INFLUENCE OF DISSOLVED-OXYGEN ON NITRIFICATION KINETICS IN A CIRCULATING BED REACTOR

The influence of dissolved oxygen concentration in nitrification kinet ics was studied in anew biofilm reactor, the circulating bed reactor ( CBR). The study was carried out partly at laboratory scale with synthe tic water containing inorganic carbon and nitrogen compounds, and part ly at pilot scale for secondary and tertiary nitrification of municipa l wastewater. The experimental results showed that either the ammonia or the oxygen concentration could be limiting for the nitrification ra te. The transition from ammonia to oxygen limiting conditions occurred for an oxygen to ammonia concentration ratio of about 1.5-2 gO(2)/gN- NH4+ for both laboratory- and pilot-scale reactors. The nitrification kinetics of the laboratory-scale reactor was close to a half order fun ction of the oxygen concentration, when oxygen was the rate limiting s ubstrate. (C) 1998 IAWQ. Published by Elsevier Science Ltd.