Greywater Management in Low and Middle-Income Countries - SSWM

coliforms to minimise the food crop contamination risk (see Table 4-9), while the
The surface water pollution problem caused by untreated wastewater discharge
has been globally recognised and prioritised, leading to the establishment of
quality standards for wastewater discharge into surface waters. The most widely
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by most other countries in the world, often ignoring the reason behind it (Mara,
2003). Whether these standards are meaningful or not may, however, be seriously
questioned. Most national discharge standards set maximum concentrations rather
than pollution loads. In regions where little water is used given constant water scarcity
(notably Middle East and Sub-Saharan Africa), contaminant concentrations may be
high and discharge standards will hardly be met. The interested reader is invited to
standards, especially in low and middle-income countries.
WHO’s wastewater reuse guidelines (Mara and Cairncross, 1989) set stringent
water quality standards for irrigation. However, many developing countries cannot
currently developed by WHO (WHO, 2005) are based on the Stockholm Framework
and suggest that countries should adapt guidelines to their own social, technical,
The framework involves the assessment of health risks (using the Quantitative
Microbial Risk Assessment Methodology, QMRA) prior to setting health-based
targets and developing guideline values. The basic approach of the guidelines is to
and health-based targets, such as excreta and greywater treatment performance,
as well as other technical, practical and behavioural measures. Non-technical risk
management options could include e.g. hygiene education, handling methods,
control of human exposure, crop restrictions, mosquito breeding control measures,
irrigation methods etc.
The new WHO guidelines for greywater reuse are described in
Table 4-8 (WHO, 2005). According to WHO (2005), compliance with these
standards is feasible in large treatment systems. In small-scale systems,
where frequent microbiological analyses are not possible, linking treatment
scale systems, WHO suggests
more general performance
criteria for treatment and
Helminth eggs
E. coli
handling of excreta and greywater.
Primary treatment is
No./l
cfu/100 ml
recommended in all cases to
10
(extended to 10 6 when
1
exposure is limited or
prevent clogging of subsequent
regrowth is likely)
are discharged into lakes or
eaten raw
1 10 3
rivers, secondary treatment
Greywater Management in Low and Middle-Income Countries
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