Gathering this week at the Water Desalination Symposium Africa 2017, water experts have offered their experience and insight into building and operating desalination plants in South Africa, with some saying the real cost of desalinated water has worked out to between R7/m3 and R10/m3.
The price excludes finance and major civil works associated with reticulation systems and is based on 24/7 operations, says Veolia Water Solutions senior process engineer Thys Els, sharing Veolia’s experience with other symposium delegates.
Veolia Water has designed, built and operated four desalination projects in South Africa, namely the Amatola Water board’s desalination plant, the Plettenberg Bay desalination plant, the Mossel Bay desalination plant and Transnet’s desalination plant.
Els said the plant in Plettenberg Bay, which took five months to construct, was established following severe drought in the Southern Cape in 2010. It continues to run during peak consumption months during the holiday and tourist season from December 1 to April 30.
Meanwhile, Veolia Water’s Mossel Bay plant was envisaged to secure water supply in Mossel Bay during the drought towards the end of 2010.
“As it turned out, the moment we commissioned it, it started raining, with normal rainfall resuming towards the end of commissioning,” said Els. Various operational scenarios therefore had to be considered. “It was decided that continuous 24-hour operation could not be justified. The plant has been put in zero mode until it is needed.”
Els noted that the decision to mothball a plant or put it in zero mode was a serious consideration for desalination operators. With mothballing, the plant is simply closed up and left until needed. This could lead to hidden costs.
“The reliability of the equipment is uncertain, recommissioning could be lengthy and you may discover all sorts of gremlins when you start up the equipment.”
As part of its zero mode strategy, Els said Veolia did daily checks for leaks and corrosion, as well as pump, motor and equipment maintenance at the Mossel Bay plant. This ensures that it is ready to start up at any time it is needed. Four dedicated people are currently on site five days a week.
Els believes public perception and participation are key to helping people understand the desalination industry.
He added that the desalination process cost more in winter, owing to lower water temperatures, which led to higher electricity costs.
India-based Ion Exchange Safic executive director and CEO Gourish Chakravorty said the advantages of seawater desalination were obvious.
“Seawater is available in abundant quantities. It is a reliable source and the quality is consistent,” he said, adding that the investment cost of desalination was lower compared with other technologies, with less space required for installation. Designs for temporary and permanent plants are modular and can be increased based on future demand.
Chakravorty noted that the process could also be adapted depending on whether drinking water or industrial water was required.
He said that much research was going into the reverse osmosis technology used by most desalination companies. Chakravorty said this could ultimately reduce operating costs.
He explained that a desalination scheme has three basic steps.
“Pre-treatment is essential to protect the membranes and extend the operating cycles. Reverse osmosis is at the heart of the system. It removes the dissolved minerals. Post treatment is essential to get the desired water quality, as per the requirements.”
The company is among companies that provide containerised units that could be put into operation in a short time frame.
The City of Cape Town recently advertised its first bids for the supply of temporary desalination solutions.