Advanced oxidation processes (AOPs) have garnered recent consideration as an option to reduce organic loading, and the recalcitrance of mature landfill leachate. Hydroxyl radicals (•OH) are produced during AOPs, which are effective in destroying organic chemicals. The aim of this research was to quantify the impact of pre-ozonation (O3 and O3/H2O2) on further anaerobic biological treatment. Raw and abiotic leachates following anaerobic treatment were compared with pre-ozonation treatments (O3/H2O2, and O3 alone). To investigate the efficiency of pre-ozonation treatment, low-ppm level ozone stock solutions were spiked into an ‘old’ landfill leachate (0 to 7.5mg/L O3). The stoichiometric ratio of 1.1:1 was determined to be the optimal molar ratio of O3 to H2O2 (or 0.9 H2O2:O3, as it is often listed) based on the biodegradability of the sampled landfill leachate. O3/H2O2 treatment was proven to have better treatment efficiency than O3 alone on three model contaminants by direct contaminant oxidation. These contaminants were tris-(2-chloroethyl) phosphate (TCEP), tris-(butoxyethyl)-phosphate (TBEP) and 17ß–estradiol (E2), and were selected based on their reported occurrence in municipal landfill leachates. One-way ANOVA was conducted to assess treatments on the three leachate contaminants. O3/H2O2 treatment showed the best significant treatment effect on E2 compared with the other two contaminants in direct oxidation. O3 alone pre-treatment had a better effect on post-ozone degradation of TCEP and TBEP followed by anaerobic incubation compared with O3/H2O2. In general, a low-mg/L ozone pre-treatment, prior to anaerobic incubation, was found to be beneficial for overall removal efficiencies for multiple model contaminants. However, overall anaerobic activity was not observed to increase following ozone pre-treatments, as measured by methane formation, total gas formation, and COD removal

 

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