Grantee Research Project Results

Final Report: Innovative Oxidation Treatment for Removal of MTBE From Drinking Water Using a Combined Photocatalytic Reactor and Ozone Generator

EPA Contract Number: 68D02011
Title: Innovative Oxidation Treatment for Removal of MTBE From Drinking Water Using a Combined Photocatalytic Reactor and Ozone Generator
Investigators: Steppan, James
Small Business: Ceramatec Inc.
EPA Contact: Richards, April
Phase: I
Project Period: April 1, 2002 through September 1, 2002
Project Amount: $69,926
RFA: Small Business Innovation Research (SBIR) - Phase I (2002) RFA Text |  Recipients Lists
Research Category: SBIR - Water and Wastewater , Watersheds , Small Business Innovation Research (SBIR)

Description:

The objective of this Phase I research project was to design, develop, and demonstrate the feasibility of utilizing a reactor with an embedded ceramic electrode system to simultaneously generate ozone and photoactivate a nanostructured titania coating for methyl tertiary butyl ether (MTBE) destruction. Ceramatec, Inc.'s reactor with combined photocatalytic and ozone oxidation was designed to achieve more complete oxidation more cost effectively than either a photocatalytic or ozone reactor alone. In addition, the need for subsequent purification and/or separation steps is eliminated, because MTBE is effectively oxidized to carbon dioxide and water. The quality of the water produced from this process may meet or exceed drinking water standards. This feature will be advantageous for the remediation of MTBE-contaminated drinking wells.

Ceramatec, Inc., designed and built a prototype reactor to demonstrate the feasibility of the technology. Reactor optimization and scale-up will be performed as part of future Phase II efforts. The prototype reactor consists of two concentric tubes. The outer tube contains ceramic embedded electrodes that generate a surface corona and ozone. The inner tube is a glass tube reaction vessel. The inside of the glass tube is coated with a thin uniform coating of a high surface area titania material that is well suited for photocatalytic activation in water treatment applications. The ultraviolet (UV) radiation generated from the surface corona passes through the glass tube and activates the titania surface that is in contact with the MTBE-contaminated water. The reactor is plumbed so that the ozone is removed from the reactor and then directed back into the reaction vessel at the bottom of the column. This provides the ability to perform oxidation experiments with and without ozone sparging, and with and without UV activation of the titania in the reactor.

Summary/Accomplishments (Outputs/Outcomes):

A Taguchi (L9 [3⁴]) designed set of experiments (Department of Energy [DOE]) was performed in the prototype reactor. The DOE results were used to define operating conditions to perform oxidation experiments to completely remove MTBE. Long-term (up to 10 hours) oxidation runs were performed at high ozone, high UV, and an initial MTBE concentration of 100 mg/L. The combined ozone/UV-activated titania oxidation method is extremely effective in reducing the MTBE concentration by more than four orders of magnitude (from 100 mg/L to less than 0.1 mg/L). Kinetic analyses indicated that combined ozone/UV-activated titania oxidation of MTBE exhibits pseudo first-order kinetics (R² = 0.996), with a rate constant of 0.7523/hour or 2.09 x10-⁴/second. More than 90 percent of the initial MTBE (100 mg/L) is removed in the first 3 hours.

Conclusions:

Phase I results demonstrate the technical feasibility of our approach. An independent commercialization assessment performed by Foresight Science & Technology, Inc. (http://www.seeport.com Exit ), using their Technology Niche Analysis, indicates that this technique shows commercialization promise and may offer significant cost advantages over UV/H2O2. Cost advantages can be realized with Ceramatec, Inc.'s approach, because there are no recurring consumable supply costs as the titania coating is not consumed and generates hydroxyl radicals from the water. There is an unlimited supply of air to directly supply the ozonator or to supply a low-cost oxygen generator that subsequently supplies the ozone generator. Potential commercial applications for this technique include remediation of groundwater contaminated with MTBE and other volatile organic compounds as well as oxidation of organic industrial waste. Proposed Phase II efforts will focus on reactor optimization, reactor scale-up, and increasing the contribution of UV-titania to MTBE oxidation by reactor optimization as well as increasing the wetted surface area of titania.

Supplemental Keywords:

titania, oxidation, methyl tertiary butyl ether, MTBE, drinking water, photocatalytic reactor, ozone generator, carbon dioxide, SBIR, RFA, Scientific Discipline, Water, Toxics, Ecosystem Protection, Chemistry, Contaminant Candidate List, Environmental Chemistry, Engineering, Chemistry, & Physics, exploratory research environmental biology, Ecological Effects - Human Health, Drinking Water, Environmental Engineering, gasoline, Safe Drinking Water, treatment, water quality, MTBE, contaminant removal, treatment plants, chemical contaminants, monitoring, photocatalytic reactor, drinking water contaminants, exposure, groundwater, water treatment, ecological exposure, drinking water treatment, ozone generator, human health effects, alternative disinfection methods, exposure and effects