Effects of reduced return activated sludge flows and volume on anaerobic zone performance for a septic wastewater biological phosphorus removal system

    Authors

    D. Magro; S. L. Elias;A. A. Randall

    Comments

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    Abbreviated Journal Title

    Water Environ. Res.

    Keywords

    phosphorous; wastewater; enhanced biological phosphorous removal; return-activated sludge; anaerobic volume; Engineering, Environmental; Environmental Sciences; Limnology; Water; Resources

    Abstract

    Enhanced biological phosphorous removal (EBPR) performance was found to be adequate with reduced return -activated sludge (RAS) flows (50% of available RAS) to the anaerobic tank and smaller-than-typical anaerobic zone volume (1.08 hours hydraulic retention time [HRT]). Three identical parallel biological nutrient removal pilot plants were fed with strong, highly fermented (160 mg/L volatile fatty acids [VFAs]), domestic and industrial wastewater from a full-scale wastewater treatment facility. The pilot plants were operated at 100, 50, 40, and 25% RAS (percent of available RAS) flows to the anaerobic tank, with the remaining RAS to the anoxic tank. In addition, varying anaerobic HRT (1.08 and 1.5 hours) and increased hydraulic loading (35% increase) were examined. The study was divided into four phases, and the effect of these process variations on EBPR were studied by having one different variable between two identical systems. The most significant conclusion was that returning part of the RAS to the anaerobic zone did not decrease EBPR performance; instead, it changed the location of phosphorous release and uptake. Bringing less RAS to the anaerobic and more to the anoxic tank decreased anaerobic phosphorus release and increased anoxic phosphor-us release (or decreased anoxic phosphorus uptake). Equally important is that, with VFA-rich influent wastewater, excessive anaerobic volume was shown to hurt overall phosphorus removal, even when it resulted in increased anaerobic phosphorus release.

    Journal Title

    Water Environment Research

    Volume

    77

    Issue/Number

    5

    Publication Date

    1-1-2005

    Document Type

    Article

    Language

    English

    First Page

    455

    Last Page

    464

    WOS Identifier

    WOS:000232072600005

    ISSN

    1061-4303

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