Full Description

Zone 7 of Alameda County Flood Control and Water Conservation District ownsand operates the Patterson Pass WTP. The conventional plant's process consistsof upflow clarification followed by dual media filtration, with a maximum designcapacity of 13.5 mgd. In an effort to increase the plant's capacity, it was expandedby adding a solids contact clarifier and an Aquasource membrane filtration system.The 8 mgd addition, ultrafiltration WTP, began operating in 2003. Although the UF planthas consistently produced an effluent of acceptable quality, the system hasexperienced difficulties related to operation and meeting its capacity. Anevaluation was conducted to identify options to optimize the UF WTP operationand to more reliably meet its 8 mgd capacity, and to identify alternatives forincreasing the capacity to 10-12 mgd. The evaluation consisted of reviewingoperating data and conducting a site visit to gather information about the plantoperating procedures and past performance. Issues were identified that createoperating difficulties and ultimately restrict the ability of the system to reliablymeet its 8 mgd design capacity. One of the key issues identified is failure of thewater quality from the pretreatment unit to meet the membrane feed water qualityrequirements, primarily the iron concentrations which exceed the membranewarranty limits. In addition, issues such as diurnal pH fluctuations, algae growth,and return of neutralized citric acid cause process upsets that increase the iron andparticle loading on the membranes. Analysis of the membranes has shownirrecoverable fouling (loss of permeability) and accelerated aging of themembranes, which have been linked to elevated iron concentrations. Includes tables, figure.

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Edition: Vol. - No. Published: 03/01/2007 Number of Pages: 10File Size: 1 file , 380 KB