RECLAMATION OF WASTE-WATER FROM A STEEL-MAKING PLANT USING AN AIRLIFTSUBMERGED BIOFILM REACTOR

A bench-scale airlift submerged biofilm reactor was developed to test the possibility of nitrification of the final effluent discharged from a wastewater treatment process of a steel-making plant with an aim of reusing it as irrigation water. Despite the fluctuation of ammonia co ncentration in the wastewater (55-90 mg NH3-N dm(-3)), the ammonia was completely converted to nitrate in the hydraulic retention time of 8 h. When decreasing the hydraulic retention time further down to 4 h, t he nitrification efficiency decreased to 67.9%. However, the nitrifica tion efficiency could be significantly enhanced by increasing the airf low rate due to an increase in both of the oxygen transfer rate and li quid circulation rate. At the aeration rate of 4 dm(3) min(-1) and the hydraulic retention time of 4 h, the nitrification efficiency was as high as 92.6% and the nitrification rate was 34.6 mg NH3-N dm(-3) bed h(-1). (C) 1998 Society of Chemical Industry.