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State Water Resources Control Board Division of Water Quality GAMA Program REMEDIATION AND TREATMENT TECHNOLOGIES Bacteria can be removed from water by disinfection and/or filtration. While filtration alone may not be effective in completely removing bacteria, it does improve the performance of disinfectants by eliminating sediment that may house bacteria. Disinfecting methods include chlorination, iodization, ozonation, ultraviolet (UV) light and physical methods such as boiling or steam sterilization. Depending on the source and use of a water supply, disinfection can be used occasionally over short periods or continuously. The following treatment methods are simple and do not require special equipment or setup: • Boiling water for one minute. • Adding two drops of unscented household bleach to each liter (quart) of water, and letting the water/bleach mixture stand for 30 minutes. • Using water purification tablets that release iodine or chlorine. There are several devices that can be installed within the main water supply system that can treat water prior to distribution: • Chlorinators: Chlorination is the most common water treatment process used worldwide. Chlorine kills most bacteria and viruses, but may be less effective on waterborne parasites such as Giardia and Cryptosporidium. Chlorine may also react with organic material present in the water, releasing byproducts such as trihalomethanes (THMs). There may be some chronic health risk associated with THMs. • lodinators: Iodine is effective but should be used for emergency or occasional use only. Iodine is physiologically active and ingestion in high concentrations may be harmful over long time periods. • UV Devices. Exposure to UV light is effective in eliminating bacteria, viruses, and protozoa. However, UV light does not ensure the safety of the water beyond the exposure area. • Filters. Ceramic or glass fiber filters can remove bacteria and protozoa, but not viruses. Filters should be used in conjunction with disinfection. • Ozonators. Ozone is effective in eradicating pathogens over short time period. Ozone breaks down fast and cannot be used to maintain disinfection throughout a large public distribution system. • Reverse Osmosis: Reverse osmosis systems are effective in eliminating bacteria and most viruses. However, bacteria may grow within the system itself, and in general RO systems are not recommended as the sole method of disinfection. • Distillation: Distillation is effective in reducing the level of all pathogens in drinking water. Revised September, 2019 6