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The City and County of San Francisco (“City”) embarked upon a 30-year master planning process in part prompted by public concerns related to the neighbourhood impacts of the Southeast Water Pollution Control Plant (SEP). The Sewer System Master Plan, as it is called, developed a long term Integrated Urban Watershed Management Plan for the City's treatment plants and collection system. This paper focuses on the planning framework and public input to the process, particularly as it relates to proposed changes to the SEP. The resulting improvements address issues of replacing aging infrastructure, eliminating odor emissions, and visually screening the treatment plants that are situated within an urban setting. The recommended project addresses the needed repair of the existing infrastructure; and proposes that the City move towards an integrated urban watershed approach, initially through localized rainwater harvesting and opportunistic water reclamation.

A study at the Southeast Water Pollution Control Plant, San Francisco, California, was undertaken to evaluate the feasibility of replacing its current secondary effluent chlorination system with a 6.57 m 3 /s ultraviolet (UV) disinfection system. Two vertical lamp units and one horizontal lamp unit were pilot tested in parallel. The effective UV dose for coliform removal and the effects of feedwater characteristics and reactor hydraulics were examined. The horizontal pilot unit gave a more consistent performance than the vertical pilot units. Based on the test results, a UV dose of 65 mW s/cm 2 would be required for the plant to achieve the target effluent total coliform level (240 CFU/100 mL) 95% of the time. The large fluctuation of UV disinfection results could be attributed to the wide range of feedwater quality inherent to a combined sewer system. High suspended solids, characteristic of the plant's secondary effluent during storm events, significantly increased the UV dose required to achieve the target coliform level. Existing UV inactivation models were evaluated. The hydraulic behavior of the pilot units was found to significantly affect their test results. Higher virus removal efficiency was observed with the UV systems than the full-scale chlorination system.

The City and County of San Francisco embarked on a 30 year master planning process in part prompted by public concerns over environmental justice related to the neighborhood impacts of the Southeast Water Pollution Control Plant. The Sewer System Master Plan, as it is called, developed a long term Integrated Watershed Management Plan for the City's treatment plants and collection system. This paper will focus on the planning framework and public input to the process and how the master plan of 2009 evolved into the current implementation plan, the Sewer System Improvement Program. The paper describes the public process and public concerns; and compares the master plan project recommendations with the implementation projects.

Solids retention time (SRT), biological scum trapping and recycle, and the dynamic equilibrium between Nocardioform populations in the foam and the mixed liquor are the controlling factors in activated sludge foaming events caused by Nocardioform bacteria. For the operating modes described in this paper, a cured mixed liquor foaming condition (filament counts of approximately 10(5) intersections/g volatile suspended solids) was only achieved when SRT control, selective wasting, and polymer addition were in effect. Solids retention time control, with the SRT remaining below 1.5 days, and selective wasting will cure a severely foaming mixed liquor, but effects will only be observed after 3 or 4 months after implementation. The combined wastage of Nocardioform bacteria from selective wasting and SRT control can ensure long-term foam control to the operation of a pure-oxygen activated sludge system with foam-trapping features. An SRT of 0.3 days will result in the complete washout of Nocardioform bacteria from the activated sludge system, which can then operate at an SRT of 3 days free of Nocardioform. Polymer addition to mixed liquor is only effective for foam control when a large portion of the system biomass exists as a heavy layer of foam above the mixed liquor.