Characterization of wastewater from hog slaughterhouses in Eastern Canada and evaluation of their in-plant wastewater treatment systems

Literature on existing systems for slaughterhouse wastewater treatment was reviewed and discussed in terms of technology usefulness and relevance unde r Canadian conditions. The wastewater from six hog slaughterhouses in Quebe c and Ontario was also characterised before and after treatment at the plan t. In raw wastewater, total chemical oxygen demand (TCOD) ranged from 2333 to 8627 mg/L and suspended solids (SS) varied between 736 and 2099 mg/L. Sl aughterhouse wastewater composition in terms of organic strength, inorganic elements, alkalinity, and pH is adequate for biological treatment. Two sla ughterhouses only settled their wastewater before discharging it to the: mu nicipal sewer. Three plants used primary treatment to precipitate blood and remove floating fat, while one further treated its wastewater using an aer obic trickling filter. Although preliminary treatment at the slaughterhouse reduced the level of pollutants, TCOD and SS concentrations were still too high for sewer discharge without being imposed a municipal surcharge. In a ddition, all treatments produced large amounts of putrefactive and bulky sl udge, which required special handling and/or further treatment.