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Evaluation of Ceramic and Membrane Diffusers under Operating Conditions with the Dynamic Offgas Method

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The aeration systems of two full-scale, activated-sludge basins were compared during a period of three years, under the same operating conditions, using dynamic offgas testing. Only the material of the diffuser was different (membrane versus ceramic-tube diffusers). The investigation has shown that, although the membrane diffusers have higher initial standard-oxygen-transfer efficiency (αSOTE) and standard-aeration efficiency (αSAE), these decreased over time, while the αSAE of the ceramic diffusers started lower, but increased slightly over the whole period.

A cost comparison makes clear how important it is to evaluate the aeration system under process conditions. The operating costs were the dominant factor (∼10× higher than capital costs), and operating costs were approximately 20% higher for membrane versus ceramic diffusers. The poor performance of the membrane-tube diffusers under process conditions could be explained on the basis of the actual αAE values in the basin, not the standardized values.

Keywords: activated sludge; aeration efficiency; capital costs; ceramic diffuser; membrane diffuser; offgas testing; operation costs; oxygen transfer

Document Type: Research Article


Publication date: September 1, 2005

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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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