Phytoremediation of MTBE—A Review of the State of the Technology

Abstract

California State Water Resources Control BoardPhytoremediation is the use of plants to clean up environmental problems. While some have termed this technology a niche strategy, there are almost as many uses of phytoremediation as there are sites and problems. No plant will be able to survive in pure phase contamination, but in areas with low to moderate levels of contaminants, plants can perform a variety of functions. They can enhance the metabolism of microorganisms in the soil and thus the degradation of contaminants by the soil bacteria and fungi. Plants can be used in alternating methods to either immobilize soil metals, or to transport those metals out of the soil and into the aboveground portions of the plants for harvest and removal of the metals from the site. Plants have been used in aquatic situations, in wetlands, and in mountainous regions. But perhaps the most promising use of plants is in the control of ground water pollutants. Plants can be used to minimize the recharge of soil-based contaminants into the ground water, exert hydraulic control of a contaminant plume, or take up impacted water from the aquifer and degrade the contaminant within the plant tissues.Much work has been done with ground water-based contaminants, including industrial solvents like TCE (Newman et ai., 1999), pesticides such as atrazine (Burken and Schnoor, 1997), or energetics such as trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) (Thompson et ai., 1998).Early studies with soluble compounds often focused on the ability of a plant to take up the contaminant. There has been much said about the Briggs coefficient (Briggs et ai., 1982), where it was stated that a plant could only take up a compound with a mid-range octanol-water partition coefficient (Kow), and that compounds that were strongly hydrophobic or hydrophilic would not be

Performance Evaluation Using a Three Compartment Mass Balance for the Removal of Volatile Organic Compounds in Pilot Scale Constructed Wetlands

“…Therefore, the results of the present study suggest microbial turnover of MTBE within the wetland plants. Actual potential of MTBE for phytodegradation is outlined by Newman and Arnold, including studies with alfalfa and hybrid poplars.…”

Phytodegradation of organic compounds

“…In laboratory studies, Ma et al [9] found that not only was MTBE released from the leaves, as reported in several previous studies, but it also diffused from the trunk of the plants. A more recent study of five mature Monterey pines exposed to MTBE in the aquifer reported much higher levels of tert-butyl alcohol (TBA) than MTBE through the transpiration stream, indicating that metabolism was taking place either in the rhizosphere or within the plant system [10 ]. This study also showed a significant decrease in MTBE levels in the aquifer as it passed under the trees, indicating that phytoremediation may be a viable option for MTBE, even if the fate of the compound in the plant is not yet fully understood.…”

Introduction to Phytoremediation of Contaminated Groundwater

“…The fate of MTBE that is not transpired in plant cells is not entirely known (Newman and Arnold 2003). Typically, the transformation of ethers like MTBE would follow an oxidation pathway of Phase I detoxification.…”