Treatment of the effluent from a red meat slaughterhouse by electrocoagulation flotation with iron electrodes
The effluent of the municipal slaughterhouse in Meknes City, Morocco, is characterized by a high organic pollution load and red colour due to the high concentration of blood. Physicochemical and microbiological analyzes revealed significant levels of pollution and microbiological load marked by the dominance of coliform bacteria. The average chemical oxygen demand (COD) is 2,240 mg O2•L‐1. The average concentration of total nitrogen is 290 mg•L‐1 and that for orthophosphates is 35 mg•L‐1. Fat and grease content varies between 900 and 1,100 mg•L‐1. The number of fecal coliforms is 67•103 UFC•mL‐1. Treatment by electrocoagulation-flotation using iron plate electrodes, with a voltage of 12 V and a contact time of 25 min, gave good results. It can achieve reductions in chemical oxygen demand (COD) of 92.6%. Total nitrogen removal was 76.2%, and the reduction of orthophosphate was 95.4%. Fat and grease can be reduced by 62.5% thanks to the flotation step, favoured by the release of hydrogen bubbles from the reduction of water at the cathode and the mixing of the effluent by stirring in the electrolytic cell. This process also enabled the reduction of the red colour, as illustrated by the decrease in absorbance at 450 nm, a reduction exceeding 90%, and a remarkable decrease in UV absorbance at 254 nm, reflecting the removal of dissolved organic material by electrochemical oxidation mechanisms. Fecal coliforms are reduced by three logarithmic units.