Continuous Fixed-Film Biological Nitrification and Denitrification of Wastewater

Abstract

<p> This work examines the feasibility of continuous biological nitrification and denitrification for nitrogen removal from municipal wastewater. Pilot plant'studies were conducted using a rotating biological contactor (RBC) for nitrification and upflow packed columns for denitrification. Of primary interest were the effects of temperature on the systems. </p> <P> It was found that an Arrhenius model adequately described nitrification rates measured over a range of temperatures from 7 degrees C to 250 degrees C. Direct comparison of the Arrhenius Activation Energies determined for the RBC and a two stage activated sludge system with intermediate clarification showed that nitrification in the RBC was less temperature sensitive than in the activated sludge process. At 10 degrees C, roughly 20 mg/hr·m^2 (0.10 lb/day•1000 ft^2 ) of ammonia as nitrogen was removed from the system. </p> <p> The rate of denitrification in the packed column reactors displayed great variability. The temperature dependency of the data could not be characterized by an Arrhenius model or any other simple relationship. Although significant nitrate removal was observed at all temperatures between 5°C and 25°C, severe short circuiting due to solids accumulation tended to limit minimum nitrate effluent concentrations to 1 or 2 mg N03^-N/~. </p>