Most restaurant operators in Hong Kong run their business in commercial buildings. Many of them fail to meet oil and grease (O & G) limits. The O & G and Chemical Oxygen Demand (COD) content of the effluents can be reduced to meet government prescribed standards using a combination of compressed air and chemical treatment in existing two-chamber grease traps. A mean level of 41 mg/L and a mean removal of 92.7% of O & G can be achieved for a typical fast food restaurant. COD reduction can further be improved by dissolved air flotation enhanced with chemicals. Sludge generated from flotation treatment of the wastewaters can be recycled as a fertilizer to give a mean total nitrogen content of 13,217 mg/kg and a mean total phosphorus level of 1133 mg/kg. Moreover, it can also be utilized as a biofuel to give a mean calorific value of 6690 Cal/g which is equivalent to that of coal. (C) 2010 Elsevier Ltd. All rights reserved.