In order to expand the treatment scale and improve effluent quality of wastewater, a modification project of a slaughterhouse wastewater treatment was conducted. According to original wastewater treatment process and other similar wastewater treatment experience, processes of pretreatment, UASB and A/O were adopted to treat the slaughtering wastewater, and the main structures and related design parameters were introduced. The practical results indicated that the removal rates of COD, BOD5, SS and NH3-N reac...