EXPERIMENTAL STUDIES ON SOLAR WATER DISINFECTION

Abstract

The present study was undertaken to investigate solar inactivation of bacteria with a view to use the information in effective field application of solar water disinfection. Substantial inactivation (90 - 100%) of bacteria (E. coli, faecal streptococci, total heterotrophic bacteria and ,bacteria on MacConkey agar) was observed in both sewage-spiked ground water and surface water. (Ganga canal water), though surface-water bacteria were slightly more resistant. Except for exposure to low radiation dose (30 min exposure), inactivation was usually found to be irreversible. From practical consideration, E. coli was selected as the indicator for efficacy of the process. Interruption in solar water disinfection process or presence of non-inactivated bacteria in water after first day's exposure would require exposure the next day. Considerable inactivation of E. coli was observed after two days exposure in succession. Turbidity affected, inactivation of both E. coli and the results indicated that turbidity must be reduced to a low value (below 2 NTU) for effective solar water disinfection. Based on the information obtained from the present and previous studies and the solar radiation data, available time range of exposure and time required for effective disinfection of contaminated ground and surface water in different seasons were estimated. Solar water disinfection tests using 0.1% sewage-spiked ground water and Ganga canal water confirmed applicability of the process for effective disinfection.