Bioremediation of BTEX contaminated aquifers using biologically active barriers

A groundwater remediation barrier containing nutrient briquets was developed to remediate a fuel-contaminated aquifer under enhanced denitrifying or aerobic conditions. This barrier system is expected to be less expensive to construct and simpler to maintain than other techniques currently in use.; In this study, laboratory microcosm experiments were conducted to evaluate the feasibility of biodegradation of benzene, toluene, ethylbenzene, m-xylene, and o-xylene (BTEX) using nitrate as the terminal electron acceptor. Because nitrate is less expensive and more water soluble than oxygen, it may be more economical to restore fuel-contaminated aquifers using nitrate rather than oxygen. Nine different sources of inocula including sludge, contaminated and uncontaminated subsurface soil cores from four different petroleum contaminated sites were used to establish microcosms. Results indicate that TEX could be degraded by some of the inocula under denitrifying conditions, but benzene was recalcitrant in this study.; Nutrient briquets were developed to continuously supply nitrate as the electron acceptor for biodegradation of BTEX in fuel-contaminated aquifers. A laboratory scale nutrient briquet and peat barrier system was operated in a series of continuous-flow columns. In this column study, up to 85% of toluene and 71% of ethylbenzene were removed in the briquet column and the soil column immediately downstream. Results indicate that the released nitrate enhanced biodegradation of TEX and the proposed barrier system is a potentially useful remediation technology.; An oxygen releasing barrier system was designed and field-tested at a gasoline spill site. Oxygen-releasing chemical (ORC) concrete was prepared and installed in a series of fully screened wells perpendicular to the contaminant plume. These wells formed a barrier and enhanced the biodegradation of dissolved hydrocarbons by native microorganisms by releasing oxygen to the barrier and the downgradient aquifer. Field monitoring results indicate that oxygen is being released from the ORC concrete enhancing biodegradation of the groundwater contaminants.; This dissertation is divided into three manuscripts which are chapters 1 to 3. These chapters are independent from each other and all include an abstract, an introduction, methods, results, conclusions, references, and data appendices.