1 February 2018

South Africa: Rush to Get Cape Town's Temporary Desalination Plants Online

The City of Cape Town's R240m temporary desalination plant at Strandfontein Pavilion is on track, but it will only start producing the first two million litres of an expected seven million a day in March.

This is according to the City's mayoral committee member for water, Xanthea Limberg, who was speaking at a site tour on Thursday.

"Given the severity of the drought and the uncertainty around rainfall, we needed to be flexible in our approach and allow for both permanent and temporary solutions in order to ensure that we minimise any risk of acute water shortages," Limberg said.

With a grader levelling a site behind the public toilets at the pavilion and workmen throwing concrete for a 1km pipeline to the sea, the site is one of three temporary seawater desalination plants being built around the city.

While it will not be done in time to avoid Day Zero at current water consumption rates, it is expected to bring more drinking water into the system to help the city limp through the drought until it rains and recovers water supplies.

'Temporary solution'

The contract is only for water supply for 24 months. After that, the equipment which is owned by the contractor, will be removed and the area rehabilitated.

"This is going to be a temporary solution, said Wynand Wessels, project manager for Proxa South Africa.

"Phase one being an initial supply of 2ml (megalitres) a day - two million litres, and phase two, being a final supply of the seven million litres - the seven ML per day into the potable reticulation."

The contract for the Strandfontein and the Monwabisi plants was awarded to Water Solutions South Africa-Proxa South Africa JV (Joint Venture) after a tender process last year.

The Strandfontein contract for the purchase of water is worth between R240 to R250m and the Monwabisi contract is worth between R250m to R260m, according to the City's information sheet, which was distributed at the visit.

The Strandfontein plant will be in place for two years, pulling the water from almost 1km out at sea, via a pipeline near the popular pool.

The seawater will be filtered through reverse osmosis which will split the sea water 50/50 into half clean water and half brine.

The brine will be sent back into the sea by pipeline, released again around 200 metres offshore and is expected to disperse quickly.

Gift Phiri , Owen Mareya, Kyle Whitfield, Dube Magadani and Thembalethu Fihlani take a break from the hot work of drilling into an aquifer on Mitchells Plain during a site tour (Jenni Evans, News24)

The City will buy the water from the company at a cost of between R30 to R40 per kilolitre (one thousand litres) which works out to 0.03c a litre at the R30 a litre estimate, according to a quick calculation by Kevin Balfour, a bulk water project manager for the City.

Limberg said the Monwabisi desalination plant was delayed because the community wanted a bigger stake in the work at the plant, which is using expertise mostly from outside the area.

Stefanutti Stocks is sub-contracting to the joint venture as the marine works sub-contractor for offshore piping installation.

Some of the contractors on site at Strandfontein were from iX Engineers, appointed by the City. According to its website, it is a company that was established following the incorporation of WorleyParsons' Public Infrastructure (PI) business with the consulting business of Black Jills Engineers. Its CEO is civil engineer Lebo Leshabane, according to its website.

Vetus Schola, the private company that kept protesters at bay at the end of 2017 at the Cape Peninsula University of Technology, was appointed by the main contractor, in line with the tender's security specifications, to keep the heavy machinery safe at the exposed site, according to Limberg in information provided in January.Vetus Schola guards with dogs were spotted patrolling the perimeter, while bathers enjoyed a swim.

Limberg said the first phase at Monwabisi should be online in April, with 2 ML per day and a full capacity of 7ML per day by May. 'Natural reservoirs' The tender for the V&A Waterfront desalination plant was awarded to Quality Filtration Systems (Pty) Ltd. Information on the company was not immediately available.Aquifer extraction is also being finalised to bring the maximum yield in the shortest time, and waste water treatment is also being ramped up.

"I think we are focused on action," said Limberg.At the Mitchells Plain aquifer, water gushed out of a borehole after drilling a few weeks ago confirmed the availability of water stores in rocky "natural reservoirs" deep underground and testing began.

That water was not drinkable and was left to run down a trench and to sink back into the aquifer.The next stage is to finalise getting the water to the nearby water treatment plant to turn it into drinking water. The start of the Strandfontein temporary desalination plant (Jenni Evans, News24) The City is also exploring the use of the Table Mountain group aquifer, the Cape Flats aquifer and the Atlantis Silwerstroom aquifer to supplement surface water supplies.

The Atlantis aquifer is already supplying some water to the West Coast town and by June, it is expected to put 25ML of water into the City's overall supply.The vast Cape Flats aquifer spans 400km squared from False Bay to Tygerberg Hills and Milnerton, and the boreholes planned should add another 25ML by June, according to the City.

The Table Mountain group aquifer - the second largest aquifer in the world - consists of a number of aquifers from the southern peninsula to the Hottentots Holland mountains and beyond. It is not underneath Table Mountain as some think, the City's fact sheet stated. Specialists are being cautious with this phase due to over-extraction and possible environmental damage.However, the first phase should pump 10ML per day into Steenbras Dam and the yields from others will be about 50 to 60 ML per day.

The City will also reroute water from the Newlands spring to a swimming pool site 700 meters down the road to share it, after long queues started forming there.

The current daily consumption for the city has dropped from just over one billion litres a day before the drought, to 566ML a day on January 29, but it has to plummet to a further 450ML a day to avoid the dreaded Day Zero - predicted for April 16.

Water pressure is also being decreased city-wide by a team of engineers to cut down on waste and regulate usage in areas where residents are stubborn about saving.

However, Farouk Robertson, spokesperson for the City's department of water and sanitation, said the only way to avoid Day Zero in the 26 towns that were amalgamated to form the city, was to use no more than 50 litres per person per day and to not use drinking water for toilet flushing.

Source: News24

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