SOLAR DISINFECTION OF DRINKING-WATER CONTAINED IN TRANSPARENT PLASTICBOTTLES - CHARACTERIZING THE BACTERIAL INACTIVATION PROCESS

A series of experiments is reported to identify and characterize the i nactivation process in operation when drinking water, heavily contamin ated with a Kenyan isolate of Escherichia call, is stored in transpare nt plastic bottles that are then exposed to sunlight, The roles of opt ical and thermal inactivation mechanisms are studied in detail by simu lating conditions of optical irradiance, water turbidity and temperatu re, which were recorded during a series of solar disinfection measurem ents carried out in the Kenyan Rift Valley. Optical inactivation effec ts are observed even in highly turbid water (200 ntu) and at low irrad iances of only 10 mW cm(-2). Thermal inactivation is found to be impor tant only at water temperatures above 45 degrees C, at which point str ong synergy between optical and thermal inactivation processes is obse rved. The results confirm that, where strong sunshine is available, so lar disinfection of drinking water is an effective, low cost method fo r improving mater quality and may be of particular use to refugee camp s in disaster areas. Strategies for improving bacterial inactivation a re discussed.