Tuesday, January 18

New data shows how polluted Cape Town’s vleis are


  • The city of Cape Town has published the results of the water quality tests for the Zeekoevlei, Zandvlei, Rietvlei and Milnerton lagoons.
  • All four bodies of water show dangerously high levels of E. coli.
  • In some places, E. coli levels have resurfaced after they appeared to be under control.
  • The City says it is “working around the clock to determine the source of the high levels” of E. coli.

The city of Cape Town has published the results of the water quality tests of the Zeekoevlei, Zandvlei, Rietvlei and Milnerton lagoons from May to October 2021. All four bodies of water have been closed to the public for months due to dangerously high levels. high levels of E. coli (a bacteria found in human feces).

The results show that all four bodies of water still have levels of E. coli much higher than what the City considers acceptable for contact.

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E. coli is measured in colony forming units (cfu) per 100 ml. The city considers levels above 4001 cfu / 100 ml constitute an “unacceptable risk” to public health and recreational use.

These are measurements of E. coli levels at six locations in Zeekoevlei from May to October 2021. At five of the six test sites, CFU / 100 ml exceeded the acceptable risk level of 4001 CFU / 100 ml for most of the days analyzed. The average reading across all Zeekoevlei sites and every day was approximately 64,000 CFU / 100ml, with the highest average reading at the ZEV2S test site, over 190,000 CFU / 100ml.

The results of Zeekoevlei, which closed in July this year, taken on October 29, show at three different sampling points more than 100,000 cfu / 100 ml. Outside of the Zeekoevlei Yacht Club, it reached 980,000 cfu / 100 ml and 940,000 cfu / 100 ml at the entrance to the Big Lotus River.

The City was implementing measures to rehabilitate the water, but a sewage spill in mid-October caused E. coli levels to rise dramatically again.

Tom Schwerdtfeger, vice president of the Friends of Zeekoevlei and Rondevlei, said they had been “almost there”, with the opening of the vlei again. Now another concern is that the hyacinth, an invasive species, is spreading rapidly as a result of sewage in the water.

In Zandvlei, the average reading was 32,094 CFU / 100 ml.

The Zandvlei estuary initially closed in May for four months before reopening to the public in early October. The water quality results showed that before the vlei reopened, the E. coli count had been declining from August until it was again acceptable for public use.

But the vlei was only open for about two weeks before the city announced that it had to close again on October 22.

The E. coli count in the water soared on October 15. Five sampling points on this date measured more than 100,000 cfu / 100 ml.

The latest results, taken on October 29, measured 430,000 cfu / 100 ml at a sampling point in front of the Imperial Yacht Club. On the same day, some lower E. coli counts were also recorded with 7,800 cfu / 100 ml in the northern area of ​​the vlei, 5,800 cfu / 100 ml at a sampling point in the outlet channel, and 3,800 cfu / 100 ml in the rubber dump.

After Zandvlei closed again, the city said in a statement that it is “working around the clock to determine the source of the high levels of E. coli.”

In Rietvlei, the average reading was 198,318 CFU / 100 ml.

The latest water quality tests conducted at Rietvlei, which has been closed since late June, measure E. coli counts well above acceptable levels at two sampling points.

On October 29, 460,000 cfu / 100 ml were measured in a stormwater canal and 82,000 cfu / 100 ml in another sampling point. However, three other samples on this same day showed levels well below the 4001 cfu / 100 ml benchmark.

The City also released the results of water quality testing of the Milnerton Lagoon and the Diep River from January 2020 to October 2021. The lagoon has had contamination problems for many years due to raw sewage flowing from informal settlements and failures in Potsdam’s wastewater treatment works. according to a statement from the city.

The water quality results show that sampling points in the lagoon and the Diep River have often measured levels of E. coli well above the acceptable limit; however, the readings have changed dramatically since January of last year.

The latest measurements on October 15 showed more than 1 million cfu / 100 ml at a sampling point on the Diep River and 69,000 cfu / 100 ml at the mouth of the Diep River.

The Organization Undoing Tax Abuse (OUTA) has recently published a statement calling on the City to make the results of the Diep River Estuary and Milnerton Lagoon water quality tests “readily available” to residents, and to be published regularly.

The results of the water quality test can be accessed here:

© 2021 GroundUp. This article was published for the first time here.


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