An attempt at biodegradation of the most toxic substances (phenols and cyanides) formed in the coke industry is described. An ultrafiltration process was carried out in the batch mode of operation using a flat polyacrylonitrile membrane with an immobilized enzymatic fraction isolated from a bacterial strain of Pseudomonas, The optimal ultrafiltration process parameters, i.e. transmembrane pressure and stirring rate in the bioreactor, as well as the influence of the concentration of xenobiotics on the effectiveness of the process, are determined. The dynamics of the decomposition of phenol and cyanides has been found.