Kansas State University

Research Collaborative for Aquaponics Technology System Design

Final Report

Victoria Eastman, Shannon Bellamy, Luke Alpers, Riley Arthur, Katelyn O’Brien

BAE 231

Dr. Lisa Wilken

13 December 2018

Table of Contents

Executive Summary…………………………………………………………………….…………Client needsDesign Goals, Principles and Constraints Description of DesignRecommendations, Limitations and Conclusions

Introduction and Justifications ……………..…………………………………………………...Objectives and Limitations…………………...………………………………………………….Background Research …………………………………………………………………………..

IntroductionGeneral Aquaponics

Background StandardsSystem Components Previous Solutions Potential Plant Option for Aquaponics SystemMaintenance

Background on NamibiaGeography Namibian ClimateFood CultureTechnology Available Restrictions and Regulations Cost

Conclusion Alternatives Considered………………………………………………………………………….

Design FeaturesFilter Components

Final Design Description…………………………………………………………………………General designDimensions and logisticsSystem ComponentsFishPlantsPathogen BiosensorImplementation of System in NamibiaAdvantages and DisadvantagesDesign Recommendations

Testing Needs …………………………………………………………………………………….Summary ………………………………………………………………………………………..References………………………………………………………………………………………...

Executive Summary

Client Needs

It was requested that the team design an aquaponic system, which is an integrated aquaculture

(fish farming) and hydroponic system (the production of plants in water without soil) equipped with a

pathogen (E. coli) biosensor for a Gästefarm in Namibia. Aquaponics systems are composed of

aquaculture (fish farming) and hydroponics (the production of plants in water without soil), which

provides a more sustainable and cost-effective way to produce food. The design team must ensure that the

system produces enough vegetation to assist in feeding the sheep and diversify farming practices.

The design team must take into consideration that there are restrictions on what types of fish and

plants can be used for the aquaponics system. The design must also be low in cost and easily maintainable

to ensure sustainability.

Design Goals & Principles and Constraints

The objective of this design was to develop a food production system capable of feeding a small

subsistence farmer’s herd of 25 sheep and provide a supplementary protein source for the community. In

the process of designing a food production system RCAT adapted principles from a conventional

aquaponics system to fit the needs of the client.

Within the objective were a few imperative constraints. The client required the system to feed 25

sheep continuously. RCAT also identified that it would be important for the system to require little

maintenance and labor. Though the farmer will be experienced in farming operations, aquaponics systems

can be complex and may require some special knowledge to operate. RCAT proposed a simplified, yet

effective, design because of the customer's inexperience with aquaponics systems and the design was

simplified, but runs just as effectively. RCAT’s simple design means the cost for the system is much less

than conventional aquaponics systems. Lastly, the client requested there be an E-coli sensor integrated

into the water circulation system to test water quality along with a filtration system. This would allow for

a sustainable enclosed environment while monitoring the health of the aquaponics system as a whole.

Description of the design The Research Collaborative for Aquaponic Technology (RCAT) Design is a collapsible cubic

plant-above water design which consists of one tank for plants and growing media, offset on top of a

larger water fish tank below. The main tank is a 5 ft x 5 ft x 5 ft cube made of polyethylene terephthalate

(PET) fish and water, with another 1.25 ft x 5 ft x 5 ft offset top to hold the growing media and produce.

A single pipe, attached to a pump connects the water tank to the plant box and transports the water from

tank to plants. The base of the plant bed is slightly slanted and will contain several evenly-spaced small

holes with a radius of 1in to allow water to drain from the plant bed back into the fish tank. The growing

media used in the plant bed is soil, rocks, and pebbles small enough to not fall through drainage pores.

Finally, a PET pipe with radius 0.30 ft will be connecting the two systems with a 250 gal/h Hydrofarm

Active Aqua AAPW250 Submersible Water Pump to pull the water from the tank into the growing bed.

The fish selected are Nile Tilapia (Oreochromis niloticus) which are very disease resistant, spawn

quickly and can be found locally in Africa. While the system can support a variety of crops, the ideal

produce selected to grow in this system will be the cowpea (Vigna unguicalata) which are resilient

legumes that serve as a staple in Namibia, where their seeds can be locally sourced. In addition, this

system will also include a disposable, cost-effective, simple biosensor which is capable of detecting

Salmonella typhimurium, and Escherichia coli strains JM109 and DH5-α.

Recommendations, Limitations, and Conclusions

The Research Collaborative for Aquaponic Technology (RCAT) team recommends this small,

simplistic design to demonstrate feasibility. The small design also eases the labor of construction as well

as ease of transportation. The recommended fish are Nile tilapia, native to Africa, and the plants grown

will be cowpeas. All the components of the system are kept in close proximity to ease the flow of the

system and make it simpler to construct. Additionally, the symbiotic relationship between the plants and

fish are easier to maintain and observe.

The system can independently function on its own, with the exception of a source of food for the

fish, which will need to be provided by an outside source. The small-scale structure limits the produce of

the fish and plant, but the design can be replicated to increase the potential yield. Water flow is controlled

to an extent, but there could be enough stagnant water in the fish tank that the ammonia and nitrate levels

could affect the fish. Overall, the final design meets all the criteria the client is looking for, while also

providing room to grow.

Introduction and Justifications

A farmer in Namibia requested a small-scale aquaponics system to implement on his farm that

would aid in feeding a small herd of sheep as well as providing a food source, from the fish, for the

farmer and his family. Aquaponics systems are a symbiotic relationship between aquaculture (fish

farming) and hydroponics (growing plants in water without soil), which is a more sustainable way to

produce food. The client wants a simple system that is cost effective, simple in design and requires low

every day maintenance. The RCAT team was tasked with designing a system that met all the client’s

requirements.

Design Objectives and Limitations

In order to create a design that met all of the client’s needs, RCAT had to first identify all

the possible design constraints. The most important constraint the client specified was the need

for a simplistic, easy to use design that requires minimal maintenance. Because this is the

farmer’s first experience with aquaponic systems, RCAT wanted the design to be as

straightforward and easy to use as possible. The next main constraint was the need for a

biosensor capable of detecting E. Coli to ensure health and safety associated with the system.

Another key constraint was that the farmer wanted the design to incorporate produce and fish

food that was readily accessible, familiar, and complied with all fish restrictions in Namibia.

Finally, the last constraint RCAT was focused on was that the design needs to effective, with the

ability to produce a sustainable, reliable yield within the harsh Namibian climate.

Background Research:

Introduction:

Aquaponics systems play a big role in finding a more efficient and sustainable way to

produce food. They are a beneficial way for people, especially those in more under-developed

countries like Namibia, to grow food conservatively. To design one of these self-sustainable, low

maintenance systems, one must first understand what exactly an aquaponics system is, what

components are needed, and what fish and plants can be used. When designing for another

country like Namibia, one also has to account for the culture, restrictions and regulations,

climate, and geography of the country.

General Aquaponics:

Background

To fully understand the project, a basic understanding of aquaponic fundamentals and

standards is essential. Aquaponics is a combination of aquaculture and hydroponics. It consists

of a body of water, like a pond, containing fish or other aquatic animals and plants. Image 1

(below) shows the flow and basic functions of a typical aquaponics system.

The water in the fish tank contains nutrients and waste from the fish that help the plants

grow. Aquaponics systems are an ideal solution for making food production sustainable,

especially in developing urban countries (Goddek et al., 2015). Aquaculture and hydroponics

have a symbiotic relationship in this single system, this allows for less maintenance as the water

does not need to be replaced because of excess nutrients (Goddek et al., 2015).

Aquaponics cycle (Small Garden

Ideas, 2016)

Image 1. Aquaponics cycle (Small Garden Ideas, 2016)

In aquaculture, which is also known as aquafarming, fish are raised in a controlled

environment. A caveat of aquaculture is that ammonia from fish waste can end up killing the

fish, so the water has to be tended regularly. In hydroponics, plants grow in water that has

nutrients added. In aquaponics, the fish waste is used as food for the plants which resembles the

nature in lakes and ponds. Aquaponics systems are not only a sufficient way to grow food, but

they also conserve water, so water is only lost through evaporation and transpiration, thus being

a sustainable solution to food production (Marklin et al., 2013).

Standards

Understanding the current aquaponics standards are essential to developing a design

capable of performing essential functions in the field. The current industry standard for grow

beds are at least 12 inches deep and must be made out of food safe materials that do not alter pH

(Bernstein and Lennard, 2018). In addition, systems that contain upwards of 250 gal of water for

the fish tanks tend to be the most successful as they allow room for error as impacts take longer

to see at larger volumes. The standard for fish-to-water ratio is one fish for every five to ten

gallons of water. Similarly, the standard for grow beds is one fish for every one square foot of

grow bed surface (Bernstein and Lennard, 2018).

System Components

Having researched the basic backgrounds and standards regarding aquaponic systems, the

next step in preparing a design is to consider the more specific system components such as power

sources, filtration systems, pumps, biosensors and maintenance. The first component researched

was the potential power sources for the system, as determining a powersource is one of the first

steps when considering a design. Solar power is one of the cleanest forms of renewable energy,

but also one of the most expensive (Grimes, 2011). However, as solar panels are becoming more

prevalent, the demand is increasing so the prices are decreasing. One drawback to using solar

power is the need for an inverter to convert the electricity from DC to AC. Water pumps and air

pumps used in aquaponics systems require AC power. All components necessary to operate an

aquaponics system include a solar panel, voltage regulator, battery, microcontroller and relay,

and DC step up inverter. The power collected by the solar panel is stored in the battery and the

microcontroller and relay determine where the power goes(Murmson, 2018). It can determine

when the water pump needs to turn on or the air pump can turn off to make the best use of

energy in the system. During the nighttime hours, the battery supplies all necessary power to

keep the system functioning until the sun returns.

Each solar panel is built on a frame of any material and rotates on a pivot to capture the

maximum amount of sun possible in a day. The rotation is determined by a microcontroller

which communicates with other electrical sensors in the system to determine the most efficient

orientation of the solar panels. These sensors include thermocouples, photoresistors, and

thermistors. Rotation of the panels is caused by the actuation of servo motors, linear actuators,

and solenoids. This design of solar panel is usually attached to a fixed structure such as a

greenhouse or building with multiple solar panels working in sequence. The fixed structure

allows the pivot point to be secured to the frame of the building (Hall et al., 2010).

Having considered the power source, the next key component of an aquaponics system to

focus on would be the filtration and pump systems. To begin with, there needs to be two

filtration systems, one for solid particles and one for nitrification. A biofilter is needed so that the

toxins from ammonia in fish urine and excretion of the gills do not affect the plants which could

harm the people that consume said plants. Water flows through the fish pond into a biofilter

which consists of nitroso-bacteria and nitro-bacteria that can break down ammonia. This way the

ammonia can be converted into nitrite, then into nitrate. Nitrate is less harmful to the fish and

serves as the main nitrogen source for the plants (Goddek et al., 2015).

Biofilters typically contain nitrifying bacteria that grow attached to a submerged surface

or in a water column. The bacteria takes the ammonia from the water and oxidizes it into nitrate

automatically reducing the need for maintenance and another external filter. In order for the

majority of the ammonia in the pond to be broken down, the filter has to be fairly large since the

pond itself is large. Recommended components of a biofilter are sand, crushed rock, river gravel,

or plastic shaped into small beads. Biofilters must be non-degradable and long-lasting so less

maintenance is required (Ebeling, n.d).

In addition to filters and pumps, this project also requires a biosensor capable of detecting

harmful E. Coli in the system. Likewise, installing a pathogen biosensor to detect any harmful

bacteria within in the aquaponic system is crucial for the well-being of those who will be

consuming the products of the system. Harmful pathogens such as Escherichia coli can cause

many health issues, such as diarrhea, urinary tract infections, respiratory issues and more (Lui,

2007). Damaging E. Coli bacteria can develop and mature in raw vegetables due to contaminated

water from runoff of animal farms (Lui, 2007).

A disposable biosensor that can detection pathogens is ideal for an aquaponic system.

The biosensor within this system must be as simple to use as possible for the Namibian farmers

using it. One sensor, developed by Ali et al. (2018), provides a reading and classification of

Salmonella typhimurium, and the Escherichia coli strains JM109 and DH5-α within only 8 min

after the injection (Ali, 2018). This biosensor is has a small strip like shape. The sample that is in

need of analysis is then injected onto the strip with probes connecting to an impedance analyzer

and computer providing an accurate reading within a short period of time (Ali et al. 2018).

Previous Solutions

In addition to understanding the basics of aquaponics, it is also essential to consider the

design of the system. This is best done by evaluating the current project requirements and

comparing them to current designs and standards. For this project, the farmer wants the design to

be simple and efficient. One example of a successful design is big greenhouses stocked with

different plants for diversity and pools with the fish are made out of concrete (Agribusiness TV

(n.d.)). Applying his methods on a smaller scale could be an option, but his options are a little

pricey. Some of the materials he uses are items he has transformed from their everyday purpose

to use, which could be an option. He has cut pipes to form hanging garden plants that are watered

by the filter system that comes from the fish. He also uses bioenergy as well as solar energy, so

the greenhouse is running night and day which could be considered as well.

Another design option is to use giant bins or again a concrete structure that could use

gravity (weir gravity flow) and sloping bottoms to also help with cleaning (Wicoff, 2011).

Instead of a system where the water is pumped to the plants, the plants could be grown in netting

or on a sturdy surface with holes that is set on open pipes, so the plants could soak up the

nutrients while the water is circulating. This would allow less space to be taken up by rows of

vegetation, but it could also limit the amount of vegetation (Wicoff, 2011).

Potential Plant Options for Aquaponics Systems

While considering the design structure of the aquaponics system, it is also important to

determine which produce should be used. For example, in a recirculating aquaponics system, it is

imperative to stock plants that can efficiently remove inorganic nitrogen and phosphorous from

the water. Water spinach (Ipomoea aquatica) was observed to reduce the total ammonia

nitrogen, nitrite-N, nitrate-N and orthophosphate with efficiencies of 78.32–85.48%, 82.93–

92.22%, 79.17–87.10%, and 75.36–84.94% (Enduta et al., 2012). In this experiment, water

spinach exhibited qualities in its root system which harbored superior populations of microbial

life. The surface area of the root system not only improved microbe populations, it allowed for

more water pollutants to be taken up by the plant (Enduta et al., 2012).

Leafy greens are generally grown in aquaponics system because they are easy to grow,

and they are in high demand. Small roots and shoots can be grown in an aquaponic system and in

fact grow faster than leafy greens. In an aquaponic environment, they should be harvested prior

to being fully grown. Harvesting roots like turnips, radishes, and carrots in their earlier stages in

growth makes them softer, sweeter, and more desirable to consumers (Kozai et al., 2016). Leafy

greens and herbs are grown more prevalently in aquaponics systems in urban areas because they

can be harvested and consumed without any extra processing (Kozai et al., 2016). No pesticides

are used in aquaponics systems, so when the leafy greens are harvested there is no need to wash

them prior to serving.

A few examples of leafy greens which are indigenous to Namibia include Amaranthus,

Corchorus and cleome (Araya, 2014). Below is a list of several commonly found edible plants in

Namibia. They have high levels of calcium, iron, vitamins A and C, and are rich in protein and

fiber (Araya, 2014). Plants like Amaranthus and Corchorus are considered low management

crops because of their ability to grow in low quality soil. In an aquaponic application where the

nutrients found in soil are highly concentrated, it is possible that the yields may increase. Many

of these indigenous species have not been studied for cultivation since they are simply wild

vegetation. However, they could prove to be useful in a cultivation-type environment due to their

extreme drought tolerance and ability to grow in poor soil.

Indigenous Plant Species to Namibia (Araya, 2014):

● Amaranthus retroflexus (Pigweed)

● Cleome gynandra (Spider Plant)

● Corchorus spp (Gushe)

● Brasica carinata (Kale)

● Solanum retroflexum (Nightshade)

● Cucurbuta spp (traditional pumpkin)

● Citrallus lanatus (Bitter melon)

● Vigna unguicalata (cowpea)

● Colocasia esculenta (Amadumbe)

Maintenance

Having evaluated the main components of an aquaponics system, the next main area of

focus would be on maintenance. A healthy ecological balance in an aquaponics system starts

with a well-maintained system. The primary waste product that collects in an aquaponics system

is solid waste produced by the chosen aquatic animal species. This solid waste can be dealt with

in two ways; recycling the waste back into the system or removing it from the system

(Bodlovich, Gleeson, 2006). A partially closed-circuit aquaponics system would recycle a

majority of the waste back through the system (Bodlovich, Gleeson, 2006). The waste is taken

into a bio-waste digestion unit allowing the waste to degrade within the system and eventually be

used by the plants in the system. Keeping the waste in the system means minimal water is

expelled thus the system requires minimal water to be added (Bodlovich, Gleeson, 2006).

The second method of dealing with solid waste is to remove it from the system entirely.

This can be accomplished by filtering or separating the solid waste from the water (Bodlovich,

Gleeson, 2006). When removing solid waste from the system it is preferred to use a filtration

system using any appropriate media filter. A second option is the swirl separator. Solids are

settled in a waste stream and removed from the system while smaller particles would still have to

be filtered out by a media filter as previously described.

A thorough yearly cleaning is necessary to keep an aquaponics system functioning at its

highest capacity (Martell, 2016). Generally, this cleaning takes place in the spring when plant

varieties are being rotated. Solid waste removal is the first priority during the yearly cleaning

process. Place a pump in the bottom of the tank and remove one third of the water from the tank.

This water can be then applied to other plants or vegetation as a fertilizer. After the water is

drained refill the tank with dechlorinated water. Calcium and potassium deposits will form on all

exposed parts of an aquaponics system including plumbing components. These deposits can be

removed by scrubbing with a clean towel and low concentration phosphoric acid.

Background Information on Namibia:

In order to more fully understand the location in which this system would be utilized, a

general understanding of Namibia is needed. In this section, Namibia's food culture, climate,

town layout and available technology are all evaluated, beginning with the most relevant topic,

Namibian food culture.

Geography

With a detailed understanding of the climate around the farm, it is then important to learn

more about the layout of the country in general in order to more fully understand the area in

which the design is to be implemented. For example, Namibia is roughly 824,000 km2. It is

mostly desert and water is limited. Even the rivers are dry, except during the rainy months. It is

made up of four main geographical sections, the Namib Desert which consists of sand dunes and

gravel fields, a mountain that resembles a wall, the Central Plateau which is where most of the

population is, and the Kalahari Desert which consists of sand dunes and little vegetation

(Namibia Travel, 2010). Even though it does not rain throughout the year, there are underground

water reservoirs because of layers of clay and rock which supply water to the farms (Namibia

Travel, 2010).

Looking at a map of Namibia (image 2), Helmeringhausen is located in the south

western part of Namibia, just on the edge of the mountain wall and the central plateau (Expert

Africa, 2016).

Image 2. A map of Namibia (Expert Africa, 2016)

Namibian Climate

Although an aquaponic system is capable of producing plants and aquatic life forms

without the use of soil and natural rainfall, the climate and weather of whatever region where the

system is located still plays a significant role in which plants and animals can be used within the

system. The Southern African country of Namibia has a very arid climate meaning as the rate of

evaporation is much higher than the rate of precipitation (Singh, 2018). Namibia has an average

of 300 days each year of sunshine (Singh, 2018). This excessive amount of sunlight creates a

design constraints on which plants can be farmed within the aquaponic system and the overall

design of the system. Plants that cannot survive with full sunlight must be shaded in some way,

so a plant that can tolerate full sunlight may thrive within this system.

In the town of Helmeringhausen, where this aquaponics system will be located, the

average annual precipitation is 203 mm (Mountney, 1999). Combined with an average summer

high of 90°F (Mountney, 1999), water is not readily available or accessible in this town. Finding

a regular source of water capable of being pumped into the system is a very important factor in

having successful food output. Namibia’s climate is harsh, but that is why there is a need for an

aquaponics system.

Food Culture

To determine which produce should be utilized in an aquaponics system, a general

understanding of the cultures cuisine is needed. Namibian cuisine culture is centered around

traditional cooking methods, with most dishes having German and South African influences

(Gale, 2001). In addition, most of the Namibian cuisine is centered around beef and fish, as cattle

farming and fishing are two of the main agricultural productions. Some common dishes include

Kapana (raw beef cooked on an open flame), Kabeljou (Silver Cob) and Luderitz crayfish (Gale,

2001).

A good understanding of the meal culture is also essential to planning a successful

aquaponics system. Many Namibians eat only one to two meals a day, and as a result, need very

protein-rich, high carb meals. They find these protein and carbs in vegetables and meat sources.

Pap (maize meal porridge), beef and fish being three of their primary staples (Shusko 2015). The

type of foods they eat depends heavily on their location in the country, as it is such a culturally

diverse area. Those in the Kavango and Zambezi regions consume fish frequently and would

therefore benefit the most from an aquaponics system (Shusko, 2015).

Having gained a thorough understanding of the Namibian food culture in terms of

aquaponic systems, it is then necessary to consider the weather and climate in order to design an

effective food-producing system.

Technology Available

With a basic understanding of the culture and layout of the country, the next main

component that needs to be evaluated is the available technology. A knowledge of the

availability of technology in the host country is essential when designing such a system. That

being said, the aquaponics system being designed for farmers of Namibia is going to be equipped

with a pathogen biosensor, so the technological advancements of the country are an important

thing to consider when designing the system. Namibia is slowly but surely moving towards a

technologically advanced country. Coding is in-fact being integrated into the nationwide school

curriculum of Namibia (Matengu, 2016). Although late to the game, Namibia as a whole realizes

that the future is technology, so they have made large efforts to keep up with the ever growing

cyber world we know today (Matengu, 2016). There should be very few issues with the

Namibian people capable of using and reading a pathogen biosensor fixated within an

aquaponics system.

Since Namibia became an independent country in 1990, mining has been largest

contributor to the economy of the country (Kiangi, 1997). Being the world leader in diamond

mining, Namibia has made substantial technological advancements in machinery and over all

technique and extraction of diamonds. Fresh of gaining independence in 1990, the mining

industry created the Namibian Institute of Mining and Technology (NIMT) (Kiangi, 1997).

Education and technology are of the utmost importance to the Namibian government and people.

Finally, having taken the country’s culture and technology into consideration, the final

component that needs to be discussed is the availability of resources at the exact location the

system is to be implemented into. To begin, the resources available at the site of interest are two

reservoirs about a 15 minute drive apart from each other, that could be used as a water supply.

The farmers have also already implemented solar panels that could provide electricity if needed

to the aquaponic site as well as a small generator. The aquaponic system will need to feed all the

sheep on the farm, since the farm is located next to a desert and mountain area and plant life is

not overly abundant (Cline, 2018). While there is nothing already set up in the location, the

farmer is willing to invest in building a system.

To make the benefit worth the cost, the aquaponic system will need to be cost efficient to

build and maintain. Starting on a smaller scale may be the best option to start with then

expanding on the business. Right now, the primary need is to feed the sheep and fish, and the

sheep are easier to feed for, since the sheep also eat the vegetation on the land. The fish,

however, will completely need their own food from the aquaponics system, since fish food is

pricey (Cline, 2018). Seed for the sheep food should be cheap; however, fish food could be

tricky to grow based on the fish picked. Location will also be essential. There are two reservoirs

and there is the option to use both or only one to begin with. To be safe, using one simple and

smaller design may be smarter than trying to make a giant aquaponics system that could be

costly and not effective.

Restrictions and Regulations

Careful consideration of restrictions and regulations is needed to design a safe, effective

aquaponics system. In addition to the basic fish and plant set-ups, there are also essential

standards for filtration and resource cycling as well. The ideal standard for water flow is moving

the entire volume of the fish tank through the grow beds every hour using a 15 min on, 45 min

off system. Fishless cycling is also recommended because it allows for the buildup of bacteria in

the tank which will later result in faster fish stocking. A test kit should be used to measure

ammonia, nitrate, nitrite and pH, ensuring that ammonia and nitrite levels are always under 0.75

ppm. In addition, aeration devices are also recommended for adequate oxygen levels (Bernstein

and Lennard, 2018). All of these aquaponics standards should be taken into consideration when

designing a model.

In addition the general restrictions and standards, understanding the current Namibian

laws that pertain to aquaculture is also important when considering a design specified for this

country. In 2002, Namibia founded the Aquaculture Act which is managed by the Ministry of

Fisheries for the overall purpose of promoting sustainable aquaculture and manage and

protecting marine and inland aquatic ecosystems (Leicht and Gerhardt, 2014). This is the main

legal guidelines for any aquaculture-related topic such as health management, disease control,

environmental protection and access to land and water. One key regulation outlined in this text

includes the requirement of a license, which is granted by the Ministry of Fisheries to anyone

who has obtained the proper paperwork and who has designed an acceptable system in the eyes

of said Ministry. This includes designing a system that has water-access and an acceptable

method of wastewater disposal. In addition, it the Ministry of Fisheries will oversee all license

holders’ practices to ensure there is no accidental or intentional release of alien species, nor the

spread of harmful diseases. All aquaponics systems and license holders must keep detailed

records to be subjected to viewing by the Ministry at any given time (Leicht and Gerhardt, 2014).

In addition to knowing the regulations and restrictions, in order to implement an effective

Aquaponics system, it is also important to understand the availability of agriculture and fishing

in the area. Namibia, or the Republic of Namibia is a largely arid desert country on the

southwestern coast of Africa (Green, 2018). Despite being a coastal country with five permanent

rivers, the sharp reefs and impassable rivers makes it difficult for residents to obtain imported

goods. Similarly, the barren sandy and rocky soils that span across much of the country make

farming difficult. These agricultural issues stem not only from the lack of fertile soil, but from

the water availability in the more arid desert regions. In addition, fishing in Namibia is limited by

stock levels, which have increased significantly with recent conservation attempts (Green, 2018).

These factors should both be taken into consideration for designing an aquaponics system.

Since the aquaponics system in question requires local fish food, understanding the

availability of fish in Namibia is essential to consider when determining stock. Currently,

offshore boating and rock-and-fish angling are common techniques to catch Snoek, Steenbras,

Galjoen, Kabeljou, Blacktail and other well-sought after fish. These fishing techniques are all

strictly monitored by the Namibian sport-fishing industry and the Ministry of Fisheries and

Marine Resources (MFMR) that restricts how much of which fish can be caught and farmed at a

time (Jacobi, 2011). The goal in this effort is to conserve dwindling stock. When transporting

fish to the farm site, the most relevant regulation is the maximum of 30 fish which may be

transported in a vehicle at a time per fisherman (Jacobi, 2011).

Cost:

Having gained insight on general aquaponic system components and the country of

Namibia, another component to consider is cost and the amount the customer is willing to pay..

The items potentially needed for constructing an aquaponics farm are: lumber, pipe, fish tank,

greenhouse, and filters to keep the system sanitary according to Portable Farms (Davis, and

Davis, 2018). The materials for the final aquaponics design will be mostly made of plastic, (pipes

and tank) or recycled materials to keep the design cost effective. Most of the price for the system

will come from the biosensor and the filtering components.

Shipping items out of the country could be an option for materials if the cost remains

cheap enough, however, the farmer would like the most affordable plan. The only item that

might need to be potentially shipped is either the biosensor or fish, but domestic fish and plants

is the best option. Another important component to consider the durability of the materials long-

term. Maintaining a low cost while also ensuring the long-term sustainability of the aquaponics

system will be taken into consideration for the design.

Conclusion:

In conclusion, it is incredibly beneficial to find more sustainable ways to produce food.

Aquaponic systems are an efficient way to help people in underdeveloped countries, like

Namibia, grow food conservatively. These systems are a more efficient way of conserving

limited resources, like water and space, while also maximizing produce. In order to design the

most effective system, it is important to understand what an aquaponics system is, what

components are needed, what fish and plants can be used, and also the culture, restrictions and

regulations, climate, and geography of the country.

Alternatives Considered

Design FeaturesThe RCAT design team focused on a wheel design, evaporative cooling, plants on top of

the fish tank, below ground tank, and retractable awning as our design features to be compared in

the decision matrix. As a group, it was decided that all aquaponics have the same basic design.

Rather than re-inventing the entire system, RCAT focused on individual components which

could improve the efficiency of the system.

The wheel design is an alternative plant growing structure where the plants are situated

on racks fixed between two wheels. As the wheels spin, the racks will individually pass through

the water to collect water and nutrients from the fish tank. The evaporative cooling system is

based on ancient terracotta air cooling systems. Water passes vertically through a cluster of

horizontally oriented terracotta tubes. As air passes through the tube cluster water vapor cools

the air. This design was thought to be more applicable to cooling the water and sheep. Placing

the plants on top of the fish tank simply removes a growing bed from beside the fish tank and

places it on top of the tank instead. The team also considered installing the tank below ground.

All parts of the aquaponics system would remain the same as they would above ground except

that they would be below ground. The last design feature to be considered was installing a

retractable awning above the entire system. This would provide shade to the plants and fish

during the day.

For the project’s specific objectives and constraints, the team selected cost, most effective

method of growing plants, how the overall design would affect the stress levels of the fish,

maintenance, design simplicity, and overall “coolness” of the design. The system should be

within a reasonable and preferably low cost and also be able to produce a fair amount of plants to

sustain the herd of sheep while maintaining the fish, stress-wise and population-wise. The need

for maintenance everyday should also be low. In addition, some designs have more complex

components that may break, which also falls into the simplicity factor of the design. The

aesthetics also varies with each design. For example, consider the wheel design. This design was

ranked as having the highest coolness factor because it simply would be the coolest design.

Every component was put on a 1-10 scale with 1 being low and 10 being the highest. That

number is then multiplied by the importance factor of that component of the design and then all

the numbers are added together to get the final total number for that component for that design.

All the numbers are then compared with the highest total number being the best option on paper.

Using these criteria, the team determined the best overall design was the plants directly

on top of the fish tank design. The team agrees with the results of this decision matrix. This is the

cheapest, simplest, most effective system that will be most readily implemented at the Namibia

site. While that will be the basis of our system, the team also plans to add a couple features to

enhance the simplistic design. The team is still discussing how the plants will be positioned

above the tank, in what way the plants will be stationed there, and how the filtration will be

implemented.

Filter Components

The alternatives selected for filtering the aquaponics system are bottom feeders as water

filters, fish as water filters, manually removing solid waste, plants as water filters, an electric

pump filter, and bacteria filters. Bottom feeders and fish were considered to be incorporated into

the aquaponics system as a filtering system because there is not much cost and would eliminate

the need or a mechanical filter or at least aid in the filtration process. Manually removing solid

waste is another very cost-effective option to filter the water, because the only action needed is

hosing out the tank occasionally. Using plants as filters to clean the water does not negatively

affect the fish within the system in any way. An electric pump filter is highly recommended

because it is a very effective and easy way to keep the water clean. Bacteria filtering the water is

the final potential filter option, because there is essentially no cost, no impact on fish life, and is

very accessible.

For filtration system constraints for the aquaponic system, cost, filtration efficiency, accessibility

of material, maintenance requirements, impacts on fish and overall durability were compared.

These constraints were compared because they are all key aspects to consider when determining

an appropriate filtration system. Using these constraints and a general knowledge of our

Namibian location, the team determined that an ideal filtration system would incorporate easily

accessible parts and be cheap, efficient, durable, non-disturbing to the fish, and would require

very little maintenance.

Using these criteria, all of the alternatives were evaluated and the bacterial filtration

system was determined to be the best filtration system . RCAT did not agree with the results of

this decision. While the team does agree that this system is the cheapest, simplest and most

readily available system, the team does not believe that it will be the most effective overall.

Instead, second-place winner of the decision matrix is the better option which was the bottom

feeder filtration system. This system is simple, has a reasonable cost, and will be the most

effective system overall. It is likely that these systems used in combination would be the

cheapest, most effective filtration system overall.

Final Design description

General design

The RCAT design team designed an aquaponic system for a client located at a small

Namibian farm. Figure 1 below shows multiple 3D views of the general design of the

aquaponics system. This is a simplistic plant-on-water design which consists of one tank for

plants and growing media, (fig. 1B), offset on top of a larger water fish tank below (fig. 1A). A

single pipe, (fig. 1C) attached to a pump connects the water tank to the plant box and

transports the water from tank to plants. Additional system components include a biosensor,

Cowpeas and Tilapia which are outlined in detail below.

Figure 1. RCAT Aquaponics 3D design including: A) fish tank, B) plants with growing media, and C)

water flow pipe.

Dimensions & Logistics:

The main tank seen fig. 1A will be a collapsible 5 ft x 5 ft x 5 ft tank made of

Polyethylene Terephthalate (PET) for fish and water, with another 1.25 ft x 5 ft x 5 ft offset top,

part B, to hold the growing media and produce. The base of the plant bed is slightly slanted and

will contain several evenly-spaced small holes with radiuses of 1 in to allow water to drain from

the plant bed back into the fish tank. The growing media used in the plant bed will be soil, rocks,

and 1.25 in pebbles that are large enough to not fall through drainage pores. Finally, a PET

pipe, fig. 1C, with radius 0.30 ft will connect the two systems with a 250 gal/h Hydrofarm Active

Aqua AAPW250 Submersible Water Pump to pull the water from the tank into the growing bed.

System Components:

As seen in Fig 2, fish in the water tank eat and then excrete ammonia while naturally

occuring bacteria within the system convert ammonia to nitrate. This nitrate-rich water is

pumped from the fish tank into the plant bed through the pipe. The water and nitrate is absorbed

by the plants, helping support healthy plant growth. Water not absorbed by the plants is filtered

through the plant growth medium which consists of a layer of soil on top of a bed of rocks and

pebbles. The slanted plant bed combined with small holes in the base of the plant bed allows for

excess water to drain back into the fish tank. The water is then pumped from the fish tank into

the plant bed again, repeating the cycle. The design team selected components (plants, fish,

and pathogen biosensors) most suitable to the design needs and constraints are highlighted

below.

Figure 2. Flow of Aquaponics system components (RPBAOnline, 2016)

Fish:

Tilapia, shown in Figure 3, is an industry standard for aquaculture and

aquaponics systems around the world (Aquaponics USA, 2017). They are native to the

Nile river basin in lower Egypt as well as other parts of Africa (Jauregui). A local, native

stock of fish would be more cost-effective and accessible. The Nile and Mozambique

are the two subspecies of tilapia that are farmed throughout the continent of Africa.

These two types of tilapia mature at a fast rate (Aquaponics USA, 2017). Female tilapia

spawn every 4-6 weeks, and the fertilized eggs are held in the mother’s mouth for 4-8

days. After the eggs hatch, the mother will continue to hold the “fry” in her mouth for

another 3-5 days. Tilapia is referred to as a “beginner fish” because they are extremely

resistant to disease and drastic temperature changes in the water.

All variables pertaining to the fish are determined by the stocking density of the

fish tank. The determined harvest weight for this system is about 1.5 pounds. The fish

will be stocked at a density of .25 pounds per gallon which would be 155 total fish in the

tank. The feed rate should be between 1.0 - 1.5 percent of the harvest weight (DeLong

et al., 2017) which would amount to 10g of food per fish every day. The tank will be fed

a total of 1550g of food per day. This population of fish will be more than enough to

sustain a single family. The purpose of such a substantial starting population is to allow

the fish to breed freely without human consumption stressing population. There will

always be a large enough population that the client will be able to consume freely within

reason. Tilapia will breed at a rate of 2 females for every male although some

commercial systems operate at up to 5 females per male. Each female will lay about 10

eggs depending on the size and age of the female (Towers, 2005). From the time the

eggs hatch until they are at harvest weight, which is between 10 and 12 months.

Figure 3. An adult tilapia ready for harvest. (EatPress, 2009)

Plants:

The plant chosen to grow in the proposed aquaponics system is the cowpea (Vigna

unguicalata) as seen in figure 4. Cowpeas are currently prevalently grown and cultivated

throughout the African continent (Gomez, 2004), so seed will be easily sourced within Namibia.

Cowpeas have superior drought resistance as compared to most other beans and perform best

in sandy soils (Davis et. al, 1991) making it the most fitting choice for Namibia.

Figure 4. Mature cowpeas (AgriFarming, ND)

Without knowing the species of sheep being farmed in Namibia it is difficult to know

exactly how much feed is necessary to provide to the herd. Assuming in the herd of 25 sheep

each sheep weighs about 150 pounds at full maturity each sheep would need to consume about

2.6 pounds of dry matter per day (Schoenian, 2018). In total, the herd of sheep will need 65

pounds of dry matter per day. Cowpeas have a much higher nutrient density as compared to

traditional livestock feed. One cup of cowpeas contains 13.22g of protein (HealthBenefits, 2018)

whereas one cup of alfalfa only contains 1.32g per cup (HealthBenefits, 2018). Therefore, a

smaller quantity of dry matter will need to be fed to keep the sheep at their desired growth rate.

Cowpeas can be used in every stage of growth (Davis et. Al. 1991). In many areas of the

world, the cowpea is the only available high-quality legume hay for livestock feed. Digestibility

and yield of certain species are comparable to alfalfa (Davis et. Al. 1991). Cowpeas are not only

beneficial to the animals they are feeding, but they are also beneficial for human consumption.

The International Livestock Research Institute (ILRI) identified cowpeas as a superior crop to be

cultivated for animal and human consumption (Kristjanson et. Al. 2002).

Cowpeas are not only beneficial for plant and animal consumption, but they would also

be easily integrated into Namibian culture. Cowpeas originated in West Africa and have been

cultivated by subsistence farmers there ever since (Abberton 2018). Cowpeas are a crop that

Namibian farmers would be familiar with growing and could integrate it into their production

systems. As a result, farmers would be more likely to accept cowpeas as opposed to a plant

that they were not familiar with growing, and the integration of the aquaponics system would be

more successful.

In RCAT’s designed system, not enough cowpeas are produced to fully sustain a herd of

25 sheep. The team believes that, though plant production falls short, the proposed system will

be the foundation on which more growing beds can be added and more cowpeas can be

produced. During further research and development RCAT is optimistic that the tank system

could support many more growing beds to expand the farmer’s production capabilities.

Pathogen Biosensor:

Figure 5. Schematic diagram of bacteria

Figure 6. (a) Comb type electrodes on a PET measurement and classification (Ali, 2018).substrate, the zoomed image shows Ag

nanowires in the space between two electrodes.

(b) Bacteria engaged with sensor that

varies the impedance of

the sensor (Ali, 2018).

Lastly, the design includes a biosensor for detecting Escherichia coli to ensure

that any pathogen breakouts within the aquaponics system can be dealt with before any

damage is caused. The biosensor used with this aquaponics system is disposable and

has instantaneous detection and classification of pathogens. The three pathogens this

biosensor can detect are Salmonella typhimurium, and the Escherichia coli strains

JM109 and DH5-α. There are three main components that play various roles in

detecting pathogens, as seen in Fig. 4. The sensor itself consists of silver electrodes

which are assembled onto plastic polyethylene terephthalate (PET) substrate by a

Fujifilm inkjet Dimatix material printer (Fig. 5). Silver nanowires are then added onto the

electrodes increasing the sensitivity of the sensor. Connected to the sensor is an

impedance analyzer which measures changes to the impedance of the sensor(Ali,

2018). After the reading, the impedance analyzer sends the recorded data to the

computer which is displayed. To operate the system, a small sample of water taken

from the aquaponics system is placed on the sensor. Based on the concentration of

pathogens present, the impedance levels will be recorded and displayed accordingly.

This system is cost effective and simple to use. If a pathogen is detected, the proper

protocol to treat the pathogen should be utilized.

Implementation of System in Namibia:

Figure 7. Map of Namibia (ExpertAfrica)

Figure 8 (a): The photo shows one of the two reservoirs located on the rural farm that the aquaponics

system will be constructed next to (Cline, 2018).

Figure 8 (b): This picture depicts the environment and basic set-up of the farm in Namibia (Cline, 2018).

The aquaponics system was designed with the Namibian climate and environment in

mind. To ensure the system will succeed in the desert-like area, the tilapia are native to the

country, and the selected plants will be accustomed to hot weather and arid climate. The

structure of the box is sturdy to withstand the weather in the area. With little vegetation to feed

the livestock, the aquaponics system will assist providing nutrition to farm animals.

Advantages and Disadvantages:

This aquaponics system design is a simplistic structure that would not be complicated to

replicate should the farmer want to expand. Also, the necessary materials are cheap and

affordable. This design meets the client’s preference to start on a smaller scale to experiment

with the effectiveness of an aquaponic system in the area. One problem with the design is the

plant and fish production has a small potential due to the small-scale structure of the design.

The fish are also going to be in a tight proximity. Water flow is controlled to an extent, but there

could still be enough stagnant water in the fish tank that the ammonia and nitrate levels could

affect the fish.

Design Recommendations:

The RCAT team recommends this small, simple design to observe how successfully the

system can be integrated. The system can independently function on its own, with the exception

of a source of food for the fish, which will need to be provided by an outside source. The fish

and plant components are kept in close proximity to ease the flow of the system and make it

simpler to construct. Additionally, the symbiotic relationship between the plants and fish are

easier to maintain and observe.

Testing Needs:

To ensure the selected aquaponics system would be successful in Namibia, there are preliminary

tests to judge the overall performance of the design. The system will be put in an environment similar to

the desert-like region to test the functionality and temperature regulation. This will also test the durability

of the system to withstand harsh weather conditions. To ensure the compatibility between the fish and

plants, one full production cycle of both the fish and plants will be observed. The data collected

throughout this test will provide a real-world timeline of how the system will perform in Namibia. During

the test, the fish will be observed on how they deal with stress. An individual who is inexperienced in

operating aquaponics systems will be selected to operate the proposed system. This individual will

provide feedback on how to further simplify system components.

Summary:

In conclusion, RCAT was able to design a simple plant-over-water aquaponic system that

consists of a fish tank, growing bed, filtration system and detached biosensor. When designing

the system, the team took into account all of the client’s needs and constraints regarding the

climate, geography, and regulations of Namibia. The system was designed specifically for the

Namibian climate and culture, utilizing Tilapia and cowpeas, both of which are produce that can

be found locally in Namibia. In the end, the team was able to design a system that met the clients

most important constraints by serving as a cost-effective, low-maintenance aquaponics system

that would supply enough food for a herd of sheep on a farm in Namibia. Should the farmer want

to expand in the future, the design would be easy to replicate. Overall, the design successfully

accomplished all the criteria and should aid the farmer in Namibia.

References

Agribusiness TV: Kenya: Aquaponics, produce more in less space. (n.d). Agribusiness

TV, broadcast.

Ali, S., Hassan, A., Hassan, G., Eun, C., Bae, J., Lee, C. H. & Kim, I.. (2018). Disposable

all-printed electronic biosensor for instantaneous detection and classification of

pathogens. Scientific Reports 8(1): 5920

Araya, D. H.. (2014). Indigenous / Traditional African Leafy Vegetables. Agricultural Research

Council.

Bernstein, S. & Lennard, W. (2018). Aquaponic source rules of thumb. Retrieved from

https://www.theaquaponicsource.com/rules-of-thumb/

Bodlovich, A. & Gleeson, K. (2006). Aquaponics System. US Patent No. US8677942B2.

Cline, M. (2018). Self-Sustaining Aquaponics System. personal.

Cline, M. (2018). Self-Sustaining Aquaponics System: Feasibility report. Rep.

Davis, C., and Davis, P. (2018). Cost of An Aquaponics System and Operating Tasks.

Portable Farms®.

DeLong, Dennis, Losordo, Thomas, Rakocy, James. 2018. Tank Culture of Tilapia.

Ebeling, J. (n.d). Biofiltration‐Nitrification. PhD diss. University of Arizona, Department

of Engineering.

Enduta, A., Jusoh, A., Ali, N. & Wan Nik, W. B. (2011). Nutrient removal from

aquaculture wastewater by vegetable production in aquaponics recirculation system.

Desalination and Water Treatment 32(1-3): 422-430.

Expert Africa. (2016). Namibia Map for Holidays and Safaris.

Gale, T. (2001). Namibia; Countries and their Cultures, 3, 1537-1544.

Goddek, S., Delaide, B., Mankasingh, U., Ragnarsdottir, K., Jijakli, H. & Thorarinsdottir,

R.. 2015. Challenges of sustainable and commercial aquaponics. Sustainability 7(4):

4199-4224.

Green, R. (2018). Namibia.

Grimes, G. 2011. What is the cheapest new alternative energy? .

Hall, D. R., Boswell, C., Gardner, E. & Allred, D. 2010. Rotatable panels on an exterior

of a Structure that directs solar energy within the Structure. US Patent No.

US20120067337A1.

HealthBenefits. 2018. Alfalfa – Medicago sativa

HealthBenefits. 2018. Cowpeas facts and health benefits.

Jacobi, N. (2011). Namibian fishing waters among the best. Travel News Namibia.

Kiangi, G. E. (1998). Computer education and human capacity building for Information

Technology in Namibia. In Capacity Building for IT in Education in Developing

Countries: IFIP TC3 WG3.1, 3.4 & 3.5 Working Conference on Capacity

Building for IT in Education in Developing Countries 19–25 August 1997,

Harare, Zimbabwe, 39-47. ed. G. Marshall and Ruohonen, M., Boston, MA: Springer

US.

Kozai, T., Niu, G., Takagaki, M. (2016). Plant Factory: An Indoor Vertical Farming

System for Efficient Quality Food Production. 1st ed. Elsevier.

Leicht, A., & Gerhardt, R. (2014). Namibia. Hamburg: Jahreszeiten-Verl.

Liu, Y., Chakrabartty, S. & Alocilja, C. (2007). Fundamental building blocks for molecular

biowire based forward error-correcting biosensors. Nanotechnology

18(42):424017.

Marklin Jr., R., Mathison, M., Mayer, B., Nagurka, M., Cariapa, V. & Schabelski.. (2013)

Mechanical Engineering Faculty Research, Mechanical Engineering and Department of

Publications. e-Publications@Marquette.

Martell, C. (2016). Aquaponics System Spring Cleaning.

Matengu, K. K. (2011). Successful technology and innovation policy for Namibia: A review of

issues and lessons for a developing country.

Mohamad, N. R. (2013). Development of Aquaponic System using Solar Powered

Control Pump. IOSR Journal of Electrical and Electronics Engineering 8(6): 1-6.

Mountney, N., Howell, J., Flint, S. & Jerram, D. (1999) . Climate, sediment supply and tectonics

as controls on the deposition and preservation of the aeolian-fluvial Etjo

Sandstone Formation, Namibia. Journal of the Geological Society 156(4): 771.

Murmson, S. 2018. What Are the Items Needed to Make a Solar Panel System? .

Namibia Travel. (2010). Geography of Namibia.

Schoenian, S. 2018. Sheep 201.

Shusko, L. (2015). Traditional foods of Namibia.

Singh, C., Daron, J., Bazaz, A., Ziervogel, G., Spear, D., Krishnaswamy, J., Zaroug, M.,

& Kituyi, E. 2018. The utility of weather and climate information for adaptation decision-

making: current uses and future prospects in Africa and India. Climate and Development

10(5): 389-405.

Towers, L. 2005. Farming tilapia: life history and biology.

Wicoff, E. (2011). Develop of a simplified commercial-scale aquaponic facility for

implementation in northern Uganda. Kansas State Research Exchange, thesis.