Study of sewage at sea made public soon

  • 04/04/2017

  • News 24 (South Africa)

A draft report on the state of three marine outfalls has been completed. The City of Cape Town commissioned the CSIR to study the sewage outfalls at Hout Bay, Green Point and Camps Bay last year. The CSIR has been monitoring over 80 sites in and around the outfalls, as well as collecting ocean floor sediment samples and tissue samples from bottom-dwelling animals. The extensive investigation into the marine outfalls is aimed to help the City monitor any impact from the outfalls and give up to date scientific information to the public (“Water, filth out to sea”, People’s Post, 8 March). The final report is still being finalised, explains Xanthea Limberg, Mayco member for informal settlements, water and waste services, and energy. “[The draft report] is being reviewed by a few internal specialists before it is sent for an external peer review. Only once that reviewing process is complete will the report be finalised,” she explains. The study was done over a year to control for changes between seasons. “During previous studies, the CSIR has found only limited ecological impact from the outfalls, limited to the immediate area surrounding the outfall. In terms of dispersing pathogens such as E. coli into the ocean, the risk to human health is insignificant,” Limberg adds. City officials will comment on the study’s findings after the report is finalised, she says. Preliminary studies showed contaminated stormwater is more likely to cause sea pollution than the City’s sewage outfalls. This was stated following a sea trip to monitor the outfalls at Green Point and Camps Bay with representatives of the local ratepayers’ associations. These outflows came under renewed scrutiny after the City advertised a permit application to keep on discharging effluent water into the sea at Green Point, Camps Bay and Hout Bay (“Sewage nothing new”, People’s Post, 16 June 2015). The permit application was needed after a change in national regulation necessitated a public participation process. The City has since been carrying out various tests to assess the impact of the outfalls, which appear to show the water quality at the time of testing is low in bacteria levels. The City’s sewage outfalls expel roughly 5% of all the water treated at the City’s water treatment plants. The sewage is treated before it is discharged. The Green Point outfall discharges sewage 1.7 km out to sea at a depth of 30m. At Camps Bay the discharge takes place 1.3 km off the coast.