The article presents a general characteristic of the fat-containing effluents of an oil and fat enterprise, taking into account the composition of the raw materials, the industrial chemicals used for their processing, and the technological scheme of production. It has been revealed that most oil and fats enterprises, due to the specific nature and high pollution of their wastewaters, require a process audit of their treatment plants to optimize water use, effectively reduce operating costs, and improve effluent treatment efficiency, etc. The main steps of a process audit are presented. Frequent shortcomings in the existing process and irregularities in the operation of the wastewater treatment plants are identified. Recommendations have been developed to modernize the wastewater treatment plants of the oil and fats enterprises to increase their efficiency and minimize the possible negative impact on the environment: equipment replacement containing defects and addition of a technological scheme with biological treatment step, as well as a post-treatment stage for the use of treated water in production. The study developed a modernized and most appropriate wastewater treatment process for this food industry segment, including automation and recovery systems. It is concluded that the proposed technological scheme improves the wastewater treatment plant's efficiency and minimizes the possible negative impact on the environment.