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Innovative Operating Strategy Helps Meet Challenging NOx Limits

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The Metro Wastewater Reclamation District in Denver, Colorado (Metro) operates the 220-mgd (maximum month) Robert W. Hite Treatment Facility (RWHTF) that includes two separate primary and secondary complexes with combined solids treatment. The two secondary complexes are operated in different modes, with the north secondary complex (NSEC) air activated sludge process being operated in nitrification-denitrification mode, and the south secondary complex high-purity oxygen activated sludge process being operated for carbonaceous BOD removal only. The effluent criteria for discharge, which are applied on the combined RWHTF final effluent, include monthly limits for ammonia (ranging from 9.7 mg/L to 15 mg/L), and a weekly maximum limit of 8.68 mg/L for NOx (nitrates plus nitrites). Weekly maximum NOx limits are relatively rare in the industry, and this one, which took effect on March 1, 2008, posed some unique operating challenges. This paper describes the innovative operating strategy developed by Metro to address these challenges. Key elements of the strategy included the development of compliance profiles using online monitoring and the implementation of corrective action plans to meet the prescribed limits.

Document Type: Research Article


Publication date: January 1, 2008

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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