Treatment of Coal Gasification Wastewater by Full Scale Activated Sludge Process with Fixed Media

Full scale two-stage activated sludge process (ASP) with fixed biological media was used to treat coal gasification wastewater. The ASP has operated for more than one year and COD, total phenol and NH₄-N removal effects were illuminated. COD and total phenol removal rates were around 85% and 90% during long term operation. Effluent COD and total phenol of the first stage of the ASP had an abnormal increase and turned to normal after several weeks. Nitrification of the ASP increased slowly and NH₄-N removal rates achieved 80% after 15 weeks. A majority of the organic pollutants in the wastewater were removed in the first stage of the ASP. NH₄-N was removed mainly in the second stage of the ASP.