Municipalities should lead by example…

22 June 2011

The Cape Town suburban press (Tatler etc) recently reported on the abominable conditions in the aptly-named Black River.  As with so many rivers in or downstream of built-up areas, wastewater effluents are a major source of contamination.

Public concern about Cape Town waterways

Cape Town, for example, has set laudable, some would say onerous, conditions on new developments to prevent relatively minor amounts of pollution reaching rivers and streams.  This approach is important if the “death by a thousand cuts” scenario of pollutant build-up is to be avoided.  The City, however, remains the largest polluter of all and shows little evidence of being willing to do anything about it – even in high visibility areas such as the Black River, alongside of which runs a main road artery, the N2.

Cape Town has 24 points at which wastewater is discharged, either to rivers or to the ocean.  Combined, these discharges annually dump a volume equivalent to half of that which can be stored in the City’s largest dam, Theewaterskloof.  Contained in this volume are, conservatively-estimated, some 1500 metric tons (1500 000 kg) of phosphorus! – a quantity 10x that dumped into Hartbeespoort Dam on an annual basis.  If we add to this the load from all City surfaces, the number may double.

There is no economic or technical reason why this situation needs to continue.  Removal of phosphorus from detergents would reduce the load by 25% or 375 tons per year, making the work of the treatment plants that much easier.  Optimization of the treatment processes could further reduce the phosphorus content of the final effluents by a factor of 10, reducing the 1500 tons to a little over 100 tons per annum!

If this were to happen then the City would not be able to dictate “do as I say, but do not say as I do” and lead by real example!



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