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Sewage and Satori The Creation of a Living Ecological Infrastructure
A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR A
BACHELOR OF DESIGN (HONS)
NUMBER OF WORDS IN MAIN BODY OF TEXT
9446
Frances Wright INTERIOR AND ENVIRONMENTAL DESIGN
DUNCAN OF JORDANSTONE COLLEGE OF ART AND DESIGN THE UNIVERSITY OF DUNDEE
SCOTLAND
JANUARY 2013
CONTENTS
FIGURES
TABLES
ACKNOWLEDGEMENTS
Sewage and Satori The Creation of a Living Ecological Infrastructure
INTRODUCTION
A Living Infrastructure 1
CHAPTER 1
Making Connections 2
An Emerging World View 2
A Psycho-Physiological Need 4
CHAPTER 2
Air 7
The Symbiotic World 7
Pure Air 8
Contained Environments 12
Sick Buildings 14
CHAPTER 3
The Nature of Decay 17
Transformations 17 Nitrogen 18 Phosphorus 20 Pathogens 21 The Effect on Ecosystems 22
CHAPTER 4 Water, Water, Everywhere . . . 24
A Problem of Our Own Making 24
Conventional Systems 24
Ecological Approaches 26
CHAPTER 5 Wetlands 27
Natural Wetlands 27
Constructed Wetlands 28 Horizontal Surface Flow Constructed Wetlands (HSFCW) 28
Vertical Flow Constructed Wetlands (VFCW) 30
Horizontal Subsurface Flow Constructed Wetlands (HSSFCW) 33
Complex Ecological Wetlands 36
WET Systems 40
Bioshelters to Living Machines 43
CONCLUSIONS A Holistic Approach 52
A New Mindset 52
Appropriate Use of Resources 53
Composting 54
Water Recycling 55 The Earthship’s Botanical Cells 56
Green Walls 59
Symbiotic Landscapes 61
APPENDIX 1
Earthship Fife 63
The Greywater Botanical Cell 64 The System: Loads & Sizing 64
The Planted Cell 65
Maintenance 66
Effectiveness 68
The Blackwater Botanical Cell 69 The System: Loads & Sizing 69
The Infiltrator 70
The Planted Cell 70
Maintenance 72
Effectiveness 73
Conclusions 74
APPENDIX 2
Dufftown Distillery 75
The Distillery Wetland 76 Overview of System 76
The System: Loads & Sizing 77
Design and Planting Details 79
Maintenance 80
Conclusions 82
GLOSSARY 83
REFERENCES 86
FIGURES
Figure 1: Basement Green Wall at the Origami House, Singapore by
Formwerkz creates a psychological link to the outside.
5
Figure 2: Simple Compost Biofilter. 9
Figure 3: Bio-Home Interior Wastewater and Air Purification Systems. 12
Figure 4: The Plant Air Purifier a modern development of the Bio-Home
planter claims to have the same cleaning power as 100 houseplants
grown in soil.
13
Figure 5: Extensive Indoor Planting at the Paharpur Business Centre, India. 15
Figure 6: Eutrophication at a wastewater outlet on the Potomac River,
Washington, D.C.
23
Figure 7: Section through a Horizontal Surface Flow Constructed Wetland. 29
Figure 8: Schematic Section through a Vertical Flow Constructed Wetland by
Elemental Solutions.
31
Figure 9: Constructional Section through a Vertical Flow Constructed
Wetland by Elemental Solutions.
32
Figure 10: Section through a Horizontal Subsurface Flow Constructed Wetland
by Elemental Solutions.
34
Figure 11: Horizontal Subsurface Flow Wetland at Birdwell Downs, Australia,
by Nelson and Tredwell.
36
Figure 12: A Multiple Stage Constructed Wetland at the Centre of Alternative
Technology, Machenllyth, Wales.
37
Figure 13: A Mature Farmland WET System. 40
Figure 14: Typical Section through the Swales of a WET System. 41
Figure 15: Graded Basket Willow from WET System at Shepherds Dairy Ice
Cream, Cwm Farm, Herefordshire.
42
Figure 16: Solar Aquaculture Cells and Lemon Trees at the Cape Cod Ark
Bioshelter (1976) by Solsearch Architects.
44
Figure 17: Typical components and sequence of flow in a Hydroponic Based
Living Machine.
45
Figure 18: A Cellular Living Machine designed by John Todd. 46
Figure 19: A Biological Fluidized Bed. 47
Figure 20: The Living Machine Tidal Wetland System. 48
Figure 21: Living Machine at the Port of Portland Headquarters, Oregon. 50
Figure 22: An Earthship. 56
Figure 23: A Greywater Botanical Cell. 57
Figure 24: Plan and Section of the Blackwater Botanical Cell at Earthship Fife. 58
Figure 25: Jamieson Place Biowall, Calgary, Alberto , 2010. 59
Figure 26: Schematic diagram of Greywater Phytoremediation at Bertschi
School Science Wing, Seattle, 2011; by GGLO using GSky Pro Wall
System.
60
TABLES
Table 1: The Emerging Precepts of Biologic Design. 3
Table 2 Indoor Plants for VOC Removal. 11
Table 3: Typical End Products of Aerobic and Anaerobic Decomposition. 18
Table 4: Sizing for First Stage Vertical Flow Constructed Wetlands. 33
Table 5: Native Plants suitable for use in UK Wetlands. 39
ACKNOWLEDGEMENTS
I’d like to extend my thanks to the subjects of my Primary Research Visits for their time
and patience showing me around their particular facilities.
Thanks to; Geetam van der Dussen for showing me around Earthship Fife, in
Craigencault and discussing in detail the Black and Greywater Botanical Cells. It was an
extremely pleasant afternoon sat in the sun discussing sewage systems!
My appreciation also goes to Alison Campbell (and Jane Shields) from Living Water
Ecosystems Ltd. for putting me in contact with their previous clients William Grant and
Sons. Dave Stewart for showing me around the Constructed Wetland at the
Glenfiddich Distillery in Dufftown and for proof reading my transcription of our
discussion; ensuring that all my details were correct and adding further points of
clarification as necessary; many thanks Dave.
Finally, I would also like thank my tutor Shaleph O’Neill, for his perseverance and
advice.
Sewage and Satori The Creation of a Living Ecological Infrastructure
1
INTRODUCTION
A Living Infrastructure
This dissertation will argue that our growing understanding of the ecological web of
life, has led to the realization that we can - and indeed must - design our future built
environment to physically and psychologically re-integrate man and his processes with
those of the natural world.
It will describe how working in symbiosis; plants, microorganisms and fungi essentially
clean our environment and explain how awareness of these processes has been
translated by designers and architects into simple and practical means of both
improving indoor air quality and cleaning wastewater.
I will examine in detail the processes of decay found in natural wetlands and discuss
how this knowledge has been practically applied in the design of Constructed
Wetlands; critically assessing these ecological approaches against Conventional
Wastewater Treatment Systems.
In closing; I will reflect on how the development of an increasingly holistic mindset has
allowed designers to expand their perception of these systems to encompass a more
ecological, multi-functional approach. In this vision; Landscape and the Built
Environment could develop together in symbiosis; creating a truly Living Ecological
Infrastructure and firmly rooting Mankind back within Nature.
2
CHAPTER 1
Making Connections
An Emerging World View
In 1962, the biologist Rachel Carson published her seminal work, ‘Silent Spring’.
Explaining in detail how the widespread and indiscriminate use of chemical herbicides
and pesticides were poisoning the entire food chain and destroying the natural balance
of ecosystems; she argued that we must recognize that human beings are an integral
part of this living world, and ultimately comprehend that what we do to it; we are
effectively doing to ourselves (Carson, 1991).
A decade later, James Lovelock and Lynn Margulis proposed the ‘Gaia Hypothesis’,
which states that; ‘Life, or the biosphere, regulates or maintains the climate and the
atmospheric composition at an optimum for itself’ (Lovelock, 1991, p. 11). In effect,
Gaia - the planet as a whole - behaves as though it is a living self-regulating
superorganism;
‘Rainforests act as the earth’s lungs, producing oxygen and removing carbon
dioxide – the opposite process to human and animal lungs. Wetlands function
as the earth’s kidneys. Aquatic plants filter nutrients and environmental toxins
from the water as it flows back into streams, rivers and oceans in much the
same way as kidneys filter impurities from our blood.’
(Wolverton, 2008 pp. 14-15)
Unfortunately the ability of the natural world to maintain this balance is becoming
increasingly stressed by mankind’s activities (Lovelock, 1991). This has led to the
3
realisation that we need to reassess the way we currently live and work, and take a
more sustainable approach.
‘The urgency of the situation demands tackling the problems we have created
on as many levels with as many strategies as we can muster. . . What is
required is nothing less than a fundamental technological revolution that will
integrate advanced societies with the natural world to the mutual benefit of
both.’
(Todd and Todd, 1993, p. 166)
John and Nancy Jack Todd, both members of ‘The New Alchemy Institute’, were among
the early pioneers who proposed a different approach to design: using knowledge of
how the natural world works as the basis for designing human processes and
environments that could exist in symbiosis with it (table 1). They envisioned a
reintegration of Man and Nature; of Architecture and Biology which they called
‘Biologic Design’ (Todd and Todd, 1993). They were not alone; comparable ideas exist
in ‘Permaculture’, ‘Biomimicry’ and ‘Biotecture’.
Table 1: The Emerging Precepts of Biologic Design (Todd and Todd, 1993).
4
A Psycho-Physiological Need
Restoring our relationship with the natural world is not just a practical necessity or an
aesthetic sensibility, we, as a species, have a deep psycho-physiological connection
with nature.
An innate positive reaction to plants and natural landscapes is virtually universal; a fact
that has been illustrated by a number of research studies.
A series of controlled experiments conducted by Ulrich et al. (1979, 1981 & 1986)
measured the responses of subjects shown images of natural as opposed to urban
landscapes. They found that subjects who had viewed natural scenes showed a
markedly more positive emotional state than those who had seen urban images. They
also recovered faster and more completely from stressful events, both psychologically
and physiologically, exhibiting lower muscle tension, skin conductivity and blood
pressure (cited in Seignot, 2000). In other studies, Ulrich observed that patients
recovered faster, had less post-surgical complications and took less medication if they
had a view of trees rather than brick walls during their hospital stay (cited in Edwards
and Torcellini, 2002).
Further experiments by J. V. Stiles (1995) and H. Russell (1997) recorded the blood
pressure, heart rate and skin conductivity, of volunteers subjected to stressful
situations, whilst in spaces with and without interior planting. They concluded that
people recovered from stress and mental fatigue quicker, had a greater sense of
relaxed psychological well-being, and a better ability to concentrate and be vigilant in
spaces with plants (cited in Seignot, 2000).
5
Although it is obviously difficult to quantify emotional responses; these
‘Studies of interactions between plants and people have provided
overwhelming evidence that plants have a measurable beneficial effect on
people and the space they inhabit.’
(Wolverton, 2008, p. 20)
Figure 1: Basement Green Wall at the Origami House in Singapore, by Formwerkz creates a
psychological link to the outside (Richardson, 2011).
It would also appear that the problems associated with urban life: stress, anger,
alienation . . . may actually be made worse by the simple lack of soothing vegetation.
6
One could conclude then, that the incorporation of external and internal planting into
our built environment is essential, both for our physical and emotional health; and as
Singapore-based Designers ‘Formwerkz’ affirm (figure 1), we should direct our efforts
towards
‘. . . the restoration of primordial relationships between man and nature.’
(Richardson, 2011, p. 70)
7
CHAPTER 2
Air
The Symbiotic World
We are only really just beginning to comprehend, through the study of natural
ecosystems, the complex and often intimate relationships living organisms have with
one another and their non-living environment.
Perhaps because they are rooted in one place and their movements and processes
indiscernible to the naked eye; we have a tendency to perceive plants as rather passive
organisms when in fact they are fundamental to all life. Through a series of complex
reactions called Photosynthesis, green plants use energy obtained from sunlight to
convert carbon dioxide and water into sugars and oxygen. This process not only
creates the energy rich sugars on which all life depends; it also effectively removes
atmospheric carbon dioxide and replaces it with oxygen - without which animals could
not survive (Thompson, 2012).
Study on this microscopic level also reveals that, far from being inactive, each plant
creates and emits an invisible cloud of complex organic compounds from its leaves and
roots and is, in fact, the dynamic centre of its own mini-ecosystem. The zone
surrounding plant roots, known as the Rhizosphere, contains much more intense
microbial activity than is found elsewhere in the soil (Wolverton, 2008). It is here that
plants actively form symbiotic relationships with both microorganisms and fungi.
8
The specific compounds a plant excretes from its roots (sugars, amino acids,
hormones, organic acids etc.) stimulate those organisms that are beneficial to it and
inhibit those that aren’t. These substances, decaying plant matter and the air the plant
draws into the soil by the process of transpiration provide sustenance for a thriving
microbial population. These microbes, in return, make nutrients available to the plant
by breaking down organic wastes, releasing soil minerals, fixing atmospheric nitrogen
and in the decay of their own dead cells. They also excrete mucopolysacheride gels
which enhance the water retentive properties of the soil and are responsible for
detoxifying a wide range of environmental pollutants which both protects the plant
and creates a healthy environment for all other living organisms (Abrahams, 1996;
Wolverton, 2008).
The roots of 90% of all terrestrial plants are also commonly colonized by Mycorrhizal
fungi (Bonfante, 2003). In this symbiotic relationship the plant provides the fungus
with a constant supply of sugars whilst the fine mass of thread-like Mycorrhizal
mycelia vastly increases the ability of the plant to absorb water and nutrients, in
particular phosphates, from the soil. This can be extremely significant to plants and
trees growing in poor soils or difficult conditions.
Pure Air
The concept of harnessing the natural ability of plants and their symbiotic soil
microorganisms to purify air, although relatively modern, does have some precedents.
9
Soil Biofilters were actually first invented in Germany in the 1920’s as a means to
remove malodour or pollution from sewage plant and industrial air exhausts (figure 2).
It wasn’t, however, until the 1970’s and 1980’s that Soil Biofilters were truly developed
and accepted as a relatively inexpensive but highly effective means of air purification
(Nelson and Bohn, 2011; Nelson and Wolverton, 2011).
Figure 2: Simple Compost Biofilter (Nelson and Bohn, 2011).
During the 1980’s and 1990’s Dr B. C. Wolverton and other NASA scientists at the John
C. Stennis Space Centre began to investigate the possibility of creating completely
closed ecological life-support systems for future spacecraft. It was understood that
plants, through photosynthesis and respiration regulate the amount of carbon dioxide
and oxygen in the air; however initial tests showed that air quality within a spacecraft
would still be a concern because of the build-up of Volatile Organic Compounds (VOCs)
of both chemical and biological origin within a sealed environment (Wolverton, 2008).
10
Wolverton speculated that plants might also be able to affect the levels of these other
gases, and began a series of sealed chamber tests using various plants and VOCs. The
findings, published in 1984 and 1989, clearly demonstrated the ability of houseplants
to remove benzene, formaldehyde and trichloroethylene - all common indoor
pollutants - from a sealed chamber (Seignot, 2000; Wolverton, 2008; Nelson and
Wolverton, 2011).
Some of these gases, which are absorbed through the leaves, are destroyed by the
plant’s own biological processes; the majority however are translocated unchanged to
the rhizosphere where they are broken down by microorganisms. With such short
lifespans, microorganisms mutate rapidly in response to changes in their environment,
adapting so they can assimilate these pollutants for their own nourishment. As a result
their ability to remove specific pollutants actually improves with time and exposure
(Wolverton, 2008).
Questioning the extent of the role plants played in this process; later research showed
that the rate of chemical absorption went up with increased light levels – i.e. during
photosynthesis and differs between plant species. It was therefore concluded that
‘plants have the ability to absorb chemicals from the air, translocate these chemicals
and biodegrade them’ (Seignot, 2000, p.109).
Wolverton and other scientists have expanded on this initial research by
comprehensively testing a wide variety of houseplants for their ability to remove
indoor air pollutants (table 2). As a result, it is now considered a proven scientific fact
that plants do improve indoor air quality (Wolverton, 2008).
11
12
Contained Environments
Sceptics claimed that sealed chambers did not represent the real world, so in 1989
NASA created a small hermetically sealed environment in which a student lived for
several months (figure 3). Constructed of mainly synthetic materials; the ‘Bio-Home’
was a closed environment with wastewater initially cleaned in an indoor constructed
wetland and then reused for the irrigation of a plant based air purification system
(Wolverton, 2008; Nelson and Wolverton, 2011).
Figure 3: Bio-Home Interior Wastewater and Air Purification Systems (Takenaka Garden
Afforestation Inc., 2011).
Using the knowledge gained through Wolverton’s research, NASA also developed and
tested a fan-assisted activated-carbon planter, in the Bio-Home (figure 4). This simple
device, by increasing the flow of air through the microbe rich rooting media of
13
expanded clay and activated carbon, was able remove 87% of indoor air pollutants in
just a few hours, resulting in a VOC removal equivalent to at least 15 houseplants
(Seignot, 2000; Wolverton, 2008; Nelson and Wolverton, 2011).
Figure 4: The Plant Air Purifier a modern development of the Bio-Home planter claims to have
the same cleaning power as 100 houseplants grown in soil (US Health Equipment Company,
Inc., 2011).
Research into closed artificial ecological systems continued with the ‘Biosphere2’
Project, built by Space Biosphere Ventures in 1991. Biosphere2 contained several
biomes representative of natural habitats, agricultural areas, workshops, laboratories
and living facilities for 10 people (Nelson and Bohn, 2011). Many problems were
highlighted over the course of the closure experiments, notably the gradual decrease
14
in oxygen due to a lower rate of photosynthesis than estimated, however the systems
for cleaning wastewater and purifying the air worked well.
Interior Air Quality was managed naturally by using plants, microorganisms and soil.
The agricultural beds served not only to grow crops but also as soil bio-filters through
which the entire internal volume of air was pumped every 24 hours. Although this
system is very robust and can adapt itself to whatever pollutants present; efficiency is
increased if the soils have been previously conditioned by exposure to the pollutants in
question or contain more organic matter (Nelson and Bohn, 2011). With the one
exception of nitrous oxide;
‘Biosphere2 demonstrated effective control of all trace gases through passive
adsorption by the abundant soils and microbial/plant biomass of the facility.’
(Nelson and Wolverton, 2011, p. 586)
Sick Buildings
In the last 50 years the range of chemicals to which we are regularly exposed has
increased dramatically. These chemicals not only include those we choose to use such
as toiletries and household cleaners, but also those that continue to off-gas from
materials in our environment e.g. plastics, paints, preservatives, adhesives, textiles,
and a wide range of modern building materials (Pearson, 1989; EcoLogic Design Lab,
2009).
In poorly ventilated spaces, a build-up of chemical and biological contaminants,
together with low relative humidity, raised carbon dioxide and reduced oxygen levels
15
reduces indoor air quality and results in the phenomenon known as ‘Sick Building
Syndrome’ (Seignot, 2000). Occupants in these spaces may suffer from a wide range of
symptoms; respiratory, eye, nose and throat problems, headaches, dizziness, nausea,
fatigue, disorientation and even temporary memory loss, but typically these symptoms
soon abate after leaving the building (Seignot, 2000; NHS Choices, 2012).
Unfortunately, these conditions are widespread in many modern air-conditioned
buildings, where concerns about energy efficiency and heat loss have led to ventilation
being reduced to a minimum.
An obvious way to tackle this problem would be to reduce the use of these chemical
and increase ventilation. However, research into contained environments suggests
that plants could be used to clean and re-oxygenate the air and incidentally increase
relative humidity through transpiration, thereby alleviating all these symptoms
without increasing ventilation levels (EcoLogic Design Lab, 2009).
Figure 5: Extensive indoor planting at the Paharpur Business Centre, India (Perfect Cube, 2009).
16
At the Paharpur Business Centre, New Delhi, they have been doing just that for nearly
20 years. The building is approximately 4650 m2 and contains 1200 plants for 300
occupants (figure 5). New Dehli has particularly poor outdoor air quality, and
compared to other buildings in the city, the Paharpur Business Centre reports an
impressive reduction in; eye irritation by 52%, respiratory system complaints by 34 %,
headaches by 24 %, lung impairment by 12%, Asthma by 9%, as well as; a 32%
probability of blood oxygen levels actually rising 1% if you stay in the building for 10
hours. They also attest to a 20% increase in human productivity, and with less need for
air-conditioned fresh air, the centre uses 15% less energy – a truly environmentally
significant factor when you consider where the developing world economies are
(Meattle, 2009).
17
CHAPTER 3
The Nature of Decay
To garner a better understanding of how we might design ecological systems to clean
wastewater, we must first understand some of the processes involved in nutrient
recycling in nature and what problematic effects specific elements may have on the
natural ecosystems.
Transformations
All organic matter is made up of complex carbon based molecules. As well as carbon;
these molecules may contain hydrogen, oxygen, nitrogen, phosphorus, sulphur and
trace amounts of other elements such as cobalt and zinc. In decomposition; fungi and
microorganisms break down these long chained organic molecules into successively
smaller fragments. Splitting these chemical bonds releases energy, but in doing so the
microorganisms consume oxygen, creating a Biochemical Oxygen Demand or BOD.
Given the correct conditions, decomposition continues until all that remain are simple
inorganic molecules, and it is therefore commonly known as Mineralisation (Grant,
Moodie and Weedon, 2005).
In nature, this process of catabolism can take place in both aerobic (e.g. forest floor)
and anaerobic (e.g. wetland) conditions (table 3), although the latter is a much slower
process. In aerobic conditions, the elements generally emerge combined with oxygen
18
to form odourless, non-toxic and water soluble compounds. In anaerobic conditions
they tend to combine with hydrogen to form noxious gases. These are typically smelly,
potentially explosive or toxic to organisms adapted to an oxygen rich environment
(Grant, Moodie and Weedon, 2005; Van der Ryn, 1995).
Table 3: Typical End Products of Aerobic and Anaerobic Decomposition (Grant, Moodie and
Weedon, 2005).
It is important to understand the possible pathways taken by these elements,
particularly nitrogen and phosphorus; because these elements have the capability of
disrupting and degrading downstream ecosystems.
Nitrogen
In both aerobic and anaerobic decomposition organic nitrogen is transformed into
ammonia (NH3). Some of this will escape as a gas; however it also readily combines
with water to form ammonium ions (NH4+) (Grant, Moodie and Weedon, 2005).
NH3 + H2O ←→ NH4
+ + OH-
19
In anaerobic wetland soils, the ammonium ion (NH4+) is fairly stable, held
electrostatically to the surfaces of soil particles (adsorption) or easily re-absorbed by
plants and algae and converted back to organic matter (Wastewater Gardens, 2012).
However in aerobic conditions, where sources of inorganic carbon are available for cell
synthesis; nitrifying bacteria convert the ammonium ions (NH4+) into nitrite (NO2
-) and
then nitrate (NO3-), in a process known as Nitrification (Scragg, 1999; Grant, Moodie
and Weedon, 2005; Wastewater Gardens, 2012).
Nitrosomonas
2NH4+ + 3O2 → 2NO2
- + 4H+ + 2H2O + (energy 480 – 700 kJ)
Nitrobacter
2NO2- + O2 → 2NO3
- + (energy 130 – 180 kJ)
Because nitrifying bacteria have to compete for oxygen with other bacteria, this
process only starts in earnest when decomposition has progressed to the stage where
most of the carbon bonds have already been broken and BOD5 has fallen below 20mg/l
(Grant, Moodie and Weedon, 2005; Wastewater Gardens, 2012).
Ammonium ions (NH4+), nitrite (NO2
-) and nitrate (NO3-) are all forms of inorganic
nitrogen that can be readily used by plants, fungi and microorganisms, and converted
back into organic nitrogen (Wastewater Gardens, 2012).
In anoxic conditions, where there is little or no unbound oxygen, certain bacteria have
also developed the capability of taking the oxygen they need for respiration from
nitrate (NO3-) instead. In wetland soils where there are plentiful sources of organic
carbon and nitrate (NO3-), these denitrifying bacteria convert nitrate (NO3
-) through a
number of intermediary stages to nitrogen gas (N2); which escapes harmlessly to the
20
atmosphere (Scragg, 1999; Grant, Moodie and Weedon, 2005; Wastewater Gardens,
2012).
Denitrifying Bacteria
NO3- → NO2
- → NO → N2O → N2
It is important to note that Decomposition precedes Nitrification which precedes
Denitrification.
Phosphorus
In wetlands, there is no escape mechanism comparable to denitrification for
phosphorus, so although it is removed by processes of assimilation, sedimentation and
adsorption, it also tends to accumulate at a greater rate than nitrogen (Wastewater
Gardens, 2012).
Phosphate (PO43-) is a key nutrient for life. It is readily taken up by living organisms and
assimilated as part of their tissue. In wetlands, when the detritus of these organisms
decompose, the phosphorus they contain may be stored in the sediment as peat or
released back into the ecosystem (Wastewater Gardens, 2012). However if the
biomass is harvested, this phosphorus can be removed.
Phosphates (PO43-) have a particular affinity with the elements Aluminium (Al), Calcium
(Ca) and Iron (Fe). Where these are present, insoluble phosphate minerals may
precipitate out and enter long term storage in soil and sediments. Phosphates will also
readily adsorb to the surface of stones, soils and particularly clay with high Aluminium,
21
Calcium or Iron content. Unfortunately these binding sites can eventually become full,
so the efficiency of this mechanism is reduced with time. Furthermore changes in pH
or an increase in anaerobic conditions can trigger a release of these stored phosphates
into downstream ecosystems (Grant, Moodie and Weedon, 2005; Wastewater
Gardens, 2012).
Pathogens
Effluent from wastewater treatment systems is not expected to reach drinking or
bathing quality standards, however it is essential that human pathogens present in
faecal matter are removed to a large extent to reduce the risk of transmitting
waterborne diseases downstream.
Although some pathogens may live for months or even years; the longer they are
separated from their host the more likely they are to die. Several mechanisms are
responsible for this, including: adverse physical conditions such as temperature or pH,
UV destruction, contact with anti-bacterial compounds produced by plants and other
microorganisms, competition for food with other microbes, predation by larger
organisms such as protozoa or simply by natural death (Stottmeister et al., 2003;
Grant, Moodie and Weedon, 2005).
22
The Effect on Ecosystems
Decomposing organic matter and its products; ammonia (NH3), ammonium ions (NH4+),
nitrite (NO2-), nitrate (NO3
-) and phosphate (PO43-) can have drastic effects on natural
ecosystems, particularly those of small water bodies and lakes (Montgomery, 1997).
When organic matter decomposes in water, the microorganisms involved consume
oxygen dissolved in the water, which can drastically reduce the amount available for
other organisms (Montgomery, 1997). Ammonia (NH3), ammonium ions (NH4+) and
nitrite (NO2-) are also toxic to some freshwater organisms, especially young fish
(Halestrap, 1998; Grant, Moodie and Weedon, 2005).
Nitrates and phosphates are particularly problematic because they are critical
nutrients for plant growth. In lakes an overabundance of these nutrients (especially
phosphate, which is often limiting nutrient in freshwater ecosystems) promotes rapid
growth in both plants and algae and can trigger Eutrophication (Montgomery, 1997;
Grant, Moodie and Weedon, 2005; Wastewater Gardens, 2012). If this happens, algae
blooms (figure 6) may cover the entire water surface, blocking light to other
oxygenating plants, releasing toxins and creating wide diurnal swings in the amount of
dissolved oxygen in the water. Further, when the algae die, they sink to the bottom
and become decaying organic matter themselves, consequently removing more
oxygen and releasing more nutrients back into the water to fuel another cycle of
growth. This process of Eutrophication can cause a dead zone at the bottom of lakes,
where oxygen levels fall so low that fish and other aquatic animals suffocate
(Montgomery, 1997; Grant, Moodie and Weedon, 2005).
23
Figure 6: Eutrophication at a wastewater outlet in the Potomac River, Washington, D.C. (photo
by Sasha Trubetskoy, 2012).
24
CHAPTER 4
Water, Water, Everywhere
A Problem of Our Own Making
In the UK we each use approximately 150 litres of clean drinking water every day; but
only 4% is actually used for that purpose, whilst a massive 30% is used to flush the
toilet (Waterwise, 2012). We effectively use a large amount of an expensive to
produce commodity, drinking water; to transport a tiny amount of human faeces. If
that was not ridiculous enough, we then have to use an equally large amount of energy
trying to remove these wastes, which include human pathogenic organisms, from this
water, because if we are not careful
‘Our excreta – not wastes but misplaced resources – end up destroying food
chains, food supply and water quality in rivers and oceans’
(Van der Ryn, 1995, p. 11)
This whole process consumes 3% of the total energy used in the UK every year and is
responsible for 1% of all Greenhouse Gas Emissions (Consumer Council for Water,
2012; Waterwise, 2012).
Conventional Systems
Conventional Wastewater Treatment Systems consist of vast networks of sewers that
transport a mixed stream of residential, commercial and industrial effluents to a
25
centralised point for processing. This infrastructure itself is extremely expensive to
build and maintain and is in addition to the cost of the highly technical treatment plant
to which everything flows (Abrahams, 1996; Nelson and Tredwell, 2002; Harland
2012).
These established systems can be characterised as; biologically simple, but
mechanically complex. Microorganisms are actually responsible for treating the
sewage; however these treatment methods rely on additional chemicals and
mechanical components e.g. heaters, mixers, aerators and pumps, to function
properly; making them extremely energy intensive and potentially polluting processes
(Abrahams, 1996; Nelson and Tredwell, 2002; Kirksey, 2009).
Often complex computerised control systems are required to monitor pH, temperature
and the incoming nutrient load to ensure the ideal conditions for the select microbial
populations are maintained (Appendix 2, p. 76; Abrahams, 1996). This complex
technology requires highly skilled engineers and technicians to operate, regular
maintenance and eventual costly replacement as components wear out or no longer
satisfy standards or demand.
Centralising treatment in this manner also reduces the possibility of on-site water
recycling and results in water; cleaned to drinking water standard, being used only
once and then discarded (Kirksey, 2009). The current indiscriminate mixing of a wide
range of effluents also makes it impossible to treat specific residues e.g. heavy metals,
industrial chemicals, complex organochlorides, dioxins etc. and results in the
production of a potentially toxic sludge that must be dried and disposed of (Nelson and
Tredwell, 2002; Kirksey, 2009).
26
Conventional Wastewater Treatment Systems can therefore be typified as having high
Capital, Running and Maintenance Costs and not representing a particularly efficient
use of natural resources (Nelson and Tredwell, 2002; Kirksey, 2009; Nelson and
Wolverton, 2010).
Ecological Approaches
The Ecological Approaches I will discuss in the next chapter, whilst varying greatly in
their biological and mechanical complexity, all utilise similar microbial populations to
conventional systems. The difference is, that these microorganisms live in symbiosis
with plants, fungi, invertebrates and animals under more naturalistic conditions, and
are allowed to self-organise into robust and adaptable ecosystems (Abrahams, 1996).
They are also all decentralised systems designed to deal with specific effluents
(domestic, commercial, agricultural or industrial) at source, thereby reducing the need
for expensive infrastructure and allowing the possibility of water reuse on-site (Kirksey,
2009).
27
CHAPTER 5
Wetlands
Natural Wetlands
The ability of Natural Wetlands to efficiently remove nutrients and environmental
toxins from water has been long recognised, and in some areas e.g. the USA, they have
been traditionally used for wastewater treatment.
Many wetland plants, with the need to survive in inhospitable environments, have
evolved specifically to cope with highly anaerobic, acid or alkaline conditions, toxic
compounds such as heavy metals, organic pollutants and salinity (Stottmeister et al.,
2003). The fine root hairs of these plants physically filter suspended particles from the
flow of water and provide their rhizospherical microorganisms with sugars, oxygen and
huge surface areas for colonisation (Grant, Moodie and Weedon, 2005; Harland, 2012).
It is these symbiotic microorganisms that are mainly responsible for the decomposition
of organic matter and the sequestration of heavy metals (Scragg, 1999).
Experiments by Seidal (1971, 1972 and 1973), Burger and Weise (1984) and Vincent et
al. (1994) have also revealed that certain plant have bactericidal effects on pathogenic
organisms and increase their rate of elimination (cited in Stottmeister et al., 2003).
These species include Water Plantain (Alisma plantago), Reed Sweet Grass (Glyceria
maxima), Soft Rush (Juncus effuses), Water Mint (Mentha aquatic), Common Reed
(Phragmites australis) and Common Club Rush (Scirpus lacustris).
28
Constructed Wetlands
Constructed Wetlands attempt to practically harness these natural aptitudes for
wastewater treatment; by designing systems that either concentrate this complex
biological activity into a much smaller area or create multifunctional landscapes.
They are particularly appropriate as small to medium scale treatment systems,
providing highly effective sewage treatment in remote or developing regions where
the cost of infrastructure and complex mechanical systems is prohibitory (Nelson and
Tredwell, 2002; Nelson et al, 2007). Costs differ widely depending on specific design
details e.g. whether the medium is gravel or soil; if waterproofing is supplied by a
geotextile membrane or on-site clay; if pumps and distribution pipes are used or
simple gravity feed; or simply with labour costs. Nevertheless all are fairly conceptually
and mechanically simple and once built the maintenance is quite rudimentary; simply
monitoring water levels and basic gardening skills. Compared to Conventional Systems
they have low capital, running and maintenance costs (Nelson and Tredwell, 2002;
Nelson et al., 2007; Nelson and Wolverton, 2010). Their only real drawback is that they
are land intensive.
Horizontal Surface Flow Constructed Wetlands
(HSFCW)
Used as Secondary or Tertiary Wastewater Treatment, Horizontal Surface Flow
Wetlands are simple and cheap to construct and maintain. They consist of a shallow
planted excavation (figure 7), designed to retain a standing depth of between 100 -
29
300 mm water, with an inlet at one end and an outflow at the other (Nelson and
Tredwell, 2002; Grant, Moodie and Weedon, 2005).
Figure 7: Section through a Horizontal Surface Flow Constructed Wetland (Natural Systems
International, 2012).
As the effluent flows across the wetland, solids settle out or are captured on the
stems, foliage and leaf litter of the wetland plants, which provide abundant surfaces
for microorganisms to colonise (Grant, Moodie and Weedon, 2005). Although Common
Reed (Phragmites australis) and Reedmace (Typha latifolia) are often recommended, a
range of emergent and floating wetland plants can be included, essentially creating a
habitat akin to a natural wetland which is capable of supporting a wide variety of
microbes, invertebrates, amphibians and birds (Nelson and Tredwell, 2002; Grant,
Moodie and Weedon, 2005).
Biological activity takes place in the water, on the plants and in the top layers of the
soil/sediment (Wastewater Gardens, 2012). The large surface area relative to depth
30
permits good oxygen diffusion into the water, creating aerobic conditions suitable for
mineralisation and nitrification. In contrast the sediments are anaerobic and allow
denitrification to occur (Grant, Moodie and Weedon, 2005).
Because Surface Flow Wetlands do not have the depth of cross-section of other
Constructed Wetlands they require a relatively larger land area. The exact area also
depends on the prevailing climate. All constructed wetlands depend on the actions of
plants and microorganisms. In cooler, wetter climates these are less active, particularly
in winter, so Constructed Wetlands built in these climatic zones need to be 2 or 3 times
the size of those in warm semi-tropical areas to achieve similar results (Wastewater
Gardens, 2012). The British Research Establishment suggests a surface area of 10m2/PE
(Grant and Griggs, 2001).
Other disadvantages of Surface Flow Wetlands are the risk of the public coming into
direct contact with the exposed effluent, smell and the possibility that the standing
water might become a mosquito breeding ground (Nelson and Tredwell, 2002;
Wastewater Gardens, 2012).
Vertical Flow Constructed Wetlands (VFCW)
Vertical Flow Constructed Wetlands (figures 8 and 9) are usually used for Secondary
Wastewater Treatment. Typically the beds are approximately 1 m deep, lined with an
impermeable membrane and filled with a matrix consisting of layers of graded sand,
gravel and stone, and then planted with emergent aquatic plants, such as Common
Reed (Phragmites australis). The effluent is distributed in intermittent bursts, evenly
across the surface, via a network of pipes; it percolates through the layers of the
31
matrix and is drained from the bottom of the bed (Grant and Griggs, 2001; Grant,
Moodie and Weedon, 2005).
Figure 8: Schematic Section through a Vertical Flow Constructed Wetland by Elemental
Solutions (Grant and Griggs, 2001).
As there is no water standing in the bed, the Vertical Flow Wetlands provides a free-
draining aerobic environment for plants and microorganisms, and share many
similarities with both Sand and Percolating Filters (Grant and Griggs, 2001; Grant,
Moodie and Weedon, 2005).
The sand layer filters any remaining Suspended Solids from the effluent, and supports
a biological community of aerobic microorganisms, which actively decompose this
retained organic matter. If this material accumulates faster than these microorganisms
can degrade it, the sand loses its permeability and the bed has to be taken out of use
and permitted time to recover naturally. Vertical Flow Systems are therefore usually
designed with two or more parallel beds; depending on demand one or more may be
in use whilst others are resting (Grant and Griggs, 2001; Grant, Moodie and Weedon,
2005).
32
Beneath the sand, the gravel matrix and the extensive root systems provide enormous
surface areas for microbial colonisation. As the effluent percolates through this free
draining aerobic environment, it clings to these surfaces, creating a thin nutritious
layer in which many aerobic microorganisms thrive. In this Biofilm the microorganisms
continue the process of mineralisation and nitrification. Cells within this biofilm are
continually being renewed, and as they die, they are sloughed off and flushed from the
bed. Normally these secondary Suspended Solids are settled out in a Humus Tank,
prior to the effluent receiving further treatment (Grant, Moodie and Weedon, 2005).
The plants in these wetlands not only support the rhizosperical and surface microbial
populations, they also help to keep the sand layer permeable, stabilize the bed against
erosion and in winter provide insulation against the cold which improves the activity of
the microbes (Appendix 2, p. 80; Grant and Griggs, 2001; Wastewater Gardens, 2012).
Figure 9: Constructional Section through a Vertical Flow Constructed Wetland by Elemental
Solutions (Grant and Griggs, 2001).
33
The level of treatment provided by a Vertical Flow Wetland is dependent on both the
bed depth and its surface area. A bed 1 – 1.5 m deep should be sized at 1 – 3 m2/PE
(table 4). The more generous the sizing, the more tolerant the system is to peak
loadings and inclement weather. Instead of a single deep bed, some designers prefer
two or more shallower vertical stages connected in series; in such cases, second and
subsequent beds need only be half the size of the first (Grant and Griggs, 2001).
Table 4: Sizing for First Stage Vertical Flow Constructed Wetlands (Cooper, Job, Green and
Shutes, 1996 cited in Grant and Griggs, 2001).
Maintenance of a Vertical Flow Wetland is technically simple, but must be done
regularly. Beds should be monitored and alternated on a weekly basis; the Humus Tank
frequently desludged and invasive weeds kept in check (Grant and Griggs, 2001).
Horizontal Subsurface Flow Constructed Wetlands
(HSSFCW)
A Horizontal Subsurface Flow Wetland (figure 10) is typically a simple excavation,
approximately 600 mm deep with a length to width ratio of 4:1 (Grant and Griggs,
34
2001). This bed is lined with an impermeable membrane; filled with a gravel or soil
matrix; and planted. Unlike the free-draining Vertical Flow Wetland, the Horizontal
Subsurface Flow Wetland contains a standing depth of 300 – 500 mm water. This
water level, however, is kept at least 50 – 100 mm below the surface of the gravel, so
there is little risk of exposure to the effluent and no smell (Grant, Moodie and
Weedon, 2005; Wastewater Gardens, 2012).
Figure 10: Section through a Horizontal Subsurface Flow Constructed Wetland by Elemental
Solutions (Grant and Griggs, 2001).
Above the water level aerobic conditions prevail, but within the flooded matrix the
environment is anaerobic and ideal for denitrification. Consequently these wetlands
provide excellent Tertiary Wastewater Treatment, removing nitrates from the
wastewater prior to its release into the environment (Grant and Griggs, 2001; Grant,
Moodie and Weedon, 2005).
Operation is simple; fresh effluent enters the wetland at one end, forcing water to
overflow from the other. This natural circulation slowly pushes the wastewater across
the bed, without the need for mechanical pumps (Grant, Moodie and Weedon, 2005;
Wastewater Gardens, 2012). As the effluent gradually moves through the bed, fine
35
suspended particles are physically filtered out by the matrix and the plant roots, and
nutrients are either absorbed by the plants and microorganisms or adsorbed to the
surface of the gravel (Grant and Griggs, 2001; Grant, Moodie and Weedon, 2005;
Wastewater Gardens, 2012).
The particle size of the gravel determines the overall permeability and retention time
of the bed. A pea gravel, 4 – 8 mm in diameter, clean and graded to a uniform size to
maximise void space, is commonly specified (Grant and Griggs, 2001; Wastewater
Gardens, 2012). With a deep matrix and long retention times; Horizontal Subsurface
Flow Wetlands presents a much larger active cross-sectional area than Surface Flow
Wetlands, so require less land (Nelson and Tredwell, 2002). The British Research
Establishment suggest an area of 5 m2/PE for Secondary and 0.5 - 1 m2/PE for Tertiary
Treatment (Grant and Griggs, 2001).
The main problem inherent with Subsurface Flow Wetlands is a tendency for the
matrix to eventually clog with particles, which may lead to the effluent simply flowing
across the top of the matrix and not receiving sufficient processing (Appendix 2, p. 78).
This tendency can be minimized by creating areas within the matrix at both inlet and
outflow composed of larger 40 - 80 mm diameter rocks (Wastewater Gardens, 2012).
Overall, a lifespan of 15 - 25 years can be expected; however if clogging occurs, or the
gravel loses its ability to adsorb elements (e.g. phosphates), the matrix may have to be
dug out and either cleaned or replaced (Grant, Moodie and Weedon, 2005;
Wastewater Gardens, 2012).
Plants tend to grow large and vigorously in this nutrient rich environment (figure 11)
and with the effluent kept below the surface these wetlands can support a wide
36
variety of species; ornamentals, crops or even trees (Weedon, 1992; Wastewater
Gardens, 2012). However, the water level must be monitored, especially in periods of
low use, to ensure that it doesn’t drop below the root zone. This has been a recurring
problem with the enclosed beds at Earthship Fife (Appendix 1, pp. 66-67). Otherwise
maintenance of these beds is relatively simple; just basic gardening skills and
occasional biomass removal.
Figure 11: Horizontal Subsurface Flow Wetland at Birdwell Downs, Australia, by Nelson and
Tredwell (Franklyn, 2006).
Complex Ecological Wetlands
Vertical and Horizontal Flow Wetlands, each comprising of their own distinctive
environments and communities of microorganisms, have very different effects on
wastewater. Consequently, many modern Constructed Wetlands do not take a singular
approach; but instead use a carefully considered combination of wetland beds, ponds,
37
Figure 12: A Multiple Stage Constructed Wetland at the Centre of Alternative Technology,
Machenllyth, Wales (Weedon, 1995).
38
swales, and willow plantations to create a series of environments through which the
effluent must pass (figure 12). At each stage the effluent encounters a different set of
conditions, plants and microorganisms; and consequently receives a different type of
treatment (Appendix 2, p. 76; Grant, Moodie and Weedon, 2005).
In nature, organisms play many roles within their ecosystem and these are often
complex and not immediately obvious to us. Each plant species not only thrives under
certain conditions, but also as a result of symbiotic relationships with specific fungi,
microorganisms and animals (Living Water Ecosystems Ltd., 2000 – 2012).
As understanding of the importance of these relationships has improved, many
wetland designers have moved away from simple reed monocultures. As a result it is
now common to find Wetlands designed with 30 - 60 different species of native
wetland plants (Table 5). These offer a greater variety of root systems, seasonal cycles,
metabolic requirements and specialist capabilities. They also supports a wider variety
of life; which allows the self-organisation of these plants, fungi, microorganisms,
invertebrates, amphibians, birds and mammals into robust, highly efficient and well
adapted ecosystems (Nelson and Tredwell, 2002).
These developments by creating biodiverse natural habitats have also essentially
broadened the fundamental objective of Constructed Wetlands to the extent that
these Complex Ecological Wetlands can now be perceived as mutually beneficial,
multi-functional landscapes.
39
40
WET Systems
Wetland Ecosystem Treatment (WET) Systems (figure 13) are conceived as not only a
bespoke site and effluent specific wastewater treatment system but also a biodiverse
wildlife habitat that additionally provide an opportunity to produce a yield in the form
of a useful crop (Biologic Design, 2012). Jay Abrahams, the principal designer at
‘Biologic Design’ constructs these systems in line with the design principles of the
‘Permaculture Association’, of which he is a Trustee (Harland 2012).
Figure 13: A mature Farmland WET System (Biologic Design, 2012).
WET systems are designed to be inherently low entropy systems. Initially,
contamination in the wastewater is identified, and if at all feasible removed at source
and recycled as a valuable resource for another process. This attitude immediately
reduces the size, complexity and cost of the treatment system required (Abrahams,
1996). Where possible site specific resources and wastes are reappropriated rather
41
than bringing in outside materials e.g. deposits of clay for waterproofing; limestone for
neutralizing acidic wastes; or waste cardboard, organic matter, straw or woodchip as a
mulch material (Abrahams, 1996). However, the major difference to most other
constructed wetlands is that WET Systems use the on-site soil instead of gravel as a
filter medium. This has the advantage of not only reducing the costs, energy and
environmental degradation involved in quarrying and transporting gravel to site; but it
also doesn’t clog over time (Biologic Design, 2012; Harland, 2012).
Typically a WET System consists of a series ponds and earth banks built along contour
through which the effluent slowly passes by gravity (figure 14). Planted with a large
range of aquatic and marginal plants, willows and wetland trees, these swales halt the
natural downward flow of the wastewater, forcing it to be absorbed into successive
earth berms before passing into the next pond.
Fig 14: Typical Section through the Swales of a WET System (Harland, 2012).
Here, in the soil, mycorrhizal fungi and microorganisms living in symbiosis with the
wetland plants and trees purify the wastewater, and make nutrients available for plant
growth. The plants and trees themselves reduce the volume of wastewater through
evapotranspiration, whilst the ponds give the system an overall large volume holding
42
capacity which enables the system to cope with shock loading that would disrupt other
Constructed Wetlands (Abrahams, 1996; Biologic Design, 2012; Harland, 2012). As the
WET System is fundamentally this complex living ecosystem it actually become more
robust and efficient at cleaning the effluent overtime as the habitat matures,
organisms self-organise, root zones increase and soil is built.
With its simple earthwork construction, minimal plastic distribution pipes and a
reliance on gravity flow rather than pumps; the WET system not only has a low
embodied energy but also negligible operational costs. Further, other than a little
weeding and annual coppicing (figure 15) there is virtually no maintenance required.
The only disadvantage is its large physical footprint.
Figure 15: Graded Basket Willow from WET System at Shepherds Dairy Ice Cream, Cwm Farm,
Herefordshire (Biologic Design, 2012).
As plants sequester carbon dioxide, the result is a potentially ‘Carbon Negative’ system
which purifies wastewater, provides a rich bio-diverse natural habitat and valuable
43
crops e.g. Aquatic Plants; Reed, Sedge and Willow wands for traditional crafts;
Coppiced Timber; Biomass; Fish; Honey etc. (Abrahams, 1996; Biologic Design, 2012).
Yet these essentially low-cost, low-tech and low maintenance systems have been
successfully used to treat wastewater ranging from domestic sewage through to a
variety of high strength agro-industrial effluents.
Bioshelters to Living Machines
The concept of the ‘Living Machine’ - a mesocosm designed to accomplish a given task
such as producing food, recycling wastes or treating wastewater, is generally
accredited to biologist John Todd.
During the 1970’s, Todd et al. at the ‘New Alchemy Institute’ were experimenting with
the idea of a ‘Bioshelter’ – an amalgam of greenhouse and aquaculture to create
indoor ecosystems capable of food production throughout the year (Barnhart, 2008).
These Bioshelters consisted of a series of interconnected translucent aquaculture cells
enclosed within a greenhouse structure (figure 16). Solar energy warmed the cells and
encouraged fish growth, whilst the substantial thermal mass of the water kept the
greenhouse warm and maintained biological activity throughout the winter (Barnhart,
2007; Barnhart, 2008).
44
Fig 16: Solar Aquaculture Cells and Lemon Trees at the Cape Cod Ark Bioshelter (1976) by
Solsearch Architects (Barnhart, 2007).
45
Using their extensive knowledge of biology, Todd and his colleagues then began
experimenting with creating aquatic mesocosms that might accomplish other tasks,
such as treating wastewater (Todd and Todd, 1993). Each cell, in these First Generation
Living Machines (figures 17) contained a different artificial mesocosm; created by
seeding the cell with a unique combination of microbial, photosynthetic (algae and
plants) and animal life sourced from around the world. The intention was to create
robust self-organising ecosystems that would perform certain processes, and by linking
them together (they found a minimum of three was required), these diverse sub-
ecosystems worked in succession, with feedback loops, to completely metabolise all
the nutrients in the wastewater, leaving no sludge (Todd and Josephson, 1996). Being
cellular in nature also had its advantages, as refinements could be easily made to
individual ecosystems and the entire system scaled up or down, as demand dictated,
by the simply adding more cells.
Fig 17: Typical components and sequence of flow in a Hydroponic Based Living Machine (Kwok
and Grondzik, 2007).
46
Figure 18: A Cellular Living Machine designed by John Todd (Chen, 2008).
The rate of metabolism in these aquatic mesocosms can be increased by maximising
the number of living microorganisms exposed to the nutrient rich effluent. This can be
achieved by the inclusion of floating aquatic plants (figure 18), the root masses of
which provide huge surface areas ideal for microbial colonisation, and by aeration of
the cells to increase the circulation of nutrients through these root zones (Todd and
Josephson, 1996).
Todd, with James Shaw, increased the efficiency further by combining these ideas with
those of conventional Percolating Filters, to create Ecological Fluidized Beds (figure
19). These consist of two concentric chambers, an outer aquatic section and an inner
one filled with a buoyant medium e.g. pumice, on which emergent and semi-aquatic
plants and even wet tolerant trees can be grown. The roots of these plants together
with the porous matrix offer an enormous surface area that supports a complex
microbial, benthic and zooplankton community. The wastewater is cleansed by these
47
organisms as it is aerated and rapidly and repeatedly circulated between these two
zones (Todd and Josephson, 1996).
Fig 19: A Biological Fluidized Bed (Grant, Moodie & Weedon, 1996).
The latest generation of Living Machines are based on Tidal Flow Wetlands. They share
several similarities with other Constructed Wetlands notably that each cell is filled with
an matrix, in this instance lightweight expanded shale aggregate (LESA), providing both
a large surface area for Biofilm growth and the ability to support a large range of other
microorganisms, plants and animals in a dense and diverse ecosystem (Living
Machines, 2012a).
48
Figure 20: The Living Machine Tidal Wetland System (Kirksey, 2009).
49
Wastewater Treatment in these Living Machines is a multistage process (Living
Machines, 2012a). Typically, most of the solids are removed from the effluent as it
passes through settlement and equalisation tanks before entering the First Stage Tidal
Flow Wetland cells (Maciolek and Lohan, 2012). These cells are repeatedly filled and
drained, as often as 18 times a day, in an accelerated simulation of tidal environments.
This rapid alternation between aerobic and anoxic environments increases the rate of
mineralisation, nitrification and denitrification (figure 20), and therefore allows for a
much smaller physical size than other Constructed Wetlands (Living Machines, 2012a).
After this, the effluent receives a Second Stage of treatment in either Tidal Flow or
Vertical Flow Wetland cells that contain a finer LESA. Finally the cleaned effluent is
filtered again and undergoes UV and Chlorine disinfection prior to reuse (Living
Machines, 2012b).
All of these processes take place below the surface of the LECA, eliminating both smell
and the risk of exposure to the effluent. This allows these latest Living Machines (figure
21) to be incorporated into our built environment as external and internal landscaping,
where the plants can serve a dual purpose by improving air quality (Kirksey, 2009;
Living Machines, 2012a).
Although designed to be as energy efficient as possible, the reliance on technology;
both mechanical components and continuous computerised monitoring, adds greatly
to both the capital and running costs of these systems (Kwok and Grondzik, 2007). This
must be balanced against the corresponding reduction in physical size. Consequently
these Living Machines are probably best suited to large scale developments in Urban
Environments, where land is at a premium.
50
Fig 21: Living Machine at the Port of Portland Headquarters, Oregon (Living Machine, 2012b).
51
Nevertheless they still compare extremely favourably on cost with Conventional
Wastewater Treatments and use only a small fraction of the energy consumed by
comparable Activated Sludge Systems (Kirksey, 2009; McNair, 2009; Maciolek and
Lohan, 2012).
52
CONCLUSION
A Holistic Approach
A New Mindset
Healthy Natural Ecosystems are robust self-organisations of plants, animals, fungi and
microorganisms living in mutually beneficial communities. In these ecosystems;
‘Resources are used and reused multiple times in close proximity, using low
energy processes . . .’
(Kirksey, 2009, p. 8)
There is no such thing as waste. The end product of one process becomes the raw
materials of another.
This complex web of life, ‘Gaia’ if you prefer, has been efficiently managing Earth’s
resources for its own benefit for millions of years. This is the model we, as designers,
need to learn from (Todd and Todd, 1993).
Yet; despite the proficiency with which Natural Ecosystems sustain air and water
quality, scientific verification of this ability and the proven capability of Constructed
Wetlands to successfully treat agricultural and industrial effluents (even those heavily
contaminated with mine leachates containing arsenic, cadmium, copper, iron and
zinc); designers of Ecological Systems are often met with scepticism (Appendix 2,
pp. 76-77; Scragg, 1999; Stottmeister et al., 2003). This blinkered view particularly
holds in the Industrial West, where officials and professionals are conditioned to think
53
in terms of centralised mechanical systems and people are generally more divorced
from nature (Nelson et al., 2007; McNair, 2009). This has led to the;
‘. . . erroneous perception that a system that “only” holds gravel and plants
cannot possibly be as effective as a mechanical or chemical product based plant
and is a romantic and “hippy” sort of system.’
(Nelson et al., 2007, p. 12)
We have to challenge this outmoded way of thinking. Conventional high-energy, high-
tech and high-cost centralised systems are just not sustainable economically or
ecologically. We need to pursue low-energy, low-tech and low-cost decentralised
alternatives. In effect we need to change our focus from a technical to a more
biological approach; or create some synthesis of the two which is greater than the sum
of the parts.
Appropriate Use of Resources
Nature teaches us that what we habitually think of as ‘waste’ is actually a valuable
resource if utilised properly. The systems we design therefore need to;
‘. . . do far more than simply prevent pollution and the degradation of natural
ecosystems . . . (they) should also accomplish the return of nutrients and water
to productive use.’
(Nelson and Tredwell, 2002, pp. 1-2)
To design sustainable wastewater systems, a re-evaluation of what we consider to be
‘waste’ is essential. Identifying and removing potential resources prior to them
entering the waste stream, effectively reduces the size, complexity and cost of
subsequent wastewater treatment. For example, when Biologic Design proposed a
54
WET System for Weston Cider Mill, one of the major sources of pollution in their
wastewater was the yeast rich tank bottoms or lees. This potential problem was
removed from the waste stream, and instead considered an asset, to be sold as a high
protein, vitamin B rich pig food (Abrahams, 1996).
The separation of Industrial, Commercial and Domestic effluents by decentralising
wastewater treatment would reduce infrastructure costs and enable more efficient,
effluent specific systems to be designed (Nelson and Tredwell, 2002). For example;
William Grant and Sons, employ a constructed wetland at their Dufftown site to
explicitly remove copper, a recognised pollutant of the Whisky Industry, from their
wastewater (Appendix 2, pp. 76-77).
Decentralisation would also leave Domestic Sewage relatively untainted by industrial
chemicals. This nutrient-rich effluent could be treated locally in constructed wetlands
and the settled solids composted to create a valuable soil conditioner.
Alternatively we could consider more radical solutions . . .
Composting
Throughout history, many societies have recognised the value of the nutrients in our
faeces in maintaining soil fertility. In China and Japan, this ‘Night Soil’ was considered a
resource; collected, paid for and returned to farmlands to increase crop yields and
incidentally maintain good sanitary conditions in towns and cities (Van der Ryn, 1995).
It would seem sensible, therefore, to find more efficient ways of recycling this valuable
resource; a method that would simultaneously reduce water consumption and the
55
incidence of diseases caused by human pathogens contaminating our waterways (Van
der Ryn, 1995).
Composting, a simple aerobic process that speeds up the natural process of
decomposition, would be a viable alternative. Pathogens die off natural within a few
months of leaving the human body; however the high temperature within a
composting chamber increases this rate significantly (Van der Ryn, 1995).
Through decomposition and evaporation; composting reduces the volume of organic
material to about 1/20 of its original state. Annually, the faeces from one person would
condense down to approximately 1 ft3 of a highly fertile humus; a volume that would
be easy to transport and return to agricultural use. Here it would reduce the need for
chemical fertilizers, and the environmental problems associated with their use (Van
der Ryn, 1995; Nelson and Tredwell, 2002).
Unfortunately, despite Composting Toilets being clean and odourless, for many people
there are still social and psychological obstacles to overcome in their use (Appendix 1,
p. 73).
Water Recycling
We could further reduce our demand for fresh water, by accepting that not all the
water we use need be of drinking water standard; some could be water recycled from
other processes (Kirksey, 2009; Nelson and Wolverton, 2010).
Greywater, as it contains few or no pathogens, is relatively simple to clean and could
be safely treated on-site and reused for toilet flushing or irrigation.
56
The Earthships’ Botanical Cells
Michael Reynolds has been building earth-sheltered, passive solar housing constructed
from rammed-earth filled tyres and other recycled materials since the early 1970’s
(figure 22). These ‘Earthships’, as he has calls them, are designed to have completely
autonomous water and sewage provision (Earthship, 2012).
Fig 22: An Earthship.
The roof of the Earthship is designed to collect rainwater, which is then filtered,
purified and used for drinking, cooking and washing. After this initial use, the
greywater is passed through a grease and particle filter before being directed into a
Botanical Cell for treatment. This Greywater Botanical Cell (figure 23), located in a
conservatory sunspace to maximise plant growth, is essentially an Indoor Horizontal
Subsurface Flow Constructed Wetland.
Construction typically consists of a rubber lined trench (90 – 180 cm deep) the base of
which slopes downwards in the direction of flow to create a reservoir for cleaned
57
water at the outlet. The bed is filled with layers of gravel, sand, soil and compost, and
then planted with either edible or ornamental houseplants. At either end larger
substrata form high drainage areas and at approximately ¾ the way along there are
two additional filters, one of Sphagnum moss and one of activated charcoal, which
further purify and remove any residual smell from the water. As the water passes
through this gravel and soil bed, what isn’t used directly by the plants is cleansed
sufficiently to be reused as irrigation water for the garden or to flush the toilet
(Appendix 1, pp. 64-68; Cowie and Kemp, 2007).
Fig 23: A Greywater Botanical Cell.
Blackwater from the toilet is similarly reused in External Botanical Cells. This
arrangement typically consists of an underground infiltrator, followed by a series of
Subsurface Horizontal Flow Cells (figure 24). Unlike other Constructed Wetlands these
cells form a closed system. All the nutrients and water fed into them are either
58
consumed or evapotranspired; no water leaves the system and no sludge residue is
produced (Appendix 1, pp. 69-73; Cowie and Kemp, 2007).
Fig 24: Plan and Section of the Blackwater Botanical Cell at Earthship Fife (Cowie and Kemp,
2007).
The Earthship’s Botanical Cells are inspirational for their sheer simplicity, ease of
maintenance and ability to totally recycle wastewater (Appendix 1 pp. 66-68, 72).
Whilst they may not be suitable in their entirety for every situation; Greywater
Botanical Cells could be easily incorporated into many buildings. With the appearance
of an Indoor Garden these Botanical Cells would not only recycle wastewater, improve
indoor air quality and provide psycho-physiological benefits to the occupants; they
would also be an aesthetic asset to the built environment.
59
Green Walls
Green Walls have grown in popularity in recent years as much for their dramatic
impact on interior spaces as for their ability to improve indoor air quality (figure 25).
For architects and designers, the major advantage they have, is that they take up little
valuable floor space.
The Structural Media Type is the most appropriate for indoor landscaping because it
has the greatest longevity, creates the least mess and the blocks are easy to handle so
maintenance or replacement can be carried out without damaging surrounding plants
(Anderson, 2011). These Green Walls use hydroponics technology and are drip fed,
which opens up the exciting possibility of using them to phytoremediate both air and
greywater.
Figure 25: Jamieson Place Biowall, Calgary, Alberto, 2010 (Anderson, 2011).
60
The Green Wall at the recently completed Bertschi School Science Wing is just such a
development (figure 26). Greywater, filtered to remove large particles, is collected in a
tank. This water is then continually circulated through a closed loop, watering the
Green Wall by a vertical drip feed. The plants use the water or it is evapotranspired
from the wall; none leaves the building.
Because of the volumes of water involved, it is necessary to use plants that are either
very wet or bog tolerant e.g. Dwarf Umbrella Tree (Schefflera Aboricola Kuseane),
Brake Fern (Pteris sp.), Xanadu Philodendron (Philodendron x ‘Xanadu’) and Petite
Peace Lily (Spathiphyllum sp.) (GSky, 2011).
Figure 26: Schematic diagram of Greywater Phytoremediation at Bertschi School Science Wing,
Seattle, 2011; by GGLO using GSky Pro Wall System (GGLO, 2012).
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Symbiotic Landscapes
By incorporating these innovative systems into our built environment, we have the
potentially to create an adaptable, virtually self-sustaining ecological infrastructure
and recreate our cities with nature at their very hearts.
Instead of Conventional Technology: we could choose to take nutrient-rich
wastewater; the very resource that we are currently paying a fortune to throw away,
and use it to create bio-diverse habitats which support forms of life that would
naturally clean pollutants from the air, water and soil. These designed ecosystems
could also provide for us physically by producing crops, timber, biomass or clean water
to irrigate gardens, orchards, parks and playing fields (Nelson and Tredwell, 2002;
Nelson and Wolverton, 2010; Biologic Design, 2012).
Plants would become an integral part of every building: an internal landscape that
would clean wastewater; improve indoor air quality; and make our homes, businesses
and factories places of intrinsic beauty where we can enjoy physical and psychological
wellbeing.
This would be a living technology; one that is
‘both garden and machine’, one that would ‘bring people and nature together
in fundamentally radical and transformative ways’
(Todd and Todd, 1993, p. 171)
And perhaps, in this reintegration of Man and Nature; we might be humbled by the
realisation that underlying it all is a symbiotic web of life, and become aware that it
has never been just about us and our needs, because this isn’t just our world;
62
. . . and we might just glimpse a moment of ‘Satori’.
63
APPENDIX 1
Earthship Fife
A conversation with Geetam van der Dussen:
with regards to the Greywater and Blackwater
Botanical Cells at the Craigencault Earthship.
Geetam is a volunteer with the ‘Sustainable Communities Initiatives’ who has been
personally involved in both the building and running of the Earthship at Craigencault in
Fife.
11/08/2012
FRANCES WRIGHT
64
The Greywater Botanical Cell
‘Greywater’ is all waste water other than that from the toilet.
Greywater is firstly filtered to remove grease and particles and then fed into a
waterproof planted bed, situated in a south facing conservatory space within the
Earthship. As the water moves through the bed of gravel and soil, the water is
effectively cleaned and evapotranspired by plants and microorganisms. Any remaining
cleaned water collects by gravity at the opposite end of the bed. It can be used for
garden irrigation or toilet flushing.
The System: Loads & Sizing
What feeds into the Greywater Botanical Cell?
The originally intention was to include a sink, a wash hand basin and a shower and the
cell was sized accordingly, however the shower was not included in the final design.
What is the estimated loading e.g. litres/day?
No idea. Originally the Earthship was used as a small visitor & demonstration centre
for Craigencault Ecology Centre and occupied all week, but in recent years it has only
been open a couple of days a week so there is a lot less water going through the
system than it was designed for.
It is also worth noting that the bed was sized as if the toilet was also flowing into it,
even though this was never the case!
Is there a rule of thumb sizing:
Volume of greywater to be cleaned (litres): Volume of Botanical Cell (m3)?
Mike Reynolds, the designer of the Earthship concept uses a rule of thumb in his books
that is related to the number of water using appliances, not the actual water usage in
litres. You could probably extrapolate from that, but the cultural differences in
attitudes to water between an arid region such as New Mexico and our wetter climate
would also have to be considered, as well as actual expected usage.
Can you estimate what percentage of the greywater is cleaned and available for reuse
(in either toilet flushing or external garden irrigation) and how much is used and
evapotranspired by the plants in the bed themselves?
65
No idea; however the Botanical Cell is a closed system and designed to use the
greywater primarily to grow plants within the bed, rather than provide cleaned water
for other uses.
Roughly how long does it take for greywater to feed through and be cleaned by the
bed?
We haven’t made any scientific measurements regarding how much water is going into
and coming out of the cell or how long it takes to do so.
Are there certain household chemicals that mustn’t be used with this system?
We tend to use ‘Ecover’ or similar biologically safe chemicals; obviously no chemicals
that can kill plants and microbes.
Is there any smell?
No; not as a rule.
How much energy does the system use e.g. the pump?
The only energy required is for the pump, which uses very little.
The Planted Cell
Are there any species of plants in particular you would recommend for the cell e.g.
particularly effective at cleaning or evapotranspiring the greywater?
We weren’t given any particular advice on what plants to use, so have experimented
with both outdoor and indoor plants. We have found that house plants are ideal
because they like the warmth of the conservatory and don’t die back in winter.
We have tended to choose plants that have lots of leafy surface area and rainforest
species that have a high rate of transpiration. We avoid plants with waxy leaves or
other adaptions to conserve water.
Is there any perceivable difference in how well the system works in summer as opposed
to winter, due to the seasonal rate of growth?
No; the plants grow better in summer, but as they are in leaf all year they continue to
grow and evapotranspire even in winter.
The South facing conservatory is obviously part of the overall passive solar design of an
Earthship, but given the use of house plants that might prefer less direct sunlight,
would the greywater system function just as well facing East or West?
66
I think the plants would be fine in terms of light, but I would be concerned if there was
a lack of warmth during winter.
I was surprised to learn that you used subsoil, not topsoil, as the top layer of the bed. Is
there a reason for this?
No. We weren’t given any advice to use either, we just had a lot of subsoil left from
digging out the Earthship so used that. The plants are taking their nutrients from the
greywater so theoretically should grow as well on either.
Have you had any specific problems?
We have had problems establishing small plants because of a lack of water in the top
few inches of soil. We have found that they need to be top watered until they can get
their roots down far enough. We have also encountered problems establishing plants
at either end of the bed where areas of larger sized substrata form high drainage
areas.
We have had a few greenhouse pests; aphids, red spidermite and mealybugs.
Do you have any condensation problems because of the botanical cell or does the
hydroscopic nature of the earth walls and plaster counteract this?
The plants add a lot of humidity to the air, which can be both a good and bad thing for
health. We do have condensation, not on the walls but on the glass even though it is
double glazed. In the hot arid climate of New Mexico this and any excess heat build-up
could be simply vented from the Earthship. In our cool wet climate this high humidity
really needs to be seriously considered and dealt with.
Maintenance
The ‘Grease and Particle Filter’ removes grease, food and soap scraps from the
greywater before it enters the botanical cell. How often does it need to be cleaned, how
long does it take and can the contents be composted?
That is really dependent on what you’re flushing down the plug hole! It is a rather
messy and not very pleasant task, but doesn’t take long and does not need to be done
very often. Having to clean it makes you aware of what you are flushing into the
system – and makes you more careful in future. In general the contents can be
composted.
How much garden maintenance does the Botanical Cell require per month?
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Very little; some months there is nothing to do. The House Plants require very little
maintenance; just the occasional dead-heading, tidying up, cutting back and keeping
an eye out for pests.
Towards the end of the bed you have ‘Activated Charcoal’ and ‘Sphagnum Moss’ filters.
Do these need to be replaced on a regular basis?
Both are mechanical filters, so you would presume that they would eventually grow
less efficient, in addition the activated charcoal has a limited lifespan. However, we
have never replaced them, which make me wonder how necessary they are.
Do you need to keep a regular check on the water levels and if so how often?
Yes, we monitor and record the water level in the reservoir at least twice a month. The
state of the plants themselves indicates whether the bed might be too wet or too dry,
but the water level reading is a helpful way to keep track of this accurately for those
less green-fingered.
I noticed an overflow pipe in the schematics which will obviously stop the bed getting
too wet; at what depth below the surface did you place this?
300 mm.
Do you find the water in the bed reaches this overflow level often and if so is the water
stored or used in any way?
No, I don’t think it ever has overflowed.
What about if the water levels fall too low; do you water the bed manually?
With the building being used less than anticipated we have occasionally had to top up
the bed with clean water. Initially we added this to the start of the bed but this had the
effect of flushing the greywater through the bed too quickly and led to a sulphurous
smell. If the bed is too dry, we now add water at the end of the bed which pushes the
greywater backwards and does not cause the bed to smell.
Have you had any problems with leaks?
Not that we know of!
After passing through the botanical cell some of the water is used to flush the toilet. Is
this recycled water pumped to the toilet on demand or is it pumped to a storage tank
intermittently when it reaches a certain level?
The pump operates on demand. When the toilet is flushed, the ball cock drops and the
pump kicks in to refill the cistern. The pump system also includes another filter that
ensures that the recycled water appears clear and colourless. This needs replaced at
intervals. We have also added a 2 litre water reservoir to prevent shunting.
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Are there any specific skills required to run the system?
This is a living system so a willingness to respond to and maintain the system is
necessary. Gardening skills and basic mechanical knowhow would be advantageous.
Effectiveness
Have you monitored the quality of the water once it has been through the cell?
No, not scientifically. Visually it is usually clear and colourless; occasionally however it
has a sulphurous smell.
Could it be released back into the natural environment at this stage or would it require
further treatment?
I suspect it would contain little or no pathogenic organisms at that stage, so I think it
probably could. You would have to ask SEPA.
What is the system like to live with; is it an easy and simple to use?
Yes
Do you think the system could be easily adopted by a household if incorporated into
standard house designs?
Yes. You have to consciously take responsibility and ownership of the system, but it
would not be difficult to adapt to.
Could you foresee any problems in doing so?
Worst case scenario would be putting some chemical into the system that killed all the
plants and contaminated the soil.
Are there any improvements that you think could be made to the system?
The original Earthships were designed for the hot arid climate of New Mexico, where
water is scarce and every drop precious. The botanical cell was therefore designed to
be an closed system that reuses greywater to grow (edible) plants; rather than a
means of cleaning it so it could be released back into the environment.
That begs the question of whether this is the best approach in our cool and rather wet
climate. Do we really have to use all the greywater up, or should we be considering the
botanical cell as a means of filtering and cleaning it to a standard where it could be
reused to flush toilets or is safe to be release back into the natural environment.
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The Blackwater Botanical Cell
‘Blackwater’ is waste from the toilet i.e. sewage. It is common practice for greywater
and blackwater to be mixed together in our current sewage system.
The blackwater botanical cell consisting of one or more linked planted beds, isolated
from the surrounding soil by a waterproof lining. It is a completely closed system that
aims to use all the effluent, and release non back into the environment.
Blackwater initially flows into an underground chamber known as the infiltrator. The
base of the infiltrator is at a higher level than the general water level in the botanical
cell, so the liquid component of the sewage seeps out into the enclosed cell, whilst the
solids are retained and decomposed by continual cycles of wetting and drying until
they too enter the cell as a liquid nutrient. Plants and micro-organisms within the cell,
feed on and evapotranspire this liquid effluent.
The System: Loads & Sizing
How many toilets feed into the Blackwater Botanical Cell?
1
What is the estimated loading e.g. litres/day?
No idea.
Your blackwater botanical cell consist of two 12m2 beds, giving a total size of 24m2 for
4 people, how was this calculated, is there a rule of thumb?
Volume of blackwater to be cleaned (litres): Volume of Infiltrator (m3)
Volume of blackwater to be cleaned (litres): Volume of Botanical Cell (m3)
The size is for 1 toilet, rather than related to the number of people or expected usage.
Mike Reynolds took the view that if it was insufficient we would just add another bed.
Are there certain household chemicals that mustn’t be used with this system?
We tend to use ‘Ecover’ or similar biologically safe chemicals; obviously no chemicals
that can kill plants and microbes.
Is there any smell?
No – except plants and flowers!
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The Infiltrator
I had never heard of an ‘infiltrator’ before is it a concept unique to Earthships?
Mike Reynolds told us that infiltrators and leach fields are a fairly common method of
disposing of sewage in America. In this country we clean the liquid effluent and put it
back into rivers or the sea and dispose of the solids in landfill, but in America there are
many communities that are far from large bodies of surface water so they must treat
their sewage differently.
Where does the blackwater enter the infiltrator and is there a reason for this?
The intake is centre top, which allows the sewage to spread and mix across the
chamber to the maximum on impact, and thereby reduce the possibility of blockages.
Have you had any blockage problems?
No.
The infiltrator is buried; do you have any access to it e.g. a hatch for maintenance?
No. It would be a good idea though. I’d not add a manhole, just a 100mm pipe for a
rodding eye just in case we had a blockage problem.
How long does it take for the solids to decompose under the cycle of wetting and drying
and enter the beds as a liquid nutrient?
No idea.
Is this decomposition aerobic, anaerobic or a mixture of the two?
Not sure, probably aerobic.
How big are the slots in the infiltrator to allow liquid out and are they at the base or
higher up on the side? Won’t liquid seep out at the open base of the infiltrator anyway?
I believe we just made random slots at various levels up the side to about half way up,
taking care not to weaken the structure. Water can seep out at the base too.
The Planted Cell
The design of your blackwater cell is unique in its use of a greenhouse over the first of
the two cells to both promote winter growth and keep excess rain out of the growing
bed. Overall how well do you think this adaption has worked?
71
The greenhouse did keep rain out of the first cell, however with the Earthship not
being used as much as intended there is less water flowing into the system, this
resulted in the rainwater that was falling on the second cell overflowing back into the
first cell. To counteract this we have put a shelter over the second cell as well,
although this is open on one side so some rain still gets into that cell. During periods of
high rainfall ground water also tends to flow back into the second cell from the final
overflow tower.
Unfortunately the greenhouse has no additional heating and little thermal mass to
retain passive solar energy, so it is just not warm enough to achieve growth over the
winter months. The protection it provides allows some plants to retain their leaves but
others die back.
Are there real perceivable differences in how well the system functions in summer as
opposed to winter, due to the seasonal rate of growth?
Yes.
In the summer the bed goes fairly dry because the plants are using what little water
there is. In the winter when the plants are not growing and evapotranspiring the bed is
much wetter. If the system was used more, then this might cause serious problems in
the winter.
Would an open covering to keep the rain off both beds function as well, by allowing for
water vapour to escape via evaporation more easily?
I think the greenhouse is necessary to encourage as much growth and as long a
growing season as possible.
Do you use general garden plants, edible plants or perennials/shrubs from local
ecosystem?
We have experimented with a variety of plants over the years.
The greenhouse is too cool for house plants. We have grown edibles such as beans and
tomatoes; the only reserve I personally have about that is the possible uptake of
chemical compounds from the sewage i.e. from medicines and the birth control pill.
The second cell, being open on one side is a sheltered area that receives some
windblown rain. It is more naturalistic and uses garden plants.
Are there any species of plants in particular you would recommend for the bed e.g.
because of their rate of growth or because they are particularly effective at cleaning or
evapotranspiring the effluent?
I would consider any with a long growing season and a leaf that tends to evaporate
rather than conserves water.
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How much maintenance does the Botanical Cell require per month?
In terms of gardening there is very little to do; cutting plants back mostly.
Maintenance
Do you keep a regular check on the water levels in the cell? If so, how often and is this
purely monitoring or necessary to the functioning of the bed?
Yes, I check the water level whenever I visit the site. I encourage others to do so as
well, so they can become aware of how the bed is functioning. The plants themselves
are the first indicators of whether the bed is too wet or dry.
At what depth below the surface is the water table kept at maximum?
The overflow pipes are just below the level of the infiltrator shelf; 400mm below the
surface. As long as the surrounding ground is not waterlogged the overflow towers
would keep the maximum water level in the cell to at or below this.
Have the beds ever overflowed?
No. With our lower than expected usage we have had the opposite problem of ground
water flowing back into the beds during periods of high rainfall.
Do you monitor the quality of the water within the beds? If so, is it free from pathogens
and clean enough to be released back into the environment?
We have never had the water quality in the bed scientifically checked. SEPA did initially
say they would like to monitor the water quality but because it has never overflowed
they have never done so. With the ingress of rain into the second cell, I think testing it
might be fairly meaningless. We could test at the end of the first cell, but the water will
have only passed through half the soil and gravel at that point.
Have you had any problems with leaks?
Not that we know of.
Are there any specific skills required to run the system?
You just need basic gardening knowhow and an ability to respond to the system.
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Effectiveness
I can see the point of reclaiming and using every drop of water in a hot and arid climate
to grow crops. In our wetter climate too much water and too little evaporation appears
to be the problem, especially in winter. Why then was a completely contained system
chosen in preference to say a bed to clean the waste followed by e.g. a willow/wetland
soak away or leach field?
To be honest we didn’t know enough about the system and how it would work in our
climate when we installed it. I would now personally favour the type of system you
have described or a reed bed. Having said that, the benefit of having a completely
enclosed system is that SEPA approval is virtually guaranteed because you are
releasing nothing back into the environment.
How well do you think this adaption has coped with our climate and are there any
improvements that you think could be made to the system?
I think if it was used to its original design capacity, it would just not work well enough
in winter because it is too cold and wet.
Building Control insisted that it must be sited 15m away from habitable spaces, but it
really needs to be completely enclosed within its own Earthship to give enough solar
thermal mass to allow continued growth and evapotranspiration during the winter.
I believe Earthships were originally design to have composting toilets; do you think that
would be a better solution than a flush toilet/blackwater bed?
I was not aware of that, but personally I would be in favour of a composting toilet.
From my experience however, I think there is still a lot of psychological reluctance,
even among environmental groups, to take that step. I think that a composting toilet is
something that you would soon learn to live with, after an initial readjustment, and
managing it would just become part of your habitual life.
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Conclusions
What do you think are the main benefits of these systems?
The fact that the botanical beds are a closed system i.e. they have no discharge to the
environment, meant that SEPA were happy to give approval.
I think that the main advantage though is that living with the system makes you
completely aware of and responsible for your own sewage – rather than it being
something you flush away and forget about.
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APPENDIX 2
Dufftown Distillery
A conversation with Dave Stewart:
with regards to the Constructed Wetland at the
Glenfiddich Distillery, Dufftown
Dave is the Estates Team Leader for William Grant and Sons at the Dufftown site.
27/09/2012
FRANCES WRIGHT
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The Distillery Wetland
Overview of System
Constructed Wetland as a term seems to cover a number of different approaches to
wastewater treatments; could you give me an overview of your system?
The constructed wetland provides tertiary treatment (final polishing) of the effluent
coming from a large conventional aerobic effluent treatment plant which caters for the
Glenfiddich, Balvenie and Kininvie Distilleries.
This treated effluent flows initially into a large shallow planted pond, which feeds into
a series of wetland treatment beds and then into a willow wetland area. The liquid
entering the system is visibly cloudy, but is clear at the SEPA sampling point at the end
of the constructed wetland.
The clean water is then released back into the River Fiddich, which is a tributary of the
river Spey.
What type of effluent do the distilleries produce and what treatment stages does it go
through before entering the wetland?
The system has to deal with effluent from various distillery processes e.g. steep water
from maltings, spent lees from the second distillation, foul condensate from the
evaporator (Acid pH 3.5) and wash water (Alkaline pH). These effluents are carefully
monitored by computer and combined in a balance tank to create an effluent with a
pH 7. This is the preferred pH for the aerobic effluent treatment plant. The effluent
then passes through a 3 stage high-rate trickle filter (Davenport 1, 2 & 3), two low rate
polishing filters with inter stage settlement before entering the Wetland for tertiary
treatment.
What happens to settled solids and sludge?
Tanks are desludged automatically every 2 hours and this material is spread on
surrounding farmland.
Why was this particular system chosen?
Koch Membranes and Electrolysis are used by some other distilleries, as a means of
copper removal, to improve the quality of their final effluent. We looked into using
these and tested several other methods in an attempt to find a system that worked
best for us. These included: a 30 micron Microscreen Filter (unfortunately the
particulate size was discovered to be only 15 microns); a Polystyrene Bed Clarifier and
Grass Filters. We also built large scale trials of Reed Beds (which worked for tertiary
77
treatment but clogged quickly with raw influent) and a Constructed Wetland System of
Ponds, Reed Rafts and Swales.
The current system was chosen primarily because of the ability of the Wetland plants
to remove copper from the wastewater. There have been some problems, but these
have been overcome and the system is very simple to run.
Prior to the installation of this type of system, was there any scepticism about the
ability of a Constructed Wetland to achieve your aims?
No; having done large scale trials with the Reed Bed and Pond systems we were
confident that there was potential in these systems.
Are you happy with how the Constructed Wetland performs?
Yes; SEPA is happy and we’re happy.
The System: Loads & Sizing
What is the area of the constructed wetland?
The Wetlands were constructed in 2000 and further extended in 2005. It currently
covers an area of 1500 m2
Why was it extended?
The initial design proposed 7 wetland beds (total surface area of 1111 m 2) arranged in
two parallel lines. Each half of this system was designed to carry a maximum of
20m3/hour load. However this proposal was not implemented in full because
production was lower at this time.
The original system, as built, contained only 5 wetland beds (total surface area of
689m2) and these struggled to cope with the high loading, so as production increased
the system had to be extended.
What is the current loading of the system?
The usual load is approximately 36 m3/hour; the maximum design capacity is 40
m3/hour.
Does the quality and quantity of effluent change significantly at different times of year
i.e. do you have shock loadings?
No. The effluent is balanced out to be at pH 7 for the aerobic effluent treatment plant
and we no longer shutdown production for maintenance over the festive season so the
quantity is pretty steady throughout the year too.
78
Do you monitor the standard of water quality achieved?
The effluent quality is monitored daily in our on-site lab; for BOD, COD, Suspended
Solids and pH, so we can respond to any problems as they arise. SEPA also monitor the
standards we achieve closely, doing random checks at least monthly.
We discharge our cleaned effluent into the River Fiddich, which is a tributary to the
Spey. The Spey is a renowned salmon fishing river and important for tourism in the
region so we are all particularly vigilant. We have a good relationship with SEPA
because we are seen to be doing things and taking our responsibilities seriously.
Have you ever had any problems with the standard of water quality achieved after
treatment?
Most systems occasionally have problems e.g. live yeasts can upset the high rate filter
and cause it not to work as efficiently. The wetland is useful in these instances as it can
often rescue borderline situations.
Has anything ever failed and if so how was it corrected?
There have been problems in the past with the blinding of the surface of the wetland
beds by a black bacterial slime. Because of the high loading rate, when this happened
instead of flowing through the gravel matrix and wetland plant root zones, the
wastewater was collecting on the surface and effectively short circuiting the system by
either flowing directly into the outlet chamber or overflowing the sides.
This black slime was something the designers had not encountered before and they
felt it might be coming from the high rate filters or further upstream in the whisky
making process itself. They suggested several means by which the situation could be
addressed.
Firstly they felt that the source should be located so a way of capturing it before it
entered the wetland could be devised. They also suggested dramatically enlarging the
system so that each half could accommodate the total load of 40m3/hour. This would
allow each half of the system to be used alternately, allowing the beds not in use to
rest and recover. They also suggested that the maximum water level in the beds be
lowered below the gravel surface, to allow the bacterial slime to dry out and the
surface recover its porosity.
The system was enlarged but not to the extent that half the beds could be rested at a
time. Lowering the water level seems to have solved the problem. The black bacterial
slime is still present but with the lower water level it doesn’t clog the surface.
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Design and Planting Details
Living Water state that they design systems tailored to the specific needs of the client.
Did the environmental audit at the beginning of the design process bring benefits in
other areas of the process e.g. waste reduction, identifying specific areas where waste
water contamination could be reduced?
Don’t know
Does the effluent have any unusual or difficult to deal with characteristics e.g. high
organic loads, strong pH values, copper residues etc?
Yes, the COD (chemical oxygen demand) of the raw influents is very high; typically
between 1500 and 3000 mg/l and the pH of the separate components can be very acid
or alkaline. However the pH is balanced by mixing before treatment and the
conventional aerobic effluent treatment plant effectively reduces the COD to between
20 and 200 mg/l prior to the wetland.
The constructed wetland system was specifically chosen for its capability of removing
heavy metal residue (copper) from the wastewater.
What is the media used in the constructed wetlands and is the area lined?
The pond and wetland treatment beds are lined with ‘Bentomat’ to retain the effluent,
however the willows are planted directly into soil and this area is unlined. The wetland
beds themselves are filled with a gravel medium.
How many different plant species were included in the design and has this led to a good
bio-diverse habitat being created on the site?
19 different wetland marginal plants and several willow species were included in the
planting scheme. These included:
Yellow Flag (Iris pseudocorus), Reed Sweet Grass (Glycera maxima), Beaked Sedge
(Carix rostrata), Greater Tussock Sedge (Carex paniculata), Greater Pond Sedge (Carex
riparia), Lesser Pond Sedge (Carex acutiformis), Star Sedge (Carex echinata), Common
Spike Rush (Eleocharis palustris), Marsh Marigold (Caltha palustris), Common Reed
(Phragmites australis), Narrow Leaved Reedmace (Typha augustifolia), Greater
Reedmace (Typha latifolia), Soft Rush (Juncus effusus), Hard Rush (Juncus inflexus),
Great Water Dock (Rumex hydrolapathum), Meadow Sweet (Filipendula ulmaria),
Purple Loosestrife (Lythrum salicaria), Water Mint (Mentha aquatica), Blotched
Monkey Flower (Mimulus luteus) and Willow (Salix sp.).
Whilst plants establish the water levels in the beds must be kept quite high but then
they can be gradually lowered. We do seem to have lost some species over the years
but overall we still have a good bio-diverse habitat.
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Do certain plants predominate in the mature system?
Yes; Reed Sweet Grass (Glycera maxima), Common Reed (Phragmites australis) and
Greater Reedmace (Typha latifolia) seem to have taken over.
Is there any perceivable difference in how the constructed wetland performs in summer
as opposed to winter?
No; not really. The system worked adequately even from the start, when plants were
still establishing and has improved as the ecosystem has matured. In winter the
vegetation cover also provides insulation to the beds, helping to keep the system
functioning even in cold weather.
Does the wetland produce any useful or saleable by-products, e.g. timber, biomass,
willow or plants?
No, not at the present; but could be utilised as biomass in the future.
Is there any smell?
There is a slight smell by the initial ponds, but not much.
Maintenance
What sort of maintenance does the constructed wetland require?
The chambers, pipes and water levels are checked every day to ensure that there are
no blockages and the wastewater is kept flowing freely. The grass and paths
surrounding the ponds and beds need to be cut regularly to keep access clear, but
otherwise there is very little maintenance required.
The designers advise against cutting back the wetland vegetation in the beds, however
we have done so on occasion when we have felt they were becoming so choked with
plants that the water wasn’t flowing through the system correctly.
One third of the willows are coppiced every year, on a rotational basis, to maintain the
habitat for wildlife.
Is it an easy system to live with and adapt to?
Yes; once it is up and running.
Are there any improvements you would make to the current system?
I think further settlement of solids prior to the pond would benefit the system,
perhaps reducing the black bacterial slime and keeping the surface of the gravel clear
of solids.
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I also think that the willow wetland really needs to be larger and the trees further out
of the water.
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Conclusions
What do you think are the main benefits of this system?
The Constructed Wetland is a natural system that is not only easy to use and maintain,
but also does its job of providing a final polish to the effluent very well. It
demonstrates that you do not need to use environmentally damaging chemicals, such
as aluminium flocculants or complex expensive mechanical systems to achieve good
results. As such it is good Environmental Public Relations for William Grant and Sons,
and shows that the distillery takes its responsibilities in these matters seriously.
I don’t think cost was a major deciding factor in the choice of this system over others,
however I suspect that there is a long term cost saving in this type of system as well.
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GLOSSARY
Adsorption
The adherence of one substance to the surface of another.
Aerobic
Containing free Oxygen gas (O2).
Anaerobic
Containing no free Oxygen gas (O2).
Anoxic
Containing no free Oxygen gas (O2), but with Oxygen present
bound to other elements e.g. Nitrate (NO3-).
Assimilation The incorporation of nutrients into the cells and tissues of
plants and animals.
Biofilm An aggregation of microorganisms in which the cells adhere to
each other on a surface to form a thin layer.
Biome A major ecosystem e.g. tropical rain forest, tundra.
Bioremediation The use of microorganisms and plants to clean up
environmental pollutants.
Blackwater Wastewater including that from the toilet.
BOD5
Biochemical Oxygen Demand. The amount of oxygen (mg/l)
leaving a water sample of known volume during a 5 day
incubation at 20oC, in the dark. Indicates the presence of rapidly
biodegradable organic material in the sample.
Catabolism
Metabolic pathways that break down molecules into smaller
units and release energy.
Denitrification
The microbial facilitated reduction of Nitrates (NO3-), Nitrites
(NO2-) and Nitrous Oxide (N2O) to Nitrogen gas (N2).
Ecology
The scientific study of the relationships between living organisms and their interaction with their environment.
Ecosystem
A community of living organisms in conjunction with non-living components of their environment.
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Eutrophication
The biological effects of increased inorganic nutrient e.g.
Nitrates (NO3-) and Phosphates (PO4
3-) in bodies of water. Often
associated with excessive algal and plant growth and reduced
biodiversity.
Evapotranspiration The return of moisture to the air through both evaporation
from the soil and transpiration by plants.
Greywater
Wastewater not including that from the toilet.
Humus The dark brown organic component of soil derived from
decomposed plant and animal remains. Adds nutrients and
improves water retention properties of soil.
Mesocosm An experimental enclosure, containing a small natural or
designed ecosystem under controlled conditions. Often used to
evaluate how organisms and communities react to
environmental change.
Microorganism A tiny organism that can only be seen under the microscope
e.g. bacteria, protozoa and some fungi and algae.
Mineralisation The breaking down of organic matter to its mineral
constituents, water and carbon dioxide.
Mycelia The network of threadlike hyphae that form the vegetative part
of a fungus.
Mycorrhiza A symbiotic association between a fungus and the roots of a
vascular plant.
Nitrification
The microbial facilitated conversion of Ammonia (NH3) and
Ammonium (NH4+) to Nitrates (NO3
-).
Photosynthesis The process by which green plants turn carbon dioxide and
water into carbohydrates and oxygen, using light energy
trapped by chlorophyll.
Pathogen A disease producing agent e.g. a virus, bacterium or other
microorganism.
Phytoremediation
The use of plants to either sequester or degrade pollutants.
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Retention Time Average time taken for wastewater to pass through a treatment
unit.
Rhizosphere The area of soil immediately surrounding and affected by the
roots of plants and their associated microorganisms.
Satori The Zen Buddhist term for awakening; comprehension or
understanding. Often a flash of insight.
Sedimentation The tendency of particles suspended in a liquid to settle and
form deposits.
Superorganism An organism consisting of many organisms.
Suspended Solids The concentration of particulate material (mg/l) removed via a
fine filter from a water sample.
Swale A ditch dug along the contour of a slope, with the soil piled on
the downhill side to create a berm. Often used to harvest rain,
manage rainwater runoff or filter pollutants.
Symbiosis The close association of animals, plants, microorganisms or
fungi of different species, that is usually to the mutual benefit
of both.
Translocate To move or transfer from one place to another.
Transpiration The passage of water through a plant, from roots to leaves, and
its evaporation from the leaves into the air.
86
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