NGWA Event and Education Recordings Archive

Advanced Oxidation Processes (AOPs) use a variety of means to generate hydroxyl radicals, potent oxidants which can rapidly degrade a large variety of organic chemicals. AOPs are commonly used in groundwater remediation applications to remove chemicals such as 1,4-dioxane, methyl-tert­-butyl ether (MTBE), or trichloroethylene (TCE) from a contaminated water source. Combining hydrogen peroxide and ultraviolet light (H₂O₂/UV) is the most commonly used AOP, and this process works through the action of UV light on hydrogen peroxide, which produces hydroxyl radicals. While H₂O₂/UV AOPs are effective, they are often costly due to the high price of hydrogen peroxide, the low amounts of hydrogen peroxide actually used in the process, and the need for quenching residual hydrogen peroxide after AOP treatment is complete. Recently, researchers have been exploring the combination of aqueous chlorine and ultraviolet light (Cl₂/UV) as an alternative AOP. Similar to H₂O₂/UV, Cl₂/UV produces hydroxyl radicals from the photolysis of aqueous chlorine. Laboratory testing had indicated that, in some situations, Cl₂/UV AOPs are expected to be far less expensive than a comparable H₂O₂/UV process. Until now, such observations had not been corroborated through field studies, where parameters outside the control of a laboratory setting can impact AOP treatment outcome.

This presentation will describe pilot study results comparing H₂O₂/UV and Cl₂/UV AOPs for the removal of TCE from contaminated groundwater. These studies were conducted on the full scale operations of two Ground Water Extraction and Treatment facilities operated by Aerojet-Rocketdyne, and compared the TCE removal efficacy of the in-place H₂O₂/UV AOP with Cl₂/UV AOP. Data was then used to determine the expected operational costs of a full scale Cl₂/UV AOP treatment process. The impact of Cl₂/UV AOP on the photolytic removal of N-nitroso-dimethylamine (NDMA) and the acute toxicity of the AOP effluent water were also explored.