Photo-Fenton pretreatment of carbofuran – Analyses via experimental design, detoxification and biodegradability enhancement

Abstract The central composite design (CCD) and response surface methodology (RSM) were employed to evaluate the effect of H 2 O 2 dosage rate (1–10 mg L −1  min −1 ) and Fe 3+ dosage (1–100 mg L −1 ) in the photo-Fenton treatment of carbofuran and to develop the second-order polynomial equations in terms of carbofuran and dissolved organic carbon (DOC) removals and BOD 5 /DOC ratio with different reaction times. Both H 2 O 2 dosage rate and Fe 3+ dosage have significant effects on the dependable variables. Based on the results of carbofuran removal and BOD 5 /DOC ratio, H 2 O 2 dosage rate of 5.4 mg L −1  min −1 and Fe 3+ dosage of 59 mg L −1 were found to be the favorable reagent dosages for carbofuran degradation. Under these conditions, the toxicity unit measured by Microtox® test with 5 min exposure was decreased from 47 to 6 and the biodegradability evaluated by BOD 5 /COD ratio was increased from 0 to 0.76 after 60 min reaction. The results obtained in this study demonstrate that the photo-Fenton process is a promising pretreatment before the application of biological treatment for carbofuran removal from contaminated water/wastewater.