The R70 million reverse osmosis (RO) plant will supplement potable water already being obtained from the West Coast District Municipality (WCDM) of the Western Cape, where most water is pumped from surrounding dams. Around 36 million litres of water is required each month to spray iron ore stockpiles once a week and transfer points daily in the terminal using sprinkler cannon systems. This helps contain the dust which is inclined to blow excessively to areas outside the terminal.
Karl Socikwa, Chief Executive of Transnet Port Terminals (TPT), said the new plant which is approaching the end of its construction would enable increased spraying for better dust mitigation at the terminal, which exported 45 million tons of iron ore in 2010/11. The RO process pumps water from beach wells and naturally pre-filters or desalinates it to remove salt and solids. This reduces the need for separate pre-filtration units. Fresh water is then pumped out to a buffer storage tank at high pressure through to the RO membranes.
The desalinated water is piped to the potable water tank where it can be used for dust control, while the concentrated sea water (brine) is released back into the ocean through beach wells or outfall pipes. There is no negative environmental impact in the operation and after filtration the water complies with drinking water standards. Velile Dube, Western Province Terminal Executive, said Transnet had researched other possibilities including getting recycled water from the municipality. But other options were unreliable, costly or limited in capacity. “RO plants provide a guaranteed source of quality potable water since they are not vulnerable in drought situations. The method is proven and reliable and there is access to good local expertise in South Africa,” he said.
The plant consists of two RO modules each with a capacity of 1.2 million/module/day. This will meet the 36million litres/month requirement and the existing water allocation from the municipality can then be used to spray more often. Another advantage of the RO method is the plant can be constructed in modular units allowing additional modules to be added at a later stage to meet growing water demand. The Saldanha plant is built and commissioned by water engineering company Veolia Water Solutions & Technologies South Africa (formerly VWS Envig), a French company that specialises in RO technology and has been responsible for successfully introducing it commercially across the globe, including South Africa.