Fresh water from the sea?

Strandfontein Pavilion has been earmarked as one of several desalination sites.

Strandfontein residents and the area’s fishing community are sceptical about the effects a desalination plant at the Strandfontein Pavilion will have on its coastal life.

The emergency desalination plants are being constructed close to shorelines at Monwabisi, Strandfontein, the V&A Waterfront and Cape Town Harbour, where sea water would be purified to generate clean, treated water, in light of the drought.

Brine, a high-concentration solution of salt (usually sodium chloride) in water, the discarded product of the process will be released back into the sea.

The plants are designed to inject the potable water straight into the reticulation system, and there are limited locations where this is technically possible.

Residents voiced their concerns at a Ward 43 meeting at Strandfontein community hall last Thursday December 7. The ward includes Strandfontein, Weltevreden Valley (west of Jakes Gerwel Drive and east of Weltevreden Street); and the Philippi farming area.

Gregg Oelofse, City of Cape Town manager for environmental corporate governance in the environmental management department allayed residents’ concerns, saying the plant would operate at most for two years and that mayor Patricia de Lille did not want residents and beach-goers’ activities to be hampered by the plants.

Strandfontein will be one of the first plants to come online with a nine-week construction period. In addition to the Strandfontein plant, plants will be also be constructed at Monwabisi, the V&A Waterfront and Cape Town Harbour, while the Atlantis and Cape Flats Aquifer projects and the Zandvliet water recycling project also form part of the City’s first set of augmentation plans. Collectively all these sites will produce an additional 196 million litres a day between February and July 2018.

“We will be monitoring on an ongoing basis,” Mr Oelofse said.

He assured residents that in the “sacrificial zone”, where the brine is pumped back into the sea, the brine would dissolve quickly and return to “normal level”.

Mr Oelofse said while the plant would be operational 24 hours a day, there would not be noise as electricity and not a generator would be used.

Igshaan Carstens, from Strandfontein Boating Association, asked whether the brine would increase shark activity.

A fisherman, Irefaan Ryland, from Manenberg, said they added salt to sea water to preserve their bait and answered Mr Carstens’ question: “Yes, sharks prefer swimming in saltier water.”

Mr Ryland asked whether chemicals used in the process to purify would be dispersed back into the sea water. “Would this not kill animals and plants in the area?”

Ephraim Stanfield, secretary of the Strandfontein Ratepayers’ Association, told the Plainsman that pumping the brine back into the ocean, would present another environmental drawback.

He said while the process of desalination was not environmentally friendly, and seawater desalination plants also contribute to the wastewater discharges that affect coastal water quality, it was needed to address the drought.

“The effects of desalination plants are multi-component waste, with multiple effects on water, sediment and marine organisms. We were assured that a control system will be in place to check the effects on marine life in the vicinity of the plant,” he said.

Residents asked why the plants were being constructed on the False Bay coastline and not in Camps Bay or along the Atlantic coastline. Mr Oelofse said the water “on the other side” was heavily polluted and that the dynamic False Bay coastline would be most suited.

Bay View resident Mario Oostendurp, founder of the Proudly Strandfontein campaign and civic organisation, said while desalination may be a positive start in terms of short-term relief for the current water crisis, it would have an environmental impact on the ocean.

“The City of Cape Town has to ensure that this short-term solution is as environmentally friendly as possible. While I am all for any instant relief, we need to consider that the desalination intakes around the plant suck in small fish and plankton which are killed off in the process. My main concern is that, with the emergency situation, the City will cut too many corners. Proper management around the desalination plants needs to be implemented, with defaulting officials held to account should proper procedures and practices not be implemented,” he said.

Justin O’Riain, professor in behavioural ecology and conservation at the University of Cape Town, said desalination plants had a potential impact on marine life.

“The most obvious threat is mortality associated with organisms being sucked against the intake filters. This threat is mostly to smaller marine organisms like small fish species and jelly fish. Microscopic animals such as zooplankton pass through the filters but are killed in the process that separates the freshwater from the seawater,” he said.

“It is possible to avoid most marine life mortality by placing the intake pipe below the substrate with the sandy seabed acting as a macro-filter. However, this entails more cost and perhaps more time than the City has before Day Zero.”

Day Zero is when most taps will run dry and residents will have to queue for water. According to projections, Day Zero now stands at Sunday May 20 2018.

The other obvious impact, Professor O’Riain said, was the release of processed seawater back into the sea. “This water is referred to as brine and is approximately twice as salty as the seawater that went into the desalination plant. A recent presentation by the City of Cape Town revealed minimal impact of wastewater on marine organisms at the outfall site.”

He said adding salty water to polluted freshwater would dilute the brine and reduce the potential impact of excessive saltiness on marine organisms associated with the desalination plant. “When one considers the enormous ecological impacts of removing too much water from rivers, damming them and polluting them with sewage, the potential impacts of desalination seem much less. Abstracting groundwater may also have far greater long-term impacts to the terrestrial ecosystems we rely on for most of our food.

“On balance, I think desalination is the lesser of many of the evils we impose on the environment in constant abuse of freshwater resources. One can only hope that the current crisis forces us to rethink our relationship with freshwater rather than simply re-engineer ourselves out of trouble and continue to abuse this finite resource.”

Xanthea Limberg, the City’s mayoral committee member for informal settlements, water and waste services; and energy said the first drinking water generated by the desalination plants is expected to be fed into the reticulation system by March next year.

The Monwabisi and Strandfontein plants are salt water reverse osmosis (SWRO) plants. With this plant, the sea water is conveyed to the SWRO plant through a pipeline. The plant produces high quality drinking water from the sea water and injects it straight into the City’s water reticulation network.

“The waste product from this desalination process is called brine and is simply highly concentrated salt water, which is conveyed to the marine outfall pump station via a pipeline. From there the concentrated brine is mixed with the wastewater effluent and released after treatment into the ocean through multiple diffusers which are designed to ensure that any potential environmental impact is limited,” she said.

She said both the Strandfontein and the Monwabisi plant would produce seven million litres of drinking water each a day which will be fed into the water system to supplement current supply from the dams and other water sources.

She said the plants were intended to operate for two years, based on a service agreement which will see the City buy water from the service provider, Water Solutions Proxy JV, which was awarded the tender for the Strandfontein and Monwabisi plants on October 27.

Ms Limberg said the value of the tenders was approximately R430 million.

Speaking about public access to the tidal pools, Ms Limberg said there would be minimal risks to public health and safety. She said all construction areas would be clearly demarcated as being off limits to the public. “Any external pipe work will be clearly marked or placed underground. All construction work will comply with national health and safety regulations.”

She said the City would monitor the sites and regularly test the drinking water that was produced.

“A meeting will be held with the area leadership and the City thanks the leadership and the residents of Strandfontein and Monwabisi for their support to help all of us through this extreme drought,” she said.

Ms Limberg said the City was working on a range of projects to bring sufficient additional water on stream to avoid Day Zero while residents continue saving water. She said these additional water augmentation projects included desalination, groundwater abstraction, and water recycling that are in the advanced stages of planning.