An evaluation of physicochemical treatment technologies for water contaminated with MTBE

Treatment of methyl tertiary-butyl ether (MTBE) from contaminated surface a nd ground water supplies presents specific challenges due to the physicoche mical properties of MTBE that depend strongly on its hydrophilic nature, an d translate into a high solubility in water, and low Henry's constant and l ow affinity for common adsorbents. We evaluate four treatment technologies- air stripping, granular activated carbon (GAC), hydrophobic hollow fiber me mbranes, and advanced oxidation processes (AOP)-using ozone or ozone/hydrog en peroxide. Experimental work was carried out to generate parameter values necessary for the design of these processes. Ten different flow rates/conc entration combinations were evaluated in our designs to cover the range fro m high flow rate/low concentration typical of surface water and ground wate r drinking water supplies to low flow rate/high concentration typical of gr ound water remediation sites. For all cases, the processes were designed to produce effluent water of 5 mug/L or less. Capital costs and operation and maintenance costs were determined at the feasibility Level by using standa rd engineering estimating practices. Air stripping is the lowest cost technology for high flow rates (100 to 100 0 gpm) if no air treatment is required. Hollow fiber membranes are the lowe st cost technology for flow rates of 10 to 100 gpm if no air treatment is r equired, which is typical at these low flow rates. GAC will be most cost-ef fective at all flow rates if air treatment is required and the influent wat er has low levels of other organic compounds. AOP using ozone or ozone/hydr ogen peroxide is in all cases more expensive than the alternative technolog ies, and there are sufficient uncertainties at this point with respect to b yproducts of AOP to warrant further study of this technology. The cost of t reating MTBE-contaminated water for conventional technologies such as air s tripping and GAC is 40% to 80% higher than treating water contaminated only with other hydrocarbons such as benzene.