Cape Town - Researchers have long argued that grey water, which became popular after the slew of water restrictions introduced during previous dry winters and Day Zero periods, had the potential to contribute to food security if it was used to water domestic food gardens.
However, there was ongoing concern around its safety. Now research by the University of the Western Cape (UWC) geo-information science and earth observation professor Timothy Dube alleviates some of these concerns, after conducting a study examining the quality of grey water used in domestic food gardens, which found that grey water was safe for domestic irrigation.
“The study has shown that grey water can be used for home gardening, especially for vegetables that are not consumed raw. It was observed that the use of grey water for flushing toilets can help conserve tap water by about 30%. The use of grey water for home gardening also acts as a repellent to pests,” Dube said.
However, during the rainy season, Dube advised that the use of grey water be stopped completely, as its continuous use could affect soil quality and soil productivity.
“We propose that grey water is best used for home gardening when freshwater supplies fall short – it should be seen as a complement, rather than a wholesale alternative to freshwater,” Dube said.
Dube said the climate was changing and most areas were becoming drier and drier, with scientists repeatedly cautioning that this may result in further water shortages, thus use of grey water systems had to be prioritised and treated as a matter of urgency.
Local Greenlight Food Garden Project farmer Clifford Caesar used grey water during the Day Zero period, as almost all food gardens had to look for alternative water sources.
“I started collecting a grey water from different households, from two litre bottles to five litre bottles. What I found is that different washing powder contents in this water collected were not good for crops. We have to be very careful when using grey water, and more research should be done on the contents of grey water in certain areas, before its used in food gardens,” Caesar said.
WWF freshwater programme manager Klaudia Schachtschneider said: “As citizens, we should always be water conscious. Climate scientists have told us repeatedly that the Western Cape is likely to experience more frequent and severe droughts in the future, and so any efforts to save water is always a good idea.”