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EVALUATION OF A PILOT-SCALE ULTRAVIOLET (UV) LIGHT AND OZONE TREATMENT SYSTEM FOR REMOVAL OF MTBE FROM DRINKING WATER SOURCES
Citation:
Haught*, R C., P J. Clark*, H E. Moreno, L Wilsong*, C Patterson*, AND E. R. Krishnan. EVALUATION OF A PILOT-SCALE ULTRAVIOLET (UV) LIGHT AND OZONE TREATMENT SYSTEM FOR REMOVAL OF MTBE FROM DRINKING WATER SOURCES. Presented at 2002 AWWA Annual Conference, New Orleans, LA, 06/19/2002.
Description:
The U.S. Environmental Protection Agency (EPA) is currently evaluating package plant advanced oxidation process (AOP) systems to treat methyl tertiary butyl ether (MTBE) in drinking water supplies (e.g., surface water, groundwater). MTBE has been identified as a potential carcinogen, and its potential persistence in drinking water supplies has recently raised many environmental concerns. A pilot-scale ultraviolet (UV) light/ozone system and a mobile UV/Ozone system are being evaluated as AOP systems at the U.S. EPA Test and Evaluation (T&E) Facility in Cincinnati, Ohio. The pilot-scale unit and the mobile field unit are similar in design and consist of a 15-gallon (57-liter) contact tank/stainless steel pipe-loop system with a side-stream venturi injector (for dosing ozone) and a cylindrical low-pressure 254 nm UV lamp reactor. Both units were tested as closed-loop recirculating batch reactors at 10 gpm for a period of 60 minutes to determine MTBE degradation with time. The formation of MTBE oxidation byproducts was also evaluated. The mobile field unit was also tested in single-pass mode with partial recirculation at 2.5, 4, and 5 gpm for up to 30 minutes to determine removal efficiency with continuous flow. The UV/ozone system design accommodated several treatment options for comparison: UV/ozone treatment, ozone treatment, UV treatment, and a control (no treatment). Several sources of water with different water quality characteristics (dechlorinated City of Cincinnati tap water, Mill Creek industrial and domestic sewage treatment plant effluent, East Fork Lake surface water, and C.M. Bolton well water) were tested at initial MTBE concentrations of 50, 100, 300, 1200 and 3000 micrograms/liter and turbidities of <0.5, 1, 2, and >15 nephelometric turbidity units (NTU). The combined UV/ozone treatment process demonstrated the greatest removal for all initial MTBE concentrations. Laboratory analysis confirmed the formation of MTBE oxidation byproducts including tertiary butyl formate, acetic acid methyl ester, and acetone at concentrations of less than 500 micrograms/liter. The kinetics of the oxidation process for treatment of MTBE and MTBE byproducts were much faster with UV/ozone compared to ozone alone. UV treatment alone resulted in negligible MTBE removal. Single-pass treatment with partial recirculation was the most cost-effective means of UV/ozone treatment at low initial MTBE concentrations of less than 100 ppb. It is planned to employ the mobile field unit for demonstration of MTBE treatment in contaminated groundwaters at several field sites.