BIOLOGICAL PROCESS DESIGN AND PILOT TESTING FOR A CARBON OXIDATION, NITRIFICATION, AND DENITRIFICATION SYSTEM

In response to a new NPDES permit incorporating Organic Chemical, Plastic, and Synthetic Fiber (OCPSF) effluent limits for BOD (carbonaceous and nitrogenous), TSS, and priority pollutants, a treatability study was conducted to establish design criteria for a new process wastewater treatment plant for DSM Chemicals North America, Inc. The permit also requires partial removal of total nitrogen. Based on the discharge criteria, a two-stage biological process configuration was selected. The configuration consisted of an anoxic followed by an aerobic reactor with mixed liquor recirculation. To establish design criteria, a two-phase study was conducted. The first phase involved determining wastewater characteristics and kinetic and stoichiometric coefficients. These values were used as input to "Simulation of Single-Sludge Processes" (SSSP), a computer model that was used to evaluate potential process configurations. In the second phase, a pilot-scale system was operated to verify performance. With a volume distribution of 40 percent anoxic and 60 percent aerobic and a recirculation ratio of 2, BOD, COD, and total nitrogen removal efficiencies of 99, 88, and 80 percent were obtained, respectively. Aproximately 84 percent of the biodegradable COD was removed through denitrification.