DESALINATION SANITATION
Pressure sensors key throughout THE DESALINATION Pressure is a vital factor in PROCESS desalination. WASA speaks to Martijn Smit,
Managing Director for Netherlands, Belgium and Southern Africa of Keller, a global expert and manufacturer of pressure management systems.
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n the reverse osmosis desalination process, a pressure greater than the osmotic pressure applied to the saline water will cause fresh water to flow through the membrane while holding back the solutes (salts). The pressure needed is typically between 50 kPa and 60 kPa, which is the perfect range for the Keller range of sensors,” adds Smit. Furthermore, pressure sensors should be fitted to filters. “Salt water goes through a filtration process before reverse osmosis. Differential pressure sensors should be fitted to the filters to determine the contamination levels of the filters and the best time to replace them, as they are costly.” He adds that one also needs to measure the inlet pressure of the pumps, as well as the levels of the desalinated water collected in the tank. Salt in the water eventually corrodes standard stainless-steel sensors; therefore, Keller’s sensors can be manufactured in titanium or Hastelloy that gives resistance to chlorides and sulfates. The Keller pressure transmitters that can be used in the desalination process are the 23SY series, 23SX series and 33X series. The 36XiW-CTD sensor can be used to measure water levels, temperature and conductivity (amount of salt in the water), in addition to pressure.
Use in Africa “Due to Africa’s water crisis, governments and foreign investors are
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JAN/F E B 2022
Deploying desalination as a key strategy in Africa’s water security mix has been boosted in recent years as renewable energy becomes more efficient
REVERSE OSMOSIS
In the reverse osmosis desalination process, a pressure greater than the osmotic pressure applied to the saline water will cause fresh water to flow through the membrane while holding back the solutes (salts)
pouring billions into schemes to turn seawater into safe drinking water. The long-term prospects for desalination as a key strategy in Africa’s water security mix have been boosted in recent years as renewable energy becomes more efficient, and the method of converting brine and other desalination waste products into useful commodities, like hydrochloric acid, through standard chemical processes makes facilities more cost-effective,” concludes Smit.
Keller has its headquarters in Winterthur, Switzerland, and is Europe’s leading manufacturer of media-isolated pressure transducers and transmitters. The entire production process – from the manufacturing of the individual components and the calibration of the sensors through to the final quality control of the finished products – takes place at the company’s headquarters. Instrotech distributes Keller products to the South African and African markets.
