A simulated distribution system (SDS) method has been developed to predict the amounts of disinfection by-products (DBPs) that would form in a distribution system. The parameters (chlorine dosage, incubation temperature, and incubation holding time) of the method are chosen to simulate the conditions of the treatment plant and the distribution system. A study was conducted on the Metropolitan Water District of Southern California's distribution system at a time when free chlorine was being used in the distribution system. A second study was conducted on water from a utility in the eastern United States. Both studies showed good correlation between the SDS samples and the samples collected from the distribution systems.

The Metropolitan Water District of Southern California is evaluating the hydrogen peroxide‐ozone (PEROXONE) advanced oxidation process (followed by secondary disinfection with chloramines) for removal of taste and odor compounds, control of disinfection byproducts (DBPs), and inactivation of microorganisms. This article reports the results of pilot‐scale testing designed to optimize the H2O2:O3 ratio and to compare ozone and PEROXONE at different contact times. The tests described represent one phase of a five‐phase PEROXONE pilot‐scale study for treating water from the California State Water Project and from the Colorado River. Results to date indicate that the PEROXONE process requires a significantly lower applied ozone dosage to oxidize 2‐methylisobomeol and geosmin as compared with ozone alone. The levels of DBPs formed when ozone or PEROXONE is used (followed by chloramines) are low, and PEROXONE (at H2O2:O3 ratios of ≤0.3) is comparable with ozone for the inactivation of microorganisms.

Motorized recreational watercraft were the predominant mode of contamination in reservoirs. Methyl tertiary butyl ether (MTBE) is a common fuel oxygenate used in motor vehicle fuels to control emissions and boost octane. It is more water‐soluble than other fuel constituents and does not adsorb well to substrates such as soil. It can contaminate groundwater supplies through leaking underground fuel storage tanks and pipelines, and through spills, urban storm runoff, and precipitation. It can also contaminate open water reservoirs through exhaust from motorized watercraft. The Metropolitan Water District of Southern California surveyed six reservoirs that supply drinking water in Southern California. Recreation on these reservoirs ranged from none at all to high activity with personal watercraft. It was found that motorized watercraft can contribute a significant amount of MTBE to the water supply.

Results from two national surveys indicate that the gasoline oxygenate methyl tertiary butyl ether (MTBE) is one of the most frequently detected volatile organic compounds in source waters used by community water systems in the United States. Three other ether oxygenates were detected infrequently but almost always co‐occurred with MTBE. A random sampling of source waters across the United States found MTBE in almost 9% of samples. In geographic areas with high MTBE use, the compound was detected in 23% of source water samples. Although MTBE concentrations were low (<1 μg/L) in most samples, some concentrations equaled or exceeded the drinking water advisory of 20 μg/L set by the US Environmental Protection Agency. The frequent detection of even low concentrations of MTBE demonstrates the vulnerability of US source waters to anthropogenic compounds, indicating a need to include MTBE in monitoring programs to track the trend of contamination.

A pilot-scale study of ozone and PEROXONE (ozone in combination with hydrogen peroxide) for the removal of the odorous compounds 2-methylisoborneol (MIB) and geosmin in drinking water has been conducted at the Metropolitan Water District of Southern California. The study investigated the effects of ozone dosage, ratio of hydrogen peroxide to ozone (H202/03), and contact time. It was found that MIB and geosmin removal increased with higher applied ozone doses, but longer contact times over the range of 6-12 min were not significant. It was determined that 80-90 percent removal could be achieved with an ozone dose of approximately 4.0 mg/l, as compared to an ozone dose of approximately 2.0 mg/l at a H202/03 ratio of 0.2. Also investigated were the effects of alternative contactor configurations, ferrous sulfate as an alternative coagulant, bromide and ammonia addition, and simulated turbidity on the removal efficiencies of the two odorous compounds.