Desalination plants are up and running

An aerial view of the Strandfontein desalination site.

Contrary to speculation, the desalination plants were very much in working condition, said Xander Kock, director at water treatment specialists Proxa, which entered into a joint venture with Water Solutions SA in 2017, to design and commission a 7.5 MLD seawater to potable water plant at Strandfontein Pavilion and Monwabisi.

The scope of work included the marine intake, onshore process plant, product injection and brine return. The water (potable water compliant to SANS 241) is injected directly into the City’s reticulation network.

The Plainsman, Vukani’s sister paper, visited the desalination plants on Friday May 31.

The Strandfontein plant pumps 7 million litres of water a day into the surrounding areas of Strandfontein, Pelican Heights and similarly the Monwabisi plant pumps 7 million litres of water a day into Khayelitsha and its surrounding areas.

The desalination plant in Strandfontein has pipes running underground, approximately 600 metres into the sea collecting water to be converted into drinking water. The Monwabisi plant has pipes running under the road, close to the site, and into the sea.

The area around the plant is rehabilitated and well cared for by the staff, said Mr Kock.

“We have a good communication with the community on this, and understand that they are not allowed in the designated rehabilitated areas,” he said.

However, Sandra Dickson, founder of action group, Stop the City of Cape Town, said she recently visited both plants and was denied access.

This was for her safety, especially from chemicals in the workshop, said Mr Kock. They operate under strict security and would need to be accompanied by staff or professionals who work with the plant, he said.

The Water Solutions-Proxa joint venture (JV) provided an extra sand filter and reverse osmosis unit to enhance the amount of water pumped out and produced daily without any additional cost to the City of Cape Town.

“The contract with the City is to buy water from Water Solutions-Proxa JV and pay for the water pumped out daily,” said Mr Kock.

Both sites have control rooms to monitor the plants. Alarms would go off if something is wrong in the system. The plants will shut down at once, if it is an emergency threat, he said.

Keith Blake, fisherman and community activist, said he wants the City to explain who is benefiting from the plants and the operation processes.

“The City has gone quiet on us; it’s not right. They are not saying anything, not keeping us informed. The only time I actively see people at the plant in Strandfontein is when a man with a dog monitors the area. It looks deserted but we want answers,” he said.

The City’s JP Smith, acting mayoral committee member for water and waste said the plants have minimum to no measurable impact on the marine environment. The brine discharge into the sea is also continuously monitored by an independent marine contractor, as part of Coastal Water Discharge Permit requirements from the Department of Environmental Affairs (DEA).

“To date, monitoring programmes show that we are well within the limits set by the national government, that there has been no noticeable impact to change in marine life, and that brine is quickly dispersed by currents, so much so that we are recording normal salinity (a solution of salt in the water) levels within a few metres of the discharge pipe,” said Mr Smith.

The maintenance and care of the plants are the responsibility of the supplier, and the costs thereof are included in the cost per kilolitre (1 000 litres) of water that the supplier charges the City. The cost of the water is about R40 a kilolitre, he said.

The marine contractor has found that the impact on the marine environment is minimal.

He also said the brine is fed back into the sea water. Sixty percent of the water that is sucked in from the sea goes back to the sea as brine.

The brine is salt water with less than twice the salt concentration of seawater, and it mixes and dissipates quickly in the sea, he said.

Mr Kock also said there have been only a few instances in which small fish have entered the desalination plants, as the flow velocity at the intake is low and any fish should be able to swim away quite easily.

The intake also has a grid in front of it to keep fish out. The number and type of fish that have been observed in the screens is so low that it has no ecological relevance or impact, he said.

The water pumped out of the plant is clear and clean water, cleaner than the actual water coming from your tap, said Mr Kock.

However, Ms Dickson disputes this.

“Algae, turbidity water, meaning the water is murkier, and filters are a few of the already evident problems with the desalination plants. At times the plants have to be shut down to protect the filters. The plants can be filtered, but yet the filters of these plants clog up,” said Ms Dickson.

Close to the Monwabisi plant, is a sewage outlet and that also has a lot to do with the quality of the water, said Ms Dickson. “People are suffering vehemently from this. Professors have tested this water and can prove that it is affected by the sewage area. This is dynamite because we have to drink it,” said Ms Dickson.

Mr Kock said this is not true. They do, however, acknowledge that there may be sewage water, with very low concentrations of it. It goes through a robust process of removing contamination and is regularly monitored and analysed, he said.

The Plainsman tasted the difference between tap water and the water that the desalination plant pumps out at the Monwabisi plant. The water on site at the plant has more chlorine in it, once you let it stand the taste of chlorine will disappear and it will taste normal, said Mr Kock.

“The water passing through the pipes, needs the chlorine in it as it helps fight the bacteria you find inside the pipes, the water passes through,” said Mr Kock.