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1 Doulaye Koné EAWAG / SANDEC www.sandec.eawag.ch Tel.+41 44 823 55 53 Environmental sanitation planning and infrastructure in developing countries Low-cost.

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Presentation on theme: "1 Doulaye Koné EAWAG / SANDEC www.sandec.eawag.ch Tel.+41 44 823 55 53 Environmental sanitation planning and infrastructure in developing countries Low-cost."— Presentation transcript:

1 1 Doulaye Koné EAWAG / SANDEC Tel Environmental sanitation planning and infrastructure in developing countries Low-cost Options for Treating Faecal Sludges (FS) and Wastewater in Developing Countries (Part A to C)

2 2 Contents Part A: Faecal sludge characteristics Part B: Faecal sludge treatment standards Part C: Low-cost wastewater treatment options

3 3 Part A: Faecal sludge (FS) characteristics

4 4 FS specific quantities VariableSeptage 1 Public toilet sludge 1 Pit latrine sludge 2 Fresh excreta BOD g/cap·day TS g/cap·day TKN g/cap·day Volume l/cap·day 12 (includes water for toilet cleansing) (faeces and urine) 1 Estimates are based on a faecal sludge collection survey conducted in Accra, Ghana. 2 Figures have been estimated on an assumed decomposition process occurring in pit latrines. According to the frequently observed practice, only the top portions of pit latrines (~ m) are presumed to be removed by the suction tankers since the lower portions have often solidified to an extent which does not allow vacuum emptying. Hence, both per capita volumes and characteristics will range higher than in the material which has undergone more extensive decomposition.

5 5 Factors influencing faecal sludge quality

6 Low - Low - : Low + Med: med + High - : High + 1.low - viscosity zone 2.low - : low + viscosity zone 3.med : med + viscosity zone 4.high - : high + viscosity zone The latrine technology influences the FS characteristics and determines the emptying procedure and technology

7 7 Faecal and WWTP sludges compared Faecal sludge = wastewater  offside ! 1 litre faecal sludge = 100 litres wastewater !

8 8   Faecal sludge = wastewater  offside ! 1 litre faecal sludge = 100 litres wastewater !

9 9 Comparison of public toilet sludge, septage and sewage characteristics

10 10 Location Accra (Ghana) Alcorta (Argentina) Ouagadougou (Burkina Faso.) Bangkok (Thailand) Type of FS Public toilet sludge Septage TS (mg/L)52,50012,000 (6,000 – 35,000 SS) 19,000 15,350 (2,200 – 67,200) COD (mg/L)49,0007,8004,20013,500 15,700 (1,200 – 76,000) NH 4 -N (mg/L)3, (120 – 1,200) FS characteristics in selected cities in developing countries

11 11 * Different treatment schemes and design criteria FS  Wastewater FS Variability * Design basis: average from a large number of analyses * No standard characteristics, analysis on a case-to-case basis Faecal sludge = wastewater  offside ! 1 litre faecal sludge = 100 litres wastewater !

12 12 Part B: Faecal sludge (FS) treatment standards

13 13 Faecal sludge treatment standards ArgentinaBOD=50mg/l, SS=60mg/l, FC=10 5 /100 ml (Santa Fé)Biosolids used in agriculture:  1HE/4g TS China  95% HE removal and 30 days storage South Africano viable ascaris ova/10g TS, 0 salmonella/10g TS,  1000 FC/10g TS Ghana 90% BOD and FC removal for Teshie FSTP effluent

14 14 Setting standards in developing countries Development monitoring and enforcement systems still lagging far behind Define and set up a series of barriers (critical control points) select a phased approach base environmental regulations on available technology and on (local) economic and institutional resources

15 15 Setting standards in industrialized countries A phased approach Ex. COD [mg/l] Gradual development of the effluent discharge standard in Germany. For sewage treatment plants > 100,000 p.e. (Bode, 1998)

16 16 Suggested standards for developing countries

17 17 Appropriate FS treatment options in developing countries

18 18 Part C: Low-cost wastewater treatment options Comment: This part is not essential: you can see it as a reminder about how constructed wetlands and anaerobic ponds work

19 19 Wastewater treatment Constructed wetlands Pond systems Macrophyte systems (e.g. duckweed; water lettuce) Examples of treatment systems Activated sludge systems Trickling filter Rotating biodisc contactor Sequencing batch reactor Aerated lagoons Oxidation ditch UASB reactor Biogas reactor “Natural treatment systems” “Mechanical treatment systems” Centralised wastewater treatment

20 20 Waste stabilization ponds in warm climates Pond systems Wastewater treatment

21 21 Degradation of organic substances in waste stabilization pond systems Wastewater treatment

22 22 N transformations in waste stabilization ponds Nitrogen transformations and losses in a facultative waste stabilisation pond. The thickness of the arrows signifies the relative quantitative importance of the pathway; the broken arrows show mechanisms of net nitrogen removal. Wastewater treatment

23 23 Constructed wetlands Wastewater treatment

24 24 Constructed wetlands From pretreatment Variable effluent level Effluent From pretreatment Wastewater treatment

25 25 Wetland Plants

26 26 Mechanisms in constructed wetlands Wastewater constituentRemoval mechanisms Suspended solidsSedimentation Filtration Soluble organicsAerobic microbial degradation Anaerobic microbial degradation NitrogenAmmonification followed by microbial nitrification Denitrification Plant uptake Matrix adsorption Ammonia volatilisation PhosphorousMatrix sorption MetalsAdsorption and cation exchange Complexation Precipitation Plant uptake Microbial oxidation/reduction PathogensSedimentation Filtration Natural die-off Predation UV irradiation Excretion of antibiotics from roots of macrophytes Plant uptake Wastewater treatment

27 27 N transformations in constructed wetlands Wastewater treatment

28 28 Comparison of different systems ≤ 1 d +++ Activated sludge ≤ 1 d ++ Oxidation ditch ≤ 1 d + Rotating biodisc reactor < 1 d + 2) Trickling filter 2-3 d 0 (+) 1) Soil-plant filter 3-5 d 0 Maturation pond 10 d 0 Facultative (non-aerated) waste stabilisation pond Approx. hydr. retention time [days] (in warm climate) Rel. energy requirement for operation (gravity flow) Relative area requirement Aerobic systems 1) (+): To remove and treat accumulated biosolids 2) (+): Recirculation

29 29 Comparison of different systems > 6 h (-) 3) 0 (+) 1) Upflow anaerobic sludge blanket reactor, UASB h 0 (+) 1) Anaerobic filter ≥ 3 d 0 (+) 1) Anaerobic baffled reactor 1 d 0 (+) 1) Septic tank 1-3 d0 (+) 1) Anaerobic pond Approx. hydr. retention time [days] (in warm climate) Rel. energy requirement for operation (gravity flow) Relative area requirement Anaerobic systems 1) (+): To remove and treat accumulated biosolids 2) (+): Recirculation 3) (-): Gas utilization Wastewater treatment


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