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It's Getting Clearer: A New View of Seasonal Changes in Secondary Sedimentation Linked to Variable Biomass Density

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Seasonal variations in activated sludge settleability were evaluated in six full scale wastewater treatment facilities in Central New Mexico, with special attention to the role of biomass density (mass per biomass volume) on settling. Recent work has demonstrated that varying biomass density may play an important role in activated sludge settleability, with plant configuration and operation both affecting density. Density was found to vary seasonally, and was highest in the summer in the four activated sludge plants studied, but there was little variability in two membrane bioreactor systems. Both density and filament content affected settleability. Seasonal variations in non-volatile suspended solids apparently contributed to the observed variations in density. These result should help plants understand factors affecting seasonal variability in clarifier performance, in addition to other known phenomena such as changes in filament content and temperature effects on water characteristics.

Keywords: Density; phosphorus; secondary sedimentation; settleability

Document Type: Research Article


Publication date: 2009-01-01

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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