POSTTREATMENT OF EFFLUENT FROM COKE-PLANT WASTE-WATER TREATMENT SYSTEM IN SEQUENCING BATCH REACTORS

The performance of sequencing batch reactors (SBRs) for the treatment of effluent from a conventional coke-plant wastewater biological treat ment system has been evaluated. The results showed that an operating m ode that incorporated two anoxic portions, one ahead of the aeration p eriod and one after the aeration, was superior to the other modes (pre arranged denitrification and postarranged denitrification) for nitroge n removal. The 4-h anoxic fill probably allowed some substrates in the influent to be stored in the biomass and led to subsequent storage-in duced denitrification in the second anoxic portion during the reaction period. Under these conditions, the ammonia nitrogen (NH3-N) and chem ical oxygen demand (COD) reductions were 82.5 and 65.2%, respectively. During the fill period of an SBR, the organics concentration was redu ced, probably due to the adsorption of organics onto activated sludge and dilution of the mixed liquor. Some readily biodegradable organics in the influent, such as phenol and o-cresol, were utilized by denitri fiers as a carbon source. A 16-h aeration significantly reduced the co ncentrations of o-cresol, 3,4-dimethyl phenol, and 2-quinoline alcohol , while reductions in quinoline, isoquinoline, indol, and methyl quino line were limited.