Thiamethoxam removal by Fenton and biological oxidation

Abstract

AbstractBACKGROUNDThiamethoxam (TMX) is a potential insecticide pollutant of hydric resources that must be removed. Advanced oxidation processes (AOPs) are usually effective, but expensive to implement. Combining Fenton's reagent with biological oxidation circumvents the shortcomings of Fenton technology, facilitating the biodegradation of the resulting effluents in a sequencing batch reactor (SBR).RESULTSFenton‐like oxidation of TMX with variable hydrogen peroxide (H2O2) doses afforded total organic carbon (TOC) conversion and chemical oxygen demand (COD) removal by (respectively) 40% and 80% from pure TMX, and 40% and 60% from commercial TMX. The effluents from Fenton oxidation using substoichiometric H2O2 doses were less ecotoxic and more biodegradable than the initial solution and, therefore, susceptible to a biological treatment. Biological oxidation of effluents obtained from 50% and 75% H2O2 doses was accomplished for different organic loads in 6‐h cycles. Coupling Fenton and biological oxidation of TMX afforded TOC conversion and COD removal of 80% for the effluent obtained with a 75% H2O2 dose.CONCLUSIONSCoupling Fenton–biological oxidation efficiently reduces the amounts of H2O2 needed and produces biodegradable effluents. In addition, the biological treatment increases COD and TOC removal by ≤80% for the overall treatment. © 2019 Society of Chemical Industry