Abstract
Greywater is untreated household effluent from baths, showers, kitchen and hand-wash basins and laundry (i.e. all non-toilet uses). More than half of indoor household water is normally used for these purposes and can potentially be intercepted by the householder for additional beneficial uses. Greywater use is practised on an informal basis to supplement irrigation water, either in urban gardens in middle- to upper-income suburbs or in food gardens in lower-income informal, periurban and rural areas. It holds the potential to contribute significantly to food security in poor settlements by providing a source of both irrigation water and nutrients for crop plants. However, there are presently no formal guidelines for the use of greywater in South Africa. This paper presents the rationale and framework of a guidance document for the sustainable use of greywater to irrigate gardens and small-scale agriculture in South Africa, developed under the auspices of the Water Research Commission. The 3 driving principles in developing this guidance were: protection of human health; protection of plants irrigated; and protection of soil and the environment. Risk-management scenarios were developed on the basis of the extent of greywater characterisation. Water-quality constituents for inclusion were selected from among those indicated as presenting a problem in previous studies. Guidance was provided for managing greywater quality, either by mitigation of greywater quality (by practices such as irrigation method, amelioration of soil, leaching of soil and planting of tolerant plant types) or by small-scale biological treatment of greywater. Guidance was also given regarding the volumes of greywaterwhich can be applied, together with factors to adjust these volumes for site-specific conditions.Keywords: greywater, irrigation, food security, sustainable agriculture, health, soil, plant growth
Highlights
South Africa is a water-scarce country, with about 65% of the country receiving an average annual rainfall of less than 500 mm, which is normally considered to be the minimum required for rain-fed cropping (Schulze, 1997)
This paper reports on an interrelated series of investigations, conducted under the auspices of a project solicited by the Water Research Commission aimed at addressing the potential and problems of greywater use in small-scale irrigation, and reported in 2 recent WRC reports (Rodda et al, 2010a; b)
Informed members of the public who wish to plan for irrigation use of greywater on their properties or in their communities
Summary
South Africa is a water-scarce country, with about 65% of the country receiving an average annual rainfall of less than 500 mm, which is normally considered to be the minimum required for rain-fed cropping (Schulze, 1997). Innovative approaches are required to preserve both the quantity and quality of existing water supplies. Concepts such as ecological sanitation (EcoSan) have arisen to address this need. The underlying principle of EcoSan is that domestic waste should be seen as a potential resource for further use to recover water and plant nutrients that would otherwise be lost through discharge to the environment (Winblad and SimpsonHébert, 2004). Greywater is untreated household wastewater from baths, showers, kitchen and hand-wash basins, and laundry (i.e. all non-toilet uses). Using this water sustainably for irrigation in small-scale agriculture and in gardens is one possible way of alleviating water stress (Murphy, 2006). Since greywater contains some nitrogen and phosphorus (Eriksson et al, 2002; Morel and Diener, 2006), it is a potential source of nutrients for plant growth, for users who cannot
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