Capacity Building for Ecological Sanitation
Ecosan Training Courses for TSC officials
UDD-Toilets and Urine Management
Dipl. Ing. Martin Wafler, seecon international, Austria
Contents
1. Overview of Urine-Diversion Components
i. Urine-Diversion Squatting Pans and Pedestals
ii. Waterless Urinals
2. Quantification and Characterisation of Human Excreta
3. Estimated Excretion of Nutrients per capita in Different Countries
4. Double-Vault UDD-Toilets4. Double-Vault UDD-Toilets
A. Concept, Advantages and Limitations
B. UDDs implemented by
i. PEO/PPDO/GTZ (Philippines)
ii. ENPHO (Nepal)
iii. Practical Action (Sri Lanka)
iv. Chinese models
v. SCOPE (India)
vi. Rural Dev. Dep. Karnataka State (India)
vii.Ecosan Services Foundation (India)
C. Sizing of UDDs
J. Heeb
Contents
5. Single-Vault UDD-Toilets
A. Concept, Advantages and Limitations
B. UDDs implemented by
i. PEO/PPDO/GTZ (Philippines)
ii. ENPHO (Nepal)
6. UDDs in Multi-storyed Buildings and Public Places
7. UDD-Toilet Design Quiz
8. Barriers to Prevent Transmission of Disease/Spread of Pathogens
9. New WHO Guidelines
10.Guidelines Urine Application
J. Heeb
Urine-Diversion Squatting Pans & Pedestals
(photos: seecon gmbh)
• different types and designs ofurine-diversion squatting pans areavailable in the Indian market;
• the urine is collected in the frontcompartment and led away by apipe;
• feces drop through the rearopening;
• if wet anal cleansing habits prevailin a community installation of ananal clenasing water collectiondevice has to be planned for; source (1)
Urinals Without Stench Trap & with Membrane Stench Trap
• easiest way to provide a urinecollection system for males;
• divert urine to a separate collectiontank;
• don‘t provide cisterns or waterconnections for flushing urinals aftereach use to avoid dilution;
(photo: M. Wafler)
• the stench barrier consists of a thinrubber tube;
• urine passes through thismembrane, which then closes whenthe urine flow stops and effectivelyseals the urine outlet, preventingsmell;
(photos: M. Wafler)
Waterless Urinals with Liquid Stench Trap & Ladies Urinals
• urine passes through a liquid havinga lower specific gravity than theurine itself, which acts as an odourseal, overflows into the central tubeand runs down the collection pipe;
• sealing liquid has to be replenishedperiodically; frequency ofreplenishing depends upon thetraffic to the fixture;
(source: http://www.waterless.com/)
• squatting-type ladies urinals (lefthand side) are available in theIndian market;
• a ladies urinal designed by adutch company (right handside);
(source: unknown)
(source: http://www.sphinx.nl/)
Waterless Urinals with Hydrostatic or Electromagnetic Float Assembly
• a replaceable odour-locking element(A) receives the urine and channelsit (without water) into the wastepipe;
• the float assembly seals the element(without using sealing liquid) andprevents the development of odour;
• the urine flows into the cylinder-shaped piece (B) in the siphon, and
Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (Uncompressed)“
benötigt.
Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (Uncompressed)“
benötigt.
(source: http://www.urimat.com/)shaped piece (B) in the siphon, andfrom there into the overflow areasand overflow basin (C), from whereit is fed into the waste pipe;
• with the electromagnetic floatassembly an electronic signal sentfrom the capacitance sensoractivates the process-controlledmagnet which draws the floatassembly (D) down;
(source: http://www.urimat.com/)
Quantification and Characterization of Human Feces
parameter unit no of
samples min. max.
standard
deviation average median value
volume * [l/ppd] 9 0.07 0.4 0.05 0.18 0.15 0.15
weight * [g/ppd] 9 200 400 50 180 150 150
Total Solids [g/ppd] 6 30 60 8.6 44.7 45.0 45
organic Total
Solids [g/ppd] 4 26 58 6.2 44.8 42.0 42
organic carbon [g/ppd] 6 13.2 33 4.1 21.4 21.8 22
BOD [g/ppd] 1 6 18 - 11.1 11.1 11
Averaged values from various studies conducted in North America and Europe
BOD5 [g/ppd] 1 6 18 - 11.1 11.1 11
COD [g/ppd] 1 19 55 - 33.0 33.0 33
Total Nitrogen [g/ppd] 11 0.25 4.2 0.9 2.0 1.9 2
Total
Phosphorus [g/ppd] 11 0.1 1.7 0.33 0.7 0.6 0.6
Potassium [g/ppd] 7 0.2 1.3 0.21 0.7 0.6 0.6
Calcium [g/ppd] 2 0.67 1.4 0.52 1.1 1.1 1.1
Magnesium [g/ppd] 1 0.12 0.18 - 0.15 0.15 0.15
carbon to
nitrogen [-] 5 5 11.3 1.79 8.2 7.5 7.5
* density = 1.0 kg/dm3 ppd = per person per day g = grams l = liters
source (2)
Quantification and Characterization of Human Urine
parameter unit no of
samples min. max.
standard
deviation average median value
volume * [l/ppd] 16 0.5 2.0 0.26 1.2 1.2 1.2
weight * [g/ppd] 16 500 2,000 260 1,200 1,200 1,200
Total Solids [g/ppd] 7 20 147 32.9 72.4 60.0 60
organic Total
Solids [g/ppd] 5 65 85 9.58 39.1 45 45
organic
carbon [g/ppd] 5 1.8 11.9 2.83 6.6 8.4 8.5
BOD [g/ppd] 2 1.8 13.6 2.17 7.5 7.5 7.5
Averaged values from various studies conducted in North America and Europe
BOD5 [g/ppd] 2 1.8 13.6 2.17 7.5 7.5 7.5
COD [g/ppd] 2 5.4 30 4.74 15.1 15.1 15
Total
Nitrogen [g/ppd] 14 3.6 16 2.45 10.4 10.9 11
Total
Phosphorus [g/ppd] 14 0.5 2.5 0.41 1.1 1.0 1
Potassium [g/ppd] 11 1.0 4.9 0.59 2.3 2.5 2.5
Calcium [g/ppd] 6 0.15 2.2 1.06 1.3 1.4 1.4
Magnesium [g/ppd] 4 0.06 0.2 0.14 0.2 0.1 0.1
carbon to
nitrogen [-] 6 0.4 1.2 0.27 0.8 0.8 0.8
* density = 1.0 kg/dm3 ppd = per person per day g = grams l = liters
source (2)
Average Daily Quantities of Excrements Produced per Person in India
For Indian conditions, for example, daily volume of excreted feces isgiven with less than 200 ml [3] to about 300 ml [4] per person.
Let`s separate!
Specific urine production is about 1.2 litres per person per day ([5], [3]).
Jef Vivant
Estimated Excretion of Nutrients per capita in Different Countries
source (7) in (6)
Double-Vault UDD-Toilets
• designed to operate in batches;
• collection and storage of feces is done in twin pit compartments which are used alternately;
• after each use a handfull of cover material (wood ash, saw dust, soil, etc.) is sprinkled over the feces to absorb moisture and help in speeding up the dehydration process;
(photo: M. Wafler)
up the dehydration process;
• when "full", the respectivecompartment is sealed off while theother compartment is put in use;
• storage time is counted from the dateof the last faecal matter contributionto a compartment and should be atleast one year;
• urine and anal cleansing waterdiversion is recommended forpractical reasons;(photo: M. Wafler)
Double-Vault UDD-Toilets (contd.)
ADVANTAGES LIMITATIONS
• suitable for hard rock soil areas,high ground water levels andareas prone to floodings;
• increased surface area for construction of toilet (compared to Single-Vault UDDs);
• no contamination of groundwater • possibility of smell if too much• no contamination of groundwater sources due to contained processing of human feces;
• possibility of smell if too muchliquid (urine, anal cleansing water,etc.) enters the processingcompartment
Double-Vault UDD-Toilets by PEO/PPDO/GTZ (Philippines)
(photo
s: G
TZ
, P
hili
ppin
es)
Double-Vault UDD-Toilets by ENPHO (Nepal)
(photo: M. Wafler)
Double-Vault UDD-Toilets by Practical Action (Sri Lanka)
(photos: M. Wafler)
Double-Vault UDD-Toilets (China)
In-door Double-Vault UDD, China(source: UNESCO-IHE)
Double-Vault UDD-Toilets (China)
(photo
s: G
TZ
, M
ore
l)
Different sites with urine diverting toilets: in the house yard, in-house, outside the house or on upper floor, China
(photo
s: G
TZ
, M
ore
l)
(photo
: G
TZ
)
Double-Vault UDD-Toilets by SCOPE (India)
(photos: SCOPE)
Double-Vault UDD-Toilets by Rural Dev. Dep. Karnataka State (India)
(photos: M. Wafler)
Double-Vault UDD-Toilets by Ecosan Services Foundation (India)
(photos: N. Zimmermann)
Common Chamber Sizes of Double-Vault UDD-Toilets
implementing organisationsize of processing chambers
length [m] width [m] height [m]
PEO/PPDO/GTZ (Philippines)ca. 1.65 to 2.30
(sloping cover)ca. 0.60 ca. 0.80
Practical Action (Sri Lanka) ca. 0.90 ca. 0.60 0.60 to 0.75Practical Action (Sri Lanka) ca. 0.90 ca. 0.60 0.60 to 0.75
Ecosan Services Foundation (India) ca. 1.20 ca. 1.00 ca. 0.65
SCOPE (India) ca. 1.30 ca. 0.75 ca. 0.60
Sizing of Double-Vault UDD-Toilet (contd.)
Calculation of volume of processing compartments
V
PC= N �SSC �T
V
PC= 5 g0.35 g365 g1.25 ≈ 800 l
assumptions for sample design problem:
number of users (N): 5
spec. storage capacity (SSC): 0.35 l/p/d
working days (T): 365 d/a
safety margin: 25%
where:
VPC volume of one processingcompartment �l�
N number of people actually usingtoilet for defecation �heads/d�
SSC specific storage capacity �l/p/d�
T working days per year �d�
Sizing of Double-Vault UDD-Toilet (contd.)
• A list of suitable building materials is given below:
� processing compartments: natural stone masonry, bricks, cementconcrete solid blocks, cement concrete hollow blocks, solid blocks madefrom locally availabe rock (e.g. Laterite, etc.), etc.
� removeable cover: steel sheets, FRP sheets, cement concrete slabs,etc.
� squatting slab: reinforced cement concrete, etc.
Construction details and other important information
� squatting slab: reinforced cement concrete, etc.
� cubicle: natural stone masonry, bricks, ferro-cement slabs, cementconcrete solid blocks, cement concrete hollow blocks, solid blocks madefrom locally availabe rock (e.g. Laterite, etc.), corrugated sheet metal,etc.
� ventilation system: stone-ware pipes, plastic pipes, etc.
� urine and wash water collection system: flexible hoses, rigid plasticpipes, etc.
� roofing: corrugated cement sheets, corrugated sheet metal, Mangaloretiles, cement concrete slab, stone slab, etc.
Sizing of Double-Vault UDD-Toilet (contd.)
• Processing compartments shall be sealed (either by removeable concreteslabs or lockable covers) to prevent rainwater and insects from entering thecompartments.
• The bottom slab of the processing chamber shall be raised about 10 cmabove the surrounding ground level to prevent flood water from entering thecompartment.
• Plaster has to be applied to inner walls and the bottom slab to provide asmooth surface.
Construction details and other important information (contd.)
smooth surface.
• Squatting pans must either have a rim or be raised ca. 2 cm above thefinished floor level of the toilet to prevent water used for cleaning the toiletfrom entering both, the processing compartments and the urine collectionsystem.
• Squatting pans/pedestals have to be provided tight fitting covers to preventinsects from entering the processing compartments.
• Inner and outer wall areas of cubicles may be left as rough walls (withoutplastering). But, inner wall areas should be tiled up to a hight correspondingto 60 cm from the finished floor level for ease of cleaning.
Sizing of Double-Vault UDD-Toilet (contd.)
• Each processing compartment must be provided a straight ventilation pipe(Ø ≥ 150 mm) that runs above the roof (at least 50 cm), is screenedagainst flies and capped for rain.
• To avoid leakiness of the roof in rainy season, the vent pipes shall not beinstalled inside the cubicle but be attached to the outside wall for notpenetrating the roofing.
• Urine shall be drained to sealed receptacles (jerry can, transportable plastic
Construction details and other important information (contd.)
• Urine shall be drained to sealed receptacles (jerry can, transportable plastictank, etc) which may be stored out-side the toilet.
• Use corrosion resistant material (plastic) for urine pipes, provide forproper diameter (Ø ≥ 50 mm) and slope (≥ 4%) to avoid stagnation(reduces smell and slows down incrustation by crystallisation), extend urinepipe to ca. 3” above bottom of receptacle.
• If wet anal cleansing habits should prevail in a community, cleansing watermust be diverted from faecal matter for practical reason. Cleansing watermay either be used for subsurface irrigation of nearby plants or beingdisposed off by infiltration into the soil.
Urine Collection
(photo: M. Wafler)
Infiltration of Greywater & Cleansing Water
source: GTZ, Philippines
Sizing of Double-Vault UDD-Toilet (contd.)
Construction details and other important information (contd.)
• Even if a treatment is aimed at elimination of the risk of pathogentransmission and its potential has been proven, process stepps maymalfunction, resulting in a fertilizer product that is not completely hygienicallysafe. Therefore additional measures should be taken in order to furtherminimize the risk for disease transmission. Thus [10]:
� Equipment used for e.g. transportation of unsanitized faeces should notbe used for the treated (sanitized) product;be used for the treated (sanitized) product;
� When applying faeces to soil, precautions related to the handling ofpotentially infectious material should be taken. These precautions shouldinclude personal protection and hygiene. Hand washing should naturallybe done.
� Faeces should be worked into the soil as soon as possible and not beleft on the soil surface.
� Improperly sanitized faeces should not be used for vegetables, fruits orroot crops that will be consumed raw, excluding fruit trees.
Costs of UDD-Toilets in Nepal and India
ca. INR 11,000
(source: Rural Development Department Karnataka State)
USD 230 - 250(where community contributes ca. 40%)
(source: ENPHO, Nepal)
(photo: Wafler M.)(photo: Shrestha R.R.)
Costs of UDD-Toilets in India
ca. INR 12,000
(source: SCOPE) (source: http://www.eco-solutions.org/)
ca. INR 13,000
Costs of UDD-Toilets in India
Scope for cost reduction:
• construction material;
• pan (design, material, ...);
• ...
ca. INR 15,000
(photo: N. Zimmermann)
but NOT compromising on durability of UDD-Toilet
Single-Vault (Using Drums) UDD-Toilets
• Single-Vault UDD-Toilets, unlikeDouble-Vault UDD-Toilets, provide onlyone collection compartment forcollection and/or containment of feces;
• Building costs of a single vault deviceis less than of a double-vault;
• secondray storage or other types ofground level
feces drop hole
door
R.C.C. slab
ventilation pipe(¯ ³ 150 mm, raised at least 50 cmabove roof, screened at both ends
against flies and capped against rain)
window
door
• secondray storage or other types oftreatment (e.g. co-composting, etc.)must be planned for;
• urine and anal cleansing waterdiversion is equally important forSingle-Vault UDD-Toilets as fordehydration toilets providing twincompartments;
(source: UNESCO-IHE)
(source: M. Wafler)
Single-Vault (Using Drums) UDD-Toilets (contd.)
ADVANTAGES LIMITATIONS
• suitable for hard rock soil areas, high ground water levels and areas prone to floodings;
• regular shifting of drums;
• transport of unsanitised human excreta to secondary storage and/or processing site;and/or processing site;
• no contamination of groundwatersources due to containedprocessing of human feces
• reduced construction costs;
• possibility of smell if too muchliquid (urine, anal cleansing water,etc.) enters the processingcompartment;
Pictures from UUD-Toilets, Philippines
(photos: GTZ, Philippines)
Single-Vault UDD-Toilet by ENPHO (Nepal)
UDD inside building in Kathmandu, Nepal
(photos: M. Wafler)
UDD-Toilets in Multi-storyed Buildings
Winblad & Simpson-Hébert (15) (source: SEI)
Examples of Public Compost Toilet in Europe
Composting toilet at roadside facility in Sweden,
elected the best roadside facility in Sweden in 2002
(photos: P. Jenssen)
UUD-Toilet Quiz
(photo
s: M
. W
afler)
TOO CLOSE TO FENCE VENT PIPE DIA. OK, STRAIGHT, RUNS ABOVE ROOF, SCREENED & CAPPED
UUD-Toilet Quiz
(photos: M. Wafler)
COVER MATERIAL & WASTE BIN FOR DISPOSAL OF TOILET PAPER
URINAL FOR MALES, SOAP & WASH BASIN ARE PROVIDED
UUD-Toilet Quiz
VENT PIPE TOO SHORT INPROPER DISCHARGE OF GREYWATER & CLEANSING WATER
(photo
s: M
. W
afler)
UUD-Toilet Quiz
(photos: M. Wafler)
TOO SMALE DIAMETER & TOO MANY BENDS
PROPER DIAMETER & SLOPE OF PIPE OF URINE COLLECTION PIPE
UUD-Toilet Quiz
(photos: M. Wafler)
POOR DESIGN OF SLOPING COVER ALLOWING RAINWATER TO ENTER PROCESSING CHAMBERS
UUD-Toilet Quiz
source: GTZ, Philippines
DIAMETER TOO SMALEPIPE TOO SHORT (SHOULD END ABOUT 3“ ABOVE BOTTOM)
Environmental Transmission Routes and Barriers
Transmission routes for enteric pathogens • provision of water for hand washing,• elevated or lined collection chamber,• using ash, lime, etc.,• informed persons collecting and
transporting excreta,• suitable choice of location,• treatment in closed systems,• information signs in place,• informed farmers reusing excreta,• special equippment available,
source: [3]
barriers to prevent the transmission of disease/spread of pathogens
• special equippment available,• working excreta into the ground,• choice of suitable crops,• washing hands,• keeping toilet area clean,• wearing cloves and protective clothing
while handling excreta,• washing the equipment used,• avoid newly fertilized fields,• proper preparation and cooking of food
products,• cleanliness of kitchen surface & utensils
Zone of Safety - Pathogen Die-Off in Relation to Time & Temperature
new WHO guidelines for the safe use of wastewater, excreta and greywater (2006)
4 Volumes:
• Volume 1: Policy and regulatory aspects
• Volume 2: Wastewater use in agriculture
• Volume 3: Wastewater and excreta use in aquaculture
• Volume 4: Excreta and greywater use in agriculture
With these new guidelines WHO …
recognizes that the reuse of wastewater, greywater and excreta in agricultureand aquaculture is practiced worldwide on a large scale, however often withoutsufficient health production measures;
recognizes the importance of reuse of wastewater, greywater and excreta forsustainable food production and improved livelihood;
recognizes source-separation as a special and valid approach which cancontribute to risk reduction and
provides guidance on health protection measures for safe reuse.
Adapted protection level for wastewater/excreta use in agriculture in new WHO guidelines
adopted protection level for wastewater/excreta use in agriculture in the new WHO guidelines:
tolerable additional disease burden = 10-6 DALYs or 1 µDaly / person / year
= only one of a million human life years expectancy will be lost due to the potential additional disease from wastewater/excreta reuse
= same protection level as used in the WHO guideline for drinking water
Disability Adjusted Life Years (DALYs)DALYs are a measure of population health in terms of the burden due to a
specific disease or risk factor.DALYs attempt to measure healthy years of life lost because of disability or
death from a disease.DALYs account for not only acute health effects but also for delayed and chronic
effects.different health outcomes (e.g., cancer vs. diarrhea) can be compared and risk
management decisions can be prioritized.
water
Examples of health protection measures
crop restriction:a) non-food crops such as cotton, “biodiesel” crops, etc;b) food-crops that are processed before consumption (e.g. wheat);c) food-crops that have to be cooked (e.g. potatoes, rice, etc.).
wastewater application techniques:
a) flood and furrow irrigation;b) spray and sprinkler irrigation;c) localized irrigation (e.g. bubbler, drip, trickle, ect.);d) cessation of irrigation with wastewater 1 or 2 weeks prior to harvest.d) cessation of irrigation with wastewater 1 or 2 weeks prior to harvest.
pathogen die-off before consumption:
food preparation measures:
• produce washing with water; disinfecting; peeling; cooking.
human exposure control:
• field workers, consumers.
wastewater treatment:
• primary/secondary/tertiary treatment, disinfection (chlorination, UV)
Pathogen reductions achievable by various healthprotection measures
Health protection measure Pathogen reduction
(log units)
Wastewater treatment 1 - 6
Localized (drip) irrigation (low-growing crops) 2
Localized (drip) irrigation (high-growing crops) 4
Spray drift control (spray irrigation) 1
Spray buffer zone (spray irrigation) 1
Pathogen die-off 0.5 - 2 per day
Produce washing with water 1
Produce disinfection 2
Produce peeling 2
Produce cooking 6 - 7
(source: WHO)
Examples of options for pathogen reduction by different combinations of health protection measures
(source: WHO)
Different Scales of Urine Reuse Systems
Single households:
• the urine mixture can be used without storage for all type of crops, if crop is intended for the household’s own consumption;
• a withholding period of one month passes between fertilizing and harvesting;
• one reason for less stringent guidelines for single households is that the risk for person-to-person transmission will exceed the risk from urine-related environmental transmission!
(photo: M. Wafler)
(photo: M. Wafler)
Different Scales of Urine Reuse Systems (contd.)
Small domestic systems:
• direct use or use with short storage periods is applicable;
• in situations where the prevalence of some enteric infections is high, and where technical systems do not safeguard against faecal cross-contamination, an increased time of
ladies urinals
gents urinals
urinecollection/
storage tank
greywatergarden
urinecollection/
storage tank
urinecollection/
storage tank
urinecollection/
storage tank
contamination, an increased time of storage is recommended;
garden
urine storage tank
Ho
ste
l/K
itch
en
Bu
ild
ing
or
Ad
min
istr
ati
on
/Tra
inin
g B
uild
ing
transportation of urinefrom point of
collection to storagetanks by cart
urinecollection
tank (plastic)
Vurine Vurine
Vurine
inspection pipefor checking urine volume
(source: M. Wafler)
(source: M. Wafler)
Different Scales of Urine Reuse Systems (contd.)
Large scale systems:
• specific recommendations may need to be adapted, based on local conditions, and accounting for behavioural factors and the chosen technical system;
• based on the risk assessment calculations for urine, it can be concluded that a withholding time of a few weeks in the fields corresponds to the suggested storage time of one month at 20°C;
• the only difference when not requiring storage systems would thus be that the persons who apply the urine or who work in the fields are exposed to potentially higher concentrations of pathogens
Different Scales of Urine Reuse Systems (contd.)
• Inactivation of pathogens will also occur on agricultural land after application of the excreta as fertilizer
• Pathogens may even be inactivated in and on crops that may have become contaminated by fertilizer during the growth phase, or from splashes from the soil during heavy rains.from splashes from the soil during heavy rains.
• The inactivation is dependent on ambient temperature, moisture and sunshine (that will increase the temperature, decrease the moisture and affect pathogens by UV-light).
• In the soil, the naturally occurring microorganisms will also compete with the introduced pathogens and enhance their die-off.
Capacity Building for Ecological Sanitation
Ecosan Training Courses for TSC officials
Dipl. Ing. Martin Wafler, seecon international, Austria
Thank you for your attention!
++ References
(1) Austin, L.M., van Vuuren, S.J. (2002). Sanitation, Public Health and the Environment: Looking BeyondCurrent Technologies http://www.csir.co.za/websource/ptl0002/docs/boutek/akani/2002/mar/auspaper1.pdf(last accessed February 28th, 2007)
(2) Del Porto, D. (1999). The Composting Toilet System Book: A Practical Guide to Choosing, Planning andMaintaining Composting Toilet Systems. Chelsea Green Pub
(3) CDC (2003a). http://www.cdc.gov/ncidod/dbmd/diseaseinfo/leptospirosis_t.htm (last reviewed March 7th,2003)
(4) CDC (2003b). http://www.cdc.gov/ncidod/dbmd/diseaseinfo/typhoidfever_g.htm. (last reviewed June 20th,2003)
(5) Schönning, C., Stenström, A. (2004). Guidelines on the Safe Use of Urine and Faeces in EcologicalSanitation Systems
(6) SEI (2004). Guidelines on the Use of Urine and Faeces in Crop Production http://www.ecosanres.org/
(7) Jönsson, H. & Vinnerås, B. 2004. Adapting the nutrient content of urine and faeces in different countriesusing FAO and Swedish data. In: Ecosan – Closing the loop. Proceedings of the 2nd InternationalSymposium on Ecological Sanitation, incorporating the 1st IWA specialist group conference on sustainablesanitation, 7th-11th April 2003, Lübeck, Germany. pp 623-626
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