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A Control System to Optimize Biological Nutrient Removal

This Small Business Innovation Research Phase I project will investigate the feasibility of an automated process control system for optimizing biological nutrient removal wastewater treatment plants. Nitrogen and phosphorus removal is needed at many municipal wastewater treatment plants (WWTPs) to control problems of algae and plant growth in receiving waters. This is of special concern in certain coastal areas, around the Great Lakes and in other locations around the U.S. Chemicals have been used at hundreds of plants for phosphorus removal, but an alternative is to use biological phosphorus removal designs that promote the growth of bacteria with high phosphorus storage capacity. Biological phosphorus removal has many advantages over chemical addition, including cost and less sludge production. However when biological phosphorus removal is combined with biological nitrogen removal systems, phosphorus removal efficiencies may be lower than required and chemicals are still used. This problem discourages other facilities from changing to biological phosphorus removal designs. The lower phosphorus removal efficiency may be due to release of phosphorus in the nitrogen reduction zones of combined nutrient removal systems. This release, termed secondary phosphorus release, is related to the inflexibilities of current process designs, and lack of a control system to respond to plant load variations. The purpose of this proposed Phase I research is to study factors that affect secondary phosphorus release, so that a control system can be developed to prevent it. Bench-scale reactors will be set up at the Yakima, WA. WWTP to study operating conditions and factors that affect the rate and extent of secondary phosphorus release. Full-scale combined biological nutrient removal facilities will also be visited to conduct tests on secondary phosphorus release.

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