Coke plant wastewater treatment by fixed biofilm system for COD and NH3-N removal

Coke plant and coal gasification wastewater have similar characteristics. There are high concentrations of ammonia and organic compounds especially refractory and inhibitory organics in them. Coal is the main energy resource in China hence pollution caused by coke plant and coal gasification wastewater has been severe for decades. The anaerobic-anoxic-oxic (A1-A2-O) fixed biofilm system was used for coke plant wastewater treatment in this study. The experimental results showed that this system was efficient and stable in NH3-N and COD reductions. The effluent NH3-N and COD were 3.1, 114 mg/l with removal efficiencies of 98.8 and 92.4%, respectively, when the total HRT of the whole system was 31.6 hours. Microorganisms were enumerated and organic transformation in the system was analyzed by GC/MS equipment. Batch tests were also conducted and it was found that anaerobic treatment of coke plant wastewater differed from anoxic treatment. Biodegradable phenolics were removed at lower efficiencies while complicated and high molecular weight organics were removed at higher efficiencies by anaerobic treatment in comparison with anoxic treatment. The biodegradability of anaerobic effluent was higher than that of anoxic effluent.