Decontamination and toxicity removal of an industrial effluent containing pesticides via multistage treatment: Coagulation-flocculation-settling and photo-Fenton process

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This paper evaluates the combination of coagulation-flocculation-settling and photo-Fenton for the decontamination of a real effluent containing ametrine ([AMT]=403mg L−1), atrazine ([ATZ]=2153mg L−1), imidacloprid ([IMD]=2936mg L−1) and tebuthiuron ([TBT]=3354mg L−1) and which is generated during the manufacturing process of pesticides. Physicochemical treatment (coagulation-flocculation-settling) was tested using different concentrations of Al(NO3)3 and Fe(NO3)3. No significant removal was achieved using Al(NO3)3 as coagulant while best results were obtained via coagulation with Fe(NO3)3 (99 % removal of color and turbidity). Pesticides remaining in the supernatant after coagulation-flocculation-settling stages were removed via photo-Fenton under black-light or solar irradiation. 82–95 % removal of target pesticides were obtained after photo-Fenton treatment (2mmol L−1 of FeOx, 5463mgL−1 of H2O2) using black-light lamps (400kJ m−2). Solar irradiation improved the degradation of target pesticides (>99 %) leading to concentrations below quantification limits (<0.1mg L−1; 400kJ m−2). Effluent acute toxicity (Vibrio fischeri) was reduced from 100 % to 43 % after solar photo-Fenton. Highly oxidized compounds were formed as confirmed by an increase in average and carbon oxidation states. Preliminary costs calculated for the proposed treatment indicated that $ 349 may be saved per m3 of treated effluent when compared to costs associated to the conventional treatment for this effluent (incineration).