MTBE oxidation by conventional ozonation and the combination ozone/hydrogen peroxide: Efficiency of the processes and bromate formation

The present study investigates the oxidation of methyl tert-butyl ether (MTBE) by conventional ozonation and the advanced oxidation process (AOP) ozone/hydrogen peroxide under drinking water treatment conditions. The major degradation products identified were tert-butyl formate (TBF), tert-butyl alcohol (TBA), 2-methoxy-2-methyl propionaldehyde (MMP), acetone (AC), methyl acetate (MA), hydroxyisobutyraldehyde (HiBA), and formaldehyde (FA). The rate constants of the reaction of ozone and OH radicals with MTBE were found to be 0.14 and 1.9 x 10(9) M-1 s(-1), respectively. The rate constants for the same oxidation processes were also measured fort he degradation products TBF, MMP, MA, and HiBA (k(O3-TBF) = 0.78 M-1 S-1; k(OH-TBF) = 7.0 x 10(8) M-1 s(-1); k(O3-MMP) = 5 M-1 s(-1); k(OH-MMP) = 3 x 10(9) M-1 s(-1), k(O3-MA) = 0.09 M-1 s(-1), k(O3- HiBA) = 5 M-1 s(-1); k(OH-HiBA) = 3 x 10(9) M-1 s(-1)). Since all compounds reacted slowly with molecular ozone only the degradation pathway of MTBE with OH radicals as been determined, including the formation of primary degradation products. In experiments performed with several natural waters, the efficiency of MTBE elimination and the formation of bromate as disinfection byproduct have been measured. With a bromide level of 50 mug/L, only 35-50% of MTBE could be eliminated by the AOP O-3/ H2O2 without exceeding the current drinking water standard of bromate (10 mug/L). The transient concentrations of MTBE and its primary degradation products were modeled using a combination of kinetic parameters (degradation product distribution and rate constants) together with the ozone and OH radical concentration and were in good agreement with the experimental results

Endocrine disrupting chemicals-linking internal exposure to vitellogenin levels and ovotestis in Abramis brama from Dutch surface waters

The exposure of male bream from three Dutch freshwater locations to endocrine disrupting compounds (EDCs) and corresponding effects are described in this study. Fish specimen displaying reproductive disorders associated with high levels of plasma vitellogenin (VTG) concentrations and occurrence of ovotestis (OT) were investigated. To provide information on the full spectrum of EDCs in fish tissue, adipose tissue samples of individual fish were analyzed for nearly 130 chemicals targeting different compound classes (bisphenols, alkylphenols, pesticides, polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), hydroxylated polychlorinated biphenyls (OH-PCBs), polybrominated diphenyl ethers (PBDEs) and biphenyls (PBBs)) and steroid hormones. To establish whether tissue from specimen with reproductive disorders shows a spectrum of EDCs that is qualitatively and quantitatively different from that of controls free of symptoms, bioassay-directed fractionation was performed using the recombinant yeast estrogen screen (YES), the E-Screen bioassay, the human sulfotransferase 1E1 (SULT1E1) inhibition assay, and the coumestrol-based estrogen receptor α (ERα) high resolution screening (HRS) assay. No differences in estrogenicity could be observed between the cases and controls and steroidal estrogens accounted for the majority of estrogenicity found in the complex mixtures. In this study, the combination of the different assays employed to measure total estrogenicity and the SULT1E1 inhibition does not predict the outcome of unwanted physiological effects, however, it can be used to determine the presence of EDCs in fish samples and their estrogenic effects. © 2010 Elsevier B.V