LARGE-SCALE NITROGEN REMOVAL DEMONSTRATION AT THE BLUE-PLAINS-WASTE-WATER-TREATMENT-PLANT USING POSTDENITRIFICATION WITH METHANOL

The Chesapeake Bay Agreement of 1987 calls for an overall reduction in nutrient loading of forty percent of 1985 levels by the year 2000. Si gnatories to the agreement include the states located in the Bay's wat ershed and the District of Columbia. The District's 16.2 m(3)/sec (370 mgd) Blue Plains Regional Wastewater Treatment Plant is the single, l argest point source of nitrogen load to the Bay, discharging approxima tely 18 metric tons per day. In an effort toward meeting the nitrogen reduction goal, a post-denitrification demonstration study was recentl y begun to access its potential for long-term implementation. The deni trification demonstration project involves operating half of the nitri fication facilities in a nitrification-denitrification mode using meth anol as a carbon source for post-denitrification. The other half conti nues operation in a nitrification-only mode as a control. The post-den itrification process was selected for demonstration because it utilize s existing facilities and may offer substantial long-term cost savings . Objectives of the study are to demonstrate the process without a neg ative impact on effluent quality, to verify performance and capacity, to determine the stability and limitations of the project, and to comp are the process to other nitrogen-removal technologies. Thus far, the process has been successful in removing nitrogen despite problems with phosphorus limitation and with the settling characteristics of the de nitrification sludge. It is believed that insufficient phosphorus avai lability has been responsible for problems associated with settling, s ludge yield, methanol use, and denitrification rates. Recently, phosph orus input to the denitrification process has been increased by reduci ng metal salt addition in upstream processes and preliminary results h ave been promising. If performance criteria are achieved without sacri ficing plant capacity, the process will be continued at full scale. (C ) 1998 Published by Elsevier Science Ltd. All rights reserved.