Harvested rainwater in South Africa harbors pathogens, finds new study

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Feb. 26, 2014 -- According to research from the University of Stellenbosch in South Africa, pathogens are inhabiting harvested rainwater across the region, potentially posing a public health hazard, especially for children and immunocompromised individuals. Likewise, South Africa has been financing domestic rainwater harvesting tanks in informal low-income settlements and rural areas in five of the nation's nine provinces.

Local sampling was conducted in the Kleinmond Housing Scheme, which was initiated by the South African Council for Scientific and Industrial Research and the Department of Science and Technology. The houses, designed to be sustainable, are approximately 400 square feet, with alternative technologies such as solar panels along with rainwater tanks.

The list of predatory prokaryotes the investigators found includes Legionella (found in 73% of samples), Klebsiella (47%) Pseudomonas (19%), Yersinia (28%), Shigella (27%), and others. They also found some protozoan parasites, including Giardia (25%). Many of the pathogens are normal freshwater inhabitants, but Salmonella (6%) indicates human fecal contamination, whileYersinia are markers of fecal contamination by wild and domestic animals, according to the report.

Residents, many of whom are little-educated and unemployed, typically use the rainwater for washing clothes and house-cleaning, but about one quarter of people polled in the study said they used it for drinking, as well. The finding that coliforms and Escherichia coli counts from rainwater samples -- markers of fecal contamination -- always exceeded drinking water guidelines, reinforcing the World Health Organization's opinion that rainwater must be pretreated prior to use for drinking, said principal investigator Wesaal Khan.

Rainwater harvesting is needed in South Africa's informal communities because residents often depend on communal "standpipe" systems that frequently serve more than 100 people, who may have to walk as far as a third of a mile to get water, said Khan. Approximately 23,000 rainwater tanks have been installed, two thirds of them in the Eastern Cape and one third in KwaZulu Natal. Nearly 20 percent of South Africans lack sustainable access to water.

See also: "The Rainwater Harvest Supper"

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