AWWA MTC64625

In 2002, the Modesto (California) Irrigation District (District) set out on a program to expand their existing treatment works. The process, designed in the early 1990s, was state of the art at the time, consisting of pre-ozonation, flocculation/sedimentation, and deep-bed monomedia anthracite filtration. The process has worked effectively since start-up in late 1994 and treats a relatively high quality surface water. During pre-design studies in 2003, Operations and Maintenance staff suggested consideration of membrane filtration for the Phase II expansion of the Modesto Regional WTP, from 36 to 72 million gallons per day (mgd). Operational reliability and the lack of chemical pretreatment were two of the reasons cited for expanding the facility with membrane filtration technology. This paper discusses the treatment process selection, integration into the existing process, and recommended staffing requirements for the expanded plant with a firm summertime production capacity of 72-mgd with forward flow capability of over 85- mgd. Includes tables, figure.