Assessment of the real oxidation efficiency of O_3 and O_3-H_2O_2 to remove Diuron and Linuron (endocrine disrupting pesticides) from drinking water

摘要

The main goal of this work was to assess the real oxidation efficiency of O_3 and O_3H_2O_2 to remove diuron and linuron from drinking water. Oxidation trials were carried out in a « bubbling column » operated at counter-flow in continuous regime. Solutions of diuron and linuron, prepared at 2.1 × 10~(-5) mole/L in ultra pure water, were treated at pH 2 with O_3 and pH 7 with O_3 and O_3-H_2O_2. The best oxidation removal (100%) was obtained for both pesticides at 45 min of reaction time, pH= 7, 0.35 mol H_2O_2/mol O_3 and an ozone dose of 6 mg/L. Under these conditions, the measurements of dissolved organic carbon showed that diuron and linuron were mineralised 75% and 60 %, respectively. Thus a significant amount of these pesticides was degraded into oxidation by-products. Three organic by-products were identified: N-(3, 4 dichlorophenyl)-N-(methyl)-urea (DCPMU), N-(3, 4 dichlorophenyl)-urea (DCPU) and 3, 4 dichloroaniline (DCA). DCPU and DCPMU were the main organic oxidation by-products of diuron and linuron, respectively. Due to these by-products show similar toxicological characteristics than diuron and linuron, and also, an intrinsic endocrine disrupting potential, may be expected,, it is highly recommended a post-treatment to remove them efficiently from drinking water in order to avoid health risks.