Superfund Research Program
Dense Medium Plasma Remediation of VOCs in Groundwater
Project Leader: Yonghui Ma
Grant Number: R41ES015000
Funding Period: Phase I: 2007-2008
Groundwater is one of the most important freshwater resources on this planet. However, contaminated groundwater has become an ever-increasing problem in the United States. Among the many types of contaminants, volatile organic compounds (VOCs) are a major concern and a potential human health threat for those who use groundwater for drinking water. Pump-and-treat technology is one of the most widely used groundwater remediation approaches, and can be effective when combined with other remediation methods, including Advanced Oxidation Technologies (AOTs).
The Dense Medium Plasma (DMP) technology is a highly efficient AOT for treatment of VOCs in extracted groundwater. Compared to other existing AOTs that are often used to destroy saturated hydrocarbons in pump-and-treat groundwater remediation applications, the DMP technology requires less energy input, produces superior remediation performance, can operate in continuous mode for high throughput, and can be scaled up for industrial use. The DMP reactor initiates, sustains, and disperses electrical discharges through water at atmospheric pressure and ambient temperature. High energies generated by the submerged micro- discharges produce a variety of reactive species including ozone (O3), hydrogen peroxide (H2O2), and free radicals (e.g. H+ and OH-), which can interact with VOCs in groundwater and convert them into CO2, H2O, and other less harmful hydrocarbons through oxidation, fragmentation, and recombination.
Preliminary tests have been performed on the DMP reactor to decontaminate and disinfect water samples that were artificially contaminated with four VOCs or infected with 16 selected bacteria. Data obtained from the preliminary tests demonstrated that the DMP reactor, prior to any optimization, was able to reduce VOC concentrations of benzene, toluene, ethyl benzene, and xylene below the detectable range (from ppm to ppb) and bacteria contamination levels by up to 99.9 percent.
In this project, a prototype DMP reactor will be built and modified to meet the requirements typically found in groundwater remediation applications. Effectiveness of the technology against particular VOCs, including 1, 4-dioxane, TCE, MTBE, and per chlorate, will be evaluated. Treatment parameters will be optimized to achieve the best remediation performance. Byproducts will be identified and studied to evaluate the DMPs environmental impact and secondary treatment approaches will be suggested if necessary. The final product to be developed through this research study is a commercial device that can be used either alone (single unit or an array) or in combination with other existing technologies to destroy VOCs and other similar chemical contaminants in extracted groundwater. As 75 percent of public water systems in the United States rely on groundwater, VOC water contamination is an increasingly serious threat to the public health. This work provides a more efficient and effective alternative to existing technologies for treatment of VOCs in groundwater, helping to reduce the burden of human illness and dysfunction from environmental causes.