Presentation on theme: "Household and neibourghood Sanitation Infrastructures: Excreta, wastewater disposal in developing countries Doulaye Koné – Eawag/Sandec."— Presentation transcript:
2 Household and neibourghood Sanitation Infrastructures: Excreta, wastewater disposal in developing countriesDoulaye Koné – Eawag/Sandec
3 Objectives of a sanitation systems Structure of the presentationObjectives of a sanitation systemsWhat are we talking about?Wastewater sources and their characteristicsPathways of domestic wastewaterHousehold sanitation management infrastructuresRealistic holistic sanitation systems
4 Tasks of sanitation systems Prevent disease – guarantee effective barriers against sanitation related diseasesProtect 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.The first question of course is:Why do we need any sanitation facility, be it a latrine, a flush toilet, a septic tank or whatever?What conditions must be fulfilled by any sanitation system?Sanitation system must...
5 What are we talking about? Blackwatertoilet wastewater(faeces and urine with or without flushing water)Greywaterdomestic wastewater form kitchen, bath, shower (excluding faeces and urine)Brownwater Blackwater without urineYellowwater UrineDomestic wastewater consists of different fractions, with very specific characteristicsFaecal sludgeSludge accumulating in "on-site sanitation systems" (Latrines, Septic tanks, etc.)
6 The Path of Excreta and Greywater in Urban Areas The human waste systemThe Path of Excreta and Greywater in Urban Areas~ 2 billion (2004)~ 3 billion (2025)sewered sanitation(black and greywater)“on-site” sanitation(excreta, black and greywater)Latrines(trad., VIP, PF, double-pit, no-mix, ...)GreywaterSeptic tanksWastewater treatment plant (WWTP)Small-bore sewerage for effluent of interceptor or septic tanksEffluent to soakageor drainsSeptageFS treatmentPlant (FSTP)Liquid to dischargeinto receiving waters or to co-treatment in WWTP“Faecal sludge-FS”Products from double-pit and no-mix latrines might be used on-siteEffluent to agricultural use or discharged into receiving watersBiosolids to agriculture for soil conditioning and fertilizationEawag / Sandec 2004
7 Characteristics of the different wastewater sources TotalGreywaterUrineFaecesVolume [l/cap*a]25’ ’00025’ ’00050050NutrientsNitrogen2-4 kg/cap*a5%85%10%Phosphorouskg/cap*a10%**60%30%Potassiumkg/cap*a34%54%12%COD30kg/cap*a41%47%Faecal coliforms-/100ml0*/100mlMain differences are in terms of quantities, nutrient content, and level of pathogenic contamination:Urine:Contains almost all the nitrogen and large parts of the potassium and phosphorous excreted by humans.N:P:K = 10:1:2Urine is usually sterile (exceptions known by urinary tract infections). Contamination with pathogens occurs only if urine is exposed to faeces.Easily applicable, diluted or not, depending on the crop and crop stage.Faeces:Mainly undigested organic matter made up of carbon.Faeces contain almost all pathogens:bacteria (e.g. faecal coliforms, vibro cholerae)viruses (e.g. rota virus)protozoa (e.g. amoeba hystolitica)helminths (e.g. Ascaris eggs)Low nutrient content, but good characteristics as soil conditioner:increase the organic matter content,improve the water holding capacity.Greywater:Greywater is defined as household wastewater without input of human excretaIt includes used water from baths, showers, hand basins, washing machines, dishwashers, laundries and kitchen sinksBig quantities with relatively low nutrient contents.Big reuse potential:Irrigation: Agriculture, landscape, aquacultureMunicipal uses: Fire protection, street cleaning, car washing, cooling, road construction operation, ...Non-potable domestic uses: Toilet flushing, laundry, floor cleaningMain issue: Toxic substances (organic compounds, metals, chlorine etc.), fats from kitchen, can affect natural treatment and disposal systems→ source control very important component of greywater management system* healthy people** can be as high as 50%, depending on washing and dish-washing powder used
8 Of course there are many more aspects! Criteria influencing the selection of sanitation systemsEconomic, institutional and other aspectsregulations and standards (including enforcement)costs for construction, O&Mwillingness to pay (initial and monthly payments)self-help potential and initiative of local people and organizationslocal entrepreneurs, consultants, construction companies, ...Existing system!....Of course there are many more aspects!comprehensive list doesn‘t existstrongly depends on local settingslist of criteria has to be developed on-spot, in close collaboration with local people,organisations and institutions
9 Classification of Excreta and wastewater management technologies - Cesspit trucksThat means that we have a whole series of sanitation concepts (all with certain strengths and limitations) which require a whole series of technological modules.Decentralised and centralised optionsIn DC, also in urban areas, most common systems are decentralised systems. Of course historically grown, but as explained by Roland yesterday, decentralised sanitation not only because centralised systems not affordable, has its advantages:
10 Partially sewered cities Business centre of large cities with high water consumption rateLack of treatment sites and wastewater treatment plantsDischarge of wastewater into natural water bodies and open canals
11 Cities without sewersRepresent more than 90% of cities in developing countriesAre very heterogeneous in urban infrastructureOften lack financial and human resources for sanitation development and upgrading
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” approachDifferent strategies can be employed in various parts of the service area.
13 The Path of Excreta and Greywater in Urban Areas The human waste systemThe Path of Excreta and Greywater in Urban Areas~ 2 billion (2004)~ 3 billion (2025)sewered sanitation(black and greywater)“on-site” sanitation(excreta, black and greywater)Latrines(trad., VIP, PF, double-pit, no-mix, ...)GreywaterSeptic tanksWastewater treatment plant (WWTP)Small-bore sewerage for effluent of interceptor or septic tanksEffluent to soakageor drainsSeptageFS treatmentPlant (FSTP)Liquid to dischargeinto receiving waters or to co-treatment in WWTP“Faecal sludge-FS”Products from double-pit and no-mix latrines might be used on-siteEffluent to agricultural use or discharged into receiving watersBiosolids to agriculture for soil conditioning and fertilizationEawag / Sandec 2004
14 On-site dry systems Simple pit latrine 2 m or more in depth covered by latrine slabwith or without superstructurepercolation of liquids into soilpartial 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 breathingLet’s come back to normal situations in urban and peri-urban areas.Quite theoretical material, cannot go too much into detail, many source books.Interesting would be to hear from you: expertise, experiences etc.
16 On-site dry systems VIP latrine (ventilated improved pit latrine) Naturally induced ventilation with screened ventilation piperemoves odorprevents escape of flies+ bad smell and flies reduced- difficult to construct properly- more expensive than simple pit latrine
17 On-site dry systems Groundwater contamination If contamination potential is high --> raised pits or vaults completely over ground> 2m above highest groundwater levelless --> at least 20 m to next well.But: main risk of contamination is via dug well
18 On-site dry systems Double pit systems and raised pit (vault) systems Permanent pitsFilling - consolidation -emptyingdehydration and hygienisation --> reusecan be an option with urine separation+ “treatment” included+ more hygienic emptying- O&M more complicated-/+ costsAlternative to single pit: double pit
19 On-site systems Pour flush pits Flushing of excreta with 2-3 liters Permanent pits or vaultsCan be combined with double vaults+ reduced smell problem with water seal- water must be available
20 Designing latrines Site Construction materials Superstructure design Distance and position relative to housing: depending on cultural habitsat least 20 m from surface water sourceseasily accessible for all users (children, women, old people, disabled)Construction materialslocal availabilitystable and durableesthetic considerationsSuperstructure designdepending on cultural habits (open or closed)protect from rain, stormwater runoff, ...superstructure = important factor influencing the use (essential that users are involved in design)Now look closer to design of latrines, if interesting for you.
22 Designing latrines (cont.) Slabsconcrete, wood, fero-cement or plastic (local manufacturers?)keyhole shape most suitablesquat hole covers (not for VIP)Ventilation pipes15-20 cm diameterlength of VIP pipe = 0.5m higher than superstructureorientationPit excavation and liningtop 0.5 m usually lined (pre-cast concrete, bricks, cement blocks, etc.)No movable parts!
23 Designing latrines (cont.) Round pits are more suitable to distribute evenly earth pressure (natural arching effect)Hand-washing facilities must be provided!
24 Designing latrines (cont.) Pit sizingV: pit Volume (m3)N: no. of usersS: sludge accumulation rate (litres/cap year)D: design life (years) 2-3 years for single pits (where emptying required)1-2 years for double pitsyear for double pits with urine separationF: 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 40Sandy loam 25Silt loam 20Clay loam 8Clay unsuitableV = N x S x D / 1000 and F = N x W / IVolume depends onnumber of usersdesign life/emptying frequencysludge accumulationrole of pit as infiltration pit (e.g. greywater disposal)If infiltration required: provide infiltration area at the top, in order to guarantee that when full still infiltration possible
25 Sludge accumulation rates Designing latrines (cont.)Sludge accumulation ratesS depends on biodegradability of anal cleaning material (paper, stones, leaves, corncob, water)environment in which material is stored (moisture content)In emergency situations (rapid accumulation) these rates have to be multiplied by %
27 Urine diversion latrines Faeces and urine are separated before they come into contactUrine is collected in tanks and is reused as liquid fertilizerFaeces 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 fractionsNow to a very specific case of dry sanitation: UDVery „in“ at the momentMany projects in China, Africa (South Africa, Uganda, Kenia, ...), Latin America (Mexico, Guatemala)Mainly in peri-urban areas, where urban agriculture still dominant role
28 Urine diversion latrines 2 chambers, m3 each2 doors, access normally from outside1 urine pipe with jerry can, normally outsideSquatting pan with cover
29 Urine diversion latrines Operation:Addition of ash: to increase pH and to reduce moistureIn 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
30 Urine diversion latrines Processing chambers:Always 2 chambersAbove ground level, sealedAccess to the chambers should be possible from outside the houseVolume according to accumulation rate and number of users;→ guide value:l/year/user and chamber
32 Household / neighbourhood treatment systems Septic tankmost frequent on-site treatment unit worldwidesedimentation tanksettled sludge partially stabilised by anaerobic digestion1-3 compartmentsAlmost no removal of dissolved and suspended matter+ 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!
33 Septic tank design V=V1 + V2 + V3 V3=F*h V3: scum layerF: surface of the tankh: height of the scum layerh=20-30cmV1 and V3 can also be estimatedbased on existing figures:
34 Household / neighbourhood treatment systems Anaerobic baffled reactor (baffled septic tank)Improved septic tank2 to 3 chambers in series (up to 5)Intensive contact between resident sludge and fresh influentTreatment efficiency: 65 to 90% COD removalHRT = 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
36 Household / neighbourhood treatment systems Anaerobic filterUsed for pre-settled domestic wastewater with low SS concentrations (e.g. greywater)Principle: close contact of wastewater with active bacterial mass on filter mediafilter material surface: 90 to 300m2 per m3Treatment efficiency: 70 to 90% COD removalVolume: 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
37 Faecal sludge – underestimated problem 2-2.5 billion urban dwellers on on-site sanitation !Number and share growing !
38 Thick and yellow ....... Thin and black ....... Types of faecal sludge Sludges from unsewered public or family toilets emptied at weeks’ intervals “unstable”Thin and blackSludges from septic tanks emptied at years’ intervals partially “stable”
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