Removal of nitrogen from coal gasification and coke plant wastewaters in A/O submerged biofilm-activated sludge (SBF-AS) hybrid system

Experimental research involving both laboratory and full-scale studies has been carried out to evaluate the nitrification-denitrification process carried out in a submerged biofilm (in anoxic zone)-activated sludge (in oxic zone) (SBF-AS) hybrid system for nitrogen removal from coal gasification and coke plant wastewaters. The anoxic reactor in the system was packed with fibrous carriers fixed on plastic plates of circular form for the attached growth of submerged biofilm with facultative denitrifying bacteria as dominant species to carry out denitrification, and the activated sludge process was used in the aerobic reactor for nitrification. As the denitrifying and nitrifying bacteria live under anoxic and aerobic conditions respectively in the hybrid system, the process was tested under the conditions of high organic and ammonia loading rates and short hydraulic retention time (HRT). The experimental results show that ammonia nitrogen, NH₃-N removal is between 94% and 99.9% and COD removal between 80% and 95%.