the production of tanned leather from cattle hide requires a complex series of wet chemical processing steps which yield an equally complex series of high load effluents. the heat prospects for effective treatment of these effluents lie in the following steps: physical-chemical pretreatment of segregated high load waste streams, followed by the pooling and biological treatment of the chrome-free streams not suitable for reuse. a physical-chemical (p/c) pretreatment has been developed for lime-sulfide unhairing effluent $em dash$ clearly the most concentrated of the effluent streams. this p/c-treated effluent has served as the substrate in investigations into denitrification, the subject of this paper. the nitrogen removal method selected for study was a single-stage denitrification system with the influent cod used to drive the nitrogen removal. in the study reported, the approach taken was to treat nitrate simply as an alternative to oxygen in combusting cod factors that affect the rate of utilization of the appropriate oxidant were observed as a laboratory treatment system was expanded from simple activated sludge to nitrification and finally to combined nitrification/denitrification. 14 refs