High-level low-cost sanitation services in small towns and large villages Duncan Mara
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High-Level Policy Dialogue on “EU Sanitation Policies and Practices High-Level Policy Dialogue on “EU Sanitation Policies and Practices
in the 2008 International Year of Sanitation”in the 2008 International Year of Sanitation”
High-level low-cost High-level low-cost sanitation services in small sanitation services in small
towns and large villagestowns and large villages
Duncan MaraDuncan MaraUniversity of Leeds, UKUniversity of Leeds, UK
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The Options:The Options:• On-site sanitation (e.g., pour-flush toilets + On-site sanitation (e.g., pour-flush toilets +
leach pits)leach pits)
• Low-volume flush toilets + Low-volume flush toilets + simplified sewerage + low-cost simplified sewerage + low-cost wastewater treatment (e.g., waste wastewater treatment (e.g., waste stabilization ponds)stabilization ponds)
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Low-volume flush toiletLow-volume flush toilet
For example, For example, Swedish models Swedish models that use that use 3 litres3 litres per flush: per flush:
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Simplified sewerageRigorous hydraulic design based on:
• a minimum sewer diameter of 100 mm
• a minimum tractive tension of 1 N/m2
• a minimum value for peak wastewater flow of 1.5 litre/second
This results in a minimum gradient of 1 This results in a minimum gradient of 1 in 200, and a 100 mm dia. sewer being in 200, and a 100 mm dia. sewer being able to serve 234 households of 5 people able to serve 234 households of 5 people with a water consumption of 100 litres/ with a water consumption of 100 litres/ person day.person day.
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Comparative costs (1997 US$) of conventional and condominial sewerage
in Parauapebas, Pará, north Brazil
ItemConventional sewerage Condominial sewerage
Totalcost
Cost per connection
Totalcost
Cost per connection
Excavation 263,000 39 186,000 28
Inspection chambers
181,000 27 85,000 13
Sewers 185,000 28 102,000 15
Total 629,000 9494 373,000 5656
Source: Melo (2005).
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Brasília
Simplified sewerage in rich areasas well as in poor areas
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CAESB, the water & sewerage company for Brasília and the Federal District, basically asked itself:
If condominial sewerage works well in poor areas, shouldn’t it also work well in non-poor areas? Answer: Yes.Answer: Yes.
The next question is:
As condominial sewerage works well in both As condominial sewerage works well in both poor and non-poor areas, should we ever use poor and non-poor areas, should we ever use conventional sewerage in urban housing conventional sewerage in urban housing areas?areas? Answer: Answer: NO.NO.
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Waste stabilization pondsWaste stabilization ponds
• Widely used in France (>2500 systems) Widely used in France (>2500 systems) and Germany (>3000)and Germany (>3000)
• FranceFrance: Facultative pond (6 m: Facultative pond (6 m22/p.e) + two /p.e) + two maturation ponds (each 2.5 mmaturation ponds (each 2.5 m22/p.e)/p.e)
• Research in UKResearch in UK: Facultative pond (as in : Facultative pond (as in France) + aerated rock filter (1 mFrance) + aerated rock filter (1 m22/p.e) − /p.e) − produces a very high quality effluentproduces a very high quality effluent
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Facultative and maturation ponds Facultative and maturation ponds are GREEN because of the are GREEN because of the ALGAEALGAE
that grow in themthat grow in them
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Algal−bacterial mutualism
Algae
Bacteria
O2 CO2
New cells
New cells
LighLightt
Wastewater BOD
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Québec
Too cold for WSP in Europe? No!No!
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Chappelle Thouaroult, Brittany, France
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Capital and O&M costs of various wastewater
treatment processes for 1000 p.e. in France in 1998
Treatment Capital costs O&M costs process (€ p.e.–1) (€ p.e.–1 a–1)
Activated sludge 230 11.50 Trickling filter 180 7.00 RBC 220 7.00 Aerated lagoon 130 6.50 Settler-digester + CW 190 5.50 WSP 120 4.50
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1. Anaerobic pond1. Anaerobic pond
Small WSP system in Bavaria
Village of Berg, near Munich (pop. ~250)Village of Berg, near Munich (pop. ~250)Mean temp. of coldest month (Jan.): −2°C
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2. Secondary facultative pond2. Secondary facultative pond
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Capital and O&M costs of various wastewater
treatment processes for 500 p.e. in Germany in 1996
Treatment Capital costs O&M costs process (DM p.e.–1) (DM m–3)
Activated sludge 2,000 2.00 Trickling filter 1,500 1.70 Aerated lagoon 1,200 1.70 Vertical-flow CW 1,200 1.50 Horizontal-flow CW 1,500 1.30 WSP 700 1.20Average 1996 exchange rate: DM1 = €0.53
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PERTHSHIRE
SCOTLAND
Loch Achray
Tigh Mor Trossachs WSP
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The effluent from a facultative pond loaded at 80 kg BOD/ha d
complies with the UWWTD
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(91/271/EEC)
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Rock filter receiving maturation pond effluent – Veneta, Oregon
Fac. pond
Mat. pond
Rock filter
Baffle →
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Suspended solids removal
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Summer Results for
effluent ammonia-N/l:
Aerated RF: <2 mg/l
Unaerated RF: ~7 mg/l
Planted bed: ~4 mg/l
BUT Winter Results for
effluent ammonia-N/l:
Aerated RF: <2 mg/l
Unaerated RF: ~8 mg/l
Planted bed: ~7 mg/l
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Natural vs Conventional Wastewater Treatment
Basically a choice between LAND Basically a choice between LAND and ELECTRICITY:and ELECTRICITY:
• Money spent on land is an Money spent on land is an investmentinvestment
• Money spent on electricity is Money spent on electricity is money gone for evermoney gone for ever