AWWA MTC69747

This powerpoint presentation begins by providing a brief overview of Zone 7 of Alameda County Flood Control and Water Conservation District and its three treatment facilities that serve the Tri-Valley area (Livermore, California) that include: Patterson Pass Water Treatment Plant (WTP), 21.5 mgd; Del Valle WTP, 36 mgd; and, Altamont WTP, 24 mgd (in design). The purpose of evaluation was to: identify options to optimize the ultrafiltration (UF) WTP operation and more reliably meet its existing capacity of 8 million gallons per day (mgd); identify alternatives for increasing the UF WTP capacity to 10-12 mgd; and, identify improvements for the conventional plant. The approach included: a review of historical data; an on-site evaluation of operation; and, bench-scale testing. The issues identified included: diurnal pH and temperature fluctuations; algae growth in the Patterson Pass Reservoir and in the solids contactor; return of neutralized citric acid from the washwater recovery system; membrane feed water quality; irrecoverable loss of membrane permeability; DHS flux limit; excessive backwash volume and reduced recovery; scheduling of backwashes, direct integrity tests, weekly cleanings; DIT fails to accurately predict broken fibers; recent excessive fiber breaks; weekly cleaning procedures include manual steps; limited indication on HMI; inlet and backwash valve failure; and, originally-installed Asi-networked control units are no longer available. Presentation conclusions indicate the following: replacement of membranes have dramatically improved reliability; operations diligence has resolved many of the issues; now able to meet rated production of plant; and, start-up conditions may have contributed to membrane performance issues. Includes tables, figures.