Biological Phosphorus Removal to Increase Capacity and Simplify Operations

Dublin San Ramon Services District Wastewater Treatment Plant
Dublin, California

While the implementation of enhanced biological phosphorus removal (EBPR) may appear to increase the complexity of the activated sludge process, the improvement and stabilization of activated sludge quality and performance afforded by EBPR actually simplify operational requirements. Moreover, there are design features that can be included to further simplify operation. Presented is a discussion of the design features included in the expansion and upgrade of the Dublin San Ramon Services District Wastewater Treatment Plant, in particular the mixed liquor surface-wasting system for mean cell residence time (MCRT) control. Comparison of operations and performance data before and after the expansion and upgrade project confirm the design intent to simplify operations and improve and stabilize activated sludge quality and performance. Mixed liquor wasting has several benefits compared to conventional RAS wasting. Mixed liquor wasting is effective for precise and accurate MCRT control needed to allow EBPR and minimize nitrification in high-rate activated sludge systems, such as used at the DSRSD WWTP. For any type of activated sludge system, mixed liquor wasting provides a simple means of MCRT control – the aeration tank volume and target MCRT are all that are needed to calculate the waste sludge flow rate. Combined with a classifying selector, nocardioforms are quite effectively controlled. Operations and performance data from the DSRSD WWTP following EBPR implementation demonstrate that average effluent total phosphorus concentrations less than 1.0 mg/L are easily achieved with concurrent low effluent suspended solids concentrations. The design features included for MCRT control and nuisance foam and scum control have simplified activated sludge operations. Although granular media filtration for recycled water production was not considered during design of the plant expansion and modifications, the EBPR system produces a high-quality, filterable effluent. Source: WEFTEC 2009 Proceedings

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Posted: August 27th, 2010 | Filed under: Waste Water Treatment | Tags: Biological Phosphorus Removal, Environmental Impact, Increased Plant Capacity, Plant Optimization | No Comments »

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