient oxygen concentration and maintain the water circulation between the intensive and extensive units. Drugs and chemicals were not used during the experiment at all.


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Water supply canal

Water tretment unit Water tretment unit Water tretment unit 300 m2 300 m2 300 m2

Fish stocking only

Experimental system I. (IES/1) Experimental system II. (IES/2) Experimental system III. (IES/3)

: Paddle wheal aerator : direction of water circulation

Inte

nsiv

e un

it

Inte

nsiv

e un

it

Inte

nsiv

e un

it

Periphyton

Fish stocking only

Periphyton

Fish + shellfish stocking (2007)

Figure 6: Scheme of the experimental system

All ponds were subjected to the same regime of feeding and fish stocking. A pelleted fish feed (45% crude protein, C:N ratio 6) was applied daily to the intensive ponds using an automatic feeder, but there was no feeding in the extensive fishponds. The design of extensive ponds was the only difference between the systems, where the effect of periphyton application and shellfish stocking on the water quality, fish yields and nutrient utilisation were tested. The average feed loading was 0.5 and 1.2 g N/m2/day in 2007 and 2008, respectively (Table 12). The only nutrient source of the system was the fish feed used in the intensive unit. The additional area for periphyton development equalled to 0, 100 and 200 % (i.e. 0, 1 and 2 m2 periphyton area/m2 pond surface) of the pond surface area (Table 13).

Nitrogen Phosphorus Organic carbon

Average Maximum Average Maximum Average Maximum

2007 0.51 0.72 0.08 0.12 3.1 4.4

2008 1.2 1.8 0.19 0.28 7.3 10.6

Table 12: The daily feed loading of IES

IES/1 IES/2 IES/3

Average feed loading 0.5g N/m

2/day (2007)

No periphyton PA 1 m2/m2 PA 1 m2/m2 + shellfish stocking

Average feed loading 1.2 g N/m

2/day (2008)

No periphyton PA 1 m2/m2 PA 2 m2/m2

PA: Periphyton area

Table 13: Experimental set-up

The system operation in 2007

In the intensive units European catfish (Silurus glanis L.) were cultured and fed with pellets – initial stocking biomass was 100 kg (10 kg/m3) –, while in the extensive units Common carp (Cyprinus carpio L.) and Nile tilapia (Oreochromis niloticus L.) were raised without any artificial feeding – initial stocking biomass was 60 kg (stocking ratio 1:1). There was an additional freshwater mussel (Anodonta cygnea L.) stocking with the density 1 piece/m2 (size 109±69 g/individual) in the third unit. The shellfish were placed in suspended plastic net bags 10 cm above the pond bottom. 10 shellfish were placed in a bag, altogether 30 bags were installed in IES/3. In two treatments (IES/2 and IES/3) the productivity of the extensive unit was enhanced by periphyton developed on artificial substrates and without additional substrate in control setup (IES/1). Willow branches were used as substrate for the growth of periphyton. The willow substrates added an effective surface area of about 300 m2 per pond, approximating the entire pond water surface area. However, the surface of the brunches decreased continuously during the operation, and by the end of the production season, it was assumed to be only 70 m2. The experimental system was operated over 22 weeks from 10 May till 11 October of 2007.


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The system operation in 2008

In the second year of the operation the stocking density (20 kg/m3) of intensive and intensive units was doubled compared to 2007, thus the average feed loading increased to 1.2 gN/m2/day. For the safe operation, the intensive unit was stocked with African catfish (Clarias gariepinus L.) as a model fish that is a more robust species than its European counterpart (Silurus glanis L.). The experimental set-up of IES/3 was changed in 2008, it was stocked without shellfish while the artificial substrate surface was increased to 600 m2 (2 m2 periphyton area/m2 pond surface). The reason of the shellfish removal from the experimental set-up was that the shellfish mortality was high in the first year, therefore the nutrient accumulation in the shellfish biomass was not as high as expected. In addition, parasite problems occurred in the experimental unit causing high mortality among fish in the intensive unit. In the second year of the experiment artificial plastic substrate was used for periphyton growth because of its constant area instead of the willow branches. The operation lasted 16 weeks from 21 May to 10 September of 2008. In both years the net fish yield of the whole system (intensive and extensive unit together) was the highest in those ponds where the periphyton area was 100% of the pond surface (Table 14).


Energy efficiency

Only electrical energy was used to mix and aerate the water of each experimental pond by paddlewheel aerators (0.5 kW power) during the operation. Electric power consumption dominated the total energy consumption, while fuel consumption accounted for only 2-3% of the total energy requirement. The daily energy consumption was 12.2 and 12.4 kWh, in 2007 and 2008, respectively. The energy consumption of fish production is summarised in Table 15. The specific energy consumption was much higher in 2007 than in 2008, because of the lower fish yields of the first research year. The energy efficiency was improved by the additional fish production in the extensive unit with 35% and 21% in 2007 and 2008, respectively.

Water input and output

The ponds were filled up with fresh water from the nearby branch of River Körös. The evaporation and seepage were regularly compensated for in the extensive ponds during the experimental period (Table 16). No effluent water was discharged to the environment during the culture period; the water was only drained from the ponds at fish harvest.

Nutrient utilisation

The total nutrient inputs (stocked fish, inlet water, fish feed) and outputs (harvested fish and drainage water) are summarised in Table 17. The main nutrient source was the fish feed, which represented 80% of the total input of nitrogen, 75% of phosphorus and 85% of carbon. The nutrient retention was 6 300 kg/ha for organic carbon, 1 000 kg/ha for nitrogen and 180 kg/ha for phosphorus in 2008. The nutrient loading in 2008 was therefore higher than in the previous year. The retained nutrients represented on average 65 and 57% of the nitrogen and 66 and 58% of the phosphorus and 75 and 64% of the organic carbon introduced into the system in 2007 and 2008, respectively. The combined system was able to process 1 400 kg/ha of fish feed-originated nitrogen. The nutrient utilisation of fish production in IES expressed as a percentage of the introduced nutrients in fish feed is presented in Table 18. The combined fish production resulted in a higher protein utilisation of 26%;

IES/1 IES/2 IES/3

2007 Intensive unit 3,173 5,747 2,747

Extensive unit 3,619 2,078 4,044

Whole system 6,792 7,825 7,083

2008 Intensive unit 13,221 12,788 12,811

Extensive unit 2,789 5,048 2,718

Whole system 16,010 17,837 15,529

Table 14: Net fish yields in IES (kg/ha)

IES/1 IES/2 IES/3

2007 Used energy 1857 1857 1857

EC intensive unit (kWh/kg) 18.8 10.4 21.6

EC whole system (kWh/kg) 8.76 7.61 8.40

2008 Used energy 1384 1384 1384

EC intensive unit (kWh/kg) 3.35 3.47 3.46

EC whole system (kWh/kg) 2.76 2.48 2.85 EC: Energy consumption for fish production (kWh/kg net fish production)

Table 15: Energy consumption of the IES (kWh)

IES/1 IES/2 IES/3

2007 Water intake 735 518 848

Water discharge 248 242 225

WC (m3/kg fish) 3.5 2.1 3.8

2008 Water intake 956 890 850

Water discharge 245 256 260

WC (m3/kg fish) 1.9 1.6 1.8 WC: Water consumption for fish production (water intake/kg fish)

Table 16: Water budget of the IES (m3)


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with periphyton application this ratio could be increased to 40% in 2008. The total nutrient utilisation during the fish production was the highest where the periphyton area was 100% of the pond surface in both years and the nutrient utilisation decreased in the treatment with highest periphyton ratio. This indicates that the 100% periphyton ratio was sufficient to utilise the metabolites of the feed loading of 1.8 g N/m2/day. The average FCR was 3.3 and 1.6 in the intensive unit in 2007 and 2008. By the combined production the FCR was improved by 51% and 44% (to 1.6 and 0.9) due to the additional fish yield of the extensive unit.

IES/1 IES/2 IES/3

N P C N P C N P C

2007 Input (kg/ha) 930 160 5400 930 150 5400 950 160 5500

Output (kg/ha) 330 55 1200 350 59 1600 310 55 1300

Retention (%) 65 65 78 63 67 72 67 65 76

2008 Input (kg/ha) 1790 310 9700 1800 320 9700 1800 310 9700

Output (kg/ha) 760 130 3100 840 140 3900 720 130 3200

Retention (%) 58 60 67 53 55 59 60 60 67

Table 17: Partial nutrient budget of the IES

PA 0% PA 100%

PA 100%+SF (2007), PA 200% (2008)

N P C N P C N P C

2007 Intensive 8.5 7.8 5.6 17 17 11 6.4 5.6 4.1

Extensive 11 13 7.8 6.5 6.9 4.2 13 17 9.2

Total 20 21 13 24 24 16 19 24 13

2008 Intensive 23 23 16 22 22 15 22 22 15

Extensive 6.1 3.3 4.4 10 8.9 7.3 5.9 3.3 4.2

Total 29 26 20 33 31 22 28 25 19

PA: Periphyton area, SF: shellfish

Table 18: Nutrient accumulation in fish biomass as a percentage of the feed input (%)

From the experimental ponds 2.6-8.3 g nitrogen, 0.20-0.53 g phosphorus and 9-46 g organic carbon were discharged during the production of 1 kg fish biomass (Table 19). There was no effect of the periphyton application and feed loading on the nutrient content of effluents. Only the nitrogen concentration was lower in the effluent in the case of a 200% periphyton ratio.

IES/1 IES/2 IES/3

N P C N P C N P C

2007 8.3 0.48 9.2 5.1 0.48 30 5.1 0.32 25

2008 4.2 0.20 16 5.8 0.53 46 2.6 0.27 20

Table 19: Nutrient discharge of the fish production in IES (g/kg net fish yield)

In the operation of water treatment systems, besides algae nutrient uptake and bacterial decomposition, consumption of heterotrophic organisms and denitrification processes have a significant role. Hence, the regulation of the oxygen regime, to provide aerobic condition by artificial aeration is important for the efficient nutrient removal during water treatment. The pilot scale experimental combination of an intensive fish production unit and an extensive fishpond demonstrated the applicability of such systems. The combined system could process a significant part of surplus nutrients from the intensive fish production. The maximum of reused surplus nutrients by the additional fish production in the fishpond represented 13% of the nitrogen, 17% of the phosphorus and 9% of the organic carbon. The efficiency of the extensive unit was improved by periphyton developed on artificial substrates, as the periphyton can provide special foods for fish. The dry matter content of periphyton developed at different


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layers was significantly higher in the samples, which were collected from the higher parts of poles than samples which were taken from the lower parts. Comparing the annual average amounts of periphyton dry matter, there was no significant difference between the two ponds. However, the higher amount of periphyton consumption by fish resulted in a higher fish yield in the extensive unit. By following the quantitative and qualitative changes of the periphyton, we were able to derive more detailed knowledge on the functioning of the system, nutrient cycling and energy flow in the aquatic ecosystem and possibilities of increasing the system efficiency, which could then be applied to the operation and further development of the technology. Investigations on the nutrient budget of the system demonstrated that an adequate size of the extensive fish pond could treat the effluent from intensive fish culture efficiently and make the reuse of water for intensive fish production possible.

Productivity of labour and economic sustainability

31.3 and 37.3 man-hours were used for the fish production in each experimental unit. Thus, the average labour demand was 0.13-0.15 and 0.07-0.08 hours/kg net fish yield in 2007 and 2008, respectively. As both years of operation have shown that the IES/2 subsystem performed the best, it can be stated that the usage of 1 m2 artificial surface for periphyton per 1 m2 pond surface leads to the highest economic viability. The results show that the rearing of African catfish (2008) is more viable than rearing European catfish (2007).


Results proved that the combination of intensive and extensive fish farming systems is an efficient tool to reduce environmental pollution of intensive fish farming and to increase extensive fish production as co-product. The efficiency of the extensive unit can be improved by periphyton cultured on artificial substrates. The combined fish production resulted in a higher protein utilisation by 26%; with periphyton application this ratio can be increased by 40%. These substrate-attached communities provide a new food web, and a part of the additional nutrient is recovered as fish biomass. The water quality was adequate for fish growth. The general fish yields are around 1 t/ha in traditional ponds, but in combined systems it can be increased up to 20 t/ha. However, the nutrient discharge from the traditional fishponds is very low because of the improved nutrient utilisation efficiency.


The combination of intensive and extensive aquaculture exploits the advantages of both traditional pond farming and intensive fish culture systems. Valuable predatory fish species can be produced in the intensive part of the system, whilst the integration of an extensive pond as a treatment unit results in decreased nutrient loading to the environment and increased nutrient recovery in fish production. The intensive rearing can be performed in cages or in in-pond floating tanks, which are placed in the extensive pond environment. In the intensively managed part of the system valuable carnivorous fish can be cultured in controlled conditions and fed with artificial diets. The uneaten feed and the fish metabolic wastes can be utilised in the extensive part and can increase the fish yields. Compared to the nutrient utilisation efficiency of about 20-25% in most intensive culture systems, it this be increased up to 30-35% in integrated pond systems, resulting in less nutrients discharge to the receiving waters. The application of the combined intensive-extensive pond fish production system could contribute to the better use of water resources and the sustainability of aquaculture. Results of the case study proved that the combination of intensive aquaculture with extensive fishponds enhances the nutrient utilisation efficiency and fish production in a combined system. The most important sustainability indicators are summarised in Table 20.

IES/1 IES/2 IES/3

Energy consumption for fish production (kWh/kg)

Intensive unit 3.4 3.5 3.5

Whole system 2.8 2.5 2.9

Water consumption for fish production (m3/kg)

Water intake 1.8 1.6 1.6

Effluent discharge 0.5 0.4 0.5

Nutrient discharge per kg produced fish (g/kg)

N 4.2 5.8 2.6

P 0.20 0.53 0.27

C 16 46 20

Nutrient re-use from the additional fish production (% of the input)

N 6.0% 10% 5.8%

P 3.2% 8.6% 3.2%

C 4.3% 7.2% 4.1%

Table 20: Sustainability indicators of IES in 2008


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6.4. From a case study to a fish farm: Design of a theoretical combined system

6.4.1. Technology in general

The applied technology of IES is simple: a compartmentalised unit for intensive production placed in a traditional fishpond. Cages or tanks could be used as the intensive unit operating in close interaction with the fishpond. The fishpond operates as a biological filter and treats the wastes from the intensive unit. The fish yields in the extensive fishpond can be enhanced by provision of additional surface for increased periphyton production. Based on our results the additional fish production in the extensive unit was the highest where the periphyton area was 100% of the pond surface. The key to the safe operation of the system is the balance between the nutrient loading of the intensive unit and the treatment capacity of the extensive pond. Given an adequate size of the extensive pond the appropriate water quality for fish production can be maintained and the nutrient discharge into the recipient natural waters can be minimised. Paddlewheel aerators could contribute to the adequate water circulation between the intensive and extensive units and maintain the optimal oxygen levels. The pond system operates as a closed system; there is no effluent water discharge to the environment during the culture period, and the water is drained from the ponds only at fish harvest. Only evaporation water and seepage should be regularly compensated. The evaporation is higher in a continuously aerated pond system than in traditional fishponds, the expected rate of the water compensation could be 150% of the total volume annually.

Advantages Disadvantages

• Simple technology with low investment and operation costs

• Improved nutrient utilisation efficiency and additional income through additional fish production

• Low nutrient discharge into the natural waters

• Low energy demand for fish production

• Lower water consumption compared to other pond farming practices

• Concentrated production reduces the losses caused by predators

• Less controllable production conditions (i.e. temperature fluctuations)

• Water quality affected primarily by natural biological processes

• Limited growing period (from April till October in Hungary)

• Winter storage of fish needs to be be resolved

Table 21: Pros and contras of the IES application

6.4.2. Planning parameters

The maximal feed loading of the system is 1.8 gN/m2/day (this corresponds to application of fish feed containing 11.2 g crude protein or 2 kg standing stock of fish in the intensive unit). The suggested fish stocking: carp polyculture is advised in the extensive pond based on common carp stocking as omnivorous bottom feeder species together with filter feeder fish species (i.e. tilapia, silver carp). In the case of common carp monoculture in the extensive pond the mixing of different age groups of carp (1 and 2 year old) is recommended. The expected net fish yield is around 18 t/ha with stimulating periphyton production (13 t/ha from the intensive production and 5 t/ha originated from the extensive fishpond), and 16 t/ha without the provision of surface for periphyton culture (13 and 3 t/ha from the intensive and extensive production areas, respectively). The recommended additional area for periphyton development equals to about 100% of the pond surface area. Our results proved that the efficiency of the extensive unit can be improved by periphyton development on artificial substrates. The combined fish production resulted in 25% higher protein utilisation than that of intensive aquaculture alone; with periphyton-surface application this ratio can be increased to as high as 40%. The oxygen demand of the production system is higher than that of the traditional pond systems due to the high nutrient loading and fish stocking. The overall rate of the community respiration is 1.5 gO2/m

2/hour is supplied from the oxygen production of algae in daytime, but artificial oxygen supply is necessary during night-time hours. Paddle wheel aerators were used to maintain adequate oxygen levels and water circulation


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in our experiment. According to our calculation a total power of 1 kW is sufficient capacity to maintain the oxygen level in a 1500-2 000 m2 pond during night-time hours with paddle wheel aerators. During daytime – especially in sunny hours – the main function of the aerator is to maintain adequate water circulation between the intensive and extensive parts of the system and flush away the residuals from the intensive area. Mixing is important to ensure that algal cells are kept in suspension in the water column in order to enhance the primary production. The adequate velocity of water circulation is 5-10 cm/sec.

6.4.3. Critical factors of operation

The main risk of the operation is the unsteady purification efficiency resulting from unpredictable fluctuation of phytoplankton biomass and the plankton species composition in the treatment pond. Therefore, the important practical factors in this system are the homogeneous water mixing of the treatment pond and the maintenance of adequate oxygen levels in order to satisfy the oxygen demand of fish, nitrification and decomposition processes. The critical oxygen level is 4 mg/l. It is also important to avoid the development of permanent anaerobic conditions anywhere in the system. The total ammonium nitrogen (TAN) and nitrite nitrogen concentration should be lower than 0.5 mg/l. The occurrence of high ammonia levels indicates insufficient nitrification or an overloading of the system. In case of a high ammonia level the feed loading should be reduced and artificial aeration must be operated intensively until ammonium and nitrite levels decrease to acceptable levels. In order to avoid nutrient accumulation in the pond sediment, periodic aeration by drainage is needed. It is recommended to keep the pond dry in winter, since nitrogen and organic carbon mineralisation take place during this season and the dry period minimises the occurrence of parasites and other infectious agents. Feeding levels have to be adapted to the fluctuations in temperature, as the production system is exposed to changes in temperature.

6.4.4. Design of a theoretical farm of 80 t/year production

A theoretical fish farm is described below, which is characterised by an expected gross output of approximately 50 t of intensively produced predatory fish and 30 t of common carp. With an expected profit of 22.000 € (6.2 million HUF), it can be considered as a small-scale or family farm (Table 22). Based on the results of the experimental years and taking into account economical considerations, we suggest establishing a 2.5 ha intensive-extensive pond system. The system would consist of 2 ponds, both of them containing 4 cages as units for intensive rearing of predatory fish (stocking density: 20 kg/m3, FCR: 1.5). In the extensive part of the ponds it is advised to rear carp without feeding (stocking density: 6 t/ha) and to used artificial substrate in order to boost periphyton production (10 000 m2 substrate/hectare). The water should be circulated with 4 paddlewheel aerators in each pond (2 kW each)

Intensive unit Extensive pond Combined

Stocking

total (t) 16 15 31

Unit 2 t/cage (100m2) 7.5 t/pond (1.25ha)

ha (t/ha) 6.4 6 12.4

FCR 1.5 - 1.0

consumed feed 51 t - 51 t

Harvesting

total (t) 50 27.5 77.5

Unit 6.25 t/cage (100m2) 15 t/pond (1.25ha)

ha (t/ha) 20 13.75 31

Net yield

total (t) 34 t 12.5 46.5

ha (t/ha) 13.6 5 18.6

Table 22: Stocking and yields of the theoretical farm


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Figure 7: Scheme of the theoretical farm

The calculated investments costs comprise the acquisition of 3.5 ha of land (5 000 €, 1.4 million HUF), the construction of a 2.5 ha pond area (54 000 €, 15 million HUF) with a 800 m3 cage (3 000 €, 0.8 million HUF*), setting of artificial substrate for periphyton production (4 000 €, 1.2 million HUF) and creation of starting current assets (2 000 €, 0.6 million HUF). Further calculations are listed in the table below. In the Cost Benefit Analysis it is assumed that the prices are constant. The investments’ payback occurs in the 4th year, while the investment’s present net value (with 10 % discount rate) amounts to 74 000 € (20.7 million HUF) after 10 years of operation.

Table 23: Cost Benefit Analysis of the theoretical farm (EUR, calculation is based on an exchange rate of 280 EUR/HUF)

0. year 1. year 2. year 3. year 4. year 5. year 6. year 7. year 8. year 9. year 10. year

Investment 67 857

Residual value after 10 years 17 857

Feed costs 36 643 36 643 36 643 36 643 36 643 36 643 36 643 36 643 36 643 36 643

Seed costs 62 857 62 857 62 857 62 857 62 857 62 857 62 857 62 857 62 857 62 857

Labour costs 7 857 7 857 7 857 7 857 7 857 7 857 7 857 7 857 7 857 7 857

Energy costs and water fees 6 714 6 714 6 714 6 714 6 714 6 714 6 714 6 714 6 714 6 714

Total Cost 114 071 114 071 114 071 114 071 114 071 114 071 114 071 114 071 114 071 114 071

Total Revenue 136 071 136 071 136 071 136 071 136 071 136 071 136 071 136 071 136 071 136 071

Cash-flow -67 857 22 000 22 000 22 000 22 000 22 000 22 000 22 000 22 000 22 000 39 857

Discounted cash-flow (r=10%) -67 857 20 000 18 182 16 529 15 026 13 660 12 418 11 289 10 263 9 330 15 367

Cumulative discounted cash-flow -67 857 -47 857 -29 675 -13 146 1 880 15 540 27 959 39 248 49 511 58 841 74 208

Total pond area: 1.25 hectare

Intensive fish production unit

100 m2


100 m2


100 m2


100 m2


100 m2


100 m2


100 m2


100 m2

Total pond area: 1.25 hectare

SUSTAINAQUA HANDBOOK Case study in Poland

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7. Improved natural production in extensive fish ponds – Case study in Poland

7.1. New species and methods in pond fish culture: Module POLYCULTURE

7.1.1. General description of the case study

The majority of pond farms in Poland are run as a monoculture of common carp. Other fish species produced together with carp have low market value due to limited market demand. Therefore, poor production diversification does not provide an opportunity to compensate for economical losses caused by decreasing carp demand. Additionally, these monoculture stocks are not efficient in terms of nutrient utilisation. Therefore, to improve carp farms profitability and reduce their environmental impact, a new polyculture stock would be desirable. The introduction of new fish species would increase product diversity of pond farms and allow them to compete better with other fish producers by providing fish in greater demand by consumers. Due to the nature of carp pond farming, a substitute for herbivorous and planktophagous cyprinids is the most reasonable solution. Literature research and practical observations highlighted the American paddlefish (Polyodon spathula) as one of the possible species for introduction. The paddlefish is an acipenserifom fish naturally living in slow-flowing rivers of the temperate zones of North America. Throughout its life paddlefish, unlike other sturgeon, feed exclusively on plankton organisms and reach 2 m length. This fish is appreciated for its flesh taste and eggs. Paddlefish was been imported to Poland during the 1980’s, though it, never became a popular species. The paddlefish is a filter feeder and due to its fast growth rate it seems to be an excellent replacement for bighead carp. Besides its economical benefits, presence of filtrating fish species in ponds increases nutrient dynamics and retention of N and P in fish biomass, resulting in decreases of accumulation in the environment.


The technology developed under the Polyculture module provides new possibilities to current farmers running carp-type pond farms. The proposed technology introduces paddlefish into carp aquaculture as a replacement for bighead carp. The polyculture stock composition is described together with expected production and economical results as well as practical observations on the paddlefish production techniques. This innovation requires no investments costs, except for the purchase of new fish stocks.

Fish stock

Standard monoculture and polyculture fish stocks have been compared with two experimental stocks involving paddlefish and sturgeon. The fish stocks were designed to ensure that each feeding spectrum of fish (bottom feeders, filter feeders, herbivorous) carried the same biomass of fish (Table 24). These treatments (different fish stocks) were run in duplicate. The fish were introduced into the ponds at the end of April and stayed for 5 months.

Species Monoculture Polyculture tench Polyculture carp Polyculture

sturgeon

Grass carp (Ctenopharyngodon idella) -

30 kg/ha 500 g

30 kg/ha 500 g

30 kg/ha 500 g

Silver carp (Hypophthalmichthys molitrix)

- 60 kg/ha

500 g 60 kg/ha

500 g 60 kg/ha

500 g

Bighead carp (Aristichthys nobilis)

- 72 kg/ha

100 g - -

Paddlefish (Polyodon spathula)

- - 72 kg/ha

500 g 72 kg/ha

500 g

Tench (Tinca tinca)

- 45 kg/ha 250 g - -

Common carp (Cypriunus carpio)

150 kg/ha 250 g

105 kg/ha 250 g

150 kg/ha 250 g -

Sturgeon (Acipenser baerii) - - - 150 kg/ha

250 g

Table 24. Designed fish stock researched under the Polyculture module (initial biomass and average individual fish weight)


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Ponds

A pilot scale, two-season experiment, introducing paddlefish into carp-type earthen ponds was performed. All experiments were conducted at one complex of experimental earthen ponds located in southern Poland (18°45’E, 49°53’N). The ponds were 1 500 m2 each and the average depth was 1 m, thus the volume of each pond was estimated to be 1 500 m3. The ponds were fully drainable, supplied with water from the Vistula river.

Fertilisation

The ponds were fertilised with urea (46% N) and superphosphate (20% P) on a weekly basis. This resulted in a fertilisation intensity of 147 kgN/ha and 25 kgP/ha per season.


Fish production

Within all treatments tested under the module 'Polyculture', the fish stock involving paddlefish and common carp provided the highest total fish biomass gain. The obtained results are presented in Table 25. The paddlefish biomass increase was about 30% greater than carp biomass increase, whereas carp biomass gain in monoculture and polyculture with paddlefish stock was comparable. Paddlefish in the treatments ‘Polyculture carp’ and ‘Polyculture sturgeon’ stocks were responsible for the majority of total fish production (see Figure 8). Low common carp production in the ‘Polyculture tench’ treatment was a result of high mortality related to a KHV outbreak. However, biomass gain of bighead carp, in this treatment, reached only 53% of the biomass gain of paddlefish. The estimated value of the fish biomass gain in all tested treatments is presented on Figure 9. The average retail prices in Poland taken for the calculation are presented in Table 26. Assuming accuracy of prices surveyed, the value of produced paddlefish (one season biomass gain) was about three times higher than other species produced together in polyculture.

Species Monoculture Polyculture tench Polyculture carp Polyculture sturgeon

Grass carp - 85 kg/ha; 95 % 100 kg/ha; 100 % 91 kg/ha; 100 %

Silver carp - 65 kg/ha; 65 % 99 kg/ha; 70 % g 91 kg/ha; 70 %

Bighead carp - 280 kg/ha; 83 % - -

Paddlefish - - 567 kg/ha; 65 % 488 kg/ha; 67 %

Tench - 24 kg/ha; 87 % - -

Common carp 438 kg/ha; 95 % 49 kg/ha; 37 % 426 kg/ha; 65 % -

Sturgeon - - - 102 kg/ha; 89%

Table 25: Fish biomass gain and survival rate within the Polyculture module

Species Price (PLN/kg) Price (€/kg)

Common carp 10,04 2,23

Tench 13,30 2,95

Sturgeon 26,87 5,97 Silver carp 8,43 1,87 Bighead carp 8,43 1,87

Paddlefish* 26,87 5,97 Grass carp 9,00 2,00

* estimated value based on other sturgeon price (no real data available)

Table 26. Average retailer prices of fish species used in the Polyculture module


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Figure 8: Average fish biomass gain of researched stocks

Figure 9: Estimated value of fish biomass gained during researched season

The paddlefish obtained at the beginning of the project were kept under extensive conditions in carp type ponds without supplementary feeding. The fish were fed exclusively on plankton. The individual body mass on the 10th, 18th and 30th months of production is presented in Figure 10.

Primary production

Highest average net primary production of plankton (0,349 mgO2/L·h) was reported in ponds stocked with polyculture involving common carp and paddlefish. This was 53% higher compared to monoculture of carp. The difference was caused by the modification of the plankton spectrum caused by the feeding pattern of paddlefish. Paddlefish feed mainly on zooplankton. Therefore its presence in a fish stock affects qualitative composition of plankton. Grazing on zooplankton favours autothrophic algae growth, thus net primary production of the pond water body. In contrast, the less efficient bottom sediment resuspension in Polyculture sturgeon ponds resulted in a 24% lower primary production compared to polyculture involving common carp (Figure 11).


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.

Figure 10: Average (±SD) individual body weight of paddlefish in three consecutive years

Figure 11: Season average net primary production in pond of researched stocks

Energy Efficiency

The energy demand for pond farming is mainly connected to transport and handling of fish. Energy demand is very farm specific and strongly depends on the farm size, pond construction and equipment used. These factors influence the amount of energy demand much more than the production technology applied. Thus, energy efficiency in the researched pond production system was not calculated.

Water utilisation

Extensive carp farming involves large water volumes collected during the filling of ponds in spring . The water utilisation (input) expressed in litres per kg of products is tens to hundreds fold higher than in the case of intensive fish production. However, the water utilised in pond systems is not connected with fish production exclusively. The large water bodies (pond complexes) are important elements of the environment contributing to water retention of the local drainage system and local water cycling. All ponds used in the Polyculture module were in the same pond complex, situated next to each other, thus being exposed to the same climatic conditions. The same water regime was applied to all treatments. Thus, the calculations presented below were made for the whole complex of ponds, not for individual ponds. Observed differences between the treatments result from the fish gain only.


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Water input: l/kg product

The most optimal stock researched under the Polyculture module demanded water input of 8,4 m3/kg of fish produced. This is an important improvement when compared to standard monoculture where the water demand per kg of product may be twice as high (Table 27).

Water output: l/kg product

Generally, the water output from a pond system is equal to the volume of the pond harvested. However, during the rainfall of the production season, if losses caused by evapotranspiration and seepage are compensated, overflow will contribute to the total water output. In such a case, the water leaving the pond is more similar to pond water than to rainwater in terms of nutrient content. For the calculations of water output, total volume of the researched system together with rainfall has been used. Depending on stock used the values ranged between 13,81 and 43,65 m3/kg of raw product (Table 28).

Nutrient utilisation efficiency

Four major sources of nutrients were identified in the researched module:

• Fertilisers (urea and superphosphate) – main source in terms of amount of N and P delivered to the system

• Inflowing water – the river water used for filling the pond contained nutrients received from the river drainage system; the level of the nutrients is low, however not negligible. For the calculations only the single volume of the pond was used;

• Bottom sediment deposits – there are a large amount of nutrients accumulated in the bottom sediment which is bio-available. They constitute the major source of N and particularly P as a large fraction of mineral phosphate fertilisers is bound in the sediments after application. However, quantitative analysis of P and N in the bottom sediment of Polyculture module ponds before and after the production season did not reveal important changes in their concentration. The increase of the quantity of these compounds was estimated to +0,84% and +0,45% for N and P respectively. This gives an increase of 1,57 kgP/ha compared to 26,9 kgP/ha added with fertiliser and an addition of 19,35 kgN/ha compared to 159 kgN/ha added with fertilisers. Thus, the bottom soil was not taken into consideration in calculations.

• Rainfall and aerial runoff – external, uncontrolled sources of nutrients. In the case of the Polyculture module, the runoff volume was negligible in contrast to the rainfall. However, the rainfall was not analysed for P and N content, thus was omitted from the calculations.

• Nitrogen fixation – some blue-green algae and bacteria can assimilate molecular nitrogen into organic compounds enriching the ecosystem with bioavailable nitrogen. However, whilst the significance of this process can be important in warm waters, under researched climate conditions bacterially fixed nitrogen is negligible when compared to fertilisation. Because of this hypothesis, nitrogen fixation has been omitted in the calculations.

The calculations of nutrient utilisation efficiency were based on the nutrients introduced with fertilisers and water used for the pond filling as the only sources of N and P. For the most optimal 'Polyculture' stock the Nutrient Retention Efficiency has been estimated at 20,9% and 10,8% for N and P, respectively (Table 29). In the case of nitrogen no N2 fixation and N2 volatilisation caused by denitrification has been considered.

NITROGEN PHOSPHORUS

INPUT

RETENTION INPUT

RETENTION

kg/ha % kg/ha %

MONOCULTURE CARP 159,1 10,6 6,6 30,9 1,1 3,4

POLYCULTURE CARP 159,1 33,3 20,9 30,9 3,3 10,8 POLYCULTURE STURGEON 159,1 18,1 11,4 30,9 1,8 5,9

POLYCULTURE TENCH 159,1 14,0 8,8 30,9 1,4 4,6

Table 29. Retention of nitrogen and phosphorus in fish biomass

m3/kg

MONOCULTURE CARP 26,5

POLYCULTURE CARP 8,4

POLYCULTURE STURGEON 15,4

POLYCULTURE TENCH 19,9

Table 27. Water input expressed in volume per product weight

m3/kg

MONOCULTURE CARP 43,65

POLYCULTURE CARP 13,8

POLYCULTURE STURGEON 25,4

POLYCULTURE TENCH 32,8

Table 28. Water output expressed in volume per product weight


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The only external carbon source in the pond system was urea. However, the quantity of C introduced with fertiliser as well as the amount of organic C or CO2 introduced to the system with runoffs or supplying water can be neglected. Any organic carbon present in the pond system derives from primary production. The CO2 transferred to the water from the atmosphere is the main source of organic carbon in the biomass developed in a pond. The pathways of organic carbon in a pond ecosystem are very complex and fluctuate within a production season. The quantity of organic carbon in a water body can be calculated (based upon COD).

Nutrients output

A properly maintained pond system does not discharge water during the production season as any losses of nutrients are undesired. This also concerns extensively cultivated ponds such as the ones used in the Polyculture module. Throughout the production season nutrients are released only by seepage. However this is very case specific and constitutes only a minor fraction of the total nutrient release during the production season. The majority of nutrients are released during the drainage of ponds at harvest time. The amount of nutrients discharged from the system has been estimated assuming the amount discharged equals the concentration in pond water before harvest multiplied by the pond volume. Similarly to the water inflow, the differences of recorded values between treatments are related mainly to fish biomass gain. The concentration of nutrients in discharged water was far less of a consideration for the observed differences. In this case, only the amount of nitrogen and phosphorus was estimated (Table 30).

To increase productivity per unit of labour

Basically, the proposed technology (introduction of paddlefish) does not require changes in techniques and equipment involved in fish production. However, observations made during the harvest of experimental ponds used for the Polyculture module suggest an increase of labour required for harvest, especially during sorting. Harvesting of the pond stock in polyculture required approximately 10% more time or labour when compared to monoculture ponds. The amount of labour will strongly depend on facilities and equipment used as well as personnel numbers and experience. The size of ponds or the number of ponds harvested will play an important role, too.


The main successes and findings of the experiments conducted under the Polyculture module are:

• Introduction of American paddlefish into polyculture with common carp in pond culture.

• The paddlefish, as a substitute for bighead carp in sustainable, extensive carp pond culture produces an increase fish biomass gain.

• High market value of paddlefish can increase farm’s profitability providing high quality product.

• The presence of filter feeder species increases nutrients’ dynamics in ponds and higher retention of N and P in fish biomass resulting in a decrease of its accumulation in the environment.

Despite the advantages there are also constraints for the production of paddlefish:

• High stocking material price oscillating about 8 euro per 1 year old (~100 g) fish (caused by difficulties with its reproduction).

• Limitations related to production techniques: o Young paddlefish are easy prey to birds, thus production ponds should be covered with nets o When crowded and harvested fish should be handled with exceptional care as they are very

sensitive o During grading and sorting additional space and water flow is required in order to prevent

asphyxiation

• EU legislation limiting the introduction of exogenous species into aquaculture: Thus, production of paddlefish in different EU countries may encounter different difficulties. However, an increasing demand for aquaculture products in the EU may force the development of technologies providing for the production of alien species (including paddlefish) in an environmentally safe way.

Nutrient output

kgN/kg product kgP/kg product

MONOCULTURE CARP 0,39 0,079

POLYCULTURE CARP 0,1 0,023

POLYCULTURE STURGEON 0,22 0,045

POLYCULTURE TENCH 0,29 0,059

Table 30. Nutrient loss through outflow water per kg fish produced


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• Market related issues: o The paddlefish is not a recognised species on the EU fish market o Unknown demand results in uncertain retail prices o Very little information on product processing and quality available.

The issues listed above require further research.


Paddlefish introduction, as a substitute for herbivorous and planktonophagous cyprinids, is a desirable species to improve the profitability of ponds farms. The paddlefish, due its fast growth rate and appreciated flesh and roe, seems to be an excellent replacement for bighead carp. It provides greater biomass gain with a much higher market value than other filter fish species. The introduction of the new species would increase the product supply diversity of pond farms and allow them to compete with other fish producers by providing fish commanding a greater customer demand.

7.2. Practical recommendations and conclusions for stocking paddlefish in pond polyculture

7.2.1. Paddlefish growth performance

Paddlefish growth performance in carp type ponds was observed. The body mass and mortality were recorded for 24 months during every harvest. Initial average body mass of ~10 months old fish was about 90 g and increased to about 2 700 g during the first breeding season. Samples of fish were slaughtered to assess gut content before wintering in 2008. In contrast to common carp, paddlefish guts were filled with plankton originated matter. This indicates a longer feeding season, compared to common carp. Thanks to this, paddlefish did not lose body weight during wintering in contrast to common carp.

7.2.2. Paddlefish mortality

Throughout the 24 months period, the average cumulated mortality of paddlefish reached almost 50%. The recorded survival rate is comparable to that seen in common carp. However, due to the stock value of paddlefish being greater than that of common carp, the impact is more severe in terms of the fish farm’s economical performance. Therefore, this may be one of the major drawbacks of introducing paddlefish into pond culture. Observations made during the harvest, which can be considered both part of the production season and wintering, resulted in a few practical conclusions in relation to to paddlefish mortality to reduce fish loss under real production conditions:

• Workers harvesting ponds are generally used to handling carp, which is a far more resilient fish than paddlefish. However, exceptional caution should be taken when handling the new species. This regards both hand netting and sorting or grading. The staff should be sensitised to the features of the new species.

• Special attention must be paid during netting and crowding. The paddlefish’s rostrum tends to enmesh in to seine nets used for harvesting. Immobilised fish may asphyxiate. It is recommended that nets with appropriate sized holes should be used.

• Prolonged crowding with other species in a seine net may result in paddlefish asphyxiation. This is especially important if there is a break between successive fish transportation.

• After the harvest from ponds fish are kept in freshwater to flush gills clogged with bottom sediment. It has been observed that paddlefish require a much longer recovery time than common carp or bighead carp. Further, paddlefish requires ample area to swim as it does not use operculum to provide water flow through the gills. Hence, special attention must be paid to the gill flushing process.

• Due to the elongated shape of their rostrum paddlefish do not fit into most common hand nets. Hence, it these are likely to damage the rostrum or gills. It is recommended to use hand nets of a proper size to avoid body or gill laceration.

• Young paddlefish are easy prey for piscivorous birds. Therefore, ponds stocked with paddlefish up to 300-500 g need to be protected against birds with nets or strings mounted above the pond.

7.2.3. Ecological performance

Presence of filtrating fish enhances the primary production of the pond ecosystem. Due to the elevated pond productivity and the fact that the fish stock comprised species of a non-overlapping food spectrum, overall


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system production almost tripled in polyculture treatments compared with monoculture. The influence of different fish stocks was observed also in relation to hydrochemical and physical water parameters related to production of plankton organisms: water transparency and chlorophyll concentration. At the same time average concentration of dissolved oxygen in ponds stocked in monoculture was lower and more fluctuating than that observed in the other treatments. Presence of filtrating fish reduces abundance of zooplankton and hence the risk of its uncontrolled growth leading to overgrazing of autotrophic algae responsible for oxygen production, thus primary production. The feeding behaviour of common carp causes efficient resuspension of bottom sediments and thus better exchanges nutrients with water. As there were no other crops obtained from the system, only the fish biomass gain is responsible for observed differences between the treatments. The vast majority of waste biogenic compounds are deposited in the bottom sediment. These, during a pond harvest can be (by mechanical resuspension) released to waste water discharged from the pond and in turn contribute to eutrophication of natural waters. Improved nutrient utilisation through use of polyculture stocks does not eliminate, but does however, drastically reduce this phenomenon.

7.2.4. Economical performance

The introduction of paddlefish into traditional pond culture, based on common carp, is one possible solution for improving carp farms’ profitability. As the paddlefish’s flesh is similar to other sturgeons it can be assumed that it will be similarly appreciated by consumer and hence command a premium price. Besides, paddlefish, if allowed to mature, can provide very valuable and appreciated roe (caviar). The tested polyculture fish stock comprising paddlefish, common carp, silver carp and grass carp, without supplementary feeding and kept in ponds receiving only agricultural fertilisers is able to provide fish biomass gain similar to commonly used monoculture stock of common carp fed on grains (wheat and maize). Elimination of feeding costs together with increased value of produced fish gives a significant prevalence over standard monoculture production. An economic assessment of polyculture must also take into consideration the increased amount of labour especially related to harvest. More man-hours are needed due to extra sorting of harvested fish. Additional facilities or equipment may be necessary for netting, handling, transport and storage of paddlefish.

7.2.5. Recommended fish stock

Based upon the results obtained during the research, a fish stock involving paddlefish can be recommended. The following recommendations concern fish stock to be produced in a semi-extensive way in carp-type, earthen ponds, without supplementary feeding, fertilised with agricultural fertilisers.

• Different age classes of all used species can be used, however a few basic requirements should be fulfilled.

• Efficient resuspension of bottom sediment providing efficient nutrient cycling in the water column requires high enough biomass of bottom feeders and its individual body weight. Hence, common carp is only favoured for the stock during second and third production season.

• Stocking density should be calculated according to the planned fertilisation intensity and the pond fertility. Estimated common carp biomass gain from a pond fertilised with 40 kgP/ha and 240 kgN/ha per season is 450 kg/ha.

• Stocking density and individual weight must be calculated according to the desired final individual weight. Similar rules, including age class, apply to other cyprinids.

• The paddlefish biomass gain of about 600 kg/ha and the individual body weight 1750 and 3500 g after the second and third production season respectively can be expected. The paddlefish stocking density presented in Table 31 calculated on its growth performance recorded

Species

Estimated biomass

gain

Desired final individual

weight

Initial weight

Stocking density

[kg/ha] [kg/ind] [kg/ind] [ind/ha]

Common carp 400 0,3 0,05 1 600

400 1,2 0,2 400

Paddlefish

600 1 0,1 667

600 2 1 600

600 3 2 600

Silver carp 70 1,5 0,5 70

70 0,5 0,1 175

Grass carp 100 1,5 0,5 100

100 0,5 0,1 250

Table 31. Example of fish stock density design


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during the performed experiment only. The values given do not determine the maximal growth rate of paddlefish under production conditions.

Based on these recommendations, an example of fish stock design is presented above in Table 31.

7.2.6. Main constraints of paddlefish introduction

Although there are many positive aspects related to paddlefish introduction, there are some constraints, too:

• At the moment, in Poland, paddlefish is not reproduced on a commercial scale. All stocking material available is imported as fertilised eggs or fry. This is the main reason for the high price of the stocking material. The price oscillates around 8 € per 100 g fish. However, progress in reproduction is reported by some Polish fish farms. As soon as paddlefish is reproduced on a commercial basis its price will decrease significantly. Within the EU, successful reproduction of paddlefish has already been reported in the Czech Republic and Romania.

• Limitations related to production techniques: The introduction of new species demands new techniques related mainly to fish handling and staff training. The main recommendations are listed in the previous sections.

• The paddlefish is an exogenous (alien) species in Europe. The EU legislation limits the introduction of new species into aquaculture. Thus, production of paddlefish in different EU countries may encounter difficulties. However, the EU directive gives a certain freedom to member states for adoption. Important is the fact that other fish species produced in Poland and other EU Member States are also exogenous species according to the Directive From amongst the species used in the Polyculture module only tench is a native species. Increasing demand for aquaculture products in EU may force development of technologies allowing for the production of exogenous species (including paddlefish) in an environmentally safe way.

• There are some market related issues. The paddlefish is not a recognised species on the EU fish market. This affects Poland in particular, but not exclusively. Its long rostrum makes the paddlefish interesting for some people, but definitely not practical for home slaughter or preparation. Sale of live or only gutted fish does not seem to be an optimal solution because of the fish’s appearance. Overall perception of paddlefish may reduce its demand and value. However, a small but constant demand for whole fish may be expected.

• The retail price will strongly depend on the stocking material price and consumers perception of the paddlefish. A price close to other sturgeon species can be expected due to similar quality of flesh.

• The majority of paddlefish should be offered as processed fish, however certain technical difficulties can be expected due to the uncommon shape of paddlefish. No or very sparse information is available regarding paddlefish processing and the quality of final products. No scientific information on shelf life and consumer preferences is available.

• The rising awareness of consumers regarding fish welfare is an important concern. Each species has distinct environmental requirements. However, during the experiment paddlefish performed very well in terms of growth rate, but fish ponds are not its native environment. There is a potential danger that environmental conditions of carp ponds are suboptimal for paddlefish. The same concerns applies to paddlefish handling and transport. The fish welfare issue requires more research.


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7.3. Using agricultural waste nutrients in pond fish culture: Module CASCADE in Poland


Progressive specialisation of agriculture in Central Europe results in monocultural animal production farms with no option to utilise waste nutrients. Thus, discharge or on-site utilisation of manure produced becomes a concern due to legal and technical limitations. Accordingly, low cost, sustainable, environmentally friendly and easy to maintain tools providing for the utilisation of manure is highly desired. A fish pond is an ecosystem, consisting of very diverse environments, favouring large number of biochemical processes supported by the feeding activity of fish. This allows organic matter to be turned into compounds which enter the ponds’ food web resulting in primary production and eventually fish biomass increase. The source of energy and nutrients can be waste liquid manure (slurry) coming from an animal farm. Integration of an animal farm together with fish ponds, as one of its elements, is a step towards highly promoted and desired integrated agriculture. Utilisation of resources created on the farm within the same farm is an important element of farm sustainability. The proposed solution is particularly appropriate to small animal farms, run as organic or willing to improve their sustainability. A flow-through system built of fish ponds, supplied with fresh water utilises significant amounts of nitrogen, phosphorus and organic matter. Significant amounts of these compounds are retained in the system or converted into gases. Total nutrient load discharged throughout the season from the system is lower than delivered. Beside ecological benefits fish production may be an additional source of income.


The module is based on a set of four pond compartments connected in series and supplied with fresh water acting as the nutrient carrier. The only artificial source of nutrients and energy are liquid manure (slurry) and supplying water. These compounds depending on their form (mineral or organic) are responsible for biomass development in respective parts of the cascade. Each part of the pond system utilises supplied nutrients through different ecological processes. A flow-through system based on carp type ponds was constructed. The experimental setup consisted of two identical earthen ponds connected by a pipeline (35 m in length, ØIN 15 cm in diameter) in series (total area 0,3 ha). Each pond was divided in two parts by a mesh (3x3 cm) resulting in four compartments (see Figure 12). Each of the compartment carried out a different task in the constructed cascading system (see Table 32).

Part of the system Description

A Zooplankton compartment

• Compartment supplied with manure • Organic matter derived from manure was the main energy source for zooplankton and

bacterioplankton development • No fish stocked • 33% of the total system total area

B Filtrators’

compartment

• Stocked with filtering fish to utilise plankton developed in compartment A • 17% of the cascade total area

C Polyculture

compartment

• Stocked with a polyculture of common carp, bighead carp, silver carp and grass carp • Nutrients and fish to utilise plankton developed in compartment A • 25% of the cascade total area

D Sedimentation compartment

• Acting as a sedimentation tank for suspended solids coming from part C • 25% of the cascade total area

Table 32: Role of respective compartments of the cascading system

Figure 12: A diagram of the designed cascading system


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The ponds were supplied with fresh water at an average flow rate of 4,23 L/s·ha (15,3 m3/h·ha). The system received liquid bovine manure bi-weekly. The manure was applied to the zooplankton compartment, next to the water supply. During the season the system received 25 m3/ha liquid manure (slurry) (7,5 m3 per cascade), which was equivalent to 571 kgDM/ha. The amount of nutrients received by the cascade during the production season is presented in Table 33.

Main characteristics of manure used in the experiments

To provide efficient conversion of nutrients and energy into biota biomass a source of easily biodegradable organic matter is needed. Different sorts of animal manure have been used for fish culture for centuries as a nutrient source for fish culture for a number of reasons: (1) animal manures are relatively cheap, (2) readily

available on-farm, and (3) suitable for a variety of fish in polyculture. In addition, the amount of manure permitted to be spread on land is being limited by national regulations, recently. Most fish ponds in Poland are located in rural areas with a high density of agriculture livestock where liquid manure (slurry) is a predominant type of agricultural waste, which becomes a nuisance unless utilised. For use in pond culture, as an energy and nutrient source for zooplankton, bovine or pig slurry seems to be suitable. The composition of all manure selected for experiments performed under the Cascade module is provided in Table 34. However, composition and quality of slurry may change during a production season according to species, their size and age, feed and water intake as well as environmental factors. Thus, analysis of supplied manure must be repeated frequently during application.


The Cascade module was researched in two successive seasons. However, preliminary data analysis revealed poor performance of the design investigated in 2007. Thus, in 2008 the setup was re-engineered. In both seasons the cascading system was run in duplicate to ensure proper quality of data obtained. The production season was divided into five periods (of four weeks each), starting from the 12th May. The manure was applied only for the first four periods. Light conditions and temperature dropped in the last period, and did not permit the introduction of a further additions of organic matter, as this may have led to oxygen depletion.

Water input: l/kg product

The water supply aimed to transport nutrients along the cascade only and was not a nutrient resource necessary for fish production. Water input required for fish production can still be calculated. Optimum water input has been estimated at 66,9 m3/kg.

Water output: l/kg product

The same principle as above applies to the calculation of the water output. The difference between input and output results from seepage, evapotranspiration and rainfall. The water output from the system was estimated to be 44,07 m3/kg of fish.

Energy Efficiency

The researched system did not utilise energy to maintain the cascade. The only energy used was related to transport of fish before and after the production season. Other demands were related to maintaining the farms’ facilities. In case if no water can be supplied to the system by gravity it may be necessary to circulate the water in the cascade by pumping. If so, energy demand to reuse the water may present significant costs to make the module functional.

Compound Source Total

[kg/ha] Manure [kg/ha] Water [kg/ha]

C 402,5 144,3 546,8 N 39,7 78,2 117,8 P 16,3 1,1 17,4

Table 33: Nutrients load delivered with manure and supplying water to the cascade

Parameter Unit Value

Dry matter (DM) [%] 8,0

Total nitrogen (N) [%DM] 0,48

Total phosphorus (P) [%DM] 0,15

Potassium (K) [%DM] 0,26

BOD5 [gO2/dm3] 5,0

COD [gO2/dm3] 14,0

Table 34: The composition of mixed bovine/pig (~50/50 v/v) liquid manure (slurry)


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Fish production

The system is, in principle, designed to utilise waste nutrients. Fish production in the cascade is an additional, however important activity. The system is able to produce a significant biomass of fish. Although there are many variables the total fish production can be estimated to be 380 kg/ha. The breakdown of production (one season biomass gain) to fish species is presented in Figure 13.

Figure 13: Fish biomass gain obtained in the researched module

Nutrient utilisation efficiency: kg nutrient (N, P, COD) retained in product/kg nutrient input [%]

The main aim of the cascade was to retain nutrients delivered. Two main sources of nitrogen, phosphorus and organic carbon have been incorporated into calculations:

• Fresh water input – the system was constantly supplied with water coming from a river. During the researched period (20 weeks) the supplied water brought with it into the system a significant load of nutrients. In total 424 kgC/ha (organic C), 39,7 kgN/ha and 16,3 kgP/ha over 20 weeks were introduced to the system via supplied water.

• Manure supply – bi-weekly the system was supplied with manure (slurry), as the main source of nitrogen. In total 78,1 kgN/ha and 1,1 kgP/ha over 20 weeks were delivered with manure per hectare of cascade.

• Nitrogen fixation – as in the case of the polyculture module, this N source was omitted from the calculations.

Due to the basic functioning of the Cascade module, retention of the nutrients both in fish biomass and the whole cascading system is important. In the case of nutrient retention in fish biomass, only nitrogen and phosphorus were taken into consideration. Although manure introduced a significant amount of organic carbon it is unknown how much fish biomass gained via zooplankton or bacterioplankton developed on this matter. The majority of organic matter built into fish biomass derives from primary production. The amount of nitrogen and phosphorus in the harvested fish biomass was compared with the total input of these compounds. Retention of nitrogen and phosphorus in fish biomass has been calculated only (Table 35).

Input [kg/ha·season] Retention

Water Manure TOTAL kg/ha %

Nitrogen 39,7 78,1 117,8 10,4 8,8

Phosphorus 16,3 1,1 17,4 1,0 5,8

Table 35. Nutrient utilisation efficiency by fish in the Cascade module

Throughout the production season the cascading system retained significant amounts of nutrients. Loads of all measured parameters were smaller at output than at input. Presented in Figure 14 are the loads of organic carbon, nitrogen and phosphorus entering and leaving the system divided to four week periods (I to IV) of the season (16 weeks in total).


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Figure 14: Organic carbon load at inflow and outflow from the cascading system

Figure 15: Nitrogen load at inflow and outflow from the cascading system

Figure 16: Phosphorus load at inflow and outflow from the cascading system


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The nutrient retention was calculated from the difference of the total nutrient load introduced to the system (including supplying water and manure) and nutrients discharged throughout the season based on nutrients concentration in water leaving the system. The results are presented in Table 36.

Nutrient output

The cascade system was constantly supplied with water. Thus, despite high N retention, the total load of nutrients was high and reached 0,125 kg N and 0,018 kg P per kg of fish produced.

Nutrients re-use for fish feed: kg nutrient retention in the secondary products per kg nutrient input to the system as a whole [%]

In the researched module an attempt was made at the production of additional plant crops However, this experiment failed due to technical reasons. The character of the research pond favoured the development of unwanted plant species instead of desired species, though the production of potentially useful plants which could be utilised in-situ would be theoretically possible. Production of Azolla (water fern) as a feed for herbivorous fish and as an alternative source of nitrogen can be considered.

To increase productivity per unit of labour

Introduction of the cascading system requires an additional labour input related to maintaining the system (including harvest). The system does not improve the productivity/labour ratio.


Research carried out on the Cascade module resulted in the development of an environmentally friendly technology utilising waste organic matter derived from other branches of agriculture (bovine and pig farms). The main constraints of the system are:

• Water requirement - The system requires significant volumes of water to provide nutrient flow through the cascade. The water intake and its discharge to natural waters may be restricted in some countries, especially if only the output of nutrient loads is taken into consideration, as opposed to the difference between supply and discharge.

• Proper functioning of the designed system is limited to a season of about 7 months, between spring and autumn, when water temperature and sun radiation is intensive enough to sustain hydrobiological processes at sufficient levels.


• The pond cascade can act as a multifunctional segment of an integrated animal farm.

• The system creates opportunities to reduce costs of waste water discharge by retaining it in a controlled ecosystem of a pond cascade.

• The proposed technology reduces the impact of a farm on the natural environment.

• The designed system allows the production of fish in an extensive manner utilising waste nutrients.

• The fish produced on natural food can have a higher nutritive quality and can be more appreciated by consumers (see chapter 5).

• Besides utilitarian advantages of the cascade system, the construction or simple maintenance of the pond system enriches the natural environment at different levels: biodiversity, ground water levels or additional water retention. Ownership of ponds may entitle the farmer to EU or national subsidies related to their environmental value. The ponds being a cascading system may also act as sport fishing facility, bringing additional income.

Compound Load Retention

[kg/ha] Kg/ha %

C 571,61 291,44 50,99 N 117,85 88,72 75,28 P 17,33 8,64 49,86

Table 36: Retention of C,N and P introduced to the system via water and manure in the cascade


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7.4. From a case study to a fish farm: Designing a cascading module

7.4.1. Target group and basic technological requirements

The proposed solution is dedicated particularly to small animal farms run as organic farms and/or/ willing to improve their sustainability and having the possibility to cooperate with pond fish farms. Cattle and/or/ pork farms collecting and fermenting their own manure are are in a particularly good position to benefit. The farm willing to apply the technology should possess ponds or be able to build a pond system and supply it with water. The system is land demanding requiring about 1 ha of pond area per 150 kg of organic carbon derived from manure. At the same time the system must be supplied with a level of water flow allowing the maintenance of about 45 days hydraulic retention time.

7.4.2. Planning parameters of a cascade

• The researched system has been designed to merge advantages of pond farming with the needs of animal farms to utilise waste manure.

• The module is based on the set of four pond compartments connected in series and supplied with fresh water, acting as the nutrient carrier.

• The only source of nutrients and organic matter are liquid manure (slurry) and supplied water. These compounds, depending on their form (mineral or organic), are responsible for biomass development in respective parts of the cascade.

• Each part of the pond system is responsible for different processes leading to the utilisation of waste nutrients at different trophic levels.

• When the plankton biomass developed in the respective parts of the cascade, fish biomass is produced. The fish production may be an additional source of income.

The design of the cascade system for optimal performance should be composed of four compartments of different area and role in the system. The given relative area of each compartment should be controlled with minor deviations only. There are no general constraints related to the dimensions of a certain compartment, although elongated shapes are favoured to maintain the water flow through the system. The system can be composed of two or three ponds, however, the first two compartments should be placed in one pond and be separated only by a mesh to provide transport of zooplankton. The suggested setup of the cascade is presented in Figure 17. The following parts of the system do not have to be oriented in one line. Use of pipelines between compartments B-C and C-D is possible. Each compartment of the system utilises different resources and plays a different role in the cascade.

A.

B.

Figure 17: Possible setup of the cascade system: A- two-pond system; B- three-pond system


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Compartment A – Zooplankton part: This compartment is directly supplied with water and the manure. Hydraulic retention time in this compartment should be set at two weeks. This period provides sufficient time for zooplankton development. The zooplankton and bacterioplankton feed directly on organic matter derived from the manure supplied. Biogenic compounds coming from manure, supplied water or bottom deposits support primary production, however an over abundance of zooplankton suppress the development of phytoplankton. Thus, the net primary production is minimal or negative. This fact is a main limiting factor for manure utilisation. The oxygen supplied with water, expressed in moles, must be at least twice the amount of organic carbon received with the manure to sustain aerobic conditions in the pond. The zooplankton compartment should not be stocked with fish, however small (up to few dozen kg/ha) bottom feeders are admitted. The fish stock shall not cause bottom sediment resuspension, thus cyprinids are not favoured in contrast to young sturgeon (<50 kg/ha, 1-3 years old fish are recommended). A stock of <100 kg/ha of grass carp is desired to control growth of macrophytes. Compartment B – Filtrator’s part: The compartment is mainly stocked with filter feeding fish species. The plankton developed in Compartment A, transferred with the water flow, is utilised by planktonophagous fish. Stock composed of paddlefish and/or filtrating cyprinids is proposed. A stocking density of 150 kg/ha of paddlefish or bighead carp and 150 kg/ha of silver carp is sufficient to utilise the plankton (recommended individual fish weight 0,5–3 kg). The compartment should be separated from the Compartment A with a mesh only to provide efficient transfer of plankton. Use of pipelines reduces the transfer efficiency.

Part of the system Description

A Zooplankton compartment

• Compartment supplied with manure

• Organic matter derived from the manure proposed as the main energy source for zooplankton and bacterioplankton development

• No fish stocked

• 33% of the total system area

B Filtrators’ compartment

• Stocked with filtrating fish to utilise plankton developed in compartment A

• 17% of the cascade area

C Polyculture compartment

• Stocked with polyculture of common carp, bighead carp, siver carp and grass carp

• Nutrients and fish to utilise plankton developed in compartment A


D Sedimentation compartment

• Acting as a sedimentation tank for suspended solids coming from part C


Table 37. Description of respective compartments of the cascading system

Compartment C – Polyculture part: This part of the system is responsible for the utilisation of biogenic compounds coming from preceding compartments, being the only external source of nitrogen and phosphorus. Presence of common carp, as the main species, enhances nutrient turnover and the primary production. Hence, the volume of the compartment should provide hydraulic retention time close to 12 days. This compartment is responsible for the majority of the biomass yield of the cascade. The fish stock covers a wide spectrum of natural food supply developed in the compartment. Recommended fish stock is composed of cyprinids, although use of paddlefish instead of bighead carp is recommended (Table 38).

Species Individual initial weight [g] Stock density [kg/ha]

Common carp (K2) 200 - 300 g 300

Bighead carp OR paddlefish* 500 – 1 000 g 150

Silver carp 500 – 1 000 g 150

Grass carp 750 – 1 500 g 100

*recommended replacement for bighead carp

Table 38. Recommended fish stock of the Compartment C

Compartment D – Sedimentation part: The last compartment acts as a sedimentation tank. Fish stocked in part B causes a serious resuspension of bottom sediments resulting in high turbidity and suspended solids concentration. As the suspended matter contains both nutrients and organic carbon, it should not be


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released to the environment. The Sedimentation part of the cascade due to the long retention time and no fish stock provides good conditions for sedimentation of suspended solids. The water surface can be used to produce additional plant crops or can be used for recreation purposes. The absence of fish and high water transparency favours growth of water plants utilising dissolved nutrients from the water. Where plant production is planned relevant equipment and technologies must be developed.

7.4.3. Operation parameters

There are two main factors affecting the design of the cascade: water flow and manure supply. The balance between a farm’s demands for manure utilisation and available water and land must be decided. The economical calculations must also take into account environmental values and benefits of the system’s sustainability.

Water flow

The water supply efficiency may be a main limiting factor in some cases. In such a situation the total area, (thus manure utilisation capacity), will depend on water supply. Assuming an average pond depth of 1 m, the total system volume, (thus area) At, will be determined by multiplication of retention time, RT (15 days = 360h) and possible water flow, q [m3/h]): At=RT·q [m3=~m2]

Manure supply

If the water supply is not the limiting factor the system may be planned according to the organic matter supply derived from the manure. There is a strong correlation between water flow and organic carbon supply. Primary production in the Zooplankton compartment may be very limited or negative due to zooplankton development, where the only source of oxygen is water provided to the system. Each gram of organic carbon derived from manure requires ~2,7 g of oxygen. Assuming that inflowing water contains ~7 gO2/m

3, only 2,5 g of organic carbon can be delivered per cubic meter of water to sustain aerobic conditions in Compartment A. Thus, the organic carbon content in the manure must be analysed in order to design the cascade. If the supplied manure contains 5 kgC/m3 (mean), about 2000 m3 of water is needed for 1 m3 of liquid manure. However, this value may vary depending on light conditions and temperature. During mid-summer less water (~20%) can be provided (or ~20% more manure), but as the sun light intensity decreases the calculated value should be maintained. The relation of C, N and P concentrations remain within a certain range in the case of manure. Conducted research did not reveal any constraints related to N and P. Thus, the load of nitrogen and phosphorus delivered with the manure is rarely the limiting factor for the designed system.

7.4.4. Expected results

The use of manure for fertilisation of carp ponds has a long history, however it declined and has been replaced with more convenient agricultural fertilisers. Besides this, production intensification reduced the demand for primary production in the ponds and favoured feeding. The recent trend for extensification has resulted in renewed interest in utilising organic wastes and closed production cycles. Conducted research resulted in the development of an environmentally-friendly technology utilising waste organic matter coming from other branches of agriculture (bovine and pig farms). The four compartment set-up performed very well, allowing the utilisation of 25 m3 of bovine manure per one hectare of total cascade area. However, the main constraint of the system is water requirement. The system requires significant volumes of water to provide nutrient flow through the cascade. Size and capabilities of the system strongly depends on water supply efficiency, which seems to be a limiting factor. This may be an issue of particular significance, where water intake and its discharge to natural waters is restricted in some countries. Proper functioning of the designed system is limited to about 7 months between spring and autumn, when water temperature and sun radiation is intensive enough to sustain hydrobiological processes at sufficient levels.

SUSTAINAQUA HANDBOOK Case study from Denmark

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8. New methods in trout farming to reduce the farm effluents – Case study from Denmark

8.1. Introduction – General description of the case study

Farming of rainbow trout (Onchorhynchus mykiss) has taken place in Denmark for more than 100 years and rainbow trout is the most dominant species in Danish aquaculture. The total annual production is about 33 000 tonnes of fresh water and about 7 000 tonnes in sea water corresponding to about 20 % of the Danish fishery consumption. However, the value of aquaculture production is about 25 % of the total value in the Danish fishery sector. The Danish production of rainbow trout in fresh water takes place across about 250 farms. Of these, some 200 farms are run as traditional flow through systems as they have been run for decades with intake of water from a weir and with relatively limited use of energy consuming equipment (pumps etc.). The water passes through the farm by gravity and finally to a sedimentation basin (sedimentation of particulate matter) before it is returned to the watercourse. Until the 1980’s the Danish production of rainbow trout in fresh water was generally without any waste water treatment. Following increased public concern on environmental issues, such as the nutrient discharge from trout farms or the hindering of the fauna mobility along the watercourses through the weirs, a new environmental legislation was brought into force in 1989 in Denmark. Accordingly, each trout farmer was given a restricted feed quota and the quality of the feed was required to fulfil certain specifications. It became compulsory for all trout farms to construct a settling basin for removal of particulate organic matter and nutrients before water was led back to the watercourse. Farmers were also required to follow a water sampling programme in order to provide documentation of their approximate discharge of nutrients.

To adapt to this legislation a proportion of the traditional farms developed more technologically advanced farms applying various methods of water purification, reuse of water, aeration, oxygenation etc. Furthermore, a significant development took place developing efficient feeds with high nutrient utilisation, feeding technology, water treatment, reduced water intake and farming management. As a result, the amount of fish produced per kilo of feed as well as a the amount of discharged pollutants has improved significantly. However, the environmental legislation was followed by a new legislation setting a maximum limit to the allowed intake of water from the water course. According to the legislation at least half of the water flow in the watercourse shall pass by the farm. To continue the production this legislation forces the farmers to make themselves more independent of the water course, which means to reducing the consumption of unused fresh water as well as the cleaning and re-use of water. As a consequence of the restricted feed quotas, environmental legislation, restrictions on water intake from the water courses and EU’s Water Framework Directive setting standards for water quality in the recipients, a clarification of the future conditions for trout farming in Denmark became urgently needed. During subsequent discussions between aquaculture organisations, environmental authorities and NGO’s the idea of “Model fish farms” was born around the year 2000.

The model fish farm concept aims to reduce the intake of fresh water and to increase the retention of nutrients by using recirculation technology. Some of the most important parameters describing the model fish farms are summarised in Table 39 below. All data is based on the use of 100 tonnes of feed per year.

Parameter Model Trout Farm

Pond material Concrete

Water recirculation (min. %) 95

Water use (max. l · s-1) 15

Pond sludge collection Yes

Filters for removal of particles Yes

Bio filter Yes

Plant lagoons Yes

Table 39: Parameters of Danish model fish farms


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A Model Trout Farm (Ejstrupholm Dambrug): In the background to the left are the plant lagoons

consisting of former earthen ponds, inlet and outlet channels (Photo: DTU-Aqua)

The Model Trout Farm strategy involves significant environmental advantages, and perspectives:

• The model farms have made themselves independent of intake of water from the water courses as they catch water from drains under the production plant and/or nearby boreholes and recirculate water (up to 97% recirculation)

• The water consumption was reduced to about 0.15 l/sec/t feed or about 3 900 l per kg produced fish corresponding to 1/13 of that used in traditional flow through trout farms

• Free passage along the whole water course for the wild fauna

• A significant amount of the easy degradable substances (BOD), the total organic substances (COD), phosphorus, ammonia-N and total-N was removed by the cleaning devices inside the farm and in the plant lagoons

• Using the plant lagoons to grow commercial garden pond plants, edible crops as watercress or other species may provide a benefit as an integrated element of a model trout farm

• Stable farming conditions (water quality etc.)

• Potential increase in the trout production without corresponding increase in the environmental impact However, implementation of the model farm technology requires extensive knowledge and experience related to:

• Biological requirements of the species to be farmed

• Extensive knowledge about the design and function of each device on the farm, e.g. mechanical filtration, bio filter, aerators, pumps etc.

• Extensive knowledge about the implications of farming fish using recirculation technology

• Skilled experience in fish farming and running systems using recirculation technology

• Adequate water quality

• High quality fish feed and feeding strategies From an environmental as well as a commercial perspective the model fish farms are successful. Some farmers report on lower production time and, in addition to the large reduction in nutrient discharges, migration of fauna in nearby watercourses is facilitated. However, the systems need optimisation in particular with respect to lowering nitrogen discharges. Therefore, the SustainAqua Danish case study investigated different aspects/modules of the model trout farms for further optimisation: 4. Feed and feeding - Environmental impact from model trout farms 5. Energy consumption in model trout farms 6. Cultivation of pond plants in the lagoons of model farms 7. Cultivation of alternative fish species in the lagoons of model farms


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8.2. Feed and feeding - Environmental impact from model trout farms

Feed is the most important parameter in relation to fish growth and environmental impact as well as production costs. To estimate the environmental performance of model farms it is crucial to make a precise quantification of the contribution from the feed to the production water, the so-called “contribution from production” before the water is passed on for treatment in the cleaning devices on the farm. The different cleaning devices in operation on model farms have different cleaning efficiencies depending on the magnitude and composition of the waste components they receive. Therefore, development of an overall calculation model is required to be able to predict the environmental performance of a system in terms of waste components – nitrogen (N), phosphorus (P) and organic matter – transferred to the watercourse. The model should take relevant production parameters (feed type, amount of feed, fish production etc.), operation parameters (temperature, oxygen content etc.) and system set-up (components, flow-rates and dimensions) into account.

8.2.1. General description of the innovation

The physical form (dissolved, suspended, particulate) and chemical structure (N, P, BOD5 [biological oxygen demand], COD [chemical oxygen demand]) of waste components can be assessed in laboratory experiments. Based on the results of these experiments a predictive laboratory based model (module of the overall calculation model) on the direct waste contribution from relevant commercial feed types applied in intensive aquaculture systems can be derived. The laboratory model is an important input for the precision of the overall calculation model.

Figure 18: Set up for the assessment of the physical form and chemical structure of waste components and the direct waste contribution from relevant commercial feed types applied in intensive aquaculture systems.


The calculation model is primarily based on data obtained through a documentation and measuring programme that was carried out at eight “model trout farms” in Denmark during 2005-2007. These model trout farms were all equipped with sludge traps, biofilters and constructed wetlands, while a few of them also had micro-sieves installed. Data for water usage, concentration of nutrients in the water at several sites within the trout farm, amounts of feed used and ingredients in feed, biomass gains etc. have been obtained from all farms and the main results have then been integrated into the overall calculation model. Furthermore, data from traditional trout farms in Denmark (Data from By- og Landskabsstyrelsen, 2007) have been used in the model. Typically, these farms are without the facilities characterising the model trout farms, but according to Danish legislation (Bekendtgørelse om Ferskvandsdambrug) trout farms are required to have a settling basin installed immediately after the production unit(s).


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By integrating data into the calculation model from both model trout farms and traditional farms with less technology, the model offers the opportunity to obtain estimates for discharges from trout farms at different technological levels. After integration of data the model has been verified and adjusted accordingly in order to correlate optimally with actual measured discharges. In this way it aimed to optimise the model as much as it was possible at the current time. The laboratory experiments were carried out in 18 flow-through, thermoplastic tanks with a volume of 189 l. The tanks were mounted in a modified Guelph system in which the lower third of the tanks was conical and separated from the rest of the tank by a grid. This design allowed for rapid sedimentation and collection of undisturbed faecal particles in cooled, partly separated sedimentation columns. Rainbow trout of approximately 50 g each were obtained from local Danish fish farms and transferred to DTU Aqua’s research facilities in Hirtshals, Denmark. Feed consumption was recorded throughout the experiments, and faeces were collected from the sedimentation columns. The sedimentation columns were emptied daily prior to feeding, and the faecal samples were stored at -20 °C for analysis of protein, lipid, N-free extract (NFE), ash, crude fibres and P. The three feed types used had the following average composition, as can be see in Table 40 on the right hand side: Samples were taken for determination of the contribution of particulate N and P waste and of dissolved/suspended N and P waste, respectively. N and P retention by the fish was determined by analysing the N and P concentration in the fish at the start and at the end of the whole experiment. A specific experiment was set up for the determination of the contribution of dissolved BOD5 and COD waste as well as particulate BOD5 and COD waste. The apparent digestibility coefficient (ADC) of dietary nutrients and minerals was calculated using the following equation:

( )[ ] 100×−= iiii consumedexcretedconsumedADC eq. 1

where i was the percentage of protein, lipid, NFE, P, ash or DM. The specific growth rate (SGR, % d-1) was calculated based on the biomass gain in the tanks, assuming that the juvenile fish grew exponentially within the relatively short, experimental period:

( ) ( ) 100/)()(00

×−= tttWtWLnSGR ii eq. 2

where W(ti) and W(t0) were the biomass at the end (ti) and at the start (t0) of the trial, and (ti - t0) was the duration of the trial in days. The feed conversion ratio (FCR, g g-1) was calculated based on the biomass gain in the tanks, the feed amount administered and the registered feed waste during the 9 days of feeding according to:

( ) ( )00

ttgainbiomassttconsumedfeedFCR ii −−= eq. 3

The data were subjected to one-way ANOVA analysis using Sigma Stat for Windows Version 3.10. The Holm-Sidak Test was used for pair wise comparisons where dietary treatments were significantly different. A probability of P < 0.05 was considered as significant in all analyses.


Reduced nutrient discharge

The measured digestibility (ADC) was on average: Protein: 93.5 %; lipid: 91.2 %; NFE: 66.9 %; ash: 51.9 %; phosphorus: 64.2 %. The recorded specific growth rate (SGR) was on average: 1.97 % . d-1 and the average feed conversion ratio (FCR) was 0.76 (kg feed . kg weight gain). The retention of nitrogen and phosphorus by the fish was on average 49.1 % and 57.6 %, respectively (Table 41).

Protein: 46.3 % Lipid: 27.5 % NFE: 12.6 % Ash: 6.9 % Crude fibres: 1.4 % Dry matter: 94.6 % Phosphorus: 0.98 % Energy content: 23.8 kJ. g feed

Table 40: Composition of feed


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Dietary Component

BioMar Ecolife 20

Aller Aqua 576 BM XS

Dana Feed Dan-Ex2844

F2,6 P

Protein 93.9 ± 0.4a 92.8 ± 0.2b 93.7 ± 0.3a 10.81 0.010

Lipid 91.4 ± 0.6ab 88.4 ± 1.8a 93.7 ± 1.0b 14.22 0.005

NFE 66.6 ± 1.1a 67.2 ± 0.9a 67.0 ± 1.0a 0.36 0.711

Ash 46.7 ± 1.8a 57.2 ± 0.4b 51.7 ± 0.8c 62.69 <0.0001

Phosphorus 60.9 ± 0.7a 71.0 ± 0.9b 60.6 ± 0.7a 177.83 <0.0001

DM 84.7 ± 0.6a 84.4 ± 0.5a 85.6 ± 0.6a 4.09 0.076

DM calculated2 85.7 ± 0.5 85.2 ± 0.5 86.3 ± 0.6 - - 1) Values within rows not sharing a common superscript letter were significantly different (ANOVA, Tukey HSD, P < 0.05). 2) The digestibility of dry matter was calculated as the sum of the measured digestibility of protein, lipid, NFE and ash.

Table 41: Apparent digestibility coefficients (ADC) of protein, lipid, NFE, ash, phosphorus and dry matter (DM) (%, mean ± std. dev., n = 3) of the diets as well as the calculated digestibility of dry matter1.

Calculations of the BOD5 and COD contributions showed that an average of 55% of the total BOD5 waste was recovered as dissolved/suspended waste, while an average of 45% was recovered as particulate BOD5 waste. An average of 71% of the total COD waste was recovered in the particulate form, while 29% was recovered as dissolved/suspended COD waste, and the dissolved/suspended BOD5/COD ratio was 0.51. The majority of the Total N-waste was recovered as dissolved/suspended TN waste (88%), while an average of 12% was recovered in the particulate fraction. Almost all of the phosphorus P-waste was recovered as particulate waste (on average 98%), while only a very minor fraction (on average 2%) was recovered as dissolved/suspended P-waste.


The results of the laboratory experiments were important inputs for the precision of the overall calculation model. By integrating data into the calculation model from both model trout farms and traditional farms with lower technology, the model offers the opportunity to obtain estimates for discharges from trout farms at different technological levels. However, it should be noticed, that the following pre-requisites prevail in order to obtain acceptable estimates upon use of the calculation model: 1. The fish species must be rainbow trout (Oncorhynchus mykiss Walbaum)

2. The feed used must be of good quality, i.e. contain sufficient levels of vitamins and minerals to support good growth and health and digestibility of protein and lipid must not be less than 85%.

3. If water recirculation is applied then the water must reside for at least 18.5 hours in the production unit(s) and at least 20 hours in the constructed wetland.

4. If the farm is equipped with mechanical filters (drum filters or similar) and/or bio filters, then the filters must have adequate dimensions in order to optimise water treatment.

5. The daily feed amount must not exceed 800 kg. 6. Provided that these prerequisites are fulfilled, the overall calculation model serves as a convenient tool

for estimation of discharges of key nutrients from trout farms. However, it should be emphasised that the calculation model only serves as a tool to estimate the nutrient discharges from trout farms, i.e. the model can not be used for documentation of discharges.

8.3. Energy consumption on model trout farms

The model fish farms depend on transport of water in the farm (recirculation) as well as aeration/oxygenation of the water due to the low consumption of new fresh water. Furthermore, waste gases as CO2 and N2 should be be removed from the production water. The most important issue in the model trout farms is the implementation of the recirculation technology, i.e. pumping water and water purification to minimise water consumption and environmental impact. This technology requires energy input and as such energy is an important parameter, which has to be considered for a sustainable production.


The pumping of water in the model trout farms as well as the injection of air/oxygen into the farming systems requires energy. Thus, it is important to evaluate the need of oxygen during the production and in accordance to this to adjust the injection level/energy consumption. The need of air/oxygen is highest during feeding and digestion of the feed, i.e. during the metabolic processes. Furthermore, the need for oxygen


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depends on fish size and on the standing stock.


The current technologies for aeration of the water are:

• Basin aerator

• Low pressure diffuser

• Surface aerator

• Trickling filter

• Air lift pump For efficient oxygenation/degassing it should be borne in mind that:

• The solubility of gases/water saturation increases with the pressure, i.e. water exposed to pressure may contain more oxygen/CO2 than at the surface.

• The larger the contact surface between the gas- and the water phase, the quicker the gas is dissolved in the water, i.e. air bubbles created by diffusers with different sizes of holes, which in turn affects the magnitude of back pressure.

Basin aerator

Basin aerators may be designed as a simple diffuser placed about 50 cm above the bottom of a production unit with adequate proportions between length and depth of the basin to secure proper circulation.

Low pressure diffuser

A low pressure diffuser may have several diffuser tubes mounted on a steel frame. The diffuser has a relative low back pressure at moderate water depth, i.e. about 80 cm. The oxygenation efficiency is good at lower oxygen saturations and suitable for degassing due to the low depth of air injection.

Surface aerator

Surface aerators are often used on traditional farms. The water is thrown into the air, which creates a good contact surface with the air and mixing in the pond. The surface aerator is efficient to keep fish alive under low oxygen conditions and for degassing.

Trickling filter

In a trickling filter the water is pumped over a distribution grid on top of the filter. From there the water runs down through a filter media (for example. Bio-Blocks) providing a large contact surface for aeration (O2) and degassing (N2/CO2). However, the trickling filter is energy demanding (pumping) due to the lift height requirement(often at least 1 m).

Airlift (”mammut pump”)

The most common method of water transport and aeration in model trout farms is by using airlifts. The function of an airlift is both pumping and aeration of the water. The airlift consists of a well/hollow, equipped with a partition (Figure 19). On the one side (to the left in Figure 19) a number of diffusers are installed (injection of pressurised air by compressors). The driving force in an airlift is the difference in the specific gravity between the water and the air/water side. The design of the airlift determines as well its ability to manage the flow of air (avoid collapse) as the maximum head. Optimum head might be about 10 cm at a water depth of 2 m.

Figure 19: Sketch of the airlift (after Lokalenergi, 2008).


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Energy consumption

The injection of air into the farming systems is energy requiring and thus it is important to evaluate the need for air during the production and in accordance to this adjust the injection level/energy consumption. The need for air/oxygen is highest during feeding and digestion of the feed, i.e. during the metabolic processes. Further, the need for oxygen is dependent on the fish size and on the standing stock. However, to achieve optimum utilisation of the injected air, relationships between air flow, aeration principle, choice of diffuser and water depth need to be considered so as to obtain:

• maximum contact surface between air-bubbles and water

• Air-bubbles having longest possible retention time in the water column before they reach the surface

• Lowest possible back pressure/loss of pressure in the system. The most important factor for optimum efficiency of the airlift is the adequate relationship between the flow rate of the air and of the water. With too high an injection of air in relation to the water flow the air lift may loose efficiency, i.e. collapse. The experiments showed a direct relationship between the energy consumption and the aeration efficiency of the water. However, the energy consumption of the airlift in relation to the resulting pressure in the air delivery system needs further consideration in order to optimise the energy consumption. On average the energy consumption was estimated to 1.7 kWh/kg produced fish. The aeration requires energy for compressing air and the coincident increase in temperature reveal a loss of energy, i.e. further energy costs. During the experiment the energy consumption by the airlift was measured to be 5 802 W for compressing the air with the addition of the energy for heating the air the total energy consumption was 10 199 W. For comparison the corresponding energy consumption by a typical submerged propeller pump lifting the water up to 0,4 m and a total efficiency, ηtotal = 0,4 can be calculated as: Q x dp / ηtotal, where Q = 1 300 m3/h = 0,362 m3/s; dp = 0,25 mVs = 2 500 Pa, i.e. = 0,362 x 2 500 / 0,4 = 2 260 W. The calculations showed that a submerged propeller pump might move the water by using only ¼ of the energy consumed by the airlift. However, using a propeller pump would require energy for aeration by an alternative method.


Summarising the results of energy consumption investigations on three different model trout farms, the following can be concluded:

• Proper functioning of the airlift strongly depends on a balanced relationship between the flow rate of the air and that of the water, i.e. the rate of injection of air should be adjusted to the water flow.

• There was a linear relationship between the energy consumption by injection of the air and the resulting oxygen concentration of the water after aeration in the airlift.

• The energy costs of internal transport of water by submerged propeller pumps was 0.25 of the energy cost by using the airlift.

• Whilst, moving the water with a propeller pump is cheaper than by airlift, energy costs for aeration by another method (e.g. basin aerators) need to be added.

• A low flow of air provided more aeration efficiency related to the costs than a large air flow.

• Small air bubbles added corresponding to the target oxygen content, i.e. injection flow and long contact time between air/water are important for cost efficient aeration.

• The higher the level of air injection in the water column, the higher the air flow should be to obtain a given amount of oxygen per unit time.

• The energy costs for aeration were significantly dependent on the method of aeration, i.e. diffuser geometry.

• The loss of energy due to the significant increase in temperature by using rotary blowers should be considered.

• The cost efficient aeration process should be monitored and managed according to the current farming conditions (diurnal variation, season etc.).

• When using propeller pumps in place of airlifts the investment costs of pumps needs be considered as well as back up solutions to secure operational reliability.

• Evidently, it seemed easier to improve the energy costs of transport of water than of aeration.


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8.4. Cultivation of pond plants in the lagoons of model farms

In connection to the model trout farms the former earthen ponds are often left inter-connected with the old channels and thus making up a lagoon area with wild plants. After treatment by the cleaning devices (sludge traps, bio filters) of the farm, the water passes slowly through the lagoon area for further removal of nutrients by plants, i.e. final waste water treatment, before returning to the water course. The plant lagoons are important for the conversion of nitrate, BOD and precipitation of organic matter and phosphorus. However, the lagoons are not efficient in conversion of ammonia into nitrate. Due to the conversion of organic matter, anaerobic conditions may occur in bottom areas and favour denitrification, i.e. conversion of nitrate into gaseous nitrogen. Thus, anaerobic conditions in the plant lagoons may promote the removal of organic matter and nitrate.


The vegetation in the plant lagoons is of great importance for the cleaning process and has been investigated at Ejstrupholm. The main plant species observed in the plant lagoons with a degree of coverage of up to 80% at Ejstrupholm model trout farm were manna grass, lesser duckweed, water thyme, filamentous algae and water starwort. These plants are interesting in relation to both removal of nutrients and transformation/ conversion of nutrients. Thus, the plants serve as surface area for micro organisms (biofilm) and they are involved in conversion of ammonia and uptake of dissolved nitrogen and phosphorus into the plant biomass. Finally, the plants influence the water currents and facilitate the sedimentation of particles. However, apart from their function to reduce the environmental impacts from the trout production, the plant lagoons may meanwhile also be used for a secondary production of commercially high value plant species that might provide an additional income to the trout production. The market potential of different commercial plants as by-products of the fish industry has already been investigated.


The main species studied were perennial garden pond plants, which apart from their potential of high nutrient absorption might obtain reasonable prices in the market. Nine species were investigated, four belonging to Iridacaea, one to Butomaceae and one to Nymphaecea, and Watercress (Nasturtium officinale), Menyanthes trifoliata and King cup (Caltha palustris). The investigations were performed at different sites of a plant lagoon at the Ejstrupholm model farm, Denmark. The sites selected were characterised by different water flow characteristics, nutrient load and water quality parameters. Due to the dense native vegetation crowding out pond plants on the banks and in the ponds, special constructions, i.e. polystyrene floating frames, were used for growing the plants.

The floating garden method applicable on unused ponds of model trout farms (Photo: DTU-Aqua)


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The lagoons (constructed wetlands) represent a good potential to reduce nutrient discharges from the fish farm. Thus, the removal of total nitrogen was greater than 1 g per m2 per day. However, the residence time of the water in the lagoons is important for the efficiency of removing nutrients. The study showed that the natural vegetation in an established plant lagoon creates problems for the test plants to establish within ponds and channels as well as on the banks. Thus, it requires initially a lot of manual weeding for plants to establish. The sump plants of the Iris family are quite tolerant, hardy and quite easy to grow, but even these were initially crowded out by more fast growing species on the slopes and banks of the plant lagoons. Additionally, a substantial part of the plants (rhizomes) were predated by water voles. The plant species Watercress (Nasturtium officinale), Menyanthes trifoliata and King cup (Caltha palustris), which may spread fast, were grown at one of the old earthen ponds in the mid section of the plant lagoon. Some of these species survived and grew. The growth rates, however, were lower than expected, which may be related to the anaerobic conditions in the earthen ponds. One species was completely predated by water voles. The plants studied spread easily either naturally by rhizomes or could be divided manually by division of rhizomes/ seedlings. In addition to the vegetative reproduction the Iris species produced seeds. Plants grown from seeds however may have different genetic characteristics than plants multiplied by division or root shooting, which may have a negative consequence when selling due to phenotypic differences (i.e. hybrids; colour of flowers etc.) The floating garden concept was relatively successful, and floating frames may be built into larger units covering hundreds of square meters. However, trout farms in Denmark are characterised by numerous abandoned earthen ponds, which are relatively small and narrow. Consequently, the water bodies in these areas are completely covered by natural vegetation, which may be an advantage for the nutritional retention, but renders introduction of larger units of the floating concept difficult. In order to optimise commercial production of pond plants in the plant lagoons of the Ejstrupholm model trout farm it might be advantageous to restructure parts of the plant lagoon. This means establishing larger areas with shallow wasteland free of existing vegetation and then either use the floating garden concept or grow the plants directly in the ponds depending on the species. Some aspects of plant pond construction should also be considered in prospective development of new farms. These considerations should also imply the combined usage of plant lagoons both for garden ponds and for a more dense and ground based vegetation like reed (Phragmites australis) or other repository plants. These plants may contribute to increase the low oxygen conditions in the ponds. At present most of the plant lagoons at Ejstrupholm have quite anaerobic conditions, which may reduce growth of various commercial plants. In addition to this, it should be noticed, that larger units of floating frames may hinder oxygen transport/diffusion and may create anaerobic conditions for the roots. The study showed a good growth of some pond plant species especially belonging to Iridacaea, however the potential income of selling of plants may be compromised by an initial labour intensive period (weeding) and later at harvest.

8.5. Cultivation of alternative Fish Species in the lagoons of model farms

After treatment by the cleaning devices (sludge traps, bio filters) of the farm, the water passes slowly through the lagoon area for further removal of nutrients by the plants, i.e. final waste water treatment, before returning it to the water course.


Apart from their function to reduce the environmental impacts from the trout production, the plant lagoons may also be used for a secondary production of commercially high value juvenile fish that might provide an additional income to the trout production.

The general idea was to increase the profitability of the farm by optimising its production without harming the main trout production and the overall system operation. Furthermore, it was assumed, that new production activity should be exclusively based on the conditions prevailing in the lagoon without any external supply (e.g. feed).

8.5.2. Principles of the case study module

Extensive production of fish larvae and juveniles should be based on the natural zooplankton production in the plant lagoons. Therefore, it was initially investigated whether the zooplankton production at various sites


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of the lagoon was sufficient for supplying feed for the fish larvae, e.g. perch and pike-perch larvae. Based on the results of the zooplankton sampling it was concluded that the lagoons were less suitable for rearing fish larvae. However, production of juvenile fish in e.g. net-cages (including suitable lagoon sites) might be an attractive methodology to produce various fish species to be sold for on-growing (put-and-take-lakes, aquaria etc. ) To investigate the performance of net-cages experiments were performed both in the lagoon at the Ejstrupholm model farm and at two put-and-take lakes where water quality and zooplankton production were considered more favourable for the larvae. Perch and pike-perch larvae were used for the experiments.

8.5.3. Assessment of selected SustainAqua sustainability indicators: Nutrient, water and space utilisation efficiency

The results of the zooplankton sampling during spring (larval season) showed that the plankton concentrations were highly variable and generally below the level considered necessary for fish larvae to survive and grow. Furthermore, the water quality was unstable with periods of low oxygen and occurrence of toxic hydrogen sulphide formation. Therefore, the lagoons were considered less suitable for larval rearing. In the succeeding net-cage experiments the cages were stocked with perch and pike-perch larvae. The results showed that production of juvenile fish in the plant lagoons of Ejstrupholm model trout farm was not feasible due to low oxygen levels and a high production of thread algae in the lagoons. Aeration of the water within the net cages was not sufficient to increase oxygen content to acceptable levels. However, the experiments in the put-and-take lakes demonstrated that fish larvae may be reared from hatching until a size of 2-3 cm (one month) in net-cages without human interference during the production.

8.6. Summary – Success factors and constraints

Summarised, the results of the Danish Model Trout Farm case study provided valuable information and tools related to:

• Reducing nutrient and organic matter loss, i.e. reducing the environmental impacts

• Optimisation of energy costs

• Sustainability of cultivating pond plants and of growing additional, alternative juvenile fish species in the lagoon areas of the Model farms.

Specifically, the following success and limiting factors can be indicated:

• Using the plant lagoons of Ejstrupholm model farm to grow juvenile fish was not feasible due to low oxygen levels and a high production of thread algae in the lagoons. However, parallel experiments in put-and-take lakes demonstrated, that fish larvae may be reared from hatching until a size of 2-3 cm in net-cages without human interference during the production period

• Proper functioning of an airlift (pump) strongly depends on a balanced relationship between the flow rate of the air and that of the water, i.e. the rate of injection of air shall be adjusted to the water flow

• The energy costs for aeration significantly depend on the method of aeration, i.e. diffuser geometry

• The loss of energy due to the significant increase in temperature by using the rotary blowers should be considered

• Cost efficient aeration processes should be monitored and managed according to the current farming conditions (diurnal variation, season etc.)

• Increased discharge of CO2 The principles of the model trout farm concept using the recirculation technology may be generally adapted in the European aquaculture sector.


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8.7. From a case study to a fish farm: How to manage a model trout farm producing 500 t fish per year (Ejstrupholm Model Trout Farm)

8.7.1. Description of the Model Fish farm

Ejstrupholm model fish farm is located at Holtum Å (watercourse) in Mid-Jutland, Denmark. The farm is constructed with two identical production units each divided into 8 sections. Figure 20 provides a sketch of the model farm.

Rive r

Bac kch an ne l

La go oncha nn e l

Sl ud ge b ed

Con cre te fi sh ta nk s

La go oncha n ne l

La go on cha n ne l

Pl an t l ag oo n s Pla nt la go o ns

Pl an t p on dSlu dg e

o ve rf l ow

Sl ud geb ed

Slud

ge b

ed

1 Fe nc e e ntran ce

= w ate r flowTT = T rou t pr odu ction

Figure 20: Sketch of Ejstrupholm Model Trout Farm. Arrows indicate direction of water flow.

The recirculation and the aeration of water is achieved by airlifts. The function of an airlift is both the pumping and aeration of water. The airlift consists of a well/hollow, equipped with a partition. On the one side of the partition, a number of diffusers are installed (injection of pressurised air by compressors). The driving force in an airlift is the difference in the specific gravity between the water and the air/water side. By a combination of the injection of air and aeration water js lifted a few centimetres and thus creating the recirculation flow. The particulate matter from production is collected in sludge cones placed at the bottom of the production units and the sludge is pumped to sludge basins for sedimentation. The recirculated water passes through a biofilter, where the conversion of ammonia to nitrite/nitrate takes place. The outlet water from the production units and the cleaned water from the sludge basins is passed to the plant lagoons, i.e. the former earthen ponds, which are often left inter-connected with the old channels and thus making up a lagoon area with wild plants. After treatment by the cleaning devices (sludge traps, bio filters) of the farm, the water passes slowly through the lagoon area for further removal of nutrients by the plants, i.e. final waste water treatment, before returning it to the water course.

8.7.2. Description of the farm effluents

In the table below the specific contribution from production, the net discharge and the cleaning efficiency of the cleaning devices from Ejstrupholm Model Trout Farm are compared to the average specific discharge (g nutrient per kg. produced fish) from Danish trout farms.


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Nutrient Contribution from production

Net discharge

Cleaning level, % Average discharge Denmark

Ejstrupholm as % of avg. Denmark

Total Nitrogen 33.7 15.8 53 31.2 51

Total Phosphorus 4.3 0.39 91 2.9 13

BOD 78.7 3.2 96 93.6 3

COD 224.9 - -

Table 42: Specific contribution from production, the net discharge (average g nutrient per kg. produced fish) and cleaning level from Ejstrupholm Model Trout Farm compared to the average specific discharge from Danish trout farms.

The results document a very high efficiency of removal of nutrients from the production water in the model trout farm. In particular, the specific discharge of phosphorus and organic matter was significantly reduced compared to the average discharge from Danish trout farms. The ammonia, phosphorus and organic matter is removed in the sludge traps and the bio filters, while the plant lagoons efficiently remove organic matter, phosphorus (especially suspended) and total-N (especially nitrate). Calculations of the BOD5 and COD contributions showed, that an average of 55 % of the total BOD5 waste was recovered as dissolved/suspended waste, while an average of 45 % was recovered as particulate BOD5 waste. An average of 71 % of the total COD waste was recovered in the particulate form, while 29 % was recovered as dissolved/suspended COD waste, and the dissolved/suspended BOD5/COD ratio was 0.51. The majority of the Total N-waste was recovered as dissolved/suspended TN waste (88 %), while an average of 12 % was recovered in the particulate fraction. Almost all of the phosphorus P-waste was recovered as particulate waste (on average 98 %), while only a very minor fraction (on average 2 %) was recovered as dissolved/suspended P-waste.

8.7.3. Water balance of the farm

The water for production is harvested from drains under the production plant and/or boreholes nearby. The water intake was about 45 l/sec. and the time of residence on the farm was about 35 hours. The energy consumption for pumping and aeration (oxygen) of the water was about 1.7 kWh/kg fish produced.

8.7.4. Pro and contra of traditional trout farms and model trout farms

Compared to traditional farming the model farm concept has the following advantages and disadvantages:

Advantages: Disadvantages

• Water consumption reduced from about 50.000 l/kg fish to about 3.900 l/kg fish produced

• Increased need of back-up systems: Electricity, oxygen, pumps, etc.

• Independent of watercourse • Increased discharge of CO2

• Stable conditions for production • Risk of accumulation of ammonia

• Minor variations in water quality • Increased need for supervision and management

• Improved efficiency of cleaning devices • Higher energy consumption/kg fish

• Reduced environmental impact

• Use of water from bore hole implies less seasonal temperature variations

• Improved control of management and production

• Reduced external risk of infection with pathogens

• Reduced need for medicine and therapeutics

• Improved work environment

Establishment costs of a Model Trout Farm as described above costs around 3 - 3,5 EURO/kg feed, i.e about 1,6 mio. EURO for a 500 ton model farm like Ejstrupholm.

SUSTAINAQUA HANDBOOK Case study in the Netherlands

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9. Tilapia farming using Recirculating Aquaculture Systems (RAS) - Case study in the Netherlands

9.1. Module - Manure Denitrifying Reactor (MDR)

In the Netherlands fish is mainly cultured in recirculation aquaculture systems (RAS). To improve sustainability of fish culture in RAS further farmers attempt to: 1. Reduce energy and water consumption, 2. Reduce the volume of waste water discharged (manure transport costs and costs for waste discharge), 3. Improve the nutrient utilisation of fish using well designed diets and optimal culture conditions, 4. Reduce fees for pollution units, which are based on the amount of COD, Kjeldahl-N and phosphorus

discharged. To attain these goals so-called “within system” innovations must be developed which reduce the emissions of dissolved and particulate nitrogen, COD and organic matter. In this case study the integration of an up flow sludge bed manure denitrification reactor (USB-MDR) in RAS was studied to reduce water consumption, the associated energy needs for heating and nutrient discharge. The research objectives of the Dutch case study were to determine: the effect of up flow velocity on USB-MDR performance, the effect of C:N ratio in the diet on the nitrate removal and water quality; the effect of a plant protein based diet on nitrate removal and system water quality; the up scaled reactor performance; the effect of Geotube® system on waste discharge volume reduction of the USB-MDR, the effect of USB-MDR on health and welfare of the fish in a pilot scale RAS and whether the integration of an USB-MDR in a RAS prevents the presence of off flavour compounds. Finally, the research outcomes and commercial data (ZonAquafarming BV) were translated into a case study comparing a hypothetical 100 MT RAS with and without USB-MDR for the impact on sustainability indicators.


The design of a fish farm starts with the choice of the fish species to be cultured. The choice of fish species will also largely determine the growth target, the husbandry and water quality demands, and the waste production. Production of fish inevitably causes production of waste. This waste is excreted into the water in which the fish live, thereby deteriorating the water quality. Therefore a constant water flow is needed to remove these wastes from the fish. In a flow through system the flow through of the fish tanks equals the system's water exchange (Figure 21).

Figure 21: In a flow through system the flow through of the fish tanks equals the system's water exchange. In a Recirculating Aquaculture System (RAS) the water flow from the fish tanks is purified and reused. Different treatment units can require different flows and are sometimes operated in a separate loop within the system.

In a Recirculating Aquaculture System (RAS) the water flow from the fish tanks is purified and reused (Figure 21). Solids are removed by sedimentation or sieving, oxygen is added by aeration or oxygenation, carbon dioxide is removed by degassing and ammonia is mostly converted to nitrate (NO3) by nitrification in aerobic biological filters. Each treatment step reduces the system water exchange to the next limiting waste component. In the conventional RAS system water exchange is then dictated by the concentration of nitrate (Figure 21). In the latest generation of RAS’ nitrate is converted to nitrogen gas (N2) by denitrification in

fish tank

Flow through RAS

treatment unit 2

fish tank

treatment unit 1


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anaerobic biological filters. In these denitrification reactors organic matter (preferably of internal origin, i.e. the uneaten feed and faeces from the solids removal) is oxidised using the oxygen from the nitrate molecule. These latest generation RAS’ reduce thereby not only the water use and nitrogen discharge (less nitrate has to be flushed out), but also the organic matter discharge. For all compartments in a RAS, the fish holding and the treatment units, there are two fundamental questions: 1) how much water should be passed through and 2) what are the required dimensions (i.e. volume and shape). For the fish tanks the flow should be large enough to remove the amount of waste produced and to maintain an acceptable water quality for the fish. For each treatment unit the flow should be large enough to provide it with the amount of nutrients (waste) to be removed. Different treatment units can require different flows and are sometimes operated in a separate loop within the system (Figure 21). The required volume of the fish tanks will depend on the maximum stocking density for the fish species in question. The required volume, and shape, of the treatment units depends on their functional characteristics. For solids removal this mostly depends on particle size distribution. For biological filters the volume will depend on the specific activity, expressed in g Waste/m3/d removed. From the above it follows that for the design of a RAS it is crucial to know the amount of waste produced per day. Since all waste originates from the feed, i.e. everything in the feed which is not retained becomes waste, so this comes down to knowing the amount fed per day. Due to the fluctuating fish stock present on the farm, caused by harvesting and restocking, the amount fed also fluctuates. The design of the farm should be based on the maximum expected feed load to realise the planned annual production. This in turn can be calculated from the culture plan. Finally the waste production can be determined from the maximum feed load with the nutrient budget model, which uses the feed composition, the feed digestibility, the fish composition and the fish respiration to calculate the solid (faeces) and dissolved (excretion through gills and urine) waste.

9.1.2. Principles of the Manure Denitrification Module

An USB-MDR is a cylinder like anaerobic (no free oxygen) reactor fed with a waste flow of the solids removal unit (Figure 21) containing dissolved and particulate faecal organic waste, bacterial flocs and inorganic compounds. The waste flow enters the reactor at the bottom centre and creates an up flow velocity. The up flow velocity in the reactor is designed to be smaller than the settling velocity of the major fraction of the particulate waste in order to create a sludge bed in the bottom section of the reactor containing settleable particulate waste. In the sludge bed the faecal particulate carbonaceous waste is digested by the denitrifying bacteria and results in: (1) the production of bacterial biomass and (2) reduction of nitrate into nitrogen gas, production carbon dioxide (3) production of alkalinity and (4) the production of heat. The particulate waste in the sludge bed serves also as media for the denitrifying bacteria to grow on. Pre-settled water leaves the reactor through a V-shaped dented overflow at the top section of the reactor. Compared with a conventional RAS a RAS equipped with an USB-MDR allows for: the reduction of make up water supply for nitrate control, reduction of nitrate-nitrogen discharge, reduction of energy consumption due to a low make up water supply flow and heat production by the bacteria biomass in the USB-MDR, concentration of the drum filter solids flow, reduction of the size/volume of the post treatment as the USB-MDR pre-concentrates and digests the solids already, reduction of fees for nutrient discharge (TAN, nitrate, org-N, and organic matter (COD)); increased alkalinity production and allows a pH neutral fish culture operation. Disadvantages are: higher investments, more knowledge is needed to operate the system and, accumulation of total dissolved solids (TDS).


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The SustainAqua sustainability parameters applied in this module for a hypothetical 100 MT RAS without (conventional RAS) and with USB-MDR are resource use per kg harvested, nutrient utilisation as % of input, and waste discharge per kg harvested (see Table 43).

Conventional

RAS USB-MDR RAS

Conventional RAS

USB-MDR RAS

Resource use Waste discharge

Fingerlings (#/kg) 1.2 1.2 Nitrogen Feed (kg/kg) 1.22 1.22 Solid (g/kg) 8.5 2.6 Electricity (kWh/kg) 1.8 2.2 Dissolved (g/kg) 37.4 5.9 Heating (kWh/kg) 3.4 0.0 Phosphorus Water (L/kg) 238 38 Solid (g/kg) 4.5 7.2 Oxygen (kg/kg) 1.18 1.26 Dissolved (g/kg) 3.8 1.3 Bicarbonate (g/kg) 252 107 a COD Labour (h/MT) 12.5 13.1 Solid (g/kg) 189 84

Dissolved (g/kg) 40 9 Nutrient utilisation TOD Solid (g/kg) 227 95

Nitrogen (% of input) 32 32 Dissolved (g/kg) 48 11 Phorphorus (% of input) 43 43 CO2 (kg/kg incl gas) 1.58 1.10 COD (% of input) 32 32 TDS (g/kg) 62 28 TOD (% of input) 32 32 Conductivity (µS/cm) 1060 2000

a) In practice the need for bicarbonate (alkalinity) is actually nil when denitrification is applied.

Table 43: Assessment of SustainAqua sustainability indicators in the MDR module


In “The Netherlands” case study the integration of a manure denitrification reactor (MDR) in a conventional RAS indicates the following: Success factors

• Water, energy and alkalinity consumption can be significantly reduced in conventional RAS

• Energy consumption is substantially reduced compared to conventional RAS as: (a) less water has to be exchanged and thus heated to control nitrate concentrations and (b) a significant amount of heat is produced by the bacterial biomass reusing and oxidising otherwise wasted nutrients.

• Compared to a conventional RAS. waste discharge is reduced (digestion) and concentrated (through treatment process selection) in the MDR within the recirculating loop. Furthermore, waste concentration is possible treating the discharged MDR sludge with a Geotubes® system.

Prospects

• For future farming conditions where nitrate-N cannot be controlled by a USB-MDR, diet (re) formulation resulting in a higher C/N ratio in the produced fish waste can be a profitable tool to control nitrate accumulation by denitrification. Consequently, water energy and alkalinity consumption will be reduced.

• Plant protein diets might be applied in future to further improve the sustainability profile of fish cultured in RAS. This study showed no significant effect of plant protein diets on USB-MDR performance. However, ortho-phophate-P concentration was significantly higher in RAS when fish were fed the plant protein diet when compared with RAS in which fish were fed the fish meal based diet.

Constraints

• Nile tilapia of up to ±150 g can be cultured in nearly-closed recirculation systems with water exchange rates of 30 l/kg feed/day (as with MDR) without hampering fish welfare. On the other hand, larger individuals (±300 g) seem to exhibit growth retardation (tendency) when cultured on a pilot scale. RAS equipped with an USB-MDR at an similar water exchange rate. However, this effect was not observed in commercial RAS (info ZonAquafarming BV)

• Higher investments and a higher level of knowledge are needed to operate the system.


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The summarised benefits and difficulties when applying a USB-MDR in a conventional recirculating aquaculture system are based on a case study for a hypothetical 100 MT’s tilapia farm (= selling annually 100 MT) integrating research data (AFI-WUR) and commercial farming data in RAS (ZONAQUAFARMING BV). The indicated benefits and difficulties are based on comparing a conventional RAS with an RAS integrating the USB-MDR innovation. Estimated benefits and difficulties in applying an USB-MDR and Geotube® system in RAS when comparing with a RAS without USB-MDR and and Geotube® system are:

Benefits

Resource use : - Reduction in energy cost of 3 kWh/kg harvested

- Reduction in water consumption to 200 L/kg harvested

- Reduction in bicarbonate consumption to 252 g/kg harvested

Nutrient reuse: - Nutrient reuse by bacteria and converted to 0.5 kWh/kg fish produced

Nutrient discharge: - Reduced by 81% for N,

59% for COD,

61% for TOD,

30% CO2 1)

58% for TDS

Sludge volume: - Reduction in sludge volume to 7.3 L /kg feed using Geotube® system systems

Difficulties

- Higher investments (± Euro 52 800,--, USB-MDR’s and additional biofilter material and volume) when compared with conventional RAS - A drumfilter with a larger TSS removal capacity may be needed as not all TSS is

retained in the USB-MDR. In pilot scale experiments the TSS treatment efficiency (%) of the USB-MDR was 65 ± 18 (mean ± S.D; N=7).

- Higher knowledge level to operate a RAS with USB-MDR - C:N ratios in fish waste can limit the nitrate removal rate

1) Reduction in carbon dioxide discharge due to savings in fossil fuel consumption.

Overall, for the economical conditions in the Netherlands the case study indicates 10% lower production costs per kg fish harvested when comparing a RAS with USB-MDR with a conventional RAS.


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9.2. From a case study to a fish farm: Integration of a denitrifying USB-MDR in a 100 MT tilapia RAS

9.2.1. Introduction

In this case study the effects of integrating a denitrifying USB-MDR to a 100 MT Tilapia RAS on the sustainability indicators will be demonstrated. A conventional RAS will be compared with a RAS with an USB-MDR. The concept and results of ZonAquafarming B.V. with the intensive farming of tilapia in RAS will be the starting point (Figure 22).

Figure 22: In this case study a conventional RAS and a RAS with an USB-MDR, both according to the ZonAquafarming B.V. concept, will be compared.

The case study is set up in a handbook format, to offer guidelines for development of a course in USB-MDR design and operation. The steps needed for design of RAS are shown in Table 44. These steps will be discussed in the following sections.

Fish species Tilapia Waste production

Growth traject Fish composition

Stocking weight 70 gram Feed composition Market weight 845 gram Digestibility

Time 24 weeks Oxygen consumption fish Feed intake Flow rates

Feed conversion 1.34 Water quality limits Max fish density 140 kg/m3 Fish tank exchange

Mortality 0.5 % System exchange Culture plan Treatment flows

Production goal 100 MT/year Treatment systems

Growth phases 2 Results

Stocking/Harvesting scheme 3 weeks N, P and COD fluxes

Maximum feed amount 349 kg/d Sustainability indicators

Table 44: Steps in design of a RAS

9.2.2. Implementation

Fish species

The first choice to be made, of which fish species is to be cultured, has here already been made: Nile tilapia (Oreochromis niloticus). Often this choice is made based on the market price of the fish. For economic sustainability the margin between market price and cost price, which in intensive systems is largely determined by the productivity (kg/m3/year), should be the main consideration.

Growth traject

In the choice of the fish species, and its market position, one also largely determines the growth traject, i.e. the stocking and marketing weight. The growth curve of the fish is characterised by the time to reach the

Conventional USB-MDR

moving bed

fish tank

drum filter

O2 aeration

moving bed

fish tank

drum filter

O2 aeration

USB-MDR


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market weight, which in turn is determined by the feed intake and the feed conversion, both depending on the body weight. Mortality is also dependent on body weight and it is important to calculate the number of fish to be stocked per cycle. Finally the choice of fish species also determines the required culture conditions such as the maximum fish density and the required water quality (water quality will be discussed in the section Flow rates).

In this case study a stocking weight of 70 g and a harvest weight of 845 g were chosen, based on the growth and feed intake characteristics of ZonAquafarming B.V. tilapia as given in Figure 23. It should be noted that the ZonAquafarming B.V. tilapia strain is developed through several generations of selective breeding. Most commercial tilapia strains grow less fast and in particular have difficulties in reaching sizes above 600-700 g under intensive conditions. The tilapia in this case study reached the market size in 24 weeks with a cumulative survival of 99.5%. For further calculations see box 1 in section Culture plan.

Figure 23: Growth and husbandry characteristics of ZonAquafarming B.V. tilapia.

Culture plan

After the choice of fish species and growth traject one needs to determine the culture plan. This includes the production goal (here 100 MT/year), the number of growth phases (here 2, the division being halfway in time, i.e. after 12 weeks), and the stocking/harvesting scheme (here every 3 weeks). Note With a 100 MT farm a farm output of 100 MT market sized fish is implied. As this is based on an input of 8.3 MT of fingerlings, the actual production is only 91.7 MT.

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From the culture plan one can determine how many cohorts of fish will be present on the farm simultaneously and with the weights and numbers of the fish per cohort one can calculate the total feed load in kg/day. In the culture plan of ZonAquafarming B.V. 12 fishtanks (24 weeks / 2 growth phases) are used. The tanks are operated in blocks of 3 tanks, which are connected through closable swimways. In this way the fish in one tank can be divided over two tanks by opening the swimway to an adjacent empty tank. Every 3 weeks one of the 3 tanks (not the middle tank of the 3) is stocked with 6,862 fish of 70 g. After 12 weeks, when the fish are ca. 370 g, the fish are divided between 2 tanks as described above. At that same time the 3rd of the 3 tanks is stocked with a new cohort of 70 g fish. After 24 weeks the 2 tanks with market size fish are harvested, the fish in the 3rd tank is divided over 2 tanks and the 1st tank is stocked with a new cohort of 70 g fish. This culture plan is shown in Table 45, along with the resulting farm setup, tank shape, tank water volume, system water volume and labour requirement.

After start-up of the farm, the biomass of fish present will gradually increase due to growth of the fish and stocking of new cohorts. At the same time the feed load , the amount fed in kg/d, will also increase (Table 46). The maximum feed load is reached at the moment the first cohort reaches market size, after 24 weeks. After that the feed load will follow a so-called sawtooth pattern (Figure 24). Design of the farm is based on the maximum feed load, in this case study 349 kg/d.

Figure 24: The maximum feed load is reached at the moment the first cohort reaches market size, after 24 weeks. At that moment (see Table 45) there are 8 cohorts present on the farm. When the first cohort is harvested and replaced by a new cohort of small fish, the feed load first is decreased and then increases again due to growth of the fish stock. This process continues and the feed load will follow a sawtooth pattern.

Box 1. Culture plan calculations

The number of fish harvested is 100,000 (kg/year)/0.845 (kg/fish) = 118,343 #/year or 118,343*(3/52) = 6,828 #/cohort. 3/52 is the number of harvestings/stockings per year.

The number of fish stocked is then 118,343/0.995 (cumulative survival) ≈ 118,946 #/year or 118,946*(3/52) = 6,862 #/cohort.

For the first week the mortality is 1.75*70 -0.8 = 0.058% and the number per tank after 1 week is then 6,862*(1-0.00058)=6,858.

The required tank volume is taken to be the maximum of the required volumes at the end of phase 1 and 2. Here that is the required volume after 12 weeks, 2,516 (kg/tank) / (35*ln(368)-80) = 19.8m3. Due to design considerations the actual tank volume is 20.5m3 and total tank water volume is 246m3.

After 1 week the biomass per tank is 6,858*0.087 (kg/fish) = 597kg. Fish density is then 597/20.5 = 29kg/m3.

The growth of the fish after 1 week is 87 * (46*87 -0.61)/100 = 2.6g/fish/d. Total production for that tank is 0.026*6.858 = 18kg/d.

With a feed conversion of 0.57*87 0.14 = 1.07, the total feed load for that tank is 18*1.07 = 19kg/d.

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Fish tanks

Number of tanks (blocks of 3 tanks) 12 # Number of fish harvested 6,828 #/cohort 118,343 #/year Required tank volume 238 m3 Required volume per tank 19.8 m3 Number of fish stocked 6,862 #/cohort 118,946 #/year

Depth of tank in total 1.6 m Width of tankwall 0.2 m Labour general 3 h/day Water depth in tank 1.3 m stocking 3 h/cohort harvesting 6 h/cohort Required surface per tank 15 m2 Relation length : width 4 total 1251 h/year Designed length rounded with 0.1m 7.90 m Designed width rounded with 0.1m 2.00 m Tank water surface 190 m2 Tank water volume 246 m3 System volume 384 m3 Total tanksurface incl walls 239 m2

SYSTEM DIMENSIONS AND GROWTH PERFORMANCE TILAPIA BLOCKS OF 3 TANKS

Volume: 20.5 m3/tank Tanks: 12 # SPLIT FISH OVER 2 TANKS

Time Weight Density Stock Stocking Growth Production Feedload Tank 1 Tank 2 Tank 3

weeks gram/fish kg/m3 kg/tank #/tank gram/fish kg/t/day FC kg /day #/tank #/tank #/tank 1 87 29 597 6858 2.6 18 1.07 19 6858 3418 3418 2 106 35 727 6855 2.8 19 1.10 21 6855 3417 3417 3 126 42 863 6852 3.0 21 1.12 24 6852 3417 3417 4 147 49 1007 6849 3.2 22 1.15 25 6849 3417 3417 5 169 56 1157 6847 3.4 23 1.17 27 6847 3416 3416 6 193 64 1321 6845 3.6 25 1.19 30 6845 3416 3416 7 218 73 1492 6843 3.8 26 1.21 31 6843 3415 3415 8 245 82 1677 6842 3.9 27 1.23 33 6842 3415 3415 9 273 91 1868 6840 4.1 28 1.25 35 6840 3415 3415

10 303 101 2073 6839 4.3 29 1.27 37 6839 3414 3414 11 335 112 2291 6838 4.4 30 1.29 39 6838 3414 3414 12 368 122 2516 6836 4.6 31 1.30 40 6836 3414 3414 13 403 67 1377 3418 4.8 16 1.32 21 3418 3418 6858 14 439 73 1500 3417 4.9 17 1.34 23 3417 3417 6855 15 476 79 1626 3417 5.1 17 1.35 23 3417 3417 6852 16 514 85 1756 3417 5.2 18 1.37 25 3417 3417 6849 17 553 92 1889 3416 5.4 18 1.38 25 3416 3416 6847 18 592 98 2022 3416 5.5 19 1.39 26 3416 3416 6845 19 633 105 2162 3415 5.7 19 1.41 27 3415 3415 6843 20 674 112 2302 3415 5.8 20 1.42 28 3415 3415 6842 21 716 119 2445 3415 6.0 20 1.43 29 3415 3415 6840 22 759 126 2591 3414 6.1 21 1.44 30 3414 3414 6839 23 802 133 2738 3414 6.2 21 1.45 31 3414 3414 6838 24 845 140 2884 3414 6.4 22 1.46 32 3414 3414 6836

Table 45: Setup of the ZonAquafarming B.V. culture plan for tilapia. Total labour and system volume are for the conventional RAS.


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AVG. 333 kg/d STOCKING New fish 1 tank every 3 weeks MIN. 318 kg/d HARVESTING Market size fish 2 tanks per 3 weeks MAX. 349 kg/d week kg feed 1 2 3 4 5 6 7 8 9 10 11 12

1 19 19 2 21 21 3 24 24 4 44 25 19 5 48 27 21 6 53 30 24 7 76 31 25 19 8 81 33 27 21 9 88 35 30 24

10 113 37 31 25 19 11 120 39 33 27 21 12 129 40 35 30 24 13 155 21 21 19 37 31 25 14 165 23 23 21 39 33 27 15 175 23 23 24 40 35 30 16 204 25 25 25 21 21 19 37 31 17 215 25 25 27 23 23 21 39 33 18 228 26 26 30 23 23 24 40 35 19 258 27 27 31 25 25 25 21 21 19 37 20 271 28 28 33 25 25 27 23 23 21 39 21 285 29 29 35 26 26 30 23 23 24 40 22 318 30 30 37 27 27 31 25 25 25 21 21 19 23 332 31 31 39 28 28 33 25 25 27 23 23 21

24 349 32 32 40 29 29 35 26 26 30 23 23 24

25 318 19 21 21 30 30 37 27 27 31 25 25 25 26 332 21 23 23 31 31 39 28 28 33 25 25 27 27 349 24 23 23 32 32 40 29 29 35 26 26 30 28 318 25 25 25 19 21 21 30 30 37 27 27 31 29 332 27 25 25 21 23 23 31 31 39 28 28 33 30 349 30 26 26 24 23 23 32 32 40 29 29 35 31 318 31 27 27 25 25 25 19 21 21 30 30 37 32 332 33 28 28 27 25 25 21 23 23 31 31 39 33 349 35 29 29 30 26 26 24 23 23 32 32 40 34 318 37 30 30 31 27 27 25 25 25 19 21 21 35 332 39 31 31 33 28 28 27 25 25 21 23 23 36 349 40 32 32 35 29 29 30 26 26 24 23 23 37 318 21 21 19 37 30 30 31 27 27 25 25 25 38 332 23 23 21 39 31 31 33 28 28 27 25 25 39 349 23 23 24 40 32 32 35 29 29 30 26 26 40 318 25 25 25 21 21 19 37 30 30 31 27 27 41 332 25 25 27 23 23 21 39 31 31 33 28 28 42 349 26 26 30 23 23 24 40 32 32 35 29 29 43 318 27 27 31 25 25 25 21 21 19 37 30 30 44 332 28 28 33 25 25 27 23 23 21 39 31 31 45 349 29 29 35 26 26 30 23 23 24 40 32 32 46 318 30 30 37 27 27 31 25 25 25 21 21 19 47 332 31 31 39 28 28 33 25 25 27 23 23 21 48 349 32 32 40 29 29 35 26 26 30 23 23 24 49 318 19 21 21 30 30 37 27 27 31 25 25 25 50 332 21 23 23 31 31 39 28 28 33 25 25 27 51 349 24 23 23 32 32 40 29 29 35 26 26 30 52 318 25 25 25 19 21 21 30 30 37 27 27 31

Table 46: Development of the feed load from start-up. Maximum feed load is at 24 weeks (red box)


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Feed

Faeces

Excretion

Respiration

Growth

Figure 25: Nutrient budget model to calculate waste production (N, P and COD) originating from the feed supplied.

Waste production

Production of fish inevitably causes production of waste. Examples are faeces production, excretion of ammonia (NH3) and carbon dioxide (CO2), and consumption of oxygen (O2). This waste is excreted into the water in which the fish live, thereby deteriorating the water quality. Therefore a constant water flow is needed to remove these wastes from the fish. In order to calculate the flow rates required (see section Flow rates) one needs to know the amount of waste produced per unit of time. In this case study this is done with the Nutrient Budget model (Figure 25) for nitrogen (N), phosphorus (P) and Chemical Oxygen Demand (COD). COD is the amount of oxygen needed to oxidise 1 kg of material, and can thus be used as a common denominator to characterise the organic content of fish, feed, waste and bacterial material. The organic fraction consists of protein, fat and carbohydrates. Protein is not oxidised completely, organic nitrogen is not oxidised. COD can be calculated from the composition of the organic matter as the sum of 1.38 * protein, 2.78 * fat and 1.21 * carbohydrates. Note Organic nitrogen can also be oxidised, as can NH4-N, to NO3-N. This theoretically requires 4.57 g O2 /g N. Adding this to the amount of COD will give the total oxygen demand (TOD). In the process of feed utilisation and growth, the fish themselves also oxidise part of the feed organic matter. The oxygen consumption of the fish (respiration) can therefore directly be expressed in COD (1).

Fish weight Protein Fat Ash P E COD DigN DigP DigCOD

Stocking Harvesting % % % % kJ/g g/kg % % %

70 845 38 11 11.1 1.2 18.4 1 192 0.90 0.60 0.85

Table 47: Feed composition and digestibility of N, P and COD.

In order to calculate the amount of waste produced when feeding 1 kg of feed one needs to know the composition and digestibility of the feed (Table 47) and the composition of the fish (Figure 26). The excretion of N and P can be calculated as the difference between digestible intake (feed minus faeces) and growth. The oxygen consumption of the fish can be calculated as: CODrespiration = (MEm + [1-kg] * ED) / OCE (1) where:

MEm = energy requirement for maintenance, for tilapia 65 kJ/kg0.8/d ED = energy deposition (growth in energy, kJ/fish/d) kg = marginal efficiency of energy deposition, for tilapia 0.7 OCE = oxycaloric equivalent, 14.2 kJ/g O2

Based on these steps, the waste production at the maximum feed load on the 100 MT tilapia farm in the present case study is given in Table 48. Although there is no direct excretion of COD by the fish, there still is a small amount of COD missing from the budget (CODrest). This amount, probably from dissolved uneaten feed and faeces, is treated as ‘CODexcretion’.


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Figure 26: Whole body composition of ZonAquaculture B.V. tilapia as influenced by body weight.

Box 2. Calculation of the waste production at the maximum feed load.

The body composition of the fish of cohort 8 is: Nfish = 0.16 * 13.5 * 126 0.03 * 10 = 25.0 gN/kg, Pfish = 0.17 * 4.2 * 126 -

0.006 * 10 = 6.9 gP/kg, CODfish = 275 * 126 0.1 = 446 gCOD/kg and Efish = 4.5 * 126 0.09 = 7.0 MJ/kg. Note Fish protein contains 16% N and fish ash contains 17% P.

The composition and digestibility of the feed can be taken from table 4. Feed protein also contains 16% N.

The amounts of N, P and COD fed can be calculated e.g. Nfed = 24 (kg fed) * 0.0608 (kgN/kg feed) ≈ 1.43 kgN/d.

The amounts of N, P and COD in faeces can be calculated from the digestibilities as e.g. Nfaeces = (1 – 0.9) * 1.43 = 0.14 kgN/d.

The amounts of N, P and COD grown can be calculated as e.g. Ngrowth = 21 (kg growth) * 0.025 (kg Nfish/kg) ≈ 0.52 kgN/d.

For N and P the excretion can be calculated as e.g. Nfed – Ngrowth – Nfaeces = 1.43 – 0.52 – 0.14 = 0.76 kgN/d.

To calculate the COD respired by the fish one first has to calculate the energy deposition: ED = 21 (kg growth)* 7.0 (MJ/kg) = 147 MJ/d. The CODrespFish is then [(65/1000 * 0.126 0.8 * 6,852) + (1 – 0.7) * 147 ]/14.2 ≈ 9.6 kgCOD/d.

The CODrest is then CODfed – CODgrowth – CODfaeces – CODrespFish = 28.1 – 9.4 – 4.2 – 9.6 = 4.9 kgCOD/d.

protein = 13.5 bw 0.03

ash = 4.2 bw -0.006

fat = 3.1 bw 0.19

energy = 4.5 bw 0.09

COD = 275 bw 0.1

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Tank 1 2 3 4 5 6 7 8 9 10 11 12 Total Cohort 1a 1b 5 2a 2b 6 3a 3b 7 4a 4b 8 Weeks 24 24 12 21 21 9 18 18 6 15 15 3 BodyWeight 845 845 368 716 716 273 592 592 193 476 476 126 24.5 max Stock (MT) Number 3414 3414 6836 3415 3415 6840 3416 3416 6845 3417 3417 6852 Feed 32 32 40 29 29 35 26 26 30 23 23 24 349 kg/d FC 1.46 1.46 1.30 1.43 1.43 1.25 1.39 1.39 1.19 1.35 1.35 1.12 1.34 - Growth 22 22 31 20 20 28 19 19 25 17 17 21 261 kg/d Nfish 26.4 26.4 25.8 26.3 26.3 25.6 26.2 26.2 25.3 26.0 26.0 25.0 Pfish 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9 CODfish 540 540 496 531 531 482 521 521 465 509 509 446 Efish 8.3 8.3 7.7 8.1 8.1 7.5 8.0 8.0 7.2 7.8 7.8 7.0 Nfeed 60.8 60.8 60.8 60.8 60.8 60.8 60.8 60.8 60.8 60.8 60.8 60.8 Pfeed 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 CODfeed 1192 1192 1192 1192 1192 1192 1192 1192 1192 1192 1192 1192 DigN 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 DigP 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60 DigCOD 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 Nfed 1.96 1.96 2.46 1.74 1.74 2.13 1.61 1.61 1.81 1.40 1.40 1.43 21.2 kg/d Ngrowth 0.58 0.58 0.80 0.53 0.53 0.72 0.50 0.50 0.63 0.44 0.44 0.52 6.8 kg/d 32 % of intake Nfaeces 0.20 0.20 0.25 0.17 0.17 0.21 0.16 0.16 0.18 0.14 0.14 0.14 2.1 kg/d 6 g/kg feed Nexcretion 1.18 1.18 1.41 1.04 1.04 1.20 0.95 0.95 1.00 0.82 0.82 0.76 12.3 kg/d 35 g/kg feed Pfed 0.39 0.39 0.48 0.34 0.34 0.42 0.32 0.32 0.36 0.28 0.28 0.28 4.2 kg/d Pgrowth 0.15 0.15 0.21 0.14 0.14 0.19 0.13 0.13 0.17 0.12 0.12 0.15 1.8 kg/d 43 % of intake Pfaeces 0.15 0.15 0.19 0.14 0.14 0.17 0.13 0.13 0.14 0.11 0.11 0.11 1.7 kg/d 5 g/kg feed Pexcretion 0.08 0.08 0.08 0.07 0.07 0.06 0.06 0.06 0.04 0.05 0.05 0.02 0.7 kg/d 2 g/kg feed CODfed 38.4 38.4 48.2 34.1 34.1 41.7 31.6 31.6 35.5 27.4 27.4 28.1 416 kg/d CODgrowth 11.9 11.9 15.4 10.6 10.6 13.5 9.9 9.9 11.6 8.7 8.7 9.4 132 kg/d 32 % of intake CODfaeces 5.8 5.8 7.2 5.1 5.1 6.3 4.7 4.7 5.3 4.1 4.1 4.2 62 kg/d 179 g/kg feed CODrespFish 18.1 18.1 19.9 16.0 16.0 16.2 14.0 14.0 12.9 11.9 11.9 9.6 179 kg/d 512 g/kg feed CODrest 43 kg/d 124 g/kg feed

Table 48: Waste production at the maximum feed load


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Flow rates

A constant flow of water is required through the fish tanks to remove the waste, and replenish the oxygen, to such an extent that the water quality remains within acceptable limits for the fish. The treatment units also need a flow of water to provide them with the waste to be treated. The general formula to calculate the required flow rates is: Flow = abs [ k * P / ∆C] (2) Flow = Flow through the respective compartment (m3/time) k = a factor to correct for the daily variation in waste production (k ≥ 1) P = production (or consumption for O2) of waste (g/time) ∆C = the difference between Climit (the limiting (=outflow) concentration of the waste substance in question) and Cin (the inflow concentration of that waste substance), both in g/m3. Because some productions are negative and also the concentration difference has opposite values for the fish tanks and the treatment units, the absolute value is taken. This formula only works for more or less ideally mixed substances, and is therefore not applicable for suspended solids, which can occur in a variety of particle sizes, from whole feed and faecal pellets of several mm to particles of µm size. Some deviations also can occur under extreme plug flow conditions, for example in long rectangular tanks with a large hydraulic residence time. In Table 49 water quality limits and k-values for tilapia are given, along with choices made in the present case study and some water quality parameters for nitrification and denitrification (see also section Treatment systems) .

Water quality parameters Fish k - value Nitrification Denitrification

Range Choice Range Choice

Temperature (°C) 24-28 27 27 27

pH (-) 5.5-7.5 7 7 7

NH3-N (g/m3) 0.01-0.1 0.01

TAN (g/m3) 1.5 1-2 1.4

NO2-N (g/m3) 0.05-1 1

NO3-N (g/m3) 100-200 165 1-2 1 10

O2 (g/m3) 4-6 4.5 1-1.2 1.2 4.5

CO2 (g/m3) 15-20 15 1-1.2 1.2

COD dissolved (g/m3) 100-300 200 1-2 1

Suspended solids (g/m3) 25

Table 49: Water quality limits and k-values to correct for daily variation in waste production

Since it has been shown in section Waste production that the waste produced (P) is most conveniently expressed per kg of feed, it follows that the flow rates are also expressed per kg of feed. Flows through the different compartments of an aquaculture system, depending on configuration (flow through, reuse, RAS), are shown in Table 50. It can be seen that a flow through system needs large amounts of water, because the system exchange flow equals the flow through the fish tanks. By adding treatment systems, the system exchange flow can be reduced, at the expense of added flows through these treatment systems. For some treatments, which are applied in the fish tank inflow (oxygenation) or in the fish tank itself (aeration), no added flows are needed. Oxygenation and aeration actually reduce the flow through the fish tanks, and therefore also the system exchange flow. Systems with reductions in system water exchange flow of down to 15% of that in a flow through system are called reuse systems, with larger reductions we speak of recirculating systems (RAS). It can be seen that where a conventional RAS reduces the required system water exchange flow to 1% of that of a flow through system, integrating an USB-MDR gives a further reduction down to 0.15%.


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Flow through Reuse Conventional USB-MDR

Fishtank exchange TAN 32 32 61 74 O2 204 59 59 59 CO2 94 37 70 74 Suspended solids ? ? ? ?

Choice (maximum of above) 204 59 70 74

System exchange Fish tank exchange 204 59 NO3-N 0.187 0.029

Flow suspended solids removal Fish tank exchange n/a n/a 70 74

Flow nitrification Fish tank exchange n/a n/a 70 74

Flow denitrification NO3-N n/a n/a n/a 0.210

n/a = not applicable

Table 50: Water flows through the system compartments in m3/kg feed.

Treatment systems

In the above section Flow rates, it was shown that adding treatment systems can reduce the system water exchange flow. The choice of which treatment to add is based on the first limiting waste component. For example it can be seen in Table 50 that by adding oxygenation to a flow through system the required system exchange flow is reduced from 203 to 94 m3/kg feed, i.e. the first limiting waste is oxygen (-depletion). The first limiting waste after that is CO2, and so on. In this section the treatment systems will be discussed in order of consecutively first limiting wastes. For most treatment systems only the basics will be covered. Denitrification, in particular with the use of an USB-MDR, will be discussed more extensively. Two treatment systems, which do not actually reduce the system water exchange but do increase the sustainability of the farming system, heat exchange of ventilation and sludge treatment, will also briefly be mentioned.

Oxygenation

Oxygen can be added to the culture water by aeration, bringing water in contact with air, and oxygenation, bringing water in contact with oxygen enriched gas (technical oxygen). With aeration the oxygen content can only be increased up to saturation. With oxygenation the inflow water can be supersaturated. This does not mean that the water in the fish tanks is supersaturated, in completely mixed systems the water in the tanks equals the outflow concentration (see section Flow rates). In the present case study the water is oxygenated at entering the fish tanks in low head oxygenators with a gas-liquid ratio (G/L ratio) of 0.05.

Box 3. Calculation of flow rates in a RAS with an USB-MDR.

Fishtank exchange

For TAN, in flow through and reuse systems ∆C = Climit (assuming no TAN in the influent) and therefore the Flow = abs[1.5 * 35 / 1.5] = 35 m3/kg feed. In RAS the flow through the fish tanks for TAN is the same as the required flow through the nitrification filter (box 7), 61 m3/kg feed for the conventional RAS and 75 m3/kg feed for the RAS with an USB-MDR.

For O2 , P = -512 gO2/kg feed and ∆C = -10.5 g/m3 (box 4), so the Flow = abs[1.2 * -512 /-10.5] ≈ 59 m3/kg feed.

For CO2 , P = 633 gCO2/kg feed (RQfish = 0.9) and ∆C = 10.3 g/m3 (box 5), so the Flow = abs[1.2 * 633 / 10.3] = 74 m3/kg feed. System exchange

For NO3-N, P remaining after spontaneous and USB-MDR denitrification = 4.8 gN/kg feed (= 1.7kg N/349 kg feed) and ∆C = 165 – 0 = 165 g/m3 , so the Flow = abs[1 * 4.8 / 165] = 0.029 m3/kg feed

Flow denitrification

For NO3-N, P remaining after spontaneous denitrification = (15,800/349) * 0.85 = 38.5gN/kg feed (box 10) of which 85% is denitrified, and ∆C = 10 – 165 = -155 g/m3 , so the Flow = abs[1 * (38.5 * 0.85) /-155] ≈ 0.210 m3/kg feed.


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Control parameters

Contact surface, contact time, gas-liquid ratio.

Carbon dioxide removal

Removal of carbon dioxide is achieved by de-gassing or stripping. Stripping can be done by aeration or by pumping the water over a packed bed stripping tower (trickling filter). In the present case steady bubble aeration is used, both in the fish tanks and in the moving bed nitrification filter.

Control parameters

Contact surface, contact time, gas-liquid ratio.

Suspended solids removal

Removal of suspended solids from aquaculture water is accomplished by gravitational methods (sedimentation, flotation, hydrocyclone) or filtration (course filters, microscreen filters). For all types the waste particle size distribution will dictate the design, indirectly through the weight distribution of the particles for the gravitational methods and directly for the filtration methods. In the present case study a microscreen drumfilter (80 µm mesh) was used.

Control parameters

Particle size distribution.

Nitrification

Removal of TAN from the culture water in aquaculture systems is generally accomplished by nitrification. Nitrification is the biological oxidation, by bacteria, of ammonia (NH3) to nitrate (NO3). This reaction goes in two steps, mediated by different bacterial groups, with nitrite (NO2) as intermediate. The overall reaction equation is

1g NH3-N + 4.25g O2 + 5.88g NaHCO3 � 0.26g COD + 0.98g NO3-N + 2.72g CO2 (3)

From this reaction it can be seen that the process consumes oxygen and alkalinity and produces, apart from NO3, bacterial biomass and CO2. For each g of TAN 4.25 g of O2 and about 1 equivalent of alkalinity is needed and about 0.26 g COD is produced. In aquaculture systems the nitrifying bacteria are generally grown on plastic media as so-called biofilms. The reaction rate is therefore expressed per surface of plastic medium, in g/m2/d. Since the substrates of the reaction, TAN and O2, have to diffuse into the biofilm, the reaction rate is dependent on the concentration of the limiting substrate. Due to diffusion kinetics this dependency takes the form of a ½ - order reaction; the rate depends on the concentration to a power ½ (or √[Concentration]).

Nitrification rate r (g/m2/d) = a * √[TAN] + b (4)

Box 6. Drum filter

For the design of the drumfilter a specific type can be chosen (http://www.hydrotech.se/en/solutions/drumfilters) based on the matrix of Flow (L/s), Temperature (°C), expected suspended solids load (g/m3) and mesh size (µm).

Box 5. CO2 stripping

Aeration in the fish tanks increases the effective ∆C = Climit – Cin for CO2 , or as Climit is fixed (15 g/m3), decreases the effective Cin. With a stripping efficiency SE the effective ∆C = ∆C / (1 – SE). In a RAS we do not know the actual Cin , but from the CO2 production of the fish (box 3) and the fact that in practice a flow of 70 m3/kg feed is sufficient in the conventional RAS we can calculate a stripping efficiency of 0.4 and an effective Cin = 4.2 g/m3 (∆C = 10.8 g/m3). In the RAS with an USB-MDR more CO2 is produced in the biological filters and the effective Cin of the fish tanks will be Cin = 4.7 g/m3 (∆C = 10.3 g/m3).

Box 4. Oxygenation

With the low head oxygenators the O2 concentration of the fish tank influent is brought up to 200% saturation = 15 g/m3 . With the limiting O2 concentration (= outflow concentration) of the fish of 4.5 g/m3 , ∆C = -10.5 g/m3 . Note From the technical oxygen use in practice, it is assumed that that all O2 needs, of the fish and the bacteria, are met by oxygenation and that the technical oxygen is applied with an efficiency of 80% (i.e. oxygen use = 1.25 * O2 needs)


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0.0

0.1

0.2

0.3

0.4

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0.6

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0.8

0.9

0 1 2 3 4N

itri

fic

ati

on

ra

te r

(g

/m2/d

)

TAN (mg/L)

O2 = 7.5 mg/L

O2 = 5 mg/L

O2 = 3 mg/L

Actual O2

Average

nitrification

rate

Figure 27: Nitrification rate (g TAN/m2/d) as affected by the concentrations of

TAN and O2. The average nitrification rate in the 100 MT tilapia farm in this case study is also shown.

The values of a and b depend on the type of nitrification reactor used. For the moving bed filter used in the present case study a = 0.65 and b = -0.1. The ratio of the concentrations of O2 and TAN at which one or the other becomes the rate limiting substrate is 3.6. These relations are shown in Figure 27, where it can be seen that at low TAN concentrations the reaction rate is dependent on that TAN concentration, while not at higher concentrations. The TAN concentration where the transition takes place, as well as the maximum nitrification rate, are dependent on the O2 concentration. Note When Climit for TAN is close to [O2]/3.6 , the average TAN concentration will be lower than [O2]/3.6 during part of the day and the average nitrification rate will also be lower. One can correct for this by taking [TAN]avg = Climit / k (for k see equation 2 in section Flow rates). The required flow through the nitrification filter is:

Flow (m3/time) = P / ∆C (5)

The control parameters for the design of the nitrification reactor are therefore the average concentrations of TAN and O2. They will determine the actual nitrification rate and thereby the required total nitrification surface and the required flow through the nitrification reactor. With the specific surface of the biofilter material (m2/m3), the required volume of biofilter material can be calculated.

Control parameters

The concentrations of TAN and O2 in the nitrification reactor.

Denitrification

Removal of nitrate (NO3) from the culture water can be carried out by denitrification. Denitrification is the biological reduction, by bacteria, of NO3 to N2 gas. Denitrification is done by facultative aerobic hetrotrophic bacteria. The denitrification reaction goes in a number of steps, with NO2, NO and N2O as intermediates. The overall reaction equation is

1g NO3-N + 4.4g COD � 1.54g COD + 1g N2 + 0.085g NH4-N + 5.49g NaHCO3 + 0.88g CO2 (6)

From this reaction it can be seen that the process consumes COD and produces, apart from N2, alkalinity and bacterial biomass. Each g of NO3-N can ‘oxidise’ 2.86 g of COD while 0.91 equivalent of alkalinity and 1.54 g COD are produced (0.35 g COD/g COD). Total COD demand is therefore 2.86 /

Box 7. Moving bed nitrification filter.

With Climit for TAN = 1.5 g/m3 and [O2 ] = 4.5 g/m3, [O2] / [TAN] is close to 3.6 and therefore the average [TAN] in the nitrification reactor is [TAN]avg = 1.5 / 1.4 ≈ 1.1 g/m3 and the nitrification rate r = 0.65 * √[1.1] – 0.1 ≈ 0.58 gN/m2/d.

The moving bed filter is filled with biorings with a specific surface of 800 m2/m3, so with the amount of N to be oxidised at the maximum feed load of 12.6 kgN (for the conventional RAS, see box 9), 12,600 / 0.58 / 800 = 28 m3 of biorings are needed. The moving bed filter is filled with a fill factor of 0.4 , so the total volume will be 27 / 0.4 = 71 m3. It is further assumed that 95% of the total volume is water, so the nitrification water volume is 0.95 * 75 = 67 m3.

The required flow through the moving bed filter is Flow = 12,600 / 0.59 ≈ 21,360 m3/d or 21,360 / 349 = 61 m3/kg feed. Note: ∆C and the flow were determined simultaneously by iteration.

For the RAS with an USB-MDR more N has to be oxidised (15.8 kgN/d, box 10) and therefore 34 m3 biorings are required (85 m3 total volume, 81 m3 water volume) and the required flow through the moving bed filter will become 74 m3/kg feed.


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water in

water out

sludge out

stirrer

Figure 28: Upflow Sludge Bed – Manure Denitrifying Reactor (USB-MDR).

(1 – 0.35) = 4.4 g COD / g N. However, if there is less COD available the reaction rate will be lower (Figure 29). Note Even when there is no COD available there still will be a small endogenous (‘starvation’) NO3-N removal. The COD utilised by the denitrifying bacteria can be of internal (faeces and uneaten feed) or external (e.g. methanol) origin. Denitrifying bacteria can be grown on plastic media as so-called biofilms or in suspended growth as bacterial soup (sludge). In this case study a stirred Upflow Sludge Bed (USB) reactor is used. The reactor is stirred to facilitate the escape of the nitrogen gas from the sludge bed. Internal COD, also called manure, is used, hence the name USB-Manure Denitrifying Reactor (USB-MDR) (see Figure 28). The required sludge volume for the denitrification reactor is determined by the sludge specific NO3-N removal capacity (gN/m3/d). This specific removal capacity depends on the COD/NO3-N ratio of the influent waste (Figure 29) and on the amount of bacteria present, the sludge density (gVSS/m3), which in turn is dependent on the up flow velocity (m/h) (Figure 30). Figure 29 shows that with the COD waste in an intensive tilapia farm the maximum removal rate is 45 gN/kgVSS. The endogenous removal rate is 16 gN/kgVSS. For simplicity it is assumed that the sludge removal rate decreases linearly with a decrease in COD/N ratio. Total volume of the reactor is determined by the ratio of sludge volume/total volume. The diameter and height of the reactor can be calculated from the total volume and the up flow velocity.

Control parameters

COD/NO3-N ratio in the influent waste, up flow rate.

Box 8. Upflow Sludge Bed - Manure Denitrifying Reactor (USB-MDR).

The COD/NO3-N ratio in the influent waste of the USB-MDR is 5.1 (box 10), which is above 4.4 (equation 6), so the sludge removal rate is maximal at 45 gN/kg VSS/d (Figure 9).

In the present case study we have chosen an up flow rate of 0.38 m/h, so the sludge density is -22.6 * 0.38 + 26.8 = 18 kg VSS/m3 (Figure 10), and the sludge specific removal rate is 0.045 * 18 ≈ 0.82 kg N/m3/d.

With 11.3 kg NO3-N available after spontaneous denitrification, 11.3 / 0.82 = 13.9m3 of sludge is needed. The total volume of the USB-MDR is 2 * 13.9. = 27.7.m3, which brings the hydraulic residence time at HRT = 27.7 / (349/24 * 0.210) = 9h. The sludge residence time can be calculated from the amount of sludge present (13.9m3 * 18kg VSS/m3 = 250kg) and the daily amount of sludge produced (14.9/1.42=10.5kg, box 10), as SRT = 250 / 10.5 = 24d.

The diameter of the USB-MDR can be calculated from the cross sectional surface, which in turn can be calculated from the flow through the USB-MDR (box 3) and the up flow rate. For flexibility we chose to install the USB-MDR as 3 units, each with a diameter of 2*√[(349/24 * 0.210/3) / π] = 1.8m. The height of the USB-MDR is calculated to be (27.7/3)/[(1.8/2)2 * π] ≈ 3.4m.

0

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0 1 2 3 4 5 6 7

Slu

dg

e r

em

ov

al r

ate

(g

N/k

g V

SS/d

)

COD / NO3-N ratio

Figure 29: Sludge specific removal rate as influenced by the COD/NO3-N ratio of the influent waste.

y = -22.6 x + 26.8

R² = 0.662

0

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0 0.2 0.4 0.6 0.8

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dg

e d

en

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Figure 30: Sludge density as influenced by the upflow rate in an USB-MDR.


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Heat exchange ventilation

An intensive tilapia farm has to be ventilated to keep the CO2 concentration in air within acceptable levels. Heat loss through ventilation air can be substantial, 40 kW in the conventional RAS in the present case study, equivalent to 44 000 m3 gas/year. Applying heat exchange to the ventilation air would save ca. 11 kW (12 000 m3 gas/year) and simultaneously reduce the amount of water evaporation from 2.7 to 0.5 L/kg feed.

Sludge treatment

To prevent a large diluted solids waste discharge (the backwash flow of a drumfilter contains less than 0.1% dry matter) and to reduce sludge disposal costs, sludge thickening can be applied. This can be done with solid removal methods as described above, sedimentation (digestion basin), flotation and microscreen filtration. Another filtration method is the use of Geotubes, high strength woven polypropylene geotextile bags often used for the containment and dewatering of sludge. In the present case study the drumfilter backwash sludge from the conventional RAS is thickened by flotation, giving a final sludge dry matter content of 2%. The USB-MDR sludge from the USB-MDR RAS is thickened with the use of Geotubes and polymer, giving a final sludge dry matter content of 9%.

9.2.3. Assessment of results of conventional RAS compared to RAS with MDR module

Results of the conventional RAS

The fluxes and the fate of the waste components at the maximum feed load in the conventional RAS are shown in Figure 31. From the water quality observed in practice in a ZonAquaculture conventional RAS it could be inferred that 98% of the dissolved N is oxidised and 50% of the dissolved COD. Further a spontaneous denitrification of 10% of the N oxidised is assumed.

Figure 31: Flux diagram of N, P and COD in the conventional RAS.


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Results of the RAS with an USB-MDR

The fluxes and the fate of the waste components at the maximum feed load in the RAS with an USB-MDR are shown in Figure 32. From the water quality observed in practice in a ZonAquaculture RAS with denitrification it could be inferred that 56% of the dissolved COD is oxidised. Further, a spontaneous denitrification of 15% of the N oxidised is assumed, while of the remaining NO3-N 85% is denitrified. The system water exchange could be reduced further, as there is still NO3 and COD available. However, accumulation of all known and unknown substances increases exponentially when lowering water exchange further.

Box 9. Calculation of N and COD fluxes in the conventional RAS.

The 2.1kg Nfaeces is removed by the drumfilter with an efficiency of 0.65, giving 1.38kg Nsolid and 0.74kg N (re)dissolved. Together with the 12.3kg Nexcretion there is 13.1kg Ndissolved, which is all assumed to be oxidized. Nitrification has a CODyield of 0.26g COD/g N, of which again 65% is captured by the drumfilter, adding 0.65*12.6*0.26*0.077 = 0.16kg N back to the Nsolid. The rest of the 1.0kg added to the Nsolid comes from yields (biomass growth) of the spontaneous denitrification and the COD oxidation (see below). Of the Noxidised 10% (1.3kg) is spontaneously denitrified, leaving 10.7kg NO3-N remaining. To keep a NO3-N concentration in the system of 165 g/m3, the system water exchange should be 10,700/165 = 65 m3/d, or 65,000/349 ≈ 186 L/kg feed.

The 62kg CODfaeces is removed by the drumfilter with an efficiency of 0.65, giving 41kg CODsolid and 22kg COD (re-) dissolved. Together with the 43kg CODrest there is 72kg CODdissolved, of which 50% (36kg) is oxidized. Heterotrophic bacteria have a CODyield of 0.30g COD/g COD, of which again 65% is captured by the drumfilter, adding 0.65*36*0.30/(1-0.30) = 10kg COD, which can be returned to the system as CODsolid. A further 3kg CODsolid is yielded from the nitrification (see above) and the spontaneous denitrification, giving a total solid COD waste discharge of 54kg. With a sludge COD content of 21.3kg/m3 (20kg/m3 dry matter, ash content 25%), this will result in a sludge flow of 54/21.3 = 2.5 m3/d, or 2,500/349 ≈ 7.3 L/kg feed.

Based on the total system water exchange of 65 m3/d, the system CODdissolved concentration will be 12,000/65 ≈ 177 g/m3.


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Figure 32: Flux diagram of N, P and COD in the RAS with USB-MDR


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Box 10. Effect of denitrification on the N, P and COD fluxes in the RAS with USB-MDR.

In the RAS with an USB-MDR 2.7kg more N is re-dissolved in the USB-MDR (see below), bringing the total Ndissolved to 15.8kg which is assumed to all be oxidized. After spontaneous denitrification (15%, 2.4kg), and taking into account all N incorporated into bacterial biomass (2.1kg), the remaining NO3-N (11.4kg) is assumed to be 85% denitrified, leaving 1.7kg NO3-N remaining. To keep a NO3-N concentration in the system of 165 g/m3, the system water exchange should be 1,700/165 = 10 m3/d, or 10,000/349 = 30 L/kg feed. Note: the figure of 85% was in fact chosen to maintain a system water exchange of approx. 30 L/kg feed as observed in practice.

In the RAS with an USB-MDR some additional CODsolid is available (58kg). The COD/NO3-N ratio in the influent waste of the USB-MDR is 58/11.4 = 5.1 gCOD/gN. Note It can also be seen that the CODsolid in the influent waste of the USB-MDR consists of 70% (41kg/58kg) of ‘fresh’ (faeces) waste and 30% of ‘recycled’ (bacterial biomass) waste.

The 9.7kg NO3-N denitrified, ‘oxidizes’ 28kg COD (9.7 * 2.86), producing [2.86/(1-0.35)-2.86] * 9.7 = 14.9kg CODyield, of which again 65% (ca. 10kg) is captured by the drumfilter. Together with the 15kg of remaining CODsolid this gives a total solid COD waste discharge of 25kg. In a Geotube about 95% of this is captured. With a sludge COD content of 95.9kg/m3 (90kg/m3 dry matter, ash content 25%), this will result in a sludge flow of (25*0.95)/95.9 = 0.25 m3/d, or 250/349 ≈ 0.7 L/kg feed.

From the water quality observed in practice in a ZonAquaculture RAS with denitrification, a COD concentration of ca. 200g/m3 and a phosphate P concentration of ca. 35g/m3, it can be inferred that 56% of the CODdissolved is oxidised, but that also there must be a sink of phosphorus in the system as the Pyield required to maintain such a concentration (P USB sludge = 0.21 gP/gCOD) is not seen in practice.


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9.2.4. Sustainability parameters

The sustainability parameters: resource use per kg harvested, nutrient utilisation as % of input, waste discharge per kg harvested, for the conventional RAS and the RAS with USB-MDR are shown in Table 51. It can be seen that the RAS with USB-MDR has substantially lower requirements for heat, water and bicarbonate. Although the RAS with USB-MDR has somewhat higher requirements for electricity, oxygen, labour (and investments) the actual production costs per kg harvested are 10% lower than for the conventional RAS. Waste discharge is reduced by integration of an USB-MDR by 81% for N, by 59 % for COD, by 61% for TOD, by 30% for CO2 and by 58% for TDS.



Resource use Waste discharge

Fingerlings (#/kg) 1.2 1.2 Nitrogen Feed (kg/kg) 1.22 1.22 Solid (g/kg) 8.5 2.6 Electricity (kWh/kg) 1.8 2.2 Dissolved (g/kg) 37.4 5.9 Heating (kWh/kg) 3.4 0.0 Phosphorus Water (L/kg) 238 38 Solid (g/kg) 4.5 7.2 Oxygen (kg/kg) 1.18 1.26 Dissolved (g/kg) 3.8 1.3 Bicarbonate (g/kg) 252 107 a COD Labour (h/MT) 12.5 13.1 Solid (g/kg) 189 84

Dissolved (g/kg) 40 9 Nutrient utilisation TOD Solid (g/kg) 227 95

Nitrogen (% of input) 32 32 Dissolved (g/kg) 48 11 Phorphorus (% of input) 43 43 CO2 (kg/kg incl gas) 1.58 1.10 COD (% of input) 32 32 TDS (g/kg) 62 28 TOD (% of input) 32 32 Conductivity (µS/cm) 1060 2000

a) In practice the need for bicarbonate (alkalinity) is actually nil when denitrification is applied.

Table 51: Sustainability parameters, resource use per kg harvested, nutrient utilisation as % of input, waste discharge per kg harvested.


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9.3. Module – Periphyton Turf Scrubber (PTS)


A periphyton turf scrubber (PTS) is a naturally developed heterogeneous assemblage of attached microorganisms, including microalgae and bacteria, which colonise a submerged surface in a phototrophic environment. The attached microorganisms have a high relative growth rate and regenerate quickly after disturbance. A number of benthic diatoms (centric, pennate, unicellular and filamentous), coccoid and filamentous cyanobacteria, and benthic filamentous green algae dominate in the turf. A variety of bacteria, protozoa’s and metazoans (e.g. nematodes, small annelids and microcrustaceans) are also associated with the turf. Periphyton is an excellent food source for many fish species in natural water. The more nutrients there are available in the culture environment the higher the nutritional quality of the periphyton. In growing, periphyton traps particulate and dissolved matter, both organic and inorganic, and as such maintains water quality favourable for aquatic organisms. Due to constant aeration, induced by wave action over the PTS, the periphytic biofilm develops in an oxygen rich environment, enhancing nitrification. In brief, the benefits from a PTS include the production of periphyton as additional food and the improvement of water quality. The use of a PTS in a recirculation aquaculture system (RAS) is innovative. In this project, the design criteria for a PTS in RAS were explored. PTS technology for water purification in RAS is commercially not viable, because a large indoor illuminated surface area is needed, from which the turf needs to be harvested regularly, making electricity and labour input very costly. Nevertheless, indications are that algal turfs reduce coliform bacteria in tertiary waste waster and, as such, can help to maintain a favourable microbial water quality in culture tanks in RAS. Optimal conditions could be achieved by integrating a small PTS in a RAS to prevent excessive bacterial development, while relying on solid removal and biofiltration units to maintain favourable water quality. Therefore, the design parameters developed for an intensive RAS will allow for the integration of PTS technology either as a small unit in RAS, or as a larger unit in outdoor systems.


Four identical lab scale recirculation aquaculture system (RAS units) were used in the experiments. Each system consisted of one 70 l fish tank, one 70 l sump containing one submerged pump (type Eheim 1250219, 28W, 230V/50Hz, maximum capacity of 20 l/m, supplying the trickling filter with a water flow of 6 l/m) and one electrical heater (type Heizer 300, 300W, 230V, maintaining a water temperature of 25 ± 2 °C), and one 40 l PTS tank. The fish tank was placed in such a way that vibrations from the PTS (due to the splashing water from the tipping bucket in the PTS) did not reach the fish tanks. Air was supplied to every system with air stones. A small trickling filter was added to each system to avoid peaks in NO2

- concentrations. Each system had a total system volume of 185 l. For all systems, the PTS tank had a surface area of 1.96 m2 and water depth of about 1 cm. Each PTS tank was provided with 3 mm mesh stainless steel screen which supported the periphyton growth and one plastic tipping bucket which filled and emptied 4 times a minute to create waves over the screens (6 l/min). Water from the outlet of the fish tank flowed into the PTS tank and then into the sump tank where the water was heated and pumped into the trickling filter before flowing back into the fish tank. Nile tilapia (Oreochromis niloticus) were stocked in each system at a density fluctuating between 2 to 5 kg per system and fishes were fed 8 – 11 g kg-0.8 d-1 with a 43-47 % commercial protein diet. The fishes were stocked at an individual average weight of 30-70 g.


The HSL and C/N ratio studies were executed at low light intensity. The experiment comparing high and low light intensity showed that light strongly affects the water quality in the system, and to a lesser extent the amount of periphyton produced. In ponds, when periphyton grows on poles or at shallow bottoms, no sludge will be trapped and most of the sludge will sink to the bottom. Less oxygen is available at pond bottoms than in the PTS and excessive accumulation of organic matter will make the bottom quickly anaerobic. By increasing the C/N ratio from 10 to 20, mineralisation of organic matter proceeds more quickly, and less organic matter accumulates at the bottom. Hence operating periphyton systems at a high C:N ratio can be recommended. Per kg of feed (91 % dry matter) 70 g AFDM periphyton was harvested at low light intensity, 158 g AFDM at high light intensity. 52% of the DM of periphyton collected was protein, indicating the periphyton produced is a good quality fish feed. A feed conversion ratio of 1.34 for periphyton AFDM can be achieved, and considering periphyton productivity, in a one hectare pond with a substrate area for periphyton development


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equal to the pond area, a tilapia production of 5000 kg ha-1 yr-1 could be achieved (assuming a periphyton productivity of 2.5 g m-2 d-1 and a utilisation of 75%. In all experiments, the combination of PTS and trickling filter was sufficient to maintain favourable water quality for Nile tilapia production. Nitrification in both trickling filter and PTS contributed considerably to nitrification in the system, and in all cases water exchange was necessary to keep the NO3-N concentration below 150 mg l-1. Of the N input through feeding, 20-30% was discharged with exchange water. Small amounts of the input P and N were recovered through the harvested periphyton; 3% of N in the C/N ratio experiment, 9% in the HSL study and 5.6 – 9.0% in the light intensity study. For phosphorous, the amounts recuperated were 1.6% in the C/N ratio study, 12% in the HSL study and 3.2 – 4.9% in the light intensity study. Evidently, the periphyton production was very different between the three studies, even at the same light intensity. Particularly, for the C/N ratio study the periphyton production declined during the study, while this was not the case in the light intensity study. The reason for this is not clear.


The sludge accumulating in the system was an important sink for nutrients. Roughly 50% of the sludge accumulated in the PTS, the other 50% in the sump. Removing the sludge from the PTS only at the end of the experiment, or at weekly intervals, resulted in similar accumulation rates. Looking at the nitrogen mass balance 7% of the input N was removed with the sludge from the PTS in the HSL study, compared to 10 % in the C/N ratio study and 5-9% in the light intensity study. For input P, 11, 7-8 and 13-17% of the input P was removed in the PTS, C/N ratio and light intensity study, respectively. When combining the sludge and periphyton removal from the PTS, 15-30% of the input N or P were harvested, and could be processed for further use. This is an advantage over open systems, where the nutrients disappear from the system without the option to reuse them.

9.4. From a case study to a fish farm: How to manage a model fish pond producing 5 metric tonnes fish per year with the PTS module

With the PTS study, the production of periphyton and the effect on water quality were calculated per m2 biofilm. The effect of periphyton on production in extensive ponds has been tested extensively by the Wageningen research team. The performance parameters of the PTS case study were used to conceptualise an intensive pond as part of a recirculation unit.

9.4.1. Description of the production unit

Parameters for an intensive common carp pond as part of a recirculation unit are given in Table 52. The maximum fish density in the fish tank/pond is 15 kg/m3, the size 333 m3. The water depth is 80-100 cm. The aeration, circulation and overflow of the fish tank/pond is undertaken by airlifts (driven by pressurised air). The water head created by the airlifts is enough to circulate the water through the whole system. From the fish tank/pond the water flows to a sedimentation pond, with a sedimentation pit. The sedimentation pit is emptied weekly (a volume of about 10 m3 m). The collected sludge can be used as a fertiliser. The water flows by gravity through an overflow tank to a periphyton pond. This is a pond with an installed surface area twice the surface area of the pond. The maximum fish density in the periphyton pond is 0.5 kg/m2. The culture duration is about 6 months. Common carp is stocked at a density of 28 50-g fish m3. Fish grow to 500-550 g in 180 days. The biomass harvested is ± 5000 kg. A 40% protein diet is used. The initial feeding load is 10.1 kg d-1, the final feeding load is 67.8 kg d-1. About 1.5 months after stocking the common carp, 25 g all-male tilapias are stocked in the periphyton pond at a density of 2 fish m-2. The fishes grow to a maximum size of 300 g in 4.5 months. No feed is administered.

Farm's nutrient budget

The sludge removed from the pond bottom will be rich in N and P, and can be a good fertiliser for agricultural crops. The feed donated to the system is 6200 kg 40 % protein feed. 17 % of N input and 23% of the P input will be recovered in the sludge. In the periphyton pond N and P are trapped by the phytoplankton and the periphyton. Due to grazing by tilapia the plankton and periphyton will remain in a productive state (Table 53).

Fish tank 333 m2

Sedimentation pond 300

Periphyton pond 1000

Substrate area 2000

Water flow 15 l/sec

Fish production Fish tank: common carp

Periphyton pond: tilapia/carp

Table 52: Parameters for production unit


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Water use

Except for the sludge, no water leaves the farm. In addition, water loss from evaporation is compensated for. If constructed new, all ponds are lined, hence seepage losses should be negligible. The total surface area is close to 2000 m2 and the expected evaporation loss is 3000 m3.

9.4.2. Advantages and disadvantages of the intensive pond/periphyton system

Advantages:

• Nutrient retention and recovery of N and P in the system is very high: 38 % of the input N and 60 % of the input P is retained in fish. In addition, considerable fractions of the N and P input are recovered in the sludge, which can be an excellent fertiliser.

• The large biofilter surface in the system (pond surface area + area on poles) will stabilise water quality. The turnover rate in the fish tank/pond is 4 times a day, while the retention time in the periphyton pond is 1.6 days. For phytoplankton development this is short, avoiding excessive plankton blooms, while for the attached biofilms this is not a problem.

• Very low environmental impact

• Low risk of infections by pathogens and parasites

• Low requirement for medicines and chemical treatment

• Annual production cycle, with stocking tilapia during the hottest months of the year.

• If land is available adjacent to the sedimentation tank, additional income can be generated from vegetable crops.

• Risk of ammonia intoxication negligible.

• Production 5 to 10 times higher than from traditional extensive pond farming, hence smaller land use. More land available for nature development, or other activities.

Disadvantages:

• Relatively large production area is needed, with high initial investment.

• Constant aeration needed, which implies high energy costs.

• Backup power source required.

• Reliable source of fingerlings needed in spring each year

• A 5 MT unit is still very small. A pilot unit should be tested in practice.

Description kg

Total feed (40% prot, 1.2% P) 6 200 Total N in feed 397 N in sludge 77 N in periphyton 40 N in phytoplankton 24 Total P in feed 74 P in sludge 17.5 P in periphyton 3.6 P in phytoplankton 3.3 N recuperated in common carp 136 P recuperated in common carp 40 N recuperated in tilapia 16 P recuperated in tilapia 4.8 % Unaccounted for N 104 26 Unaccounted for P 5.7 8

Table 53: N and P data for an intensive common carp/tilapia production unit

SUSTAINAQUA HANDBOOK Case study in Switzerland

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Figure 34: Functional scheme of Tropenhaus Ruswil

10. Tropical polyculture production with the integrated “Tropenhaus” concept – Case study in Switzerland

10.1. Introduction – General concept of the Tropenhaus in Switzerland

The Tropenhaus concept was developed to make economic use of waste heat from a gas compressor station serving the natural gas pipeline that runs from the Netherlands to Italy. It is located in the Canton of Lucerne in Switzerland. The annual waste heat production is about 100 GWH per year. Producing fresh, organically grown papayas, guavas, bananas, star fruit and tilapia from waste heat and organic feedstock, the Tropenhaus is a model case for ecological engineering and sustainability. The main objectives of the project were:

• to consider waste as a resource,

• to seek ecosystem-based design concepts,

• to aim for high level diversification,

• to aim for high-level system integration and

• to use renewable and CO2-neutral energy.

Figure 33: Densification plant as waste heat source for Ruswil Polyculture

In the year 1999, based on the South Asian polyculture production approach, an integrated fish and tropical fruit production was piloted in a 1 500 m2 greenhouse. Since inception, applied development and research work has been carried out to optimise production in terms of quality and quantity. A core element of the Tropenhaus system is the sustainable aquaculture module for Tilapia production. The nutrient-rich water of tilapia production is used for irrigation and serves as a fertiliser for the tropical fruit grown in the greenhouse. The 10 years of first-hand experience gathered with the Tropenhaus Ruswil project clearly proves that high quality, sustainably grown fish and fruit can be produced on an economically viable basis, using waste heat as the main source of energy supply. Due to optimisation of harvesting times and short transportation distances between the Tropenhaus and the end customer (private persons, restaurants, supermarkets etc.), the quality of the products (in terms of taste) is higher, compared to that of imported tropical fish and fruit. Based on the promising results of the pilot project, two larger projects with a total investment sum of ca. 40 Million € have been developed recently. Both projects are currently in the construction phase and are expected to start operating in mid 2009. COOP, one of the two biggest retailers in Switzerland, is convinced by the Tropenhaus concept and the SustainAqua project approach and actively


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promotes Tropenhaus products. In this way, a market development can be initiated to support farmers’ decisions to invest into more sustainable fish production. The new Tropenhaus itself will serve as a platform to disseminate the concept of sustainable aquaculture and the results of SustainAqua to a broader audience in the coming years. Thus, as a very attractive “model case for sustainability”, it contributes to creating awareness for sustainable fish production amongst fish farmers, consumers, retailers, etc. Preconditions for the implementation of a „Tropenhaus System”:

• Waste heat based on process heat from industrial plants, biogas based heat-power plants, geothermal installations, etc. (1.5 – 2 MW / 10 000 m2)

• Access to markets for tropical fruit and fish

• Soil: No specific requirements but cold soil water flow is not recommended

• Topography: Flat to slightly sloped

• Radiation: Good exposition to solar radiation In the SustainAqua project, the Tropenhaus system was investigated and further developed. The research focused on the following topics:

• Integration of crustaceans in the tilapia production

• Fish feed out of biomass that was produced as by-products in Tropenhaus

• Applicability of the aquaponic filter After briefly presenting the results regarding the crustaceans and fish fodder, which are not yet finalised for commercial upscaling, the aquaponic filter will be presented in detail.

10.2. Integration of crustaceans in tilapia production and fish feed from tropical plants


Crustaceans

The tropical plants (amongst others: papayas, guavas, bananas, star fruits) grown in the Tropenhaus thrive and therefore produce a lot of plant material that has not been used intensively so far. Crustaceans in general are very good exploiters of plant material and wastes from aquaculture such as sludge, fish faeces or dead fish. The integration of crustaceans in the existing tilapia production has the potential to:

• diversify the production

• enhance the nutrient management

• use water more intensively and

• increase the economic performance of the system The isopod crustacean Asellus aquaticus is very tolerant to poor water quality and oxygen deficits. Its culture in tanks integrated into recycling systems, provided with aquaculture wastewater, is quite easy and may supplement the fish fodder of cultured fish with natural food, rich in bioactive compounds. The waste discharged from intensive aquaculture such as suspended solids and dissolved nutrients can, beside others compounds, contribute to fish nutrition as a complementary feeding approach. Natural food items provide essential amino acids, fatty acids and other nutrients necessary for an appropriate development of a fish organism. Studies on rainbow trout prosperity in pond culture, based on artificial feeding regime with a minor proportion of natural food items, proved a significant improvement of fish flesh quality and vitality in comparison with intensive, land based flow-through systems with exclusively artificial pelleted diets.

Fish feed from biomass of the Tropenhaus

The climatic conditions in the greenhouse are not favourable to the composting of plant by-products; this leads to additional costs for the handling and composting of this material. Using the material as fish feed has the potential to improve the nutrient cycle of the greenhouse and to reduce the amount expended on commercial fish feed.

10.2.2. Principles of the modules

Crustaceans

Asellus aquaticus was kept in a shallow tank together with filamentous algae. A small part of the water circulating in the fish tank–filter–system was diverted to the Asellus tank from where it drained back to the fish water circuit. The Asellus were fed with the sludge (fish faeces, fish fodder, etc.) that accumulated in the fish water, with filamentous algae growing in the Asellus tank itself and with the windfall papayas.


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Figure 35: Flow schema of the Asellus system

Figure 36: Results of biomass feeding experiment


Different plant by-products from the tropical plants grown in the Tropenhaus were chopped into small pieces or pre-treated by composting. In the feeding experiments, parts of the commercial food pellets were replaced by this material for feeding fish or crayfish.

10.2.3. Assessment of experiments

Crustaceans

The Asellus population developed well and was stable. The comparison of different substrates suitable for this culture showed that the integration of crustacean culture into recycling farming units might also bring about other benefits. By far the highest production of Asellus was recorded when using filamentous algae (Cladophora) as a substrate. The benefit of this substrate also lies in its suitability for direct Tilapia feeding together with the attached Asellus, which grow on the algae. Furthermore, dense mats of Cladophora may also serve as an efficient agent in the removal of suspended solids (organic particles). Retained organic particles provide an excellent food basis for Asellus (and are even suitable food for Tilapia when using the extra biomass of Cladophora directly attached to the Asellus for feeding). Lower, but still efficient production of Asellus was achieved when using the sludge from filters as a substrate. The advantage of the sludge as a substrate consists in effective treatment and utilisation of certain RAS wastes, but at a very low level. Similar production of Asellus was also achieved with the aquarium and ornamental plants Ludwigia and Eichhornia as substrates. Besides benefits of Asellus production and certain retention of suspended solids (by Eichhornia in particular) and nutrient removal, these plants also represent marketable by-products.


Figure 36 summarises the results of this experiment. Replacing Skretting by Compost, EM Compost, Bokashi, Taro or Papayas shows remarkable results. Nevertheless, it is recommended to use this biomass-based fodder only as an additional “co-feeding” to Skretting.


For both modules, further research is necessary. Possible success factors and constraints are indicated below.

Crustaceans

The experience in the Tropenhaus, together with the substrate experiments show that the production of Asellus aquaticus is feasible in a warm water aquaculture such as the Tropenhaus. It may contribute to produce natural food, rich in bioactive compounds to supplement the usual diet for cultured fish. Asellus can be fed with the sludge suspended in the fish water but also with plant leftovers. When using filamentous algae as substrate, this can be fed together with the attached Asellus to the fish. Dense mats of Cladophora may serve also as an efficient agent in suspended solids (organic particles) removal. Retained organic particles provide an excellent food basis for Asellus production and even suitable food for tilapia when using the extra biomass of Cladophora with attached Asellus for direct feeding.


The use of plant biomass produced in the Tropenhaus as fish fodder is a promising option to diversify the fish diet. However, it cannot replace the conventional fodder. Still, it can be an additional natural food rich in bioactive contribution. Since the stomach capacity of Tilapia is not reached by conventional feeding the additional fresh food does not compete with the dry feed but could even complement the diet.


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10.3. Warm water aquaponic filter in a "tropical" polyculture system


Each aquaculture module in the Tropenhaus consists of:

• one fish tank,

• one pond filter for the water treatment unit and

• a pump for circulating the water. In one of the modules, a new aquaponic filter was installed and assessed. The aquaponic filter consists of slotted plastic boxes filled with expanded clay pellets on which tropical plants are cultivated. The water coming from the fish tanks is charged at the top of the boxes from where it trickles through the expanded clay pellets. The slots, located at the bottom and the sides of the boxes, facilitate aeration of the filter and therefore prevent anaerobic conditions. Plant roots that establish themselves at the bottom of the filter help to improve the mechanical performance of the filter and provide a habitat for microorganisms. Aquaponic filter system with tropical fruit plants (Photo: IEES)


A system with an aquaponic filter and a system with the commonly used “conventional” pond filter were operated in parallel in order to compare the individual results. Each of these systems had a round steel tank with a membrane and a floor heating system. The tanks had a diameter of 5.5 m and were filled with 10 m3 water. The temperature of the water was 25 °C. The water was pumped through the filter system units twice an hour. Daytime temperature was 23 °C and night time temperature was 18 °C. The water in the fish tanks was used for irrigation of the greenhouse. The tanks were refilled with rainwater collected on the roof of the greenhouse. The aquaponic filter consists of 40 plastic boxes with slitted walls and bottoms. Each box was filled with 60 L of expanded clay pellets with a diameter of 13 mm – 20 mm. The total filter volume was 2.4 m3. A tube charges each box with water coming from the fish tank. The aquaponic filter contains the following principle innovations:

• Water treatment: Expanded clay pellets replace the water body

• Crop production: Aquatic plants are replaced by fruits and vegetables

• Construction: Installation on ground level is possible The system is illustrated in the following figure.

Figure 37: Flow scheme of the aquaponic filter system compared to the "conventional" pond filter


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Table 54 summarises the results regarding the SustainAqua sustainability indicators, comparing the innovative aquaponic filter with the pond filter. It clearly shows the improvement regarding nutrients efficiency and output respectively, and the increase of productivity resulting in lower labour costs.

Results System with aquaponic System with pond filter

Energy efficiency Energy consumption per tilapia produced [kWh/kg] Energy consumption per

tilapia produced [kWh/kg]

Total 214.43 Total 157.41

Heat 214.38 Heat 157.36

Electrical 0.05 Electrical 0.05

Water input Water input per tilapia produced [m3/kg]

1.4 Water input per tilapia produced [m3/kg]

1.4

Water output Water output per tilapia produced [m3/kg]

1.4 Water output per tilapia produced [m3/kg]

1.3

Nutrients: Utilisation efficiency N in tilapia biomass / N input [kg/kg] 0.28 N in tilapia biomass /

N input [kg/kg] 0.24

P in tilapia biomass / P input [kg/kg] 0.32 P in tilapia biomass /

P input [kg/kg] 0.27

Nutrients Output N load in output water / N input (fishbone) [kg/kg] 0.21 N load in output water /

N input (fishbone) [kg/kg] 0.22

P load in output water / P input (fishbone) [kg/kg] 0.17 P load in output water /

P input (fishbone) [kg/kg] 0.29

Nutrients re-use for valuable by-products

N content in by-products / N input (fishbone) [kg/kg] 0.01 N content in by-products /

N input (fishbone) [kg/kg] 0.00

P content in by-products / P input (fishbone) [kg/kg]

0.01 P content in by-products / P input (fishbone) [kg/kg]

0.00

Increase productivity per unit of labour

Time expenditure for system operation / products [h/kg] 0.04 Time expenditure for system

operation / products [h/kg] 0.27

Table 54: Key results of Aquaponic filter

Fluctuations in Ammonia, Nitrite, Nitrate, O2 and COD

The ammonia concentrations are the same and remain relatively low in both fish tanks over a wide range of time. At the end of August, the ammonia level suddenly rose in both basins. However, the measured ammonia concentrations in the fish tank with pond filter proved to be higher than in the tank with the aquaponic filter. The nitrite concentrations are generally also low. Yet, also here, there are some peaks in the fish tank with pond filter, whereas the nitrite concentration in the tank with aquaponic is more balanced. The nitrate concentrations show variations of approximately the same magnitude in both basins. The oxygen concentration varies between 1.5 and 7.2 in the fish tank with pond, and between 5.9 and 7.9 in the fish tank with aquaponic filter. COD levels are approximately the same in both tanks with the exception of a peak in the aquaponic tank in the middle of April.


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Figure 38: Comparison of fluctuations in Nitrite concentration


The aquaponic filter proved to be a cost effective way for water treatment in systems like the Tropenhaus, where the aquiculture is combined with plant production. It can be installed on the cultivated area of the greenhouse providing the same plant productivity as the remaining cultivated area. Compared with a pond filter, less work is needed for the maintenance (particularly de-sludging) of the treatment system. For the cultivation of the plants, no additional work is needed over and above that for the normal plant production. The aquaponic filter also shows a better biological performance than the pond filter, especially for the parameters ammonium and nitrite, which are both toxic to fish. When the aquaponic filter cannot be integrated in the cultivated area, the additional space requirement may be a disadvantage compared to a pond system hanging over the fish tank. Another drawback is the necessary water distribution to each single box of the filter, which requires a complex distribution system.


Compared with the pond filter, the tested aquaponic filter has some basic advantages:

• Added value due to higher economical yield from the crop

• Less fluctuations of nutrient concentrations in the fish tank

• Easy to integrate into existing system without expensive modifications

• Filter maintenance is less work intensive The new aquaponic filter is a show case of ecological engineering where “ecosystem concepts are used to serve society” and “waste is considered a resource”. Expensive manual or technical de-sludging are replaced by free natural processes. Wastewater of the tilapia ponds is used for the production of high quality by-products (tropical fruit and vegetables) and improves the economic performance of the integrated production system. The business plan of the new expanded Tropenhaus project, which includes the new aquaponic filter based fruit production, demonstrates this.


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10.4. From a case study to a fish farm: The design of a warm water aquaponic filter system in the “Tropenhaus Wolhusen”

10.4.1. Introduction: “Tropenhaus Wolhusen”

The “Tropenhaus Wolhusen” is based on the ten years of experience in the Tropenhaus Ruswil where industrial waste energy has been used to operate a tropical indoor polyculture system. The “Tropenhaus Wolhusen”, built in 2009, has a greenhouse area of 5 400 m2 which serves as the production unit. There is also an event house for about 55 000 visitors per year. The tropical polyculture comprises both a tropical garden where papayas, bananas and other tropical crop is grown, and an aquaculture incorporating aquaponic filters for tilapia production. The polyculture is powered by a waste heat source and solar energy and fish fodder serves as nutrient supply. Rainwater is harvested on the roof of the greenhouse. The fish water, enriched by the residual fish fodder, is used for the irrigation of the tropical garden and thus fertilises the plants. The outputs of this system are tropical fruit, fish and plant biomass. The event house covers a surface of 2 100 m2 and contains a tropical garden, a tilapia aquaculture, a restaurant and facilities where visitors can view ornamental tropical plants as well the same plants, which are used in the production greenhouse. The Tropenhaus Wolhusen is situated on an altitude of 680 m a.s.l. in a hilly area of the central Swiss pre-alpine zone. The region is characterised by agriculture and the greenhouse is surrounded by farmland. The climate regime can be considered temperate. The annual sunshine duration is about 1 300-1 400h. The mean annual precipitation in the region amounts to approximately 1 200 mm. The greenhouse is connected to a source of industrial waste heat providing warm water at a temperature of about 60 °C, which is used to heat the greenhouse, and the fish water. The target temperature for the greenhouse is 23 °C during daytime and 18 °C at night. The fish water temperature is 26 °C. The cultivated area is about 4 000 m2 and the annual production of tropical fruit (mainly papayas and bananas) amounts to around 60 t or more.

Figure 39: Plan of the Tropenhaus Wolhusen with the aquaculture

10.4.2. Description of the aquaculture unit

The fish production component consists of six aquaculture modules each equipped with two fish tanks and two aquaponic filters. The area necessary for a module is about 180 m2, including the 32 m2 required for the aquaponic filter.


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Figure 40: Schema of the aquaculture module

The two fish tanks of a module are interconnected with a tube for hydraulic compensation. The water for greenhouse irrigation is taken from one of the fish tanks into which the rainwater inflow is also directed. The extraction of water for irrigation is controlled by an irrigation computer, with the water re-feeding by a level control in the fish tank. The fish tanks are round steel tanks sealed with a PE membrane. The diameter is 5.5 m and the height is 1.6 m, the water depth is 1.3 m and the water volume 30 m3. The stocking density is 20 kg of fish per cubic meter water and the harvest is 920 kg per tank per year.

10.4.3. The Aquaponic Filter developed according to the results of the case study

The aquaponic filter is built of plastic boxes and filled with expanded clay pellets. The bottoms and walls of these boxes are slatted to facilitate the flow through of air and water. Tropical plants are cultivated in the boxes. The main crops are papayas and bananas, as in the remaining greenhouse, but also chilli, lemon grass, tarot and galangal. The crop production on the filter surface is at least the same per square meter as on the remaining surface of the greenhouse. The filter for a fish tank has 56 filter boxes. The filter is continuously charged with a load of 1 m3 per minute or about 18 L per box per minute. The plastic boxes are 60 x 40 x 32 in size, the slots on the sides and on the bottom are 5 mm wide. The boxes are filled with 60 L of expanded clay pellets ranging 8 – 16 mm in size. The water is pumped from the fish tank to a distributor from where tubes channel the water to each box in the filter.

A fish tank under construction (Photo: IEES)

Aquaculture module under construction (Photo: IEES)


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left: Filter boxes with water tube and chilli, right: a banana plant grown in a filter box (Photos: IEES)

Figure 41: Flow chart of the aquaculture module in the Tropenhaus Wolhusen

The aquaculture is placed on a slope so that the filter is above the fish tank and the water can flow directly back into the fish tank (see Figure 42).

Figure 42: Cross section through the aquaculture


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10.4.4. Costs and man-hour

The following table shows the costs for the construction of an aquaculture module as described above. The expenses for the construction of such a module are split between costs for the materials and labour costs (man hours) for the installation. For the installation, a skilled worker should be employed, supported by unskilled workers. Expenses for engineering and earthwork necessary to carve the fish tanks into the ground are not included. The material costs are indicated in € without any taxes but may include some customs duties.

€ % H %

Fish tank with insulation, inlet and outlet 12 048 45% 71 29%

Aquaponic filter 3 611 14% 83 34%

Filter pump, fittings and tubes 7 138 27% 59 24%

Heating; converter, pump, fittings 3 891 15% 32 13%

Total 26 687 100% 245 100%

Table 55: Expenses for an aquaculture module

10.4.5. Advantages and disadvantages of the aquaponic filter

In systems like the Tropenhaus where aquaculture is combined with plant production, the aquaponic filter is a cost effective method for water treatment. It can be installed on the cultivated area of the greenhouse providing the same plant productivity as the remaining cultivated area. Compared with a pond filter, less work is required for maintenance (particularly de-sludging) of the treatment system and for the cultivation of the plants no additional work is needed than for the normal plant production. The aquaponic filter shows a better biological performance than the pond filter, especially for the fish toxic parameters ammonium and nitrate. Where the aquaponic filter cannot be integrated in cultivated area the additional space requirement may be a disadvantage compared to a pond system hanging over the fish tank as in the Tropenhaus. The necessary water distribution to each single box of the filter requires a complex distribution system.

The new aquaponic filter after seven months of operation (Photo: IEES)

SUSTAINAQUA HANDBOOK References

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References and recommendations for further readings

Information about the SustainAqua project

Internet:

www.sustainaqua.org Project website http://wiki.sustainaqua.org Wiki based online tool to give information about the project results and about sustainable aquaculture in general. You are invited to contribute with your experiences, e.g. about further sustainable aquaculture modules, related projects, different fish species, etc.

Sustainability in aquaculture

Internet:

www.euraquaculture.info - CONSENSUS portal focusing on the theory of sustainability in aquaculture AGENDA 21: http://www.un.org/esa/sustdev/documents/agenda21/english/agenda21toc.htm EIFAC/EC Working Party on Market Perspectives for European Freshwater Aquaculture, Brussels, Belgium,

14 – 16 May 2001: 84-94 BEVERIDGE, M.C.M.; PHILLIPS, M.J. & MACINTOSH, D.J. (1997): Aquaculture and the environment: the

supply of and demand for environmental goods and services by Asian aquaculture and the implications for sustainability. In: Aquaculture Research 28, 797-807 CEC [COMMISSION OF THE EUROPEAN COMMUNITIES] (2005): Proposal for a Council Regulation on organic production and labelling of organic products. COM(2005)671 final. - Brussels

CEU [COUNCIL OF THE EUROPEAN UNION] (2006): Proposal for Council Regulations on organic production and labelling of organic products, amending Regulation (EC) no 2092/91, 10782/06. - Brussels

FAO [FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS] (1988): Aspects of FAOs policies, programmes, budget and activities aimed at contributing to sustainable development. Document to the ninety-fourth Session of the FAO Council, Rome, 15-25 November 1988. Rome, FAO,CL94/6.

FAO [FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS] (1995): Code of conduct for responsible fisheries. - Rome

FEAP [FEDERATION OF EUROPEAN AQUACULTURE PRODUCERS] (2000): Code of conduct for European Aquaculture. - Boncelles, Belgium

FOCARDI, S.; CORSI, I.; FRANCHI, E. (2005): Safety issues and sustainable development of European aquaculture: new tools for environmentally sound aquaculture. In: Aquaculture International 13, 3-17

FRANKIC, ANAMARIJA & HERSHNER, CARL (2003): Sustainable aquaculture: developing the promise of aquaculture. In: Aquaculture International 11: 517-530

HALBERG, NIELS; VAN DER WERF, HAYO M.G.; BASSET-MENS, CLAUDINE; DALGAARD, RANDI; DE BOER, IMKE J.M. (2005): Environmental assessment tools for the evaluation and improvement of European livestock production systems. In: Livestock Production Science 96, 33-50

IUCN (2006): The Future of Sustainability Re-thinking Environment and Development in the Twenty-first Century; http://cmsdata.iucn.org/downloads/iucn_future_of_sustanability.pdf

SECOND INTERNATIONAL SYMPOSIUM ON SUSTAINABLE AQUACULTURE IN OSLO (1997): Holmenkollen guidelines for sustainable aquaculture. - Oslo

WURTS, W. A. (2000): Sustainable Aquaculture in the Twenty-First Century. In: Reviews in Fisheries Science 8 (2), 141-150

BELL, S. & STEPHEN MORSE , 1999.- Sustainability indicators: measuring the immeasurable?. Earthscan, ISBN 185383498X, 9781853834981, 175 pp. http://books.google.es/books?hl=es&lr=&id=FZvLx3x9tYsC&oi=fnd&pg=PR7&dq=%22Bell%22+%22Sustainability+indicators:+measuring+the+immeasurable%3F%22+&ots=Fr5MxY7Ocv&sig=f6OR5AcsGy7eA_QkriVyYBjo5vA


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FAO/ICLARM/IIRR,2003.- Integrated agriculture-aquaculture. A primer. FAO Fisheries Technical Paper, n 407. 149 p. ( in English) http://www.fao.org/DOCREP/005/Y1187E/Y1187E00.HTM

MEA, 2005.- Ecosystems and Human Well-being. A Framework for Assessment. http://www.millenniumassessment.org/en/Framework.aspx

UNEP (1992): Rio Declaration on Environment and Development; http://www.unep.org/Documents.multilingual/Default.asp?DocumentID=78&ArticleID=1163 WORLD COMMISSION ON ENVIRONMENT AND DEVELOPMENT (1987): Report of the World Commission on Environment and Development: Our Common Future

Suggested readings about constructed wetlands and integrated intensive-extensive systems

AZIM, M.E., VERDEGEM, M.C.J., VAN DAM, A.A., BEVERIDGE, M.C.M. (2005). Periphyton: ecology, exploitation and management. CABI Publishing, Camebridge, MA 02139, USA.

COSTA-PIERCE, B.A. (1998). Preliminary investigation of an integrated aquaculture-wetland ecosystem using tertiary-treated municipal wastewater in Los Angeles County, California. Ecological Engineering, 10: 341-354.

GOPAL, B. (2003). Perspectives on wetland science, application and policy. Hydrobiologia, 490: 1-10. GÁL, D., PEKÁR, F., KEREPECZKI, É., VÁRADI, L. (2007). Experiments on the operation of a combined

aquaculture-algae system. Aquaculture International, 15: 173-180. GÁL D., KEREPECZKI É., SZABÓ P., PEKÁR F. (2008). A survey on the environmental impact of pond

aquaculture in Hungary. European Aquaculture Society, Special Publication No. 37, pp. 230-231. KADLEC, R.H., KNIGHT, R.L. (1996). Treatment wetlands. Lewis Publishers, Boca Raton, USA. KEREPECZKI É., GÁL D., SZABÓ P., PEKÁR F. (2003). Preliminary investigations on the nutrient removal

efficiency of a wetland-type ecosystem. Hydrobiologia, 506-509: 665-670. KEREPECZKI, E., PEKAR, F. (2005). Nitrogen dynamics in an integrated pond-wetland ecosystem. Verh.

Internat. Verein. Limnol., 29: 877-879.

Suggested readings about pond polyculture and cascade systems

SZUMIEC, M.A., AUGUSTYN, D. 2002. Dynamics of the surface water circulation between a river and fishponds in a sub-mountain area. IN: Rizzoli A.E. & Jakeman A.J. (Eds), Integrated assessment and decision support. Proceedings of the First biennal meeting of the International Environmental Modelling and Software Society, Lugano (Switzerland), 1, 358-362

BOYD, C. 1995. Bottom soils, sediment and pond aquaculture. Chapman & Hall, New York, p. 348 EL SAMRA, M., OLÁH. 1979. Significance of nitrogen fixation in fish ponds. Aquaculture, 18:367-372 RAHMAN, M. M., 2006.Food web interactions and nutrient dynamics in polyculture ponds PHD. Thesis.

Wageningen University, 168 p. http://library.wur.nl/wda/dissertations/dis3980.pdf WHO, 2006.- Guidelines for the safe use of wastewater, excreta and greywater . Volume 3 Wastewater and

excreta use in aquaculture. World Health Organization, ISBN 9241546840, 9789241546843, 158 pp. MARA, DUNCAN & SANDY CAIRNCROSS, 2003.- Guidelines for the Safe Use of Excreta and Wastewater

in Agriculture and Aquaculture, Executive summary -UNEP- WHO Publications, 32 p. http://www.bvsde.paho.org/bvsacd/who/waste1.pdf

YEO, S. E., BINKOWSKI F.P & MORRIS, J.P., 2004.-Aquaculture Effluents and Waste By-Products. Characteristics, Potential Recovery, and Beneficial Reuse. NCRAC Publications Office North Central Regional Aquaculture Center. Iowa State University. http://www.aqua.wisc.edu/publications/PDFs/AquacultureEffluents.pdf

Suggested readings about the model trout farms

BUREAU, D.P. AND CHO, C.Y. , 1999. Phosphorus utilization by rainbow trout (Oncorhynchus mykiss): estimation of dissolved phosphorus waste output. Aquaculture 179: 127-140.

CHO, C.Y., SLINGER, S.J., AND BAYLEY, H.S. 1982. Bioenergetics of salmonid fishes: energy intake, expenditure and productivity. Comp. Biochem. Physiol. 73B: 25–41.


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DALSGAARD, J., EKMANN, K.S., PEDERSEN, P.B., AND VERLHAC, V., 2008. Effect of supplemented fungal phytase on performance and phosphorus availability by phosphorus-depleted juvenile rainbow trout (Oncorhynchus mykiss), and on the magnitude and composition of phosphorus waste output. Aquaculture , doi:10.1016. 2008

JOKUMSEN, A. (2002). Udredning vedr. vandforbrug ved produktion af regnbueørreder i danske dambrug. DFU-rapport nr. 106-02. Report in Danish.

LOKALENERGI 2008:1: Energioptimalt design af dambrug. PEDERSEN, P.B.; GRØNBORG, O.; SVENDSEN, L.M. (2003): Modeldambrug. Specifikationer og

godkendelseskrav. Arbejdsrapport fra DMU, nr. 183, 2003. Report in Danish. SUGIURA, S.H., DONG F.M., AND HARDY, R.W., 2000b. Primary responses of rainbow trout to dietary

phosphorus concentration. Aquacult. Nutr. 6: 235-245. SVENDSEN, L.M., SORTKJÆR, O., OVESEN, N.B., SKRIVER, J., LARSEN, S.E., BOUTTRUP, S.,

PEDERSEN, P. B., RASMUSSEN, R.S., DALSGAARD, A.J.T., AND SUHR, K, 2008. Modeldambrug under forsøgsordningen. Faglig slutrapport for måle- og dokumentationsprojekt for modeldambrug "(in Danish)". DTU Aqua rapport nr.193-08 . DTU Aqua, Technical University of Denmark.

SVENDSEN, L.M., SORTKJÆR, O., OVESEN, N.B., SKRIVER, J., LARSEN, S.E., PEDERSEN, P. B., RASMUSSEN, R.S. AND DALSGAARD, A.J.T., 2008. Ejstrupholm Dambrug - et modeldambrug under forsøgsordningen. Statusrapport for 2. måleår af moniteringsprojektet med væsentlige resultater fra første måleår (”In Danish”). DTU Aqua rapport nr.188-08 . DTU Aqua, Technical University of Denmark.

Suggested readings related to tilapia farming in RAS

BOVENDEUR, J., EDING, E.H., HENKEN, A.M., 1987. Design and performance of a water recirculation system for high-density culture of the African catfish, Clarius gariepinus (Burchell 1822). Aquaculture 63, 329–353

EDING, E.H., WEERD, J.H. VAN, 1999. Grundlagen, Aufbau und Management von Kreislaufanlagen. In: M.Bohl (Ed.), Zucht und Produktion von Süsswasserfischen, DLG –Verlag, Frankfurt, München, 2nd edn., pp. 436-491.

EDING, E.H., KAMSTRA, A., VERRETH, J.A.J., HUISMAN, E.A., KLAPWIJK, A., 2006. Design and operation of nitrifying trickling filters in recirculating aquaculture: a review. Aquaculture Engineering 34, 234–260.

HEINSBROEK, L.T.N. AND KAMSTRA, A., 1990. Design and performance of water recirculation systems for eel culture. Aquacult. Engineering 9 (3), 87–207.

van RIJN, J., TAL,Y., SCHREIER, H.J., 2006. Denitrification in recirculating systems: Theory and applications. Aquacultural Engineering 34 (3), 364–376.

SCHNEIDER, O., SERETI, V., EDING, E.H., and J.A.J. VERRETH, (2005). Analysis of nutrient flows in integrated intensive aquaculture systems. Aquacultural Engineering 32, 379–401.

TIMMONS, M.B. AND J.M. EBELING, 2007. Recirculating Aquaculture, Cayuga Aqua Ventures, Ithaca, New York, p. 975

Suggested readings on PTS pond technology

ASADUZZAMAN, M., WAHAB, M.A., VERDEGEM, M.C.J., HUQUE, S., SALAM, M.A., AZIM, M.E., 2008. C/N ratio control and substrate addition for periphyton development jointly enhance freshwater prawn Macrobrachium rosenbergii production in ponds. Aquaculture 280, 117-123.

AZIM, M.E., VERDEGEM, M.C.J., VAN DAM, A.A., BEVERIDGE, M.C.M., 2005. Periphyton : ecology, exploitation and management. CABI Publishing, Cambridge, MA 02139, USA.

RAHMAN, M.M., YAKUPITIYAGE, A., 2006. Use of fishpond sediment for sustainable aquaculture-agriculture farming. International Journal of Sustainable Development and Planning 1, 192-202.

Suggested readings related to the Tropenhaus project

ADLER , PAUL R., 1998.- Phytorremediation of aquaculture effluents. Aquaponics Journal, IV4, 10-15. http://www.cepis.org.pe/bvsair/e/repindex/repi84/vleh/fulltext/acrobat/phytoaqu.pdf


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ADLER , PAUL R., STEVEN T. SUMMERFELT , D. MICHAEL GLENN , FUMIOMI TAKEDA 2002. Mechanistic approach to phytoremediation of water. Ecological Engineering 20, 251/264

http://www.ars.usda.gov/SP2UserFiles/Place/19310000/FTakeda/2003EcolEng20251-264.pdf DEZSERY, A.,1999.- Growing Notes--Australian Aquaponics--Whole Fresh Fish and a Side Salad Please!.

The Growing Edge Magazine, 11(2) http://www.growingedge.com/magazine/back_issues/view_article.php3?AID=110217

DIVER S, 2006.- Aquaponics-Integration of Hydroponics with Aquaculture. http://attra.ncat.org/new_pubs/attrapub/PDF/aquaponic.pdf?id=NewYork

HUGHEY, T. W. 2005.- Barrel- Ponics. Aquaponics in a Barrel. http://www.aces.edu/dept/fisheries/education/documents/barrel-ponics.pdf

JACKSON,L. & MYERS J., 2002.- Alternative Use of Produced Water in Aquaculture and Hydroponic Systems at Naval Petroleum Reserve No. 3. http://www.gwpc.org/GWPC_Meetings/Information/PW2002/Papers/Lorri_Jackson_PWC2002.pdf

JONES S., 2002.- Evolution of aquaponics . Aquaponics Journal , n 24 ( 1st Quarter, 2002). In : http://www.aquaponicsjournal.com/articleEvolution.htm

LENNARD W., 2004.- Aquaponics, the theory behind the integration. In GAIN (Gippsland Aquaculture Industry Network) http://www.growfish.com.au/content.asp?contentid=1060

WILSON, G. 2002a.- Saltwater aquaponics. The Growing Edge, Volume 13, Number 4, March/April 2002, page 26. http://www.growingedge.com/magazine/back_issues/view_article.php3?AID=130426

SUSTAINAQUA HANDBOOK Authors

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Authors of the handbook

Editors

Dr. László Váradi (Research Institute for Fisheries, Aquaculture and Irrigation - HAKI) Tamás Bardócz (Akvapark Association) Alexandra Oberdieck (ttz Bremerhaven)

List of authors per chapter:

1. SustainAqua – An introduction

Alexandra Oberdieck - ttz Bremerhaven

2. Sustainability in aquaculture

Christian Hildmann - Martin-Luther-University Halle Wittenberg Alexandra Oberdieck - ttz Bremerhaven

3. Technology and production of main freshwater aquaculture types in Europe

Tamás Bardócz - Akvapark Association

4. Regulatory framework and governance in European freshwater aquaculture

Tamás Bardócz - Akvapark Association László Váradi – Research Institute for Fisheries, Aquaculture and Irrigation (HAKI)

5. Product quality and diversification – Market opportunities for aquaculture farmers for their fish products and by-products

Alexandra Oberdieck - ttz Bremerhaven

6. Water treatment of intensive aquaculture systems through wetlands and extensive fish ponds – Case studies in Hungary

Dénes Gál, Éva Kerepeczki, Tünde Kosáros, Réka Hegedős, Ferenc Pekár, Lászlo Váradi – Research Institute for Fisheries, Aquaculture and Irrigation (HAKI)

7. New methods in trout farming to reduce the farm effluents – Case study in Denmark

Alfred Jokumsen, Per B. Pedersen, Anne Johanne T. Dalsgaard, Ivar Lund, Helge Paulsen, Richard S. Rasmussen, Grethe Hyldig - Technical University of Denmark, National Institute of Aquatic Resources (DTU Aqua) Lisbeth J. Plessner, Kaare Michelsen, Christian Laursen - Danish Aquaculture Organisation (ODA)

8. Improved natural production in extensive fish ponds – Case study in Poland

Maciej Pilarczyk, Joanna Ponicka, Magdalena Stanna - Polish Academy of Sciences, Institute of Ichthyobiology and Aquaculture (GOLYSZ)

9. Tilapia farming using Recirculating Aquaculture Systems (RAS) - Case study in the Netherlands

Ep Eding, Marc Verdegem, Catarina Martins, Geertje Schlaman, Leon Heinsbroek, Bob Laarhoven, Stephan Ende, Johan Verreth - Aquaculture and Fisheries Group, Wageningen University (WU-AFI) Frans Aartsen, Victor Bierbooms - Viskwekerij Royaal B.V./ ZonAquafarming B.V. (ROYAAL) 10. Tropical polyculture production with the integrated “Tropenhaus” concept - Case study in

Switzerland

Johannes Heeb, Philippe Wyss - International Ecological Engineering Society (IEES) Zdenek Adamek - Research Institute of Fish Culture and Hydrobiology, University of South Bohemia (USB)

SUSTAINAQUA HANDBOOK Acknowledgements

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Acknowledgements

This handbook is one of the outputs of the SustainAqua Collective Research project - funded by the European Commission as part of its Sixth Framework Programme (FP6). The research and training has been undertaken by a consortium of twenty-three partners: ttz Bremerhaven (ttz), Germany; International organisation for the development of fisheries in Eastern and Central Europe (EUROFISH), Denmark; Akvapark Association (AKVAPARK), Hungary; Verband der Deutschen Binnenfischerei e.V. (VDBi), Germany; Vattenbrukarnas Riksförbund (VRF), Sweden; Stowarzyszenie Producentów Ryb Lososiowatych (PTBA), Poland; Organización de Productores Piscicultores (OPP), Spain; Österreichischer Fischereiverband (ÖFV), Austria; Su Ürünleri Tanitim Dernegi (BTG), Turkey; Danish Aquaculture Organisation (ODA), Denmark; International Ecological Engineering Society (IEES), Switzerland; AquaBioTech Ltd. (ABT), Malta; Aranyponty Halászati Zrt. (ARANY), Hungary; Aquakultur Kahle (KAHLE), Germany; Hodowla Ryb "SALMO" (SALMO), Poland; Liman Enegre Balikçilik Sanayii ve Ticaret Ltd.STI. (LIMAN), Turkey; Viskwekerij Royaal B.V.

(ROYAAL), Netherlands; University of South Bohemia in Ceske Budejovice (USB), Czech Republic; Wageningen University - Aquaculture and Fisheries Group (WU-AFI), Netherlands; Polska Akademia Nauk, Zakład Ichtiobiologii i Gospodarki Rybackiej (GOLYSZ), Poland; Martin-Luther-University Halle Wittenberg (MLU), Germany; Research Institute for Fisheries, Aquaculture and Irrigation (HAKI), Hungary; Technical University of Denmark - National Institute of Aquatic Resources (DTU-AQUA), Denmark The work that lies behind the production of this handbook is the joint effort of several persons, who are too numerous to acknowledge individually, but we mention the following persons for their exceptional input: Tamás Bardócz (AKVAPARK), Alexandra Oberdieck (ttz), Dénes Gál (HAKI), Alfred Jokumsen (DTU-AQUA), Maciej Pilarczyk (GOLYSZ), Ep Eding & Marc Verdegem (WU-AFI), Johannes Heeb & Philippe Wyss (IEES) We thank them for their dedicated work.

SustainAqua consortium (Photo: ttz Bremerhaven)

Cover page, design and layout by EUROFISH

©SustainAqua, June 2009. All rights reserved. Free for distribution. More information: www.sustainaqua.org

Please cite as follows: "SustainAqua – Integrated approach for a sustainable and healthy freshwater aquaculture” (2009). SustainAqua handbook – A handbook for sustainable aquaculture"