AWWA WQTC71348

The San Francisco Public Utilities Commission (SFPUC) plans to expand the sustainable capacity of its Sunol Valley Water Treatment Plant (SVWTP) from 120 mgd to 160 mgd in order to meet the level of service goals of its $4.3 billion Water System Improvement Program. Key components of the plant expansion are construction of a new chlorine contact tank (CCT) and a new 17.5 million gallon treated water reservoir (TWR). The purpose of the CCT is to ensure adequate disinfection at higher plant flows and to minimize disinfection byproduct formation by controlling the time in which the water is in contact with free chlorine. The size of the CCT needs to be minimized to minimize construction costs, and this analysis was used to determine how small it could be while still meeting disinfection requirements. The size of the TWR was determined by an analysis of demand patterns. The treated water from the SVWTP will be chloraminated between the CCT and the TWR. Issues related to the TWR were configuration of the inlet and outlet, which also impact construction costs, and minimization of stagnant zones, which could contribute to nitrification and resultant loss of chloramine residual. This paper summarizes the results of computational fluid dynamics (CFD) modeling to predict the hydraulic characteristics of the proposed CCT and TWR. Includes 4 references, tables, figures.