As energy costs continue to increase and effluent permits become more stringent, process control has become one of the most important components of the operations of activated sludge processes. Utilizing a process controller that adjusts the dissolved oxygen (DO) set points based on real time influent loading can result in significant energy savings at a biological nutrient removal wastewater treatment plant (WWTP). This paper presents two case studies of plants that implemented such a control system. At the Metropolitan Wastewater Reclamation District's Robert W. Hite Treatment Facility in Denver, Colorodo, an average of 11% less air was used when using the process controller compared to fixed DO set-point control. At the Liuwei WWTP, located in Yangzhou, Jiangsu Province, China, the plant achieved an energy savings of 21.0% using a process controller compared to fixed aeration.
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