Slaughterhouses produce high concentration wastewater (EC, 2005), which contains high levels of biodegradable organic matter, in the form of faeces, d undigested food, blood, suspended matter (Jian and Zhang, 1999). The composition of slaughterhouse wastewater in terms of organic strength, inorganic elements, alkalinity and pH is adequate for biological treatment (Massé and Masse, 2000). The design criteria for slaughterhouse wastewater treatment plants are widely published (Travers & Lovett, 1984; Li et al, 2008). In general, variations in the composition of slaughterhouse wastewater are significant, depending on production procedures, by-product recovery and cleaning procedures (Pozo et al., 2003). The high ratio of biochemical oxygen demand (BOD) to chemical oxygen demand (COD) suggests that wastewater is readily biodegradable, the relatively low ratio of BOD to total Kjeldhal nitrogen (TKN) suggests the need nitrification and perhaps even nitrogen removal; and finally, the ratio of BOD to total Kjeldhal nitrogen (TKN) is relatively low and suggests a need for nitrification and perhaps even nitrogen removal. removal of nitrogen. suspended solids (MES) characterize slaughterhouse wastewater (Chen and Lo, 2003; Lovett et al., 1984). TKN values ​​are highly dependent on the blood handling process at the slaughterhouse. The concentration of contaminants in slaughterhouse wastewater varies, with concentrations of COD, TKN, and TSS ranging from 1,000 to 20,000 mg L-1, 150 to 10,000 mg L-1, and 250 to 5,000 mg L-1, respectively. (Li et al, 2008). For large-scale slaughterhouses, the European Commission recommends on-site biological treatment to remove organic carbon and nutrients before wastewater is discharged into surface waters or local wastewater treatment plants (EC, 2005). This has required many industries to treat their wastewater to a level that can be achieved by implementing the best available wastewater technology...... middle of paper ......s for wastewater management biosolids. Environmental Science and Pollution Research 15, 308-317.31. Wei Y., Van Houten RT, Borger AR, Eikelboom D, H., Fan Y., 2003. Minimizing excessive sludge production for biological wastewater treatment. Water Research 37, 4453-44671.32. Yasui H. and Shibata M., 1994. An innovative approach to reduce excessive sludge production in activated sludge process. Water sciences. Technology. 30, 11-20.33. Yang, S.-S., Guo, W.-Q., Zhou, X.-J., Meng, Z.-H., Liu, B., Ren, N.-Q., 2011. Operations optimization parameters for sludge process reduction under alternating aerobic/oxygen-limited conditions by response surface methodology. Bioresource. Technology. 102, 9843-9851.34. Yamamoto K, Hiasa M, Mahmood T, Matsuo T. Direct solid ± liquid separation using a hollow fiber membrane in an activated sludge aeration tank. Water Science Technology 1989;21:43±54.