Household and neibourghood Sanitation Infrastructures Excreta wastewater disposal

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

Structure of the presentation 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 3

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

What are we talking about? Blackwater toilet wastewater (faeces and urine with or without flushing water) 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

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

Characteristics of the different wastewater sources Total Greywater Urine Faeces 25’ 000 -100’ 000 25’ 000100’ 000 50 2 -4 kg/cap*a 5% 85% 10% Phosphorous 0. 3 -0. 8 kg/cap*a 10%** 60% 30% Potassium 1 -4 -2. 0 kg/cap*a 34% 54% 12% 30 kg/cap*a 41% 12% 47% - 104 -106 /100 ml 0* 107 -109 /100 ml Volume [l/cap*a] Nutrients Nitrogen COD Faecal coliforms * healthy people ** can be as high as 50%, depending on washing and dish-washing powder used 7

Criteria influencing the selection of sanitation systems Economic, institutional and other aspects • • • 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! 8

Classification of Excreta and wastewater management technologies - Cesspit trucks 9

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

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

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 12 service area.

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

On-site dry systems 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 14

On-site dry systems 15

On-site dry systems 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 16

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

On-site dry systems 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 18

On-site systems 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 19

Designing latrines 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) 20

Designing latrines 21

Designing latrines (cont. ) Slabs • concrete, wood, fero-cement or plastic (local manufacturers? ) • keyhole shape most suitable • squat hole covers (not for VIP) Ventilation pipes • 15 -20 cm diameter • length of VIP pipe = 0. 5 m higher than superstructure • orientation Pit excavation and lining • top 0. 5 m usually lined (pre-cast concrete, bricks, cement blocks, etc. ) No movable parts! 22

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

Designing latrines (cont. ) Pit sizing V = N x S x D / 1000 and F=Nx. W/I V: pit Volume (m 3) 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 0. 5 -1 year for double pits with urine separation F: Infiltration area (m 2); (water depth = F / pit circumference) W: Amount of water used for flushing (liters/cap day) I: Infiltration rates (liters/m 2 day) • • • Sandy loam Silt loam Clay 40 25 20 8 unsuitable 24

Designing latrines (cont. ) Sludge accumulation rates In emergency situations (rapid accumulation) these rates have to be multiplied by 150 -200% 25

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Urine diversion latrines • 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 27

Urine diversion latrines • • 2 chambers, 0. 5 -1 m 3 each 2 doors, access normally from outside 1 urine pipe with jerry can, normally outside Squatting pan with cover 28

Urine diversion latrines Operation: • • Addition of ash: to increase p. H 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

Urine diversion latrines Processing chambers: • 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: 100 -150 l/year/user and chamber 30

Emptying urine divertion toilet 31

Household / neighbourhood treatment systems Septic tank 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 + 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

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

Household / neighbourhood treatment systems Anaerobic baffled reactor (baffled septic tank) • • • 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 34 - construction and maintenance more complicated than conventional septic tank

Septic systems 35

Household / neighbourhood treatment systems 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 300 m 2 per m 3 Treatment efficiency: 70 to 90% COD removal Volume: 0. 5 -1. 0 m 3/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 36 - maintenance costly and difficult

Faecal sludge – underestimated problem • • 2 -2. 5 billion urban dwellers on on-site sanitation ! Number and share growing ! 37

Types of faecal sludge 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” 38