Abstract
BACKGROUND: Removal of recalcitrant chemicals is an essential step in conventional wastewater treatment plants. Among these, pesticides are of great environmental concern. Different treatment options were compared in this work: the combination of advanced oxidation processes (AOPs) with biological treatment, an aerobic process and anaerobic biological treatments. The role of chemical processes in improving solution biodegradability was verified. Oxidation by‐products were identified and biological process kinetics are reported. The performance of biological processes and their kinetics were studied.
RESULTS: Chemical oxidation increased the solution biodegradability index to 0.25. Oxidation by‐products were identified as maleic acid, phenol and a mixture of catechol, resorcinol and hydroquinone. The combined processes resulted in 98% organic matter removal. Pesticide degradation followed pseudo‐first‐order kinetics with a rate constant in the range 0.5–1.2 L g^−1^TVSS h^−1^. An anaerobic process was found to be an attractive option with 92% removal efficiency. The aerobic process had a long adaptation time (>200 days), 80% removal efficiency and an average pseudo‐first‐order rate constant of 0.18 L g^−1^TVSS h^−1^.
CONCLUSION: Comparison of the investigated processes favoured the use of combined AOPs and biological and/or aerobic biological treatment due to its practical operating conditions. Copyright © 2009 Society of Chemical Industry