RESPIROMETRIC STUDIES ON THE IMPACT OF HUMIC SUBSTANCES ON THE ACTIVATED SLUDGE TREATMENT: MITIGATION OF AN INHIBITORY EFFECT CAUSED BY DIESEL OIL

Abstract

This paper describes the results of aerobic respirometric studies on the application of humic substances (humate) to mitigate an inhibitory effect of petroleum hydrocarbons (diesel oil) on the returned activated sludge (RAS) in sewage from a municipal treatment plant. Initial results of the respirometric tests and non‐linear regression analysis showed that diesel oil had an inhibitory effect on the activity of biomass and that kinetic data complied with the Haldane model for inhibitory wastes. Humate addition significantly enhanced the oxygen uptake by RAS. Application of humate at the dose of 2000 mg l−1 to the sewage contaminated with 10 mg l−1 of diesel oil resulted in almost complete recovery of the biomass oxygen uptake. Non‐linear regression analysis of the respirometric data indicated that this system complied with the Monod model for non‐inhibitory wastes. Thus, the application of humic substances to mitigate the inhibitory effects of oil spills in wastewater treatment plants seems to be an attractive alternative to the treatments using activated carbon or specialized sorbents.