Mark Jackson, City Bowl
Astounding. If what Mr Knott says about sewage treatment is true, (“No Blue Flag status for Hout Bay beach,” Sentinel, March 17) then New York will be able to shut down its 27 treatment plants and just dilute the sewage and pump into the sea.
From Barcelona to Dubai, all across the world, coastal cities can save billions. Cape Town, too, can save a fortune by closing its 23 treatment plants because, according to Mr Knott, we can simply treat sewage by “dilution”!
Except, unfortunately, Mr Knott is talking absolute nonsense. Dilution and diffusion – that is mixing sewage with seawater – is not treatment. And despite claims by councillors (like Ernest Sonnenberg), seawater, in fact, does not kill
E. coli. If it did, then those large shallow ponds we see at treatment works would be filled with salt water. They’re not. In fact, it is the UV of sunlight that kills E.coli (hence the ponds are shallow, to allow the UV to penetrate).
So when sewage is pumped into the ocean, yes, when it floats to the surface and gets sunlight, E.coli will begin to die. Unless it is night-time, in which case the sewage has about 12 hours of darkness to float that short distance to the beach, completely unaffected. And, yes, sewage goes out 24 hours a day. So, can you see the problem?
And though E.coli can die quickly, viruses can survive up to six months at sea.
And, no, sewage doesn’t always float to the surface. Sometimes when the water is icy cold and that pretty blue colour, it means the top water has been blown out to sea, and the cold under-currents are sweeping in, (at Camps Bay, towards the beach), dragging sewage along the seabed, too deep to be killed off by UV light, and preserved by the cold water.
So, yes, unfortunately the City is pumping out raw, untreated sewage. And, no, screening for solids (like toilet paper and garbage etc) is not treatment either. As any research will tell you, it is simply pre-treatment, that is that which happens before treatment.
And even that screening is in doubt. When a resident stumbled into the Hout Bay pumping station a few years ago, he discovered all the screens were up. The City’s response was to beef up security and fence off the pumping station.
And what of Mr Knott’s argument that since Camps Bay has Blue Flag status, everything must be okay? Actually, Blue Flag (as he must know) is only for three months a year (conveniently during summer, when the south-easter blows). And it’s awarded to only half the beach.
Which means half the beach does not have Blue Flag for the whole year. And the other half does not have it for nine months.
And since I believe the City’s methods of testing for sewage are inadequate anyway,
that all adds up to Blue Flag being a bit of a sham.
I invite readers to watch my short, online “viral-hit” video Bay of Sewage on YouTube and join the conversation.
I look forward to one day working with our City officials, to enlighten the public and help solve our
* Mark Jackson is the producer of Bay of Sewage. He has a BSc Engineering degree from UCT.