Title

Effects Of Reduced Return Activated Sludge Flows And Volume On Anaerobic Zone Performance For A Septic Wastewater Biological Phosphorus Removal System

Keywords

Anaerobic volume; Enhanced biological phosphorous removal; Phosphorous; Return-activated sludge; Wastewater

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 phosphorus 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.

Publication Date

1-1-2005

Publication Title

Water Environment Research

Volume

77

Issue

5

Number of Pages

455-464

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.2175/106143005X67368

Socpus ID

25644455117 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/25644455117

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