AWWA MTC61183

The Yucaipa Valley Water District (YVWD) is currently designing a 12 MGD Water Treatment Facility. The Yucaipa Valley Regional Water Filtration Facility (YVRWFF) will treat State Project Water (SPW) that can be augmented by water from the Santa Ana River and the Mill Creek. The YVRWFF will provide an additional source of drinking water for the YVWD, which currently relies on groundwater to meet the water demand. Microfiltration has been selected as the filtration process because it provides a physical barrier that removes particulate matter and bacteria without chemical pretreatment. This paper details the efforts by the District to investigate low rejection nanofiltration membranes for the removal of DBP precursor material. The Yucaipa Valley Water District currently has approximately 40 wells producing potable water. The well water is low in total organic carbon (TOC) and YVWD uses free chlorine in the distribution system to maintain a secondary disinfection residual. SPW contains moderate amounts (3 to 5 mg/L) of TOC. This is a concern to YVWD, as they will soon be treating surface water with a moderate TOC level that will form DBPs. Microfiltration is not very effective at reducing TOC and other species that can contribute to DBPs. Therefore, YVWD examined ways to reduce the formation of DBPs of the treated surface water that included: using chloramines versus free chlorine in the distribution system to maintain a secondary disinfection residual; and, using nanofiltration (NF) membranes to treat a portion of the MF filtrate water. An NF system operating on MF treated water has the potential to produce water that is both low in hardness and low in DBP formation potential. This study produced data on various types of commercially available NF membranes to obtain information on their removal properties and assess their applicability to treat State Project Water. Includes tables, figures.