Quantitative Assessment of Disinfection By-Products Formed by Chlorine, Chlorine Dioxide and Ozone in Saudi Arabian Drinking Water

Abstract

This study investigates the effect of different disinfectants on desalinated water blended with raw ground water at different ratios. The study was conducted in three (3) parts namely: chlorination, chlorine dioxide and ozonation. The by-products resulted from these disinfection processes were quantified under different treatment conditions of disinfectant dosage, temperature and reaction time. The correlation between the type of by-products formed and the quality of the source water (desalinated seawater and groundwater) were also investigated in this study. In the first part, the study with chlorine revealed that total Trihalomethanes (TTHMs) formation increases 0 to 247 ppb as chlorine dosages increases from 1 to 5 ppm. The blending ratio of 1:10 (v/v, raw: desalinated) showed the lowest TTHMs formation at chlorine dosage of 1, 2 and 5 ppm. Results showed an increase of TTHMs formation with increasing both reaction time and temperature. In the second part, low chlorite levels resulted from chlorine dioxide disinfection of blended water with mixing ratios of 1:2 and 1:5 was found to increase with dosage of 1 to 5 ppm. But, chlorite species were not detected at blending ratio of 1:10. Finally, in the third part of the study, results showed that bromate formation increased with increase in ozone dosages from 2 to 5 ppm and increase in temperature from 25 to 45oC and reaction time from 5 to 20 min. Significant high levels of bromate were observed in water samples blended with a blending ratio of 1:2, while other blended ratios did not show significant formation of bromate.