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 city of Hartford Connecticut and its surrounding communities and which are located in the Long Island Sound (LIS) watershed. The LIS Comprehensive Conservation and Management Plan adopted by Connecticut, New York and the USEPA calls for a basin-wide reduction of nitrogen from 1999 through 2014. Connecticut enacted a nitrogen trading program for more cost effective nitrogen removal. The District implemented an interim upgrade based on step-feed biological nitrogen reduction for the 303 ML/d (80 mgd) Hartford Water Pollution Control Facility. The interim upgrade provided cost effective benefits of maximizing use of existing tankage and rapid implementation. After more than two years of operation the step-feed conversion reduced both effluent nitrogen and cost of nitrogen credit purchase. These results reflected the dedication of the plant staff to address challenges following startup and to develop operating strategies to optimize the treatment process.