The use of flotation to pretreat wastewater from animal fat rendering

A developed method of pretreating meat-processing wastewater from steam-rendering animal fats has been presented in this paper. The project also permits fats and proteins recovery for industrial applications. The method is based on the application of the air stream flotation chemically aided by coagulation, sorption and oxidation. A particular advantage of this method is the possibility of direct pretreatment of hot raw wastewater. Then, the process of pretreatment is carried out in two stages: the first including sorption, coagulation, and preliminary oxidation, and the second one with secondary coagulation and flotation aided by oxidation. A three-chamber induced air flotator of special design has been constructed for the practical application of this method, where the first chamber was of the processing character and the other two were the sorption ones. The full installation consisted of reaction chambers and the specially designed flotator. The application of this method permits 95% reduction of fats, suspended solids as well as fatty and protein colloids, more than 50% reduction of COD and 40% of BOD5. This design was implemented in order to eliminate fats and proteins and to pretreat processing wastewater up to the volume of 30.0 m^3 d^-1.