Newspaper reports the past few weeks have questioned the quality of water at Durban’s beaches.
Neil Macleod, head of water and sanitation at the eThekwini municipality says a map is produced every month of water compliance based on the requirements of the South African Water Quality Guidelines for Coastal Marine Waters: Guidelines for Recreational Use (March 2012). The guidelines are based on the World Health Organisation values, he says. Macleod says the guidelines use results over the previous 12 months to determine compliance. “We sample beach water according to a schedule if at all possible, rain or shine. Between November 2011 and June 2012, samples were taken twice a week and thereafter twice a month in accordance with the requirements of the guidelines. About 70 samples were therefore taken during this period. Only three samples needed to be above the prescribed limit for the beach not to obtain 95 percentile compliance. This is usually as a result of rainfall immediately before the sampling event.
“Failure is therefore often as a result of a few poor results in the midst of excellent ones. When the median, or most likely values of E. coli and Enterococcus are used, a very different picture emerges. Eighty-six percent of beaches show excellent water quality based on E. coli levels and 95% when based on Enterococcus values.
“According to prevalent practice, we would be within our rights to exclude poor results that are obviously caused by an event such as rain, but we chose not to do so as we gain valuable information from such outliers.” Macleod says when the beach results over the past five years were analysed, statistically, there was no significant difference – if there were no outbreaks then, it was highly unlikely there would be now. Obviously, sensible precautions such as not swimming for 24 hours after a heavy rainfall event or when the water is markedly muddy should be observed here as they would anywhere in the world.” http://www.thenewage.co.za/71805-1010-53-Beaches_follow_WHO_guides
