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The study regards 4-nitrophenol removal performed in a lab-scale sequential batch reactor with an integrated aerobic-anoxic cycle. The purpose of the study was to examine the kinetics of 4-nitrophenol biological oxidation and denitrification in order to test the feasibility of the proposed technological solution for xenobiotic removal. The results obtained show that high removal efficiency of 4-nitrophenol is easily achieved when the compound is fed into the reactor as the sole carbon source. Residual concentrations of 4-nitrophenol and nitrous/nitric nitrogen in the effluent lower than 1 mg L-1 were observed in the range of applied feed concentration (200-320 mg L-1). Low concentrations of dissolved oxygen (⩽2 mg L-1) in the feed and aerobic phases lead to appreciable simultaneous denitrification. As regards the denitrification process, while no carbon- limiting effects were observed at COD/N ratios ⩽3, a significant decrease in the rate of denitrification is detected for COD/N ratios ⩽ 2. The denitrification rate obtained in tests with no external carbon addition proved very low and unsuitable for practical application. A model of the denitrification process taking into account both the limiting effect of nitrogen and carbonaceous substrate has been proposed and applied for experimental data correlation. [ABSTRACT FROM AUTHOR]