Reclamation of wastewater from a steel-making plant using an airlift submerged biofilm reactor

Abstract

: A bench-scale airlift submerged bioÐlm reactor was developed to test the possibility of nitriÐcation of the Ðnal effluent discharged from a wastewater treatment process of a steel-making plant with an aim of reusing it as irrigation water. Despite the Ñuctuation of ammonia concentration in the wastewater (55È 90 mg dm~3), the ammonia was completely converted to nitrate in the NH 3 -N hydraulic retention time of 8 h. When decreasing the hydraulic retention time further down to 4 h, the nitriÐcation efficiency decreased to 67É9%. However, the nitriÐcation efficiency could be signiÐcantly enhanced by increasing the airÑow rate due to an increase in both of the oxygen transfer rate and liquid circulation rate. At the aeration rate of 4 dm3 min~1 and the hydraulic retention time of 4 h, the nitriÐcation efficiency was as high as 92É6% and the nitriÐcation rate was 34É6 mg dm~3 bed h~1. 1998 Society of Chemical Industry NH 3 -N (