Algae clogs up city waterworks

ct MOLTENO RES 4340 (31866554) MURKY WATERS: Algae in the Molteno Reservoir is all water off a gooses back to this bird, but many residents are highly peeved at having their geyser filters choked by an algal build-up in this and the Newlands Upper Reservoir. Photo: Ryan Jacobs

Staff Writer

BLOCKED water filters, low water pressure, problems with geysers and expensive call-outs to plumbers are some of the hassles City Bowl and southern suburb residents have had to put up with because of algal growth in two city council water reservoirs.

A plumber who spoke to the Cape Times yesterday said they had had about 20 calls for algal-related problems in the last three weeks, mostly from people living in Claremont, Newlands, Kenilworth and Bishopscourt.

“A lot of houses have problems with the algae, but they don’t realise that is the problem,” said Philip Bornman.

“It affects geysers, because there is a pressure-reducing valve in the geyser where the cold water comes in. It’s got a filter on it and this starts to get blocked from the algae and so the water pressure gets weaker and weaker. You start having a shower and then the shower starts dying.”

Another plumber, David Spence, installed a geyser in Claremont last week, and within three days was phoned by the homeowner to say he had no water pressure. He had to replace the valve because it was blocked with algae.

“Plumbers I was at college with say they are doing the same thing. The council says it’s because of an algae build-up in the reservoirs, but I’ve lived in Cape Town for 32 years and I’ve never heard of that before, and neither have my parents,” Spence said.

The city council said there were “unusual levels of algae” at the Newlands Upper Reservoir and the Molteno Reservoir in Gardens. The algae is not toxic and is not a health risk, but the city acknowledged it was a “serious inconvenience” because it clogged filters and lowered water pressure.

It is believed the cause for the algal bloom was “a change in the nature of the treated water”, and hot weather.

Added to this was a national shortage of carbon dioxide used to treat the water, which made the problem worse by creating an environment in which the algae flourished.

On Thursday the city said it had increased the level of disinfection of water that fed the reservoirs. It has also drained the Newlands Upper Reservoir so that it can be cleaned. The draining of the Molteno Reservoir began yesterday and will be completed by Sunday.

The city apologised and said there was no health risk.

l Bishopscourt residents have reported pollution of the upper reaches of the Liesbeeck River since the beginning of the month, which has turned the river flowing off the mountain into “pea soup”. It is suspected that the pollution could be clay or sand from construction work near the banks. City officials are investigating.


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