Full-scale demonstration of improvement in aeration efficiency

This paper describes the results of side-by-side full-scale aeration testin g of a plug-flow process and a modified contact stabilization process incor porating an anaerobic selector at the wastewater treatment facility in Fred onia, N.Y. Over 40 tests were completed utilizing the off-gas technique dur ing the 2-month investigation period (summer of 1995). Compared to the plug -flow process, the modified contact stabilization process with internal slu dge recycle was shown to have higher or values and to require less blower e nergy consumption when the selector operation was properly controlled. Diss olved oxygen concentration, selector COD concentration, and internal recycl e sludge levels were found to be critical parameters in the successful oper ation of the modified process. Higher internal recycle sludge levels allowe d the plant to run at more stable operating conditions in terms of the oxyg en transfer efficiency, alpha, and sludge volume index.