excreta and household wastewaters introduction n.
Skip this Video
Loading SlideShow in 5 Seconds..
Excreta and Household Wastewaters - Introduction PowerPoint Presentation
Download Presentation
Excreta and Household Wastewaters - Introduction

Excreta and Household Wastewaters - Introduction

232 Vues Download Presentation
Télécharger la présentation

Excreta and Household Wastewaters - Introduction

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Excreta and Household Wastewaters - Introduction Global Water, Sanitation and Hygiene ENVR 890-2 Mark D. Sobsey February, 2009

  2. Household Human Wastes and Wastewaters

  3. Feces - Composition Note: This number may be too low; live bacteria are shed in large quantity

  4. Feces, Microbes and Microbial Pathogens • Besides nutrients and organic matter, human and animal fecal wastes contain large numbers of microbes (>100 billion/gram). • Constitute ~1/3rd the mass of human fecal matter • Most are beneficial or essential in the gut; they are NOT pathogens • Some gut microbes ARE human pathogens; can cause disease • Humans and animals harbor pathogens some of the time • Pathogen colonization and infection is common • In some food animals (poultry, beef and swine) • In people with poor sanitation and hygiene • Esp. in developing world; carriage rates are high • Human pathogens are typically shed in human and animal feces • Enteric pathogens can be transmitted by the fecal-oral route; often 106-109 pathogens/gram of feces of an infected person • Ingested with fecally contaminated water, food, objects, • or by direct and indirect personal contact

  5. Excreta and Graywater– Definitions and Properties Excreta: Human feces and urine Managed in different ways: Direct disposal on land or in water Direct use as fertilizer, soil conditioner and for aquaculture Pre-treatment prior to use Dilution with water to convey (sewage) for disposal or use Direct use of untreated (raw) sewage Treatment and discharge to land or water Treatment and reuse (agriculture, aquaculture, horticulture, industrial and civil use Graywater: Other wastewater from human activity Not directly from human fecs and urine Wastewater from washing, bathing, etc Contains human wastes and exudates

  6. Managing Human Excreta - Options • “Dry” Collection: • Open defecation • Collect in a container • e.g., chamber pot • Discharge to the environment w/ or w/o Rx • Latrines – several kinds • Treat or dispose of or both • Separate feces and urine; • Then, treat/store, use, dispose to the environment

  7. Managing Human Excreta - Options • Semi-wet (or semi-dry) • Use some water • Pour-flush toilets and other low water use systems NO! Hanging Toilet/Latrine

  8. Managing Human Excreta - Options Septic tank - soil absorption system • Wet Systems • On-site Septic Systems • Other On-site systems • Soak pits • Sewerage • Sewage treatment systems

  9. Human Excreta – Resource or Risk? • Human excreta as a potential resource • Contains nutrients (N, P, K, and organic matter) • Nutrients and organic matter are: • Detrimental in water, esp. surface water • Eutrophication, anoxia, fish kills • Beneficial on land • Fertilizer, soil conditioner, land stabilizer • Widely used as a fertilizer and soil amendment in both developed and developing countries • Potential for excreta misuse and environmental pollution is great without proper attention to management plans and human behavior considerations Annual Amounts/Person, Kg

  10. Nutrient Content of Human Excreta • Rich source of inorganic plant nutrients: N, P K and organic matter • Daily human excretion: ~30 g of C (90 g of organic matter), ~ 10-12 g N, ~ 2 g of P and 3 g of K. • Most organic matter in feces most N and P (70-80 %) in urine. K equally distributed between urine and feces.

  11. 14.1 12.3 5.3 3.6 K Organics kg COD/ (Person·year) P N 1.0 0.8 Nutrient content kg N,P,K / (Person·year) Composition of Household Waste and Wastewater 10.000 – 200.000 l 50 l 500 l source: Otterpohl Volume Liter / (Person·year) greywater urine faeces

  12. Characteristics of Human Wastes fraction characteristic 1. feces • hygienically critical (high risk) • consists of organics, nutrients and trace elements • improves soil quality and increase its water retention capacity 2. urine • less hygienically critical (less risk) • contains the largest proportion of nutrients available to plants • may contain hormones or medical residues 3. greywater • of no major (or less) hygienic concern/risk • volumetrically the largest portion of wastewater • contains almost no (or less) nutrients (simpler treatment) • may contain spent washing powders etc.

  13. Fertilizer Potential of Human Excreta source: Drangert, 1998

  14. urine (yellowwater) greywater (shower, washing, etc.) faeces (brownwater) hygienisation by storage or drying constructedwetlands, gardening, wastewater ponds, biol.treatment, membrane-technology anaerobic digestion, drying, composting liquid or dry fertiliser biogas, soil improvement irrigation, groundwater- recharge or direct reuse Options for Excreta and Greywater Utilization substances treatment utilisation

  15. Primary Treatment or Primary Sedimentation Settle solids for 2‑3 hours in a static, unmixed tank or basin. • ~75-90% of particles and 50-75% of organics settle out as “primary sludge” • enteric microbe levels in 1o sludge are sometimes ~10X higher than in raw sewage • enriched by solids accumulation • Overall, little removal of many enteric microbes: • typically ~50% for viruses and bacteria • >50% for parasites, depending on their size

  16. Enteric Microbe/Pathogen Reductions in Secondary or Biological Treatment • Aerobic biological treatment: typically, activated sludge (AS) or trickling filtration (TF) • Then, settle out the biological solids produced (2o sludge) • ~90-99% enteric microbe/pathogen reductions from the liquid phase • Enteric microbe retention by the biologically active solids: accumulation in AS flocs or TF biofilms • Biodegradation of enteric microbes by proteolytic enzymes and other degradative enzymes/chemicals • Predation by treatment microbes/plankton (amoeba, ciliates, rotifers, etc. • Aerobic microbes utililize carbon and other nutrients to form a healthy activated sludge AS biomass (floc) • The biomass floc is allowed to settle out in the next reactor; some AS is recycled

  17. Waste Solids (Sludge) Treatment • Treatment of settled solids from 1o and 2o sewage treatment • Biological “digestion” to biologically stabilize the sludge solids • Anaerobic digestion (anaerobic biodegradation) • Aerobic digestion (aerobic biodegradation) • Mesophilic digestion: ambient temp. to ~40oC; 3-6 weeks • Thermophilic digestion: 40-60oC; 2-3 weeks • Produce digested (biologically stabilized) sludge solids for further treatment and/or disposal (often by land application) • “Thickening” or “dewatering” • drying or “curing” • Waste liquids from sludge treatment are recycled through the sewage treatment plant • Waste gases from sludge treatment are released (or burned if from anaerobic digestion: methane, hydrogen, etc.)

  18. Enteric Microbe/Pathogen Reductions by Sludge Treatment Processes • Anaerobic and aerobic digestion processes • Moderate reductions (90-99%) by mesophilic processes • High reductions (>99%) by thermophilic processes • Thermal processes • Reductions depend on temperature • Greater reductions at higher temperatures • Temperatures >55oC usually produce appreciable pathogen reductions. • Alkaline processes: lime or other alkaline material • Reductions depend on pH; greater reductions at higher pHs • pH >11 produces extensive pathogen reductions • Composting: high temperature, aerobic biological process • Reductions extensive (>99.99%) when temperatures high and waste uniformly exposed to high temperature • Drying and curing • Variable and often only moderate pathogen reductions

  19. “Processes to Further Reduce Pathogens” “PFRP”: Class A Sludge Class A sludge: • <1 virus per 4 grams dried sludge solids • <1 viable helminth ovum per 4 grams dried sludge solids • <3 Salmonella per 4 grams of dried sludge solids • <1,000 fecal coliforms per gram dry sludge solids PFRPs: • Thermal (high temperature) processes (incl. thermophilic digestion); hold sludge at 50oC or more for specified times • lime (alkaline) stabilization; raise pH 12for 2 or more hours • composting: additional aerobic treatment at elevated temperature • Class A sludge or “biosolids” disposal by a variety of options or used as a soil conditioner • Class A biosolids can be marketed/distributed as soil conditioner for use on non-edible plants

  20. Alternative Biological Treatment of Wastewater:Alternatives for Small and Rural Communities • Lagoons, Ponds and Ditches • aerobic, anaerobic and facultative • for smaller communities and farms • enteric microbes are reduced by ~90-99% per pond • multiple ponds in series increases overall microbe reductions • Constructed Wetlands • aerobic systems containing biologically active, oxidizing microbes and emergent aquatic plants • Microbial reductions comparable to or greater than ponds or lagoons. • Lagoons and constructed wetlands are practical and economical sewage treatment alternatives when land is available at reasonable cost

  21. Facultative Oxidation (Waste Stabilization) Pond Pathogen reductions of 90-99%, depending on design, operation and conditions Two or more ponds in series achieve 90-99% reduction per pond, giving 99-99.99% reduction in 2 ponds and 99.9-99.9999% reduction in 3 ponds in series, etc,

  22. Stabilization Ponds or Lagoons • Aerobic and Facultative Ponds: • Biologically Rx by complementary activity of algae and bacteria. • Used for raw sewage as well as primary‑ or secondary‑Rx’d. effluent. • Bacteria and other heterotrophs convert organic matter to carbon dioxide, inorganic nutrients, water and microbial biomass. • Algae use CO2 and inorganic nutrients, primarily N and P, in photosynthesis to produce oxygen and algal biomass. • Many different pond designs have been used to treat sewage: • facultative ponds: upper, aerobic zone and a lower anaerobic zone. • Aerobic heterotrophics and algae proliferate in the upper zone. • Biomass from upper zone settles into the anaerobic, bottom zone. • Bottom solids digested by anaerobic bacteria.

  23. Enteric Microbe/Pathogen Reductions in Stabilization Ponds • BOD (a measure of biodegradable organic matter) and enteric microbe/pathogen reductions of 90%, esp. in warm, sunny climates • Even greater enteric microbe/pathogen reductions by using two or more ponds in series • Better BOD and enteric microbe/pathogen reductions if detention (residence) times are sufficiently long (several weeks to months) • Enteric microbes reduced by 90-99% in single ponds and by multiples of 90-99% for ponds in series. • Microbe removal often quite variable, depending upon pond design, operating conditions and climate. • Reduction efficiency lower in colder weather and with shorter retention times

  24. Constructed Wetlands and Enteric Microbe Reductions • Surface flow (SF) wetlands reduce enteric microbes by ~90% • Subsurface flow (SSF) wetlands reduce enteric microbes by ~99% • Greater reduction in SSF may be due to greater biological activity in wetland bed media (porous gravel) and longer retention times • Multiple wetlands in series incrementally increase microbial reductions, with 90-99% reduction per wetland cell.

  25. Septic Tank-Soil Absorption Systems for On-Site Sewage Rx • Used where no sewers or community sewage treatment facilities: ex.: rural homes • Septic tank: solids settle and are digested • Septic tank effluent (STE) is similar to primary sewage effluent • Distribute STE to soil via a sub-surface, porous pipe in a trench • Absorption System: Distribution lines and drainfield • Septic tank effluent flows through perforated pipes 2-3 feet below the land surface in a trenches filled with gravel, preferably in the unsaturated (vadose) zone. • Effluent discharges from perforated pipes into trench gravel and then into unsaturated soil, where it is biologically treated aerobically. • Enteric microbes are removed and retained by the soil and biodegraded along with STE organic matter; extensive enteric microbe reductions are possible • But, viruses and other pathogens can migrate through the soil and reach ground water if the soil is too porous (sand) and the water table is high

  26. Ecological Sanitation (Eco-San): Circular Flow/Recycling of Nutrients and Other Materials Basis and Approach: Considers urine, feces and water as resources in an ecological loop. Seeks to protect public health, prevent pollution and return nutrients and humus to the soil. Nutrient recycling to ensure food security. Separate urine and feces at source; Do not mixed with water. - avoid contaminating large volumes of water with pathogens. - separation make it easier to recover and recycle nutrients After dilution and/or processing, separated urine can be applied to the soil as a hygienic fertilizer. Feces can be safely composted to allow incorporation of its organic matter into food production.

  27. Ecological Sanitation - EcoSan Advantages and options: • Affordable, flexible sanitation options for all • Wide range of toilet designs • Different ways to collect/treat urine/feces. • Low- and high-technology solutions for rural and urban settings. • Allows for central and/or decentralized management • Dry and/or waterborne systems

  28. Log10 Reduction of Pathogens by Wastewater Rx Processes

  29. Log10 Reduction of Pathogens by Wastewater Rx Processes

  30. REMOVAL OF ENTERIC BACTERIA BY SEWAGE TREATMENT PROCESSES ORGANISM PROCESS % REMOVAL Fecal indicators Primary sed. 0‑60% E. coli Primary sed. 32 and 50% Fecal indicators Trickling filt. 20‑80% Fecal indicators Activated sludge 40‑95% Fecal indicators Stab. ponds, 1 mo. >99.9999% @ high temp. Salmonellae Primary sed. 79%, 6‑7 hrs. Salmonellae " 73%, 6‑7 hrs. Salmenellae Trickling filt. 92% Salmonellae Activated sludge ca. 99%

  31. Entamoeba histolytica Reduction by Sewage Treatment ORGANISM PROCESS % REMOVAL E. histolytica Primary Sed. 50% E. histolytica Primary Sed., 2 hr. 64% E. histolytica Primary sed., 1 hr. 27% E. histolytica Primary sed. + Trickl. Filt. 25% E. histolytica " 74% E. histolytica " 91% E. histolytica Primary sed. + Act. Sludge 83% E. histolytica Oxidation ditch + Sedimentation 91% E. histolytica Stabilization ponds + sedimentation 100% E. histolytica " 100, 94, 87 E. histolytica " 100 E. histolytica Aerated lagoon (no settling) 84%

  32. Microbial Reductions by Wastewater Treatment

  33. Disinfection of Wastewater • Intended to reduce microbes in 1o or 2o treated effluent • Typically chlorination • Alternatives: UV radiation, ozone and chlorine dioxide • Good enteric bacterial reductions: typically, 99.99+% • Meet fecal coliform limits for effluent dicharge • Often 200-1,000 per 100 ml geometric mean as permitted discharge limit • Less effective for viruses and parasites: typically, 90-99% reduction • Toxicity of chlorine and its by‑products to aquatic life now limits wastewater chlorination; may have to: • Dechlorinate • Use an alternative, less toxic chemical disinfectant or • Use an alternative treatment process to reduce enteric microbes • granular medium (e.g., sand) filtration • membrane filtration

  34. When Wastewater Disinfection is Recommended or Required • Discharge to surface waters: • near drinking water supply intakes • used for primary contact recreation • used for shellfish harvesting • used for irrigation of crops and greenspace • other direct and indirect reuse and reclamation purposes • Discharge to ground waters waters: • used as a water supply source • used for irrigation of crops and greenspace • other direct and indirect reuse and reclamation purposes

  35. Wastewater Reuse • Wastewater is sometimes reused for beneficial, non-potable purposes in arid and other water-short regions. • Widespread in developing countries; • often done poorly with inadequate reduction of pathogens/toxins • Often uses advanced or additional treatment processes, sometimes referred to as “reclamation” • Biological treatment in “polishing” ponds, constructed wetlands and other “natural” systems • Physical-chemical treatment processes used for drinking water: • Coagulation-flocculation and sedimentation • Filtration: granular medium filters; membrane filters • Granular Activated Carbon adsorption • Disinfection (Details of these water treatment process to presented in lectures on water treatment)

  36. Indicator Microbe Levels in Raw and Treated Municipal Sewage: Sewage Treatment Efficacy 100000000 100000000 10000000 10000000 1000000 1000000 100000 100000 10000 10000 1000 1000 Number/100 ml 100 100 10 10 1 1 F. col. E. coli Ent. C. p. F+ phg. Raw (-------------Bacteria--------- Bact. spores Viruses) Treated (geom. mean values of 24 biweekly samples)

  37. Sewage Treatment Rx: % Reduction Total % Reduction Primary settling 50 50 2o biological treatment 99 99.5 Granular medium filtration 90 99.95 Disinfection 99 99.9995 Estimated Pathogen Reductions by Sewage Treatment Processes: An Example

  38. Effect of Sanitation on Health Fewtrell, L. and J.M. Colford, Jr. (2004) Water, Sanitation and Hygiene: Interventions and Diarrhoea. A Systematic Review and Meta-analysis. World Bank, Washington.

  39. Effect of Sanitation on Health • Only 2 of 4 available studies could be included in the meta-analysis • Not possible to extract data from Kumar et al. (1970) or calculate CIs for Gross et al.(1989) • Children (i.e. ≤ 60 months): random effects pooled estimate = 0.678 (95% CI: 0.529 – 0.868) Fewtrell L, Kaufmann RB, Kay D, Enanoria W, Haller L, Colford JM Jr. (2005) Water, sanitation, and hygiene interventions to reduce diarrhoea in less developed countries: a systematic review and meta-analysis. Lancet Infect Dis. 2005 Jan;5(1):42-52.

  40. Effect of Sanitation on Health (Diarrhea) - Recent DataBarreto ML Et al., Effect of city-wide sanitation programme on reduction in rate of childhood diarrhoea in northeast Brazil: assessment by two cohort studies. Lancet 2007;370:1622–28 • A city-wide sanitation intervention was started in Salvador, Brazil, in 1997 to improve sewerage coverage from 26% of households to 80%. • The effect of this programme on diarrhea morbidity in children less than 3 years of age was studied • Two longitudinal studies: 1997–98 before the intervention & 2003–04 after the intervention. • Each study consisted of a cohort of children (841 in the preintervention study and 1007 in the postintervention study; age 0–36 months at baseline); followed up to 8 months. • Children were sampled from 24 sentinel areas randomly chosen to represent the range of environmental conditions in the study site. Individual or household questionnaires were initially applied by trained fieldworkers; an environmental survey was done in each area before and after the sanitation programme to assess basic neighborhood and household sanitation conditions. • Daily diarrhoea data were obtained during home visits twice/week. • The effect of the intervention was estimated by a hierarchical modelling approach fitting a sequence of multivariate regression models. • Diarrhea prevalence fell by 21% (95% CI 18–25%), from 9·2 (9·0–9·5) days per child-year before the intervention to 7·3 (7·0–7·5) days per child-year afterwards. • After adjusting for baseline sewerage coverage and potential confounding variables, the overall prevalence reduction was 22% (19–26%). • Conclusion: urban sanitation is a highly effective health measure

  41. Effect of Sanitation on Health (Diarrhea) - Recent DataGenser Et al.. (2008) Impact of a city-wide sanitation intervention in a large urban centre on social, environmental and behavioural determinants of childhood diarrhoea: analysis of two cohort studies. Int J Epidemiol. 37(4):831-40. • Poor socioeconomic status (SES) increases diarrhea risk • mostly via lack of sanitation, poor infrastructure and living conditions. • The effectiveness of a city-wide sanitation intervention on diarrhea in a large urban site in Northeast Brazil was recently demonstrated. • The intervention altered the magnitude of relative and attributable risks of diarrhea determinants and the pathways by which those factors affect diarrhea risk. • Determinants of prevalence of diarrhea were determined in two cohort studies conducted before & after the intervention; in pre-school children followed for 8 mos. • Relative, attributable and mediated risks of diarrhea determinants were estimated. • The intervention reduced diarrhea and also changed attributable and relative risks of diarrhea determinants by altering the pathways of mediation. • Before the intervention SES was a major distal diarrhea determinant (attributable risk: 24%) with 90% of risk mediated by other factors, mostly by lack of sanitation and poor infrastructure (53%). • After the intervention, only 13% of risk was attributed to SES, with only 42% mediated by other factors (18% by lack of sanitation and poor infrastructure). • The intervention reduced diarrhea risk by reducing direct exposure to unfavurable sanitation conditions. • It also altered the effect and mediation pathways of most distal diarrhea determinants, especially SES. • The importance of public sanitation measures in reducing the impact of poverty on diarrhea was corroborated.

  42. Impact of Improved Sanitation on Health • Improved sanitation reduces infectious diseases in developing world settings • Evidence from intervention studies, case-control studies and other epid. studies. • Data are limited; few studies; poor quality • Estimate of effect: in the 25-45% range for reduction of diarrheal disease in children • Similar to the magnitude of the effect of improved water quality (or quantity)

  43. Community Led Total Sanitation (CLTS) • An approach to facilitate the process of empowering local communities to stop open defecation and to build and use latrines or other effective sanitation without the support of any external hardware (construction materials) subsidy • Focuses on creating change in sanitation behavior through community participation rather than just constructing toilets. • Done through a process of social participation; behavior focus • Focuses on the whole community not individual behaviors • Emphasizing the collective benefit from stopping open defecation by encouraging a more cooperative approach • People decide together how they will create a clean and hygienic environment that benefits everyone.  • Encourages local communities to visit the dirtiest and filthiest areas in the community, appraise and analyze their practices, to shock, disgust and shame people. • The approach is provocative and entertaining, and participatory, leaving decisions and action to the community.

  44. 10 Principles of CLTS 1. Aim/Target: 100% Total Sanitation 2. Based on creating Genuine Demand but not Charity 3. Thrives through aggressive Awareness but not through Subsidies 4. Recognizes a Wide Range of Technology Options 5. Technology Choice Based on Affordability, Appropriateness and acceptability 6. Lowest Requirement: Contain or Restrict Excreta(no open defecation) 7. Communities (Villagers) Plan, Implement Monitor their own progress 8. Government to support Long Term Sustainability of initiatives 9. Facilitation is done by an indigenous organiaations – CBO or NGO - Bottom Up approach 10. Hygiene Promotion is provided for an Initial Period of about 2 years

  45. Key Steps in CLTS1ST Step: Realization of Unhygienic Sanitary Practices Through Analysis of Community Feces • Community Led Participatory Rural Appraisal (PRA) • A Walk of Shame – see actual situation on ground • Ground Mapping of Feces – where are they/whose are they! • Calculation of Feces amounts - varies • Raising Flag of Feces (Flagging) – where they are • Village Commitment - no open defecation! • Community sanitation policing

  46. Key Steps in CLTS2nd Step: Organizing and Mobilizing the Community • Have Commitment towards No Open Defecation (NOD) Followed by Hygiene Promotion • Form Village Sub-committees – for Effective Implementation and Monitoring • Use existing community groups –child club, women and local cultural groups • Monitoring/Information using an open Board • Looking at future – community vision & dream • Family Monitoring Chart • Exchange Visits • NOD Declaration - (perhaps within 3 months) • Recognize well performing communities

  47. Sanitation Policy Issues • Sanitation policy is a challenge • Sanitation lags far behind water in coverage and effective sustained use • Sanitation intervention hardware (latrines, other toilets, sewerage and sewage treatment) is usually a major infrastructure change and investment • Sanitation requires a personal and community behavior commitment to use the sanitation facilities • The drivers for behavior change in sanitation are complex and require considerable time and effort at the personal, household and community levels • Existing sanitation infrastructure is often poor and poorly maintained • Sanitation remains one of the biggest unmet global needs; new strategies and approaches needed