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IN THE ABSENCE OF THE BLENDING POLICY: A Novel High-Rate Biological Treatment Process.
Author: Jose A. Jimenez, Denny S. Parker, John R. Bratby, Peter F. Schuler, Kevin V. Campanella, Steven D. Freedman
Date: 10/05
WEFTEC 2005 Conference

Infrequent high peak flow events during wet weather can overload wastewater treatment plants. Municipal agencies have often protected their secondary treatment process from washout by bypassing a portion of the influent flow around the process and blending secondary effluent with less treated wastewater (usually primary effluent). In an attempt to rationalize this type of occurrence, EPA proposed a draft Blending Policy in November 2003, which provided conditions under which the blending practice would be allowed. Faced with many negative public comments and resultant opposition in Congress, EPA withdrew the policy in May, 2005. In the absence of the blending policy rule, some municipalities may face future regulatory actions that cause them to eliminate the blending practice and provide for “full” secondary treatment even at peak flows. Wastewater treatment plant expansions to handle these wet weather flow events are typically very expensive, especially given that they are only needed a very small percentage of the time. The Biological Contact process is a novel, cost-effective wet weather treatment technology addressing suspended solids and BOD5 removal by bioflocculation during wet weather, high flow events. Often, it can be implemented in existing wastewater treatment facilities with the fewest modifications to the current plant configuration. And unlike physical/chemical treatment alternatives, it can achieve secondary treatment requirements for both BOD5 and SS.