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Evaluation of oxygen transfer efficiency and alpha-factor on a variety of diffused aeration systems

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Because the aeration system in an activated sludge wastewater treatment plant typically represents more than 50% of total plant energy requirements, designers and operators can substantially reduce overall plant energy costs by using accurate oxygen transfer information to make the aeration system as energy efficient as possible.

This paper presents data from 65 off-gas analysis tests performed at 21 wastewater treatment plants. The effect of various factors on oxygen transfer was evaluated by comparing pairs of tests in which all factors but one were held relatively constant. Factors evaluated were diffuser type, diffuser layout, diffuser age, solids retention time, and level of nitrification. Flexible membrane diffusers had more than a 30% higher oxygen transfer efficiency than coarse bubble diffusers. Grid layouts had higher oxygen transfer efficiencies than spiral roll layouts. Flexible membrane diffusers that were 3.5 years old had a 20% lower oxygen transfer efficiency than new flexible membrane diffusers. Systems at low solids retention times that were not nitrifying had lower oxygen transfer efficiencies than nitrifying systems at high solids retention times. For some wastewater systems, use of this information on solids retention time in plant design and operation can decrease overall energy costs despite the additional oxygen required to meet the nitrogenous oxygen demand.

Keywords: activated sludge; analysis; diffused aeration; off gas; oxygen transfer

Document Type: Research Article


Publication date: July 1, 1992

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  • Water Environment Research® (WER®) publishes peer-reviewed research papers, research notes, state-of-the-art and critical reviews on original, fundamental and applied research in all scientific and technical areas related to water quality, pollution control, and management. An annual Literature Review provides a review of published books and articles on water quality topics from the previous year.

    Published as: Sewage Works Journal, 1928 - 1949; Sewage and Industrial Wastes, 1950 - 1959; Journal Water Pollution Control Federation, 1959 - Oct 1989; Research Journal Water Pollution Control Federation, Nov 1989 - 1991; Water Environment Research, 1992 - present.
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