African Mining January - February 2019 | Page 41

Hard issue The Orano desalination plant supplies Swakopmund and mines like Rössing and Husab with water. In picture is the water pipeline that runs from the plant inland where NamWater taps into the supply. The brine stream from the plant is a mixture of the brine from the RO units, the backwash water from the UF units, and flush water from the screens. Roughly 70% of the seawater pumped to the plant is returned to the sea as brine. Costs of desalination According to Baillie, the major costs in operating the desalination plant are the cost of membranes, maintenance, and electricity. “It is an extreme environment that we operate in, and therefore the maintenance costs are high,” he says. He adds that one of the biggest challenges is dealing with the algal blooms, red tides, and sulphur events that happen frequently along the Namibian coast. “Because of the currents, we often experience sulphur outbreaks in the ocean and when this enters the plant, it creates major problems in the UF and RO sections. Sulphur is very hard to remove from the membranes — you have to be careful not to damage the membranes. As soon as we detect high sulphur levels, we shut down the plant to protect the membranes. It is a seasonal phenomenon, but it is more prevalent in summer.” The EDP is a good example of what mines can achieve and what contribution they can make to the wider society. One just has to wonder what will happen if Trekkopje eventually does start producing uranium? b www.africanmining.co.za From the intake, seawater is pumped to the screening plant. The permeate is passed through a bed of limestone to mineralise it with calcium carbonate. JANUARY - FEBRUARY 2019 AFRICAN MINING 39