News agency, Cape Town, South Africa
Sunday July 23rd 2017

Water quality decreases due to sewage and storm water waste

28.01.2013

Although high levels of sewage are to be found in the Big and Little Lotus Canals which flow into the Zeekoevlei wetland popular with canoeists, Zeekoevlei itself is still suitable for recreational use, although one might want to keep ones mouth closed upon falling out the kayak.

According to the City of Cape Town’s latest Inland and Coastal Water Quality Report covering the period October 2011 to September 2012, the monthly measurement of e.coli levels in the Lotus tributaries failed the guidelines for intermediate contact recreational use 76% of the time.

Intermediate contact recreational use refers to activities such as canoeing, waterskiing, windsurfing and sailing.

However, Zeekoevlei’s e.coli levels were below the maximum 1000 indicator organisms per 100ml 83% of the time, indicating it remained suitable for public use for most of the year.

Increases in e.coli levels occurred during and immediately after rains that wash pollutants down from storm water drains and contribute to sewer network overflows.

However, while it may remain generally suitable for intermediate contact water sports, the levels of Phospates, which are used as an indicator of ecological health of the wetland system, were in the “unacceptable” range.

The ecological state of Milnerton Lagoon – also a popular recreational water body – is also in the “unacceptable range” and also had the lowest compliance level for e.coli, passing only 65% of the water quality tests.

Rietvlei, where a lot of sailing takes place, was in the best state of the popular recreational water bodies, passing its e.coli tests 92% of the time and in a “fair” ecological state.

Zandvlei passed its e.coli tests 88% of the time and was in a “poor” ecological state.

Regarding coastal waters, which are tested against full contact (i.e. swimming) standards, six beaches in False Bay did not comply with the stringent Full Contact Recreational Standard contained within the SA Water Quality Guidelines for coastal marine waters.

These beaches, although not named, were clustered between Macassar Beach and Strand, the report noted.

“These sites have over the years been repeatedly non-compliant for short periods of time and it is thought that poor quality from the rivers (e.g. Soet and Sir Lowrys Pass Rivers) and stormwater outlets due to contamination from sewer blockages/overflows and runoff from informal settlements is the main contributing factor.”

On the Atlantic coastline three beaches, namely, Three Anchor Bay, Rocklands Beach and Saunders Rocks Beach failed to comply with the required standards and Capetonians wishing to swim there might want to proceed with caution.

The report, compiled by the City of Cape Town Transport Roads and Stormwater Directorate and  recently submitted to sub-councils, noted that of the 27 different rivers and water body systems in the City, only three rivers, the Silvermine River, Sout River and the Wildevoelvlei River, had 100% compliance with the intermediate contact recreational guideline.

The report reveals long term decline in inland water quality since 2000 which saw 80.5 percent of the water systems complying with water quality tests whereas the present overall compliance figure is at 65 percent.

Other than the Big and Little Lotus canals, which have only a 24% compliance level over the October 2011 to September 2012 period, other rivers to avoid any recreational activity on, judging by the report, are the Soet River, Disa River and Mosselbank River, all of which have compliance levels below 50%.

Talking on the report, City’s Mayoral Committee Member for Transport Roads and Stormwater Brett Herron said the rapid formation of informal settlements resulted in sanitation problems which made it difficult to ensure water quality standards.

However, the City has launched a pilot project in “three hotspots”, one of them being Imizamo Yethu in Hout Bay, where they are diverting sewage from storm water into the waste system.

The disposal of waste into stormwater drains played a part in contaminating inland water systems, said Herron.

Senior hydrologist Arthur Chapman at sustainability company OneWorld Sustainable Investments, said treatment of waste water “is a national problem that we face”.

Chapman said Cape Town, just like Johannesburg, was a fast growing City and as the population grew so too did the amount sewerage generated, yet the Waste Water Treatment Infrastructure was not upgraded to handle the amount of sewerage generated.

“Waste Water Treatment Plants need to be expanded faster to meet the need for acceptable waste treatment. That’s kind of a big picture,” said Chapman.

Inland water systems are tested monthly while coastal water quality is tested fortnightly.  — Peter Luhanga

No tags for this post.

Leave a Reply