Two surface water sources in the southwestern United States, Colorado River Water (CRW) and California State Project Water (SPW), were studied in bench-scale experiments examining two Trihalomethane (THM) precursor removal processes, activated carbon adsorption and ozone oxidation. Both source water contained bromide (Br-) ion leading to brominated THMs upon chlorination. Activated carbon removed THM precursors, as measured by dissolved organic carbon (DOC), while having little effect on bromide. The net result was an increase in the ratio of Br-/DOC and an increase in the relative abundance of brominated THMs. Ozone oxidized higher molecular weight precursor molecules into lower molecular weight by-products which were less reactive with chlorine. Moreover, ozonation transformed Br- to hypobromous acid (an "in-situ" oxidant), leading to an increase in the percentage of brominated THMs.

Pollution from nonpoint sources is a leading cause of receiving water quality impairment. The largest source of nonpoint pollution is storm water runoff, which includes pollutants such as sediment, nutrients, metals, microorganisms, and organic compounds. Sediment is of particular importance because many pollutants are readily 5 adsorbed onto particles. In the Lake Tahoe basin, sediment is also significant because of its direct contribution to clarity attenuation. The most prudent control measure for mitigating sediment flux in the Lake Tahoe basin is infiltration, which captures runoff volume, allowing it to percolate into the soil and enter groundwater. All residential parcels in the Lake Tahoe basin are required to have an on-site infiltration system. These systems require rigorous maintenance to maintain full function. Negligence can lead to premature clogging from debris and accumulated sediment, and the cost of rehabilitating or replacing the system can be significant to homeowners. It is mandatory for a sediment trapping device to be installed to pretreat runoff discharged into the infiltration system; however, there is limited infomation regarding sediment trapping devices designed for residential use. The objective of this research was to evaluate the performance of an on-site stormwater treatment device in removing sediment from simulated stormwater runoff. The sediment trapping device consists of removable, porous 200-micron nylon inserts for filtration and is designed to mitigate premature clogging infiltrative runoff control measures. Laboratory analysis of a full scale device model was performed. Removal efficiency, effluent concentration, and bulk solids removal were assessed for perfomance evaluation. The device demonstrated a median removal efficiency from grab samples of 74%, median total suspended solids effluent concentration of 72 mg/L, and removed 89% of the total solids introduced into the system. Economic and sustainability implications of the device were also assessed.