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Part A – OverviewPart B – Description of commonly used low-cost on-site excreta management systemsPart C – Comparison with UDD toilet
2
To be really precise, this presentation is about “Conventional low-cost excreta management systems”
This Unit has been made entirely by Elisabeth von Münch without editing; you can hear her on the audiofiles also on the platform.
Clarification of terms:
Latrine is used interchangeably with the term “toilet”
Pit = Hole in the ground (not water tight)
Vault = Container above ground (water tight)
Course 2 Unit 2
Part A: Overview
Course 2 Unit 2
What do we mean by “conventional” and “on-site”?
“Conventional” means here: Currently widely known and used Accepted by decision makers as a
potential option Usually it still often means little
consideration for sustainability (unfortunately)
UDD toilets could become part of conventional options in the future (this would be a good thing!)
“On-site” means: Not connected to sewer Treated “at the site where people
live” – but this is not always strictly
true, e.g. septic tanks eventually need removal of faecal sludge to a centralised treatment plant
“Decentralised” is often used interchangeably with “on-site”
The opposite of on-site is called:– off-site; or– centralised systems; or– sewer-based sanitation (the
only other alternative could be to tanker the wastewater away)
Reasons for having on-site sanitation systems rather than a sewer system
To save construction and maintenance costs– Because people cannot afford a connection to a sewer– Many municipalities cannot afford construction and maintenance of an
expensive sewer system and a wastewater treatment plantMunicipalities face huge costs to rehabilitate aging sewer
infrastructure older than 150 years (e.g. in Germany, UK) To save water (or because water is scarce or not reliably available);
however, not all on-site sanitation systems have low water use (e.g. septic tanks)
To serve remote locations (long distances)– e.g. in Australia and in the US (in the US 50% of new houses use on-site
sanitation - I heard this at the conference in Aachen in 2007 but have no exact reference for this figure)
Because housing is only temporary or illegal (slums, refugee camps) Because it is more flexible with respect to population growth and decline Because people prefer not to mix excreta with water in order to make
containment of pathogens easier (in the case of a waterless on-site sanitation system)
Can you think of other reasons?
Reminder: Sanitation consists of 4 components
1. Excreta management
Many people think of only excreta management when they talk about sanitation
2. Greywater management
Most often just dumped into the street or gutter (mixing with rainwater, soil infiltration)
Less critical from public health point of view compared to item 1 but still needs consideration
3. Solid waste management
4. Rainwater drainage
The remainder of this presentation will dealwith low-cost excreta management
Greywater = wastewater from kitchen, bath/shower, sinks, laundry (minimal excreta content) See Course 2 Unit 1 for greywater treatment aspects
On-site sanitation is quite easy if…
…Population density is low(e.g. rural areas)
…or if money is not an issue!
But big problems for:High population density and low income(peri-urban areas, slums)
My rules of thumb:Low density: < 100 people/haPeri-urban areas: 100 – 240 people/ha (e.g. Lusaka, Zambia case)Slums: > 800 people/ha (e.g. Dhaka, Bangladesh)1 ha = 10,000 m2 = 0.01 km2 (1 soccer field = 0.7 ha)
What is the population density in your city?
this is the focus of this lecture: low-cost on-site sanitation in urban areas
Course 2 Unit 2
Conventional low-cost excreta management methods (in approximate order of increasing system cost)
Excreta disposal method Needs faecal sludge mgmt.?
Can accept greywater?
Human dignity Public health risk
Open defecation No No Very low Very high
Flying toilet No No Very low Very high
Bucket latrine Yes No Low High
Simple pit latrine Yes No Can be OK Medium
Ventilated improved pit (VIP) latrine Yes No OK Low
Urine-diversion dehydrating toilet* No but faecal matter collection
No OK Low
Pour-flush latrine with pit, aqua privy Yes No OK Low
Water-flush or pour-flush toilet with septic tank
Yes Yes OK Low
Water-flush toilet with holding tanks / cess pits
Yes Yes OK Low
Course 2 Unit 2
* Not (yet) conventional but included for comparisonMore about costs: see Course 4 Unit 1 “Financial aspects”
Course 2 Unit 2
Part B: Description of commonly used low-cost on-site excreta management systems
(this part is excluding UDD toilets; UDD toilets are covered in detail in Part C)
Course 2 Unit 2
Commonly-used on-site excreta management systems described in Part B
1. Open defecation
2. Flying toilet
3. Bucket latrine
4. Simple pit latrine
5. Ventilated improved pit latrine
6. Pour-flush latrine with pit or septic tank
7. Aqua privy with septic tank
8. Water-flush toilet with septic tank
9. Water-flush toilet with holding tanks / cess pits
Remember: these are not counted as basic/improved sanitation in the MDGs
These can be counted as basic/improved sanitation in the MDGs if no open pit but pit with slab, not shared, not public toilet and adequate treatment of faecal sludge (see Course 1 Unit 1 Part C on MDGs)
UDD toilets are not (yet) commonly used – so they are not listed in this table here, but described in detail in Part C
1. Open defecation
About 2.4 billion people have no access to basic sanitation (WHO/UNICEF, 2006) and many of these use open defecation (or bucket latrines, flying toilets)
Great public health risks unless population density is very low
Rain events flush faeces into receiving water bodies– Example: Diarrhoea incidences
increase during rainy season in peri-urban areas in Lusaka, Zambia
Open drain used as public toilet in Ouagadougou, Burkina Faso (Oct. 06)
2. Flying toilet
Defecate into plastic bags and throw these away
Main problems:– Little human dignity and
comfort for the user– Plastic bags can block open
drains– Plastic bags can break and
spill their content animals and children can get in contact with fresh faeces
Defecate and urinate into a bucket which is regularly emptied manually
3. Bucket latrine
http://www.millennium-ark.net/News_Files/NBC/shelter.in.place.html
What does faecal sludge from bucket latrines look like?
A worker in Kumasi (Ghana) is transferring faecal sludge from a manhole, which is used to store faecal sludge from bucket latrines, to a bucket and then to a transport vehicle (Source: Vodounhessi (2006))
Note the lack of boots (but he does wear gloves which is good) Faecal sludge
Course 2 Unit 2
4. Simple pit latrine User urinates and defecates into a toilet placed over a
hole (pit) in the ground Pit depth: 2 m or more, covered with latrine slab Diameter of pit: 1 – 1.5 m (round or square) The hole may be lined around the top to prevent
collapsing The pit is designed so that the liquid pit content seeps
into the ground Can be squatting (top photo) or sitting (bottom photo) Very common for:
– Rural areas– Peri-urban areas, slums, schools– Emergency sanitation, refugee camps
Ouagadougou, Burkina Faso
Reminder: How can pit latrines affect the groundwater?
Based on: Werner, Ch., Mang H.-P., Klingel, F. Bracken, P. (2004): General overview of ecosan. PowerPoint-Presentation. Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH ecological sanitation programme.
Nitrate
Pathogens
Groundwater (clean)
Groundwater (polluted)
Pit latrine Shallow drinking water well
(from Course 1 Unit 3)
Question: so why don’t we build fully lined pit latrines?
If a pit latrine was fully lined, it would no longer be a pit latrine but a holding tank
The pit would fill up very quickly with all the urine (remember: about 1.5 L/cap/d of urine)
Pits are only lined at the top and perhaps the side to prevent collapsing but never at the bottom
5. Ventilated Improved Pit (VIP) Latrine
VIP latrine is the same as simple pit latrine but has a vent pipe and fly screen (reduces odour and fly breeding)
Toilet room and pit should be dark to not attract flies
Some VIPs are built as a double-pit structure (see next slide)
Vent pipe
Fly screen
Source: Harvey et al. (2007)
Substructure / pit:Liquid seeps into the
ground
Super-structure
Air flow
Pits are not water tight as they would otherwise fill up too quickly
liquid (urine)
Double Pit VIP Latrine
Source: http://web.mit.edu/urbanupgrading/waterandsanitation/resources/pdf-files
Double pit improves conditions for pit emptying and potential for reuse compared to single pit
Pits are alternated every 6 months or (better) every 12 months
But lack of faecal sludge management and potential for groundwater pollution are still problems
Pit: Liquid seeps into the ground (no separate urine collection)
Pit in use
(drying)
Pit latrines in peri-urban areas of Lusaka, Zambia
Raised pit latrine due to rocky soil (note leaking on the side)Source: Mayumbelo (2006)
More photos from pit latrines in peri-urban areas of Lusaka
Photos by Kennedy Mayumbelo (Lusaka Water and Sewerage Company), March 2007: “The pit latrine is being used by three households, all on the same plot. There are a total of 14 people currently using it and it is leaking very badly from the sides (problem of construction). It is also full and the users said they only use it because they have no choice; as expected all the three households are tenants and the landlord lives elsewhere.”
Typical problems with pit latrines in peri-urban areas
High odour levels Fly breeding Overflowing Collapsing of pits No space to dig new pits Difficult to dig new pits if ground is rocky No systems to empty pits (lack of faecal
sludge management) Pit latrines have to be outdoors Pollution of groundwater which is used for
drinking water by using shallow wells (e.g. Lusaka, Zambia)
Pits are also used to dump rubbish
Have you ever used a pit latrine?
A collapsed pit latrine (photo by Linus Dagerskog, CREPA, taken in Ouagadougou, Burkina Faso)
Linus said: “the most disgusting thing I have ever seen; a bubbling sludge, flies everywhere, and the house owner did not really know how to cover or fill it.”
A pit latrine where the hole is in the process of collapsing (seen in Maseru, capital of Lesotho (a small country inside of by South Africa), December 2006)
Course 2 Unit 2
Photo: E. v. Münch
Despite their “popularity”: pit latrines are actually not sustainable if… The groundwater table is shallow Karst geology or ground that is underlain by pervious rock leading
to:– a rapid rate of groundwater movement– potential for groundwater contamination (in combination with shallow
wells being used as a water supply source) Area has a potential for flooding Soil type is rocky (hard to excavate) No space to dig new pits or no means to empty full pits and to treat
faecal sludge Population density is high Situation has lack of security (since pit latrines have to be built in
some distance from the settlements)
Pit emptying
After some months or years of use (depending on the number of users and the size of the pit), a pit latrine fills up. It then needs to be either abandoned or emptied.
Note: water needs to be added to make faecal sludge from pit latrines pumpable!
Methods for emptying:– Manual emptying with buckets
(extremely high health risks!)– Mechanised emptying with vacuum
tankers (see Course 2 Unit 3 “Storage and transport logistics”)
Vacuum tanker collecting faecal sludge from septic tank
Why are pit latrines so wide-spread in low income areas?
Cheap and easy to construct and maintain “Drop-and-forget” mentality Can be appropriate solution if:
– population density is low; and – soil conditions are suitable (not rocky, not sandy, easy to
dig but also stable); and– area not prone to flooding; and– groundwater table not shallow but rather deep; and– good general security (no harassment for women and
children at night)
Course 2 Unit 2
6. Pour-flush latrine with pit or septic tank
• After defecation, a few litres of water must be poured into the bowl to flush the excreta into the pit or septic tank
• Water acts as a hygienic seal (reducing odour and flies)
• (The toilet’s squatting pan could be modified to include urine diversion as a first step towards ecosan)
Source: Harvey et al. (2007)
Course 2 Unit 2
Pit under toilet Pit offset from toilet
7. Aqua Privy with septic tank
• Simple latrine constructed over a septic tank
• Tank must be watertight to maintain constant liquid level in the tank
• Tank can receive greywater
• Nowadays less common (I have never seen one – have you?)
Source: Harvey et al. (2007)
8. Water-flush toilet with septic tank
Septic tanks: Underground tanks, usually one per
household Work in conjunction with water-flush toilets Combined settling, skimming and
anaerobic digestion Solution for the wealthy in developing
countries (requires water for flushing) Pre-treated, settled effluent usually
infiltrated into ground (“soakaway”) Tanks need emptying Faecal sludge
management often lacking For an ecosan concept, septic tanks could
be used just for greywater or just for blackwater (urine, faeces and small amount of water)
See “Introduction to Anaerobic Treatment” (Course 2 Unit 4) and “Conventional Faecal Sludge Management” (Course 2 Unit 7)
Underground septic tanks in Maseru, Lesotho (Dec. 2006)
Septic tank effluent discharged to soakaway or small-bore sewer(see Course 2 Unit 8 “Small-bore sewer systems”)
Source: http://web.mit.edu/urbanupgrading/waterandsanitation/resources/pdf-files
Typical problems with septic tanks (particularly, but not only, in developing countries)
Effluent quality low and often not enough space for sustainable soil infiltration– Tank is undersized (little anaerobic treatment occurring) – Population density has become too high capacity of soil to absorb
and treat liquid effluent is exceeded– Pollution of groundwater is possible (effluent soak-aways most common)
Tank may be leaking (faecal sludge is leaking out); maintenance is neglected
Need regular emptying (typically every 5-10 years, depending on size and number of users)– Faecal sludge is overflowing together with the effluent
Capacity for faecal sludge treatment lacking (resulting in illegal dumping anywhere in the environment)
Relatively expensive (not affordable for the poor) Need access roads for emptying trucks
Do you have your own experiences with septic tanks (e.g. at home or at work)? How often is it emptied (faecal sludge removed)? How do you know when to empty it? What is the effluent quality of your septic tank like? Is it
good? How do you know? Is it ever giving you odour problems? Where is the faecal sludge taken to and how is it treated?
Such individual soil-based systems are difficult to monitor!
Course 2 Unit 2
9. Water-flush toilet with holding tank (also called cess pit or conservancy tank)
Source: http://web.mit.edu/urbanupgrading/waterandsanitation/resources/pdf-files
Needs watertight tank and frequent emptying
Sometimes cess pits are (illegally) converted into a leaching pit by breaking through the base of the tank - so that the cesspit no longer fills up! This may be convenient for the owner but may lead to groundwater pollution
In the US, the word “cesspool” is used, but this is not a water-tight tank but allows infiltration
Faecal sludge management (FSM)
The following on-site systems result in the production of faecal sludge:– Household pit latrines, bucket latrines– Unsewered public toilets, e.g. aqua privies, pour flush, VIP,
cess pits – Septic tanks (households, institutions, hotels,…)
Faecal Sludge Management = FS transport, treatment, reuse
See separate lecture on FSM (Course 2 Unit 7 “Faecal sludge management”)Some handy rules of thumb:
Specific faecal sludge production (Heinss et al., 1998):1.0 L/cap/day from septic tanks0.2 L/cap/day from toilets without water use
Typical FS total solids content 25 g/L (Steiner et al., 2002)
’’Closing the loop’’
Proposed scenario Current situation= Faecal sludge crisis:
Faecal sludge management overview
uncontrolled disposal
illegal dumping no beneficial
reuse
But how to deal with liquid effluent?
(need to add water to empty pit by pumping)
Course 2 Unit 2
Part C: Comparison with UDD toilet
Course 2 Unit 2
For cost comparisons see Course 4 Unit 1 (“Financial aspects”)
UDD toilet details are given in Course 1 Unit 3 and Course 1 Unit 4
Example: Single vault urine-diversion dehydrating (UDD) toilet
Source: http://web.mit.edu/urbanupgrading/waterandsanitation/resources/pdf-files
Removal of dried material
This type of toilet is often wrongly called “composting toilet” or “ecosan toilet”
Ecosan is not limited to a specific technology, hence UDD toilets or other toilet types could be used in an ecosan project
(Double vault UDD toilet would normally have two vent pipes)
Advantages of a UDD toilet compared to a pit latrine
Can be indoors, because:– No pit required (the pit would normally allow liquid to seep into
the ground)– No odours (because urine and faeces are not mixed)
Suitable for areas with:– High-density settlements– Difficult soil conditions– A danger of groundwater pollution
Easy to recycle excreta Does not require faecal sludge management (vacuum
tankers for pit emptying) Does not require regular digging of new pits Can be more portable (e.g. the Separett foldable UDD toilet
shown in Course 1 Unit 3 Part E)
Course 2 Unit 2
Disadvantages of a UDD toilet compared to a pit latrine
Requires user training and awareness, e.g. must not urinate into the faeces compartment (one should also provide waterless urinals for men)– Can produce odours if not used correctly
Still relatively new concept amongst NGOs, municipalities, universities, consultants, manufacturers, etc.
Dried faecal matter must be removed once or twice per year Anal washing with water (if practised) must take place over a
drain which is separate from the faeces vault Urine must be collected, stored, transported and used as
fertiliser, or infiltrated into the ground or otherwise dealt with– Urine collection container could be stolen– Even the collected urine itself is known to have been
stolen once people appreciate its value as a fertiliser (experience of CREPA in West Africa)!
Course 2 Unit 2
How to select best on-site sanitation option?
Compare sustainability of available options (use sustainability criteria, see Course 1 Unit 1) – this includes: social, technical, economic, environmental, public health and institutional aspects; and/or
Use selection criteria based on local conditions (example on next slide)
Example: Short-listing of options for peri-urban areas in Lusaka, Zambia (slide 1 of 2)
Short listed options: Option 1: VIP latrine and downstream
processingOption 2: Single-vault UDD toilet and
downstream processing
Selection criteria:1. Not pollute groundwater (groundwater is used as
drinking water)2. Not require water to transport waste (water is scarce
and expensive)3. Sanitise excreta to destroy pathogens (protect public
health)4. Cost effective – low capital and O&M (people have low
income)
Source: Mayumbelo (2006)
Note: Option 1 does not meet selection criterion 1 but is included to serve as a reference point in the cost analysis
Example cont’d: Decide on the implementation level (slide 2 of 2)
Household facility – One toilet for 4 people
Plot facility– One toilet for all people living on one plot (12 in this case)
Communal facility– One toilet block that is shared by a number of plots
Good compromise between convenience and cost
Course 2 Unit 2
And at the end: Summary of conflict between (conventional) onsite sanitation and urbanization…
References for this presentation (slide 1 of 2)
Harvey, P., Bastable, A., Ferron, S., Forster, T., Hoque, E., Morris, L., Piano, E., and Smith, M. (2007) Excreta Disposal in Emergencies: A Field Manual, WEDC, Loughborough University Available: http://wedc.lboro.ac.uk/projects/new_projects3.php?id=15 *
Heinss, U., Larmie, S. A., and Strauss, M. (1998) Solids separation and pond systems for the treatment of faecal sludges in the tropics. Lessons learnt and recommendations for preliminary design. EAWAG/SANDEC, Dübendorf, Switzerland. http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_ewm/downloads_ewm/solids_sep_and_pond_treatm.pdf *
Steiner, M., Montangero, A., Koné, D., and Strauss, M. (2002) Economic aspects of low-cost faecal sludge management. Estimation of collection, haulage, treatment and disposal /reuse cost, EAWAG/SANDEC, Dübendorf, Switzerland. http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/publications_ewm/downloads_ewm/FSM_cost_report.pdf *
WHO/UNICEF (2006) Meeting the MDG Drinking Water and Sanitation Target – The Urban and Rural Challenge of the Decade. WHO/UNICEF Joint Monitoring Programme (JMP) for Water Supply and Sanitation. Available: http://www.who.int/water_sanitation_health/monitoring/jmp2006/en/index.html (provided under Course 1 Unit 1 Assigned Reading)
* Provided on the I-LE for this course unit (Extra materials)
References (slide 2 of 2)recent MSc theses at UNESCO-IHE
Mwase, H. (2006) The potential of ecosan to provide sustainable sanitation in emergency situations and to achieve “quick wins” in MDGs, MSc Thesis, UNESCO-IHE Institute for Water Education, Delft, The Netherlands
Mayumbelo, K. M. K. (2006) Cost analysis for applying ecosan in peri-urban areas to achieve the MDGs - Case study of Lusaka, Zambia, MSc Thesis MWI 2006-10, UNESCO-IHE Institute for Water Education, Delft, The Netherlands.
Vodounhessi, A. (2006) Financial and institutional challenges to make faecal sludge management integrated part of ecosan approach in West Africa. Case study of Kumasi, Ghana. MSc Thesis WM 2006.05, UNESCO-IHE Institute for Water Education, Delft, The Netherlands.
The first two are also available from the GTZ literature database:http://www.gtz.de/en/themen/umwelt-infrastruktur/wasser/9835.htm
