Greywater Management in Low and Middle-Income Countries - SSWM

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When considering irrigation with treated greywater, its microbial and biochemical properties should be evaluated and compared with reuse standards. Focus should be placed on the irrigated crop, soil properties, irrigation system used, and crop evaluate the treated greywater in terms of chemical criteria such as dissolved salts, greywater treatment systems will most probably not cause any toxic effects on the crop or pose increased health risks. Caution is recommended in households with low water consumption or with greywater potentially contaminated by pathogens. High pathogen loads may be attributed to an acute illness of one or several household members, or use of critical chemicals such as solvents and disinfectants. Use of problematic chemicals, such as solvents or disinfectants combined with low amounts of greywater generated, may lead to the accumulation of some chemicals in the soil environmental sustainability (Shafran et al., 2005). Compared with domestic wastewater, greywater will generally contain a reduced number of pathogenic viruses, bacteria, protozoa or helminth eggs. However, as indicated in Chapter 3, washing of babies and their soiled clothing and diapers may substantially raise the pathogen load in greywater. Irrespective of pathogen load or treatment system used, it should be noted that some pathogenic life forms may pass the treatment unaffected and cause a potential health risk if greywater is used for irrigation. Although treatment plant removal rates of 99% or even 99.9% may appear impressive, survival rates nevertheless amount to 1% or 0.1%. This contaminated by an acute illness of one or several household members. In low and middle-income countries, where greywater may exhibit high pathogen concentrations, survival of more than one percent is generally considered inadequate. Not only the presence of pathogens but also their survival time in the water, soil and on irrigated crops are important. Feachem et al. (1983) summarised pathogen behaviour in warm climates (20–30 °C) as shown in Table 4-12. Due to degradation processes caused by sunlight and/or desiccation, pathogen survival time on crops is much shorter than in water or soil. During primary treatment in grease and grit traps and septic tanks, helminth eggs, protozoal cysts and viruses (attached to settable solids) tend to settle and accumulate in the sludge. However, helminth eggs may survive for several months in this sludge and therefore still pose a health risk when the sludge is removed. sites for mosquitoes, important vectors of diseases such as malaria or Bancroftian may form puddles where mosquito larvae can develop in the absence of natural enemies. Even if greywater is led into open stormwater drains, mosquito problems may occur. Drains, built for occasional stormwater events are often used for sewage Low-cost Management and Treatment Options 46
Survival time, days Pathogen in fresh water and sewage in soil on crops Enteroviruses
Page 1 and 2:
Sandec: Department of Water and San
Page 3 and 4:
Foreword The issue of greywater man
Page 5 and 6: Content Glossary IV 1. Rationale fo
Page 7 and 8: FC Filtration Flotation Escherichi
Page 9 and 10: Q Flow (expressed in volume
Page 11 and 12: 1. Rationale for this Report and
Page 13 and 14: This publication is not a plea to i
Page 15 and 16: 2. Apart from toilet wastewater,
Page 17 and 18: can be minimised (see Groundwater p
Page 19 and 20: The composition of greywater mainly
Page 21 and 22: optimal range. However, Christova B
Page 23 and 24: Greywater normally contains low lev
Page 25 and 26: Surfactants are the main components
Page 27 and 28: 4. The choice of a greywater ma
Page 29 and 30: Implementation of an environmentall
Page 31 and 32: lint, skin, food particles) from en
Page 33 and 34: Grease traps must be designed to sa
Page 35 and 36: double-compartment septic tank. In
Page 37 and 38: treatment of greywater were gained
Page 39 and 40: Weaknesses Dissolved and unsettle
Page 41 and 42: Weaknesses underlying
Page 43 and 44: treatment. In case of gravel, a ro
Page 45 and 46: Tropical and subtropical climates h
Page 47 and 48: problems, also called carbon cloggi
Page 49 and 50: As explained earlier, ponds are not
Page 51 and 52: coliforms to minimise the food crop
Page 53 and 54: eused in irrigation or groundwater
Page 55: greywater improves in quality and i
Page 59 and 60: SAR The fate of surfactants in irri
Page 61 and 62: 5. This section provides an ove
Page 63 and 64: Location Greywater management syste
Page 65 and 66: 0.5 m wide and not more than 1.5 m
Page 67 and 68: Greywater garden Koulikoro with it
Page 69 and 70: Maintenance and repair of the fence
Page 71 and 72: garden tower is not available. Howe
Page 73 and 74: House 4 House 2 House 1 (with separ
Page 75 and 76: Quantity Cost/unit Total Percentage
Page 77 and 78: is planted with Phragmites karka an
Page 79 and 80: Jordan’s annual rainfall quantiti
Page 81 and 82: Two-barrel system Four-barrel syste
Page 83 and 84: Many rural communities of the West
Page 85 and 86: Costs Construction costs total USD
Page 87 and 88: Baffled septic tank Dosing chamber
Page 89 and 90: would be accepted in an urban resid
Page 91 and 92: not considered in the sanitation pl
Page 93 and 94: three septic tanks and soakage pits
Page 95 and 96: 6. Finding literature on greywater
Page 97 and 98: Most system failures are caused by
Page 99 and 100: programme. Sanitation projects look
Page 101 and 102: permisibles de contaminantes en las
Page 103 and 104: Gunther, F., 2006. The household-si
Page 105 and 106: Ottoson, J. and Stenstrom, T.A., 20
Page 107:
Eawag Überlandstrasse 133 P.O. Box
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Greywater Management in Low and Middle-Income Countries - SSWM

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