Solar treatment plants promise cleaner water


Solar panels on the roof of a water plant. FILE PHOTO | NMG

In recent years, much effort has been devoted to creating and developing innovative technologies in the field of solarised water treatment technologies and the future is promising. In Kenya, solar energy is an abundant and a widely untapped resource whose estimated daily insolation is 4-6KWh/m2.

The use of solar energy in photovoltaic (PV) systems for lighting, water heating and solar water pumping is rapidly gaining popularity due to its availability, reliability, efficiency and quick payback periods.

Solar-powered reverse osmosis plants are among the technologies being fronted as the sustainable solution to water scarcity in not just Kenya but the world over and especially at a time when an estimated 2.1 billion people still lack access to safely managed drinking water services, according to a report by WHO and Unicef; with the largest proportion coming from ‘Third World’ countries.

Reverse osmosis is a water treatment technology that utilises a semi-permeable membrane to remove dissolved ions, molecules and larger particles from water. The reverse osmosis membrane generally acts as a physical barrier to all dissolved salts, organic and inorganic molecules with a molecular weight greater than 100 and achieves rejection rates between 95 percent to 99 percent.

Reverse osmosis systems have numerous and varied applications ranging from desalination of seawater or brackish water for drinking purposes, food and beverage processing, wastewater recovery, industrial process water and purification of drinking water for domestic home use.

Water being a requisite resource requires its supply to be guaranteed with a reliable and renewable source of energy and one set back of the larger plants which require high-pressure pumps of larger capacities, is in the high operational costs caused by electricity consumed to power the system components.

With an increasing global initiative to go green and embrace more energy efficient systems, institutions have and are investing heavily in research to increase the efficiency of water treatment plants and integrate renewable energy sources such as solar.

Solar reverse osmosis plants offer a great economic advantage in that they reduce reverse osmosis operating cost by up to 50 percent compared to grid or diesel generators. Solar can operate reverse osmosis plants at 100 percent daily design capacity for six to eight hours and if required can use AC power as back up at night in hybrid mode.

This paradigm shift has offered many advantages to numerous individuals and communities who are now able to significantly cut down on operational costs which translates to an overall reduced cost of water per unit.

With the rising popularity of solar powered water treatment plants therefore and with the proper design they will provide a real solution to a real problem faced in many parts of our country.