Residual Chlorine Removal Method to Allow Drinking Water Monitoring by Biological Early Warning Systems

摘要

Aquatic biomonitors can provide continuous, real-time monitoring for toxicity in source water supplies, but they cannot be used to directly monitor chlorinated drinking waters because of aquatic organism sensitivity to residual chlorine. The threshold for a toxicity alarm by a biomonitor using bluegills (Lepomis macrochirus) was between 0.015 and 0.066 mg/L total residual chlorine (TRC). A portable dechlorinator that injected 6 mg/L sodium bisulfite into water containing 1.5 to 2.0 mg/L TRC was effective in removing TRC-related toxicity during a nine month evaluation at a water treatment plant. Three biomonitor alarms that occurred were not caused by dechlorinator malfunctions. In one-hour laboratory exposures to sodium bisulfite alone, the biomonitor did not respond until concentrations exceeded 48 mg/L. This study demonstrated the feasibility of using a biomonitor in conjunction with a portable dechlorinator for continuous monitoring of chlorinated drinking waters. Future studies should evaluate dechlorinator suitability in waters with total organic carbon levels exceeding 2 mg/L or that have been disinfected with chloramines.