In this paper, transformations of organic matter during anaerobic treatment of wastewater from the production of edible fats were analyzed. The paper describes a method for characterization of organic pollutants, taking into account their division into biodegradable compounds and not susceptible to biological degradation. In order to make physicochemical determinations, the following types of wastewater samples were collected: non-treated and treated. Methodology for COD fractions determination was developed on the basis of the guidelines ATV-131. The effect of anaerobic treatment of wastewater from production of edible fats was to decrease the proportion of biodegradable compounds from 64.1% to 44.2% and increase the proportion of non-biodegradable compounds from 35.9% to 55.8%.