Optimizing the Conversion to Step-Feed Biological Nitrogen Removal Reduces Nitrogen Credit Costs

摘要

The Metropolitan District Commission operates four wastewater treatment plants serving the cityrnof Hartford Connecticut and its surrounding communities and which are located in the LongrnIsland Sound (LIS) watershed. The LIS Comprehensive Conservation and Management Planrnadopted by Connecticut, New York and the USEPA calls for a basin-wide reduction of nitrogenrnfrom 1999 through 2014. Connecticut enacted a nitrogen trading program for more costrneffective nitrogen removal. The District implemented an interim upgrade based on step-feedrnbiological nitrogen reduction for the 303 ML/d (80 mgd) Hartford Water Pollution ControlrnFacility. The interim upgrade provided cost effective benefits of maximizing use of existingrntankage and rapid implementation. After more than two years of operation the step-feedrnconversion reduced both effluent nitrogen and cost of nitrogen credit purchase. These resultsrnreflected the dedication of the plant staff to address challenges following startup and to developrnoperating strategies to optimize the treatment process.