Combined Microbiological and Advanced Treatment of Oil Refinery and Municipal Wastewaters

A study has been done of the primary microbiolooical purification of mixed oil refinery and municipal wastewater using the active sludge process in a two-stage laboratory set-up. The advanced - secondary microbiological treatment of the mixed wastewaters was accomplished by using biologically active carbon. The highest total effect of the organic matter removal for both the primary and secondary microbiological treatment was achieved when the two wastewaters were mixed in the ratio 1:1, and it ranged from 97.7 to 99.2 %, The organic matter load in the effluent expressed as BOD₅, was 0.3 - 5.7 mg O₂/dm³. When conditions in the columns containing biologically active carbon were changed from aerobic into anaerobic ones, the denitrification bacteria were allowed to use the adsorbed organic matter as the substrate. In this way, the achieved nitrate removal was up to 72 %. It was found that active carbon had adsorbed the organic matter 1.37 - 2.10 times more than was its adsorption capacity, while the free surface degree was in the ranoe of 44.5 - 59.7 %. On the basis of the obtained results, the kinetic coefficients were calculated for both the primary and secondary microbiological treatment of the mixture of the oil refinery and municipal wastewaters. Finally, two alternatives of the technological procedure were proposed for such treatment.