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?

67

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.

68

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.

84

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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