Treatment of MTBE contaminated waters using air stripping and advanced oxidation processes.

摘要

The widespread use of the fuel oxygenate methyl tert-butyl ether (MTBE) has led to the contamination of both surface and groundwater supplies. This study evaluates the treatment of MTBE contaminated drinking water using air stripping and advanced oxidation processes (AOPs) on a pilot scale. The treatment efficiency of the air stripper was evaluated at different air/water ratios ranging from 105:1 to 206:1. Although a treatment efficiency of >99% was achieved for each of the air/water ratio studied, the depth of the packing required to achieve this efficiency increased with decreasing air/water ratio. The adsorption studies conducted on MTBE laden off-gas from the air stripper showed that granular activated carbon (GAC) has a higher adsorptive capacity than the carbonaceous polymeric resin. Experiments conducted at different off-gas relative humidity (RH) of 20%, 30% and 50% reveal that the GAC adsorptive capacity decreased with increasing RH, whereas, the RH did not impact the resin adsorptive capacity. Ozone/hydrogen peroxide (O3/H2 O2), ozone/UV (O3/UV), hydrogen peroxide/UV (H 2O2/UV), and ozone/hydrogen peroxide/UV (O3/H 2O2/UV) are the four AOPs evaluated in this study. An increase in the recycle ratio by 100% resulted in a 5% increase in the treatment efficiency. A treatment effectiveness of 98% was achieved with the use of O3/UV process at an O3 concentration of 5.8 mg/L. The experimental results have shown that the O3/H2O2 process is a slightly more effective (2 to 3% more) treatment process than the O3 /UV process at the same O3 concentrations and a H2O 2:O3 molar ratio of 1.4:1. Increased treatment efficiencies were observed with increasing H2O2:O3 molar ratios, with the optimum ratio for maximum treatment efficiency being 1:1. Non-detectable levels of MTBE were recorded in the O3/H2O 2/UV process, at an O3 dosage of 5.8 mg/L and a H2O 2:O3 molar ratio of 1.4:1. The O3/H2O 2/UV process was more effective than the O3/H2O 2 process at lower H2O2:O3 molar ratios and at ratios above 1:1, the difference in the treatment efficiencies was negligible. Tert-butyl formate, tert-butyl alcohol, methyl acetate and acetone were the major oxidation by-products identified in all the AOPs. The conducted cost analyses revealed that air stripping was the most cost effective treatment process compared to the AOPs.