Three-Stage Biological System for Treatment of Coke Oven Effluent

Abstract

A three-stage continuous biological treatment system has been developed for removal of cyanide, phenol, organics, and ammonia from a coke oven effluent. Two stages of activated sludge treatment with completely mixed aeration tanks followed by a hybrid anoxic reactor, in series, were used. The hybrid anoxic reactor uses self-immobilized microbial biomass (granular sludge) under fluidized conditions. A 5 L/day pilot plant was evaluated for a period of over 6 months to monitor organics, ammonia, phenol, and cyanide removal. The activated sludge treatment systems were operated at a hydraulic retention time of 1 day and the hybrid reactor at 16 h. Major constituents of the effluent used in the study were cyanide (9–33 mg/L), phenol (21–235 mg/L), ammoniacal nitrogen (4–1,6 mg NH3-N/L), organic load [4–1,5 mg chemical oxygen demand (COD)/L], and nitrate nitrogen (–9 mg NO3-N/L). Removal efficiencies were around 9% for organic load, 88% for ammoniacal nitrogen, 1% for nitrate nitrogen, and almost 99 and 1% for cyanide and phenol, respectively. The process is presently being scaled up to 1, L per day.