Design and management of system components for in situ methanotrophic bioremediation of chlorinated hydrocarbons

摘要

The successful operation of an in situ bioremediation system is inherent within its design. Well-organized system components enable ease of maintenance, limited down time, and relatively rapid data acquisition. The design effort in this project focused on injection of a low-pressure air/methane mixture into a horizontal well below the water table, a methane-blending system that provided control of the injected mixture, redundant safety interlocks, vapor-phase extraction from a second horizontal well, and an off-gas treatment system that provided efficient thermal catalytic oxidation of the extracted contaminant vapors. The control instrumentation provided sufficient redundancies to allow the system to remain in operation in the event of a component failure, and equally important, the safe shut down of the system should any designed safety parameters be exceeded (i.e., high methane concentration). Final design approval took into consideration the reliability of the equipment and the components specified. Product knowledge and proper application limited the risk of a component or system failure while providing a safe, efficient, and cost-effective remediation system. Microprocessor data acquisition and system control were integrated with an autodialer to provide 24 hr emergency response and operation without on-site supervision. This integrated system also insured accurate data analysis and minimum downtime. Since operations commenced, the system has operated a total of 7,760 hours out of the possible 8,837 hours available. This equates to an operating efficiency of 87.8%.