Ex situ treatment of MTBE‐containing groundwater by a UV peroxide system

Abstract

This article describes the design, implementation, and operating results for an ex situ ultraviolet/hydrogen peroxide (UVP) system to treat methyl tert-butyl ether (MTBE) in extracted groundwater. The UVP modification was designed to reduce the operation and maintenance costs of an existing groundwater pump-and-treat treatment system that relied on air stripping and carbon adsorption. The UVP system is relatively inexpensive and can easily be scaled to cope with different groundwater extraction rates up to 80 gpm by adding UV lamps in series or in parallel at the higher groundwater extraction rates. The MTBE concentration in the effluent from the UVP system to the carbon vessels decreased from an average of 590 µg/L to approximately 2 µg/L on average over 33 months of operation of the UVP. Incorporation of this UVP modification as a second-stage treatment to the groundwater pump-and-treat/soil vapor extraction system, after the air stripper and prior to the carbon vessels, significantly increased the usable life of the carbon (from two months previously to about two years after installation) and completely resolved the issue of frequent MTBE breakthroughs of the carbon that had plagued the remediation system since its inception.

Comparison of Photodegradation Performance of 1,1,1-Trichloroethane in Aqueous Solution with the Addition of H2O2 or S2O82– Oxidants

“…Whereas, the rate constants of SO 4 −• with HPO 4 2− and H 2 PO 4 − are 1.2 × 10 6 and 7× 10 4 M −1 s −1 . 37 Maruthamuthu and Neta 37 found that SO 4 −• may react with phosphate anions to propagate a chain reaction and form various phosphate radicals, the oxidation potentials of which were all less than SO 4 −• .…”

“…3 Ex-situ treatment with a UV peroxide system is an efficient and effective technology for contaminated groundwater remediation. 4 The UV/H 2 O 2 process is also a technique used in the treatment of chlorinated solvent contamination in groundwater based on the generation of the highly reactive hydroxyl radical with a standard redox potential of 2.70 V. Trichloroethene (TCE) is proved to be completely degraded by UV/H 2 O 2 processes. 5 However, chlorinated alkanes are more resistant to UV/H 2 O 2 processes than alkenes.…”

“…Being one of the strongest oxidizing agents known, persulfate (S 2 O 8 2− ) has emerged to have great potential for TCA oxidation through the activation by means of heat, ultraviolet irradiation, chelated or unchelated transition metals, hydrogen peroxide, and alkaline pH to generate sulfate radicals (SO 4 −• ) and other reactive species. 7,8 Currently, synthetic iron and manganese oxides, as well as some specific organic compounds, are confirmed to be able to activate persulfate to generate oxidants and reductants.…”