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The City of Cape Town has responded after a documentary, uploaded to YouTube, went viral. The video, titled Bay of Sewage, examines the city’s practice of pumping effluent into the sea.
The documentary alleges that the practice is creating “serious and growing problems” for marine life and humans.
However, the city has hit back against the documentary, saying it showcases “evidence in a selective and sensationalised” fashion.
“The city is confident that effluent from the outfall is not affecting inshore water quality. All available evidence contradicts the video’s assertions,” it wrote in a press release.
How does it work?
The City of Cape Town claims that the video provided no “substantive data or measurable science” to support the claims.
“The City, on the other hand, has been monitoring the impact of the outfalls and coastal water quality in general for many years,” it wrote, adding that it was working on a year-long study with the Council for Scientific and Industrial Research (CSIR).
It also gave more background into its practices, saying it operated three marine outfalls that are screened to remove litter and solids.
“The outfalls themselves make use of a diffusion system at the end of the undersea pipeline which rapidly dilutes the effluent to at least 100:1 at the immediate exit point of the outfall. This corresponds to a 99% reduction in contaminant concentrations in the receiving water, which is far beyond the capabilities of even advanced conventional treatment processes. The distance of the outfalls from the coastline then ensures that bacteria dies off before it can come into contact with humans…” it continued.
It asserted that all coastal cities around the world engage in the practice.
The City also addressed concerns over brown foam and brown water
The video showed off several plumes in the ocean, but the city claims that this is proof that the practice is working correctly.
“Highly defused wastewater released through the diffusers is less dense and warmer than the salty cold sea water and therefore rises in what as known as the ‘mixing zone’. This is the plume that, at times, is visible. It is in this mixing zone that the effluent begins to dissipate rapidly in the ocean water column,” it elaborated.
The City of Cape Town also sought to allay fears over brown foam and general brown water.
“We often have strong wave action on our beaches which, when it occurs, releases many nutrients and proteins from algae and decomposing kelp common in a healthy and productive marine ecosystem such as ours, which in turn increases natural bacterial counts as well as produces a yellowish surface foam. This foam is often misconstrued as sewage, which it is most certainly not,” it continued.
“In the past, diatom (algal) blooms have also led people to believe that there is sewage in the water.”
Read the full response on the City of Cape Town website over here.