South Africa: new plant for dust control-Transnet

[SALDANHA – 22 March 2011] Transnet is gearing up for the commissioning of a new multimillion rand plant in May 2011 that will provide the extra water resources required to control red iron ore dust at its Saldanha bulk terminal, which is located within a water scare area.

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 36 000 kilolitres 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 1200kl/module/day. This will meet the 36 000kl/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 basic components of the RO plant installation include:

• An RO plant containment building (approximately 600m² surface footprint) with room for three RO-modules,
• an electric substation,
• Submersible pumps and piping for the extraction and discharge of sea water,
• A sea water storage tank alongside the RO building,
• a motor control room,
• a pump house with pumps,
• filtration systems,
• A potable water storage tank alongside the RO building,
• Storage reservoir(s) totalling 5ML, 48 hour potable water storage capacity next to the existing reservoir,
• office; ablution facilities and space for parking,
• brine discharge system,
• A small service road connecting the RO building to the nearest road infrastructure and
• All requisite electrical and communication facilities between the RO installations and the Saldanha Bulk side.

The Saldanha plant is built and commissioned by water engineering company Veolia Water Solutions & Technologies South Africa (formerly VWS Envig), a French based company that specialises in RO technology and has been responsible for successfully introducing it commercially across the globe, including South Africa.

Below: a diagram showing the basic components of the RO plant installation.

Source: press release by Transnet

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