Desalination is often touted as a solution to shortages of clean drinking water, but the most common method, using reverse osmosis, is really a luxury. It relies on electric pumps driving salty water through a membrane, so that salt concentrates on the high-pressure side of the membrane, allowing nearly fresh water through it. This method is widespread among power-rich economies along desert coastlines, but has done nothing to help the less fortunate millions in countries where electricity is unaffordable. Indian scientists, unsurprisingly, have developed a means whereby fresh water might become accessible to most coastal people in the tropics. They have worked out how to gear bullock power to reverse-osmosis pumps, so that a pair can produce up to 3000 litres each day and supply entire villages. If a bullock can do it, then why not donkeys or camels in even more arid coastal areas?
Source: Coghlan, A 2003. All hooves to India’s pumps. New Scientist, 10 May 2003, p. 19.