Full-Scale Demonstration of Improvement in Aeration Efficiency

This paper describes the results of side-by-side full-scale aeration testing of a plug-flow process and a modified contact stabilization process incorporating an anaerobic selector at the wastewater treatment facility in Fredonia, N.Y. Over 40 tests were completed utilizing the off-gas technique during the 2-month investigation period (summer of 1995). Compared to the plug-flow process, the modified contact stabilization process with internal sludge recycle was shown to have higher (alpha)values and to require less blower energy consumption when the selector operation was properly controlled. Dissolved oxygen concentration, selector COD concentration, and internal recycle sludge levels were found to be critical parameters in the successful operation of the modified process. Higher internal recycle sludge levels allowed the plant to run at more stable operating conditions in terms of the oxygen transfer efficiency, (alpha), and sludge volume index.