Biodegradability enhancement of a pesticide-containing bio-treated wastewater using a solar photo-Fenton treatment step followed by a biological oxidation process.
This work proposes an efficient combined treatment for the decontamination of a pesticide-containing wastewater resulting from phytopharmaceutical plastic containers washing, presenting a moderate organic load (COD=1662-1960 mg O₂ L⁻¹; DOC=513-696 mg C L⁻¹), with a high biodegradable organic carbon fraction (81%; BOD₅=1350-1600 mg O₂ L⁻¹) and a remaining recalcitrant organic carbon mainly due to pesticides. Nineteen pesticides were quantified by LC-MS/MS at concentrations between 0.02 and 45 mg L⁻¹ (14-19% of DOC). The decontamination strategy involved a sequential three-step treatment: (a) biological oxidation process, leading to almost complete removal of the biodegradable organic carbon fraction; (b) solar photo-Fenton process using CPCs, enhancing the bio-treated wastewater biodegradability, mainly due to pesticides degradation into low-molecular-weight carboxylate anions; (c) and a final polishing step to remove the residual biodegradable organic carbon, using a biological oxidation process. Treatment performance was evaluated in terms of mineralization degree (DOC), pesticides content (LC-MS/MS), inorganic ions and low-molecular-weight carboxylate anions (IC) concentrations. The estimated phototreatment energy necessary to reach a biodegradable wastewater, considering pesticides and low-molecular-weight carboxylate anions concentrations, Zahn-Wellens test and BOD₅/COD ratio, was only 2.3 kJ(UV) L⁻¹ (45 min of photo-Fenton at a constant solar UV power of 30 W m⁻²), consuming 16 mM of H₂O₂, which pointed to 52% mineralization and an abatement higher than 86% for 18 pesticides. The biological oxidation/solar photo-Fenton/biological oxidation treatment system achieved pesticide removals below the respective detection limits and 79% mineralization, leading to a COD value lower than 150 mg O₂ L⁻¹, which is in agreement with Portuguese discharge limits regarding water bodies.
LSRE-Laboratory of Separation and Reaction Engineering-Associate Laboratory LSRE/LCM, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal. vilar@fe.up.pt
Vítor J P
VJ
Vilar
Francisca C
FC
Moreira
Ana C C
AC
Ferreira
M A
MA
Sousa
C
C
Gonçalves
M F
MF
Alpendurada
Rui A R
RA
Boaventura
D001673:Biodegradation, Environmental; D002853:Chromatography, Liquid; D010084:Oxidation-Reduction; D010575:Pesticides / Q000378:metabolism*; D013472:Sunlight; D053719:Tandem Mass Spectrometry; D014874:Water Pollutants, Chemical / Q000378:metabolism*
D010575:Pesticides; D014874:Water Pollutants, Chemical