Cost and Performance Evaluation of Treatment Technologies for MTBE-Contaminated Water

Treatment of Methyl Tert-Butyl Ether (MTBE) from contaminated surface and groundwater supplies presents specific challenges due to the physicochemical properties of MTBE which depend strongly on its hydrophilic nature, and translate into a high solubility in water, very low HenryÕs constant and very low affinity for common adsorbents. In this study we evaluate two common treatment technologies, air stripping and granular activated carbon (GAC), as well as two innovative treatment technologies, hydrophobic hollow fiber membranes and advanced oxidation (AOP) using ozone or ozone/hydrogen peroxide. Where available, we used design parameters from published literature, but in several instances we conducted experimental studies to determine the parameter values or corroborate the literature information. Ten different flow rates/concentration combinations were evaluated in our designs, to cover the range from high flow rate/low concentration typical of surface waters and groundwater drinking water supplies, to low flow rate/high concentration typical of groundwater remediation sites. For all cases, the processes were designed to produce an effluent water of 5 ug/L or less. Capital costs and operating and maintenance costs were determined at the feasibility level, using standard engineering estimating practices. Air stripping is the lowest cost technology for high flow rates (100 to 1000 gpm), if no air treatment is required. Air treatment can be required depending on the local or Regional Air Quality Board stipulations. Hollow fiber membranes are the lowest cost technology for flow rates of 10 to 100 gpm if no air treatment is required, which is typical at these low flow rates. GAC will be most cost-effective at all flow rates if air treatment is required and the influent water has low levels of other organic compounds. If air treatment is required and the influent has high levels of organics, air stripping is more cost effective than GAC at flow rates of 100 gpm and greater. AOP is in all cases more expensive than the alternative technologies, and there are sufficient uncertainties at this point with respect to by-products of AOP to warrant further study of this technology. It has the potential of being cost-competitive at high flow rates, provided it is fully tested at the field scale. Given that air stripping and GAC are proven technologies in the field, innovative technologies such as hollow fiber membranes and AOP should be compared on a case-by-case basis against these treatment options. Cost and Performance Evaluation of Treatment Technologies for MTBE-Contaminated Water 2 The cost of treating MTBE-contaminated water is 40 to 80% higher than treating water contaminated only with other hydrocarbons such as benzene, for conventional technologies such as air stripping and GAC.