Chemical and economical evaluation of groundwater treatment plants in Riyadh

The capital of Saudi Arabia, Riyadh is supplied with drinking water from both treated groundwater and desalinated sea water. Groundwater contributes about 35% to the total water supply and is treated in six treatment plants containing cooling, softening, filtration, reverse osmosis and posttreatment processes. An extensive two and a half years study aimed at the evaluation of Riyadh water treatment plants performance and the investigation of chemical treatment alternatives has been undertaken. The work involved an evaluation of the plants chemical treatment in which the effectiveness of softening chemicals was investigated by conducting jar test, pilot plant and full-scale implementation experiments. The results indicate that by optimizing the currently used chemicals it is possible to save 19% in chemicals cost or approximately million SR 3.71 a year. Caustic soda can be a competitive alternative in four plants replacing lime, soda ash and sodium aluminate. Moreover, there is a great potential of saving million SR 7.04 a year at the largest plant by simple pH-adjustment using sulfuric acid for the purpose of water stabilization.