Presentation is loading. Please wait.

Presentation is loading. Please wait.

2 Household and neibourghood Sanitation Infrastructures: Excreta, wastewater disposal in developing countries Doulaye Koné – Eawag/Sandec.

Similar presentations


Presentation on theme: "2 Household and neibourghood Sanitation Infrastructures: Excreta, wastewater disposal in developing countries Doulaye Koné – Eawag/Sandec."— Presentation transcript:

1 2 Household and neibourghood Sanitation Infrastructures: Excreta, wastewater disposal in developing countries Doulaye Koné – Eawag/Sandec

2 3 Objectives of a sanitation systems What are we talking about? Wastewater sources and their characteristics Pathways of domestic wastewater Household sanitation management infrastructures Realistic holistic sanitation systems Structure of the presentation

3 4 Tasks of sanitation systems Prevent disease – guarantee effective barriers against sanitation related diseases Protect the environment – prevent pollution, return nutrients to the soil, and conserve water. Be simple - operation of the system must be feasible using locally available resources (human and material). Where technical skills are limited, simple technologies should be preferred. Be affordable – total costs (incl. capital, operation, maintenance costs) must be within the users’ ability to pay. Be culturally acceptable – it should fit local customs, beliefs, and desires. Work for everyone – it should address the needs of children and adults, of women and men.

4 5 Blackwater toilet wastewater (faeces and urine with or without flushing water) What are we talking about? Greywater domestic wastewater form kitchen, bath, shower (excluding faeces and urine) Brownwater Blackwater without urine Yellowwater Urine Faecal sludge Sludge accumulating in "on-site sanitation systems" (Latrines, Septic tanks, etc.)

5 6 Latrines (trad., VIP, PF, double-pit, no- mix,...) “Faecal sludge- FS” Biosolids to agriculture for soil conditioning and fertilization The Path of Excreta and Greywater in Urban Areas sewered sanitation (black and greywater) Septic tanks Wastewater treatment plant (WWTP) “on-site” sanitation (excreta, black and greywater) FS treatment Plant (FSTP) Septage Effluent to soakage or drains Liquid to discharge into receiving waters or to co- treatment in WWTP Effluent to agricultural use or discharged into receiving waters Products from double-pit and no-mix latrines might be used on-site Greywater ~ 2 billion (2004) ~ 3 billion (2025) Small-bore sewerage for effluent of interceptor or septic tanks Eawag / Sandec 2004 The human waste system

6 7 TotalGreywaterUrineFaeces Volume [l/cap*a] 25’ ’ Nutrients Nitrogen 2-4 kg/cap*a5%85%10% Phosphorous kg/cap*a10%**60%30% Potassium kg/cap*a34%54%12% COD30kg/cap*a41%12%47% Faecal coliforms /100ml 0* /100ml Characteristics of the different wastewater sources * healthy people ** can be as high as 50%, depending on washing and dish-washing powder used

7 8 regulations and standards (including enforcement) costs for construction, O&M willingness to pay (initial and monthly payments) self-help potential and initiative of local people and organizations local entrepreneurs, consultants, construction companies,... Existing system! Economic, institutional and other aspects Criteria influencing the selection of sanitation systems

8 9 Classification of Excreta and wastewater management technologies - Cesspit trucks

9 10 Partially sewered cities Business centre of large cities with high water consumption rate Lack of treatment sites and wastewater treatment plants Discharge of wastewater into natural water bodies and open canals

10 11 Cities without sewers Represent more than 90% of cities in developing countries Are very heterogeneous in urban infrastructure Often lack financial and human resources for sanitation development and upgrading

11 12 Decentralised sanitation systems are often more suitable – why? –Existing systems are decentralised (e.g. latrines) –Treatment and reuse can be tailored to the specific waste stream (e.g. urine, faeces, greywater etc.) –Decentralised systems are easier to plan and implement (different “independent” areas with specific needs and characteristics) –Capital investments are generally less than for centralised systems (reduced investments for trunk sewers and pumping stations, lower O&M costs) –Capacity expansion and thus capital requirements can track demand much more closely (incremental approach) –No reason to impose a “one size fits all” approach –Different strategies can be employed in various parts of the service area.

12 13 Latrines (trad., VIP, PF, double-pit, no- mix,...) “Faecal sludge- FS” Biosolids to agriculture for soil conditioning and fertilization The Path of Excreta and Greywater in Urban Areas sewered sanitation (black and greywater) Septic tanks Wastewater treatment plant (WWTP) “on-site” sanitation (excreta, black and greywater) FS treatment Plant (FSTP) Septage Effluent to soakage or drains Liquid to discharge into receiving waters or to co- treatment in WWTP Effluent to agricultural use or discharged into receiving waters Products from double-pit and no-mix latrines might be used on-site Greywater ~ 2 billion (2004) ~ 3 billion (2025) Small-bore sewerage for effluent of interceptor or septic tanks Eawag / Sandec 2004 The human waste system

13 14 Simple pit latrine 2 m or more in depth covered by latrine slab with or without superstructure percolation of liquids into soil partial anaerobic decomposition of solids +cheap, easily understood -unstable soils (→ lining) -not good with high water table - hazardous and difficult emptying (depth > 2 m) - odor problems, fly breathing On-site dry systems

14 15 On-site dry systems

15 16 VIP latrine (ventilated improved pit latrine) Naturally induced ventilation with screened ventilation pipe removes odor prevents escape of flies +bad smell and flies reduced -difficult to construct properly - more expensive than simple pit latrine On-site dry systems

16 17 Groundwater contamination If contamination potential is high - -> raised pits or vaults completely over ground > 2m above highest groundwater level less --> at least 20 m to next well. But: main risk of contamination is via dug well On-site dry systems

17 18 Double pit systems and raised pit (vault) systems Permanent pits Filling - consolidation - emptying dehydration and hygienisation --> reuse can be an option with urine separation + “treatment” included +more hygienic emptying -O&M more complicated -/+ costs On-site dry systems

18 19 Pour flush pits Flushing of excreta with 2-3 liters Permanent pits or vaults Can be combined with double vaults + reduced smell problem with water seal - water must be available On-site systems

19 20 Site Distance and position relative to housing: depending on cultural habits at least 20 m from surface water sources easily accessible for all users (children, women, old people, disabled) Construction materials local availability stable and durable esthetic considerations Superstructure design depending on cultural habits (open or closed) protect from rain, stormwater runoff,... superstructure = important factor influencing the use (essential that users are involved in design) Designing latrines

20 21 Designing latrines

21 22 Slabs concrete, wood, fero-cement or plastic (local manufacturers?) keyhole shape most suitable squat hole covers (not for VIP) Ventilation pipes cm diameter length of VIP pipe = 0.5m higher than superstructure orientation Pit excavation and lining top 0.5 m usually lined (pre-cast concrete, bricks, cement blocks, etc.) No movable parts! Designing latrines (cont.)

22 23 Designing latrines (cont.) Round pits are more suitable to distribute evenly earth pressure (natural arching effect) Hand-washing facilities must be provided!

23 24 Pit sizing V: pit Volume (m3) N: no. of users S: sludge accumulation rate (litres/cap year) D: design life (years) 2-3 years for single pits (where emptying required) 1-2 years for double pits year for double pits with urine separation F: Infiltration area (m2); (water depth = F / pit circumference) W: Amount of water used for flushing (liters/cap day) I:Infiltration rates (liters/m2 day) Sand 40 Sandy loam25 Silt loam20 Clay loam8 Clayunsuitable Designing latrines (cont.) V = N x S x D / 1000and F = N x W / I

24 25 Sludge accumulation rates Designing latrines (cont.) In emergency situations (rapid accumulation) these rates have to be multiplied by %

25 26

26 27 Faeces and urine are separated before they come into contact Urine is collected in tanks and is reused as liquid fertilizer Faeces are dehydrated in the chambers and used as soil conditioner + reduced stench problems + easier handling of dried material + reduced chamber volume + no waste, but fertilizer - special squatting pan - 2 separate fractions Urine diversion latrines

27 28 2 chambers, m 3 each 2 doors, access normally from outside 1 urine pipe with jerry can, normally outside Squatting pan with cover Urine diversion latrines

28 29 Urine diversion latrines Operation: Addition of ash: to increase pH and to reduce moisture In addition: lime, sawdust, dry soil,... Toilet paper separation: Toilet paper will not decompose in the chamber (only dehydration process) → separate collection in a bucket. If the toilets are well operated and maintained, no smell problems will occur. Vent pipe and window ensure a sufficient aeration

29 30 Urine diversion latrines Always 2 chambers Above ground level, sealed Access to the chambers should be possible from outside the house Volume according to accumulation rate and number of users; → guide value: l/year/user and chamber Processing chambers:

30 31 Emptying urine divertion toilet

31 32 most frequent on-site treatment unit worldwide sedimentation tank settled sludge partially stabilised by anaerobic digestion 1-3 compartments Almost no removal of dissolved and suspended matter Septic tank Household / neighbourhood treatment systems + simple, little space required (underground) + high institutional acceptance - low treatment efficiency (COD removal approx. 50%) - O&M often neglected (desludging) or unkown!! → look for national design standards!

32 33 V=V 1 + V 2 + V 3 V 3 : scum layer F: surface of the tank h: height of the scum layer V 3 =F*h h=20-30cm V 1 and V 3 can also be estimated based on existing figures: Septic tank design

33 34 Improved septic tank 2 to 3 chambers in series (up to 5) Intensive contact between resident sludge and fresh influent Treatment efficiency: 65 to 90% COD removal HRT = 2-3 days +simple, high treatment efficiency, hardly any blockages +high removal efficiencies, also for suspended and dissolved solids -construction and maintenance more complicated than conventional septic tank Anaerobic baffled reactor (baffled septic tank) Household / neighbourhood treatment systems

34 35 Septic systems

35 36 Anaerobic filter Used for pre-settled domestic wastewater with low SS concentrations (e.g. greywater) Principle: close contact of wastewater with active bacterial mass on filter media filter material surface: 90 to 300m2 per m3 Treatment efficiency: 70 to 90% COD removal Volume: m3/cap for domestic wastewater + simple and durable if well constructed and wastewater properly pre-treated; high treatment efficiency; little space requirements - high construction costs (filter media); blockage of filter possible - maintenance costly and difficult Household / neighbourhood treatment systems

36 billion urban dwellers on on-site sanitation ! Number and share growing ! Faecal sludge – underestimated problem

37 38 Thick and yellow Sludges from unsewered public or family toilets emptied at weeks’ intervals  “unstable” Thin and black Sludges from septic tanks emptied at years’ intervals  partially “stable” Types of faecal sludge


Download ppt "2 Household and neibourghood Sanitation Infrastructures: Excreta, wastewater disposal in developing countries Doulaye Koné – Eawag/Sandec."

Similar presentations


Ads by Google