DUPONT WAYNESBORO CASE HISTORY: DENITRIFICATION MODIFICATION REDUCES OPERATIONS COSTS AND NITROGEN DISCHARGES BY 50%

This presentation discusses the drivers, benefits, implementation, and results of a voluntary modification project at a wastewater treatment plant (WWTP) to reduce nitrogen discharges to the South River at the DuPont Waynesboro manufacturing facility.DuPont manufactures Nylon, Lycra®, and Permasep® at the Waynesboro facility, which generates a high nitrogen content wastewater. Operations Management International, Inc, (OMI), a member of the CH2M HILL Ltd. family of companies, operates and maintains the Waynesboro WWTP, which was designed to remove organic chemicals and nitrogen through an aerobic treatment process (i.e., nitrification). In the aerobic system, organic nitrogen was converted first to ammonia, and then to nitrate, a less toxic form of nitrogen.In 1990, the discontinuation of a product line resulted in excess capacity and tankage at the WWTP, allowing flexibility in operation and system redundancy (i.e., the influent chemical oxygen demand [COD] loading decreased from 19,000 lb/day to 3,500 lb/day). The excess capacity provided an inexpensive opportunity to reduce nitrogen discharges to the South River, a tributary of the Chesapeake Bay, through the modification of the existing WWTP to include nitrate removal through the addition of an anoxic zone (i.e., denitrification).As a strong environmental steward, DuPont’s corporate policy is to drive toward zero emissions and protect and enhance the environment. To assist in protecting the Chesapeake Bay, DuPont – Waynesboro voluntarily committed in the Business for the Bay Program to reduce the nitrate-nitrogen being discharged from the DuPont WWTP by 50%.Added economic benefits of the proposed modification included reduced operational costs through energy reductions (reduction in aeration requirements), chemical reductions (reduction in lime usage for alkalinity), and maintenance cost reductions (reduction in parts, expendables, and labor due to equipment shut-down).The anoxic project enabled DuPont to:Reduce the pollutants being discharged to the environment.Reduce energy costsReduce chemical costsReduce maintenance costsContinue to proactively demonstrate to the community and regulatory agencies the environmental stewardship of DuPont – Waynesboro.DuPont (on-site and corporate), OMI, and OMI's parent company, CH2M HILL, formed the core project team and used outside resources as required during various phases of the project. The primary phases of the project included:Preliminary Feasibility StudiesProcess Design and Equipment SpecificationConstruction/ImplementationCommissioning & StartupThe project was implemented within the estimated budget, significantly below a third party estimate, and is meeting and/or exceeding process expectations by consistently removing more than 50% of effluent nitrogen (based on pre-denitrification data) and reducing O&M costs. The new modifications went online in October 1999.