Meat processing industries consume a lot of fresh water in the slaughterhouses and livestock industries worldwide. Currently, some slaughterhouses produce large amounts of harmful wastewater, because of the slaughtering process and cleaning of equipment. In this paper, an anaerobic and coagulation-flocculation hybrid process was explored in laboratory pilot scale for removal of contaminants from a slaughterhouse effluent. The findings indicated that anaerobic treatment as the first step caused a reduction of the portion of (COD), (TSS), and turbidity. Furthermore, it was concluded that coagulation-flocculation could reduce most of the suspended and colloidal particle with an aluminum sulfate dose of 110 mg l–1. (TSS), turbidity, (COD), (TDS) and (EC) have been reduced up to 71%, 41%, 76%, 49%, and 52%, respectively. Results show coagulation-flocculation can reduce most of the suspended and colloidal particles, and aluminum sulfate compare with ferric chloride and calcium oxide is a suitable coagulant for this special wastewater. On the other hand, adding coagulant generates various ions and causes an increase in TDS and EC. So, the optimal dose of aluminum sulfate was determined. Also results show that TDS and EC increased slightly after the coagulation-flocculation process compared with the anaerobic process which was due to the addition of coagulants to wastewater. Finally, the anaerobic and coagulation-flocculation hybrid process does not meet environmental standards to dispose of wastewater and requires a supplementary treatment process.

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