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Too much water going to waste - expert

Posted by: Saving Water SA (Cape Town, South Africa) – partnered with Water Rhapsody conservation systems – 21 February 2010

Not one of one of Cape Town’s 26 sewerage plants is working properly. The problem is not so much the quantity of waste that the Mother City’s burgeoning population produces, but rather the volume of water used to transport that waste to the processing plants.

Blue-Green algae deposits at Zeekoeivlei

“There is just too much water arriving at these plants,” says Jeremy Westgarth-Taylor, who has studied the water situation in South Africa over the past 16 years, and is a past winner of a WWF Green Trust Award.

Mr Westgarth-Taylor was addressing guests at a recent “Green Drinks”, a monthly event at which Hout Bay residents share ideas about topical environmental issues.

According to Mr Westgarth-Taylor, the catastrophic poisoning, in 1997, of Wildevoelvlei, the series of pans between the sea and Imhoff’s Gift estate in Kommetjie, was a case in point. A highly toxic blue-green bloom (thought to be algal) formed on the surface of the lakes as a result of wastewater overflowing from a nearby water treatment works. The treated and untreated water had a high concentration of phosphates – a major component of washing powder. To prevent the “blue-greens” from reproducing, SANParks had to turn the lake anoxic (without oxygen), thereby killing an entire generation of organisms.

Even more alarmingly Mr Westgarth-Taylor claims Cape Town has exhausted all damming opportunities on local rivers. Theewaterskloof Dam, which draws on the Dutoits and Riviersonderend rivers, Voelvlei, which drains the mountains west of Tulbagh, and Steenbras Dam above Gordon’s Bay together supply close to 700 million cubic metres to the metropole. Despite the addition of the Berg river scheme just last year the area’s demand for water will out-strip supply in just two years, he says.

He maintains that, because profit on the sale of water is a major contributor to municipal budgets, municipalities do not readily encourage consumers to reduce their usage of the dwindling resource – however short-sighted that might be.

Desalination of seawater is one possible solution to the imminent water crisis. However, the process is heavy on electricity usage: every 1 000 litres of potable water would cost 17kWh of energy to produce. With the cost of electricity due to rise steeply over the next three years, the process would make water a luxury.

Demand management (in which the user manages consumption) of water is therefore the only viable option left to us, asserts the water expert. By reducing the volume of water going to treatment works, we can cut our water consumption by half. Another benefit of such a strategy would be a saving of electricity since electricity usage accounts for 90% of the cost of operating a sewage treatment works. Asked about the Table Mountain aquifer as a potential water supply Mr Westgarth-Taylor explained that the underground lake is a “fossil” water supply that has existed for centuries and is not replenishable. Beneath the Cape Flats is another aquifer which is replenished by winter rains. However, the rate at which well- and borehole-owners are drawing on this supply has already reduced its level considerably. He cited the example of Strawberry Lane in Constantia, where the water table has dropped from 17m to 30m over the past 10 years. A better alternative to boreholes, he said, would be for residents to use grey water (that’s water from showers and baths) on their gardens. This would not only relieve the pressure on our sewage system, and save potable water for drinking purposes, but would also reduce their water and sewage costs.

Mr Westgarth-Taylor’s colleague, Jon Boland, a Hout Bay resident who owns a franchise for water-saving equipment, advised that by installing a grey-water system, a family could reduce its potable water usage by 35%. By installing the unique Water Rhapsody Multi Flush as well, that households could save an additional 20% or more on its water bill.

He said families could cut their water consumption by as much as 90% by installing additional water-saving devices such as a rainwater tank, which takes water from the roof and by installing a pool-side tank.

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