WRRCSR No. 7.2:85 Exploratory Study Using Water Disinfectants to Remove EDB from Clean Water

Abstract

A reliable and practical method is required to reduce the concentrations of hazardous chemicals (EDB, DBCP, TCP) which have been detected in some of the groundwaters used for drinking on O'ahu. This study evaluates the feasibility of using high concentrations of water disinfectants to oxidize (reduce) the concentrations of EDB in water. Water seeded with 100 ppt to 20 ppb of EDB were treated with various doses of disinfectants (chlorine, chlorine dioxide, hydrogen peroxide, ultraviolet light, ultraviolet light plus hydrogen peroxide). The concentrations of ED3 in water samples before and after treatment with these disinfectants were determined using liquid-liquid partitioning to extract the EDB and gas chromatography to measure the concentrations of EDB. The results of this study indicated that 5 to 5,000 mg/l of chlorine and 2 to 50 mg/l of chlorine dioxide are incapable of reducing the concentrations of EDB in water. The ability of 3 and 10% hydrogen peroxide to reduce the concentrations of EDB in water was erratic. In some experiments, no reduction of EDB was observed while in other experiments up to 45% of the EDB was apparently oxidized. Ultraviolet (UV) light alone removed only 10% of the EDB. The most promising system was the use of UV light plus 3 or 10% hydrogen peroxide. When this system was used, 33 to 75% of the EDB in the water was reduced. Thus, further studies assessing the feasibility of using UV light and hydrogen peroxide to remove and other toxic chemicals in water is recommended. However, hydrogen peroxide is available in a liquid state at 30% and therefore it is impractical to treat large volumes of water with high concentrations of hydrogen peroxide. In this regard, ozone is chemically similar to hydrogen peroxide but is more reactive. Ozone can also be generated as a concentrated gas and apparatus for the treatment of large volumes of water with UV light and ozone is commercially available. It is therefore recommended that further studies be done to determine the feasibility of using UV light and ozone to remove the concentrations of EDB in water.