Inhibition effects of petroleum products on nitrogen and phosphorous removal

One of the main challenges in pet roleum-containing wastewater treatment in municipal wastewater treatment plants is their interference with the microbiological processes of nitrogen and phosphorus removal. The purpose of the study is to assess the effect of commercial petroleum products on the conversion of nitrogen and phosphorus compounds during the biological treatment of municipal wastewater in activated sludge systems. The presence of commercial petroleum products in wastewater was found to inhibit the process of conversion of NH₄-N and the absorption of PO₄-P in cells. The main inhibiting effect results from additives introduced into commercial petroleum products. Variations in the removal efficiencies of NH₄-N and PO₄-P are due to the variable distribution of commercial petroleum products in the mixed liquor of activated sludge. An increase in the degree of dispersion of commercial petroleum products, which results in an increase in the contact surface, increases the inhibitory effect on the activated sludge process. The toxic effect of gasoline is more pronounced in comparison with diesel fuel and hydraulic oil. During the first 30 minutes of incubation of samples with oil products, an increase in the concentration of PO₄-P in the solution was observed due to the death of microorganisms from toxic effects, mainly from gasoline.