ENHANCED NUTRIENT REMOVAL AND RECYCLING OF WASTEWATER IN THE ORGANIC CHEMICALS INDUSTRY

The DuPont plant at Hamm-Uentrop, Germany supports multiple business units producing polyester and nylon fibers, polyamide and polyester flakes for use in molding and extrusion, and laminating plastic layers for safety glass and other applications. The site purchased 800,000 cubic meters (m3) of water annually for production uses and until recently discharged about 600,000 m3 of treated wastewater into a nearby river. The site's activated sludge wastewater treatment plant was recently modified to allow recycle of nearly 90 % of this chemical plant's wastewater while also reducing the pollutant load to the nearby river. Wastewater recycling was achieved through addition of a novel dead end membrane filtration unit followed by a multi-staged refining train consisting of granulated activated carbon (GAC) polishing, ultraviolet (UV) disinfection, reverse osmosis (RO) and ion exchange (IE). An integrated pilot unit was used to establish the feasibility of the approach. A key aspect of the wastewater recycling system is reduction of pollutant loading on the nearby river. Without incorporation of a few key operations, pollutant loadings would not decrease much as a result of recycling alone since the membrane based system requires disposal of a reject stream. These real reductions are achieved through operation of an Alternating Aerobic Anoxic (AAA) Sludge Process in wastewater treatment for reducing nitrogen loading, ferric chloride addition for insolubilization and removal of soluble phosphorus loading, the membrane system to reduce suspended solids and the GAC beds for reducing organic loadings. This paper discusses the performance of the water recycling system in general since full-scale implementation, but focuses primarily on the performance of the nutrient and pollutant removal systems.