Chlorine Disinfection of Ground Water Obtained from 200M Deep Wells

The effect of chlorine concentration, ground water pH, and contact time on chlorine demand and the inactivation of coliform bacteria, Escherichia coli , was studied in the laboratory using a batch reactor under controlled environmental conditions. Ground water for this study was obtained from 200m deep wells in Bangkok, Thailand. The test results demonstrate that the kinetics of chlorine inactivation of coliforms in ground water consist of an initial rapid kill rate followed by a slower rate. Disinfection was more effective in acidic pH (5.5) than basic pH (8.5). Chlorine demand exerted by ground water increased with chlorine dose, contact time, and hydrogen ion concentration. Based on the applied chlorine dose, inactivation of E. coli by chlorine at neutral pH and room temperature was over two orders of magnitude less effective in ground water than in demand-free water. Because of the high chlorine demand exerted by this ground water, chlorine residuals leaving the treatment plant are likely to be unstable.