Field Demonstration of a Permeable Bioreactive Barrier for Leachate Control.

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Courtesy of REGENESIS

ABSTRACT: A biostimulation technique was selected for a pilot study to treat groundwater at a former New Jersey municipal landfill. The process will address a mixture of chlorinated compounds (e.g. vinyl chloride and chlorobenzene), hydrocarbons (e.g. benzene and methyl ethyl ketone) and heavy metals. The reactive barrier will be constructed using a series of injection points to implace a slurry of Oxygen Releasing Compound (ORC®) to enhance both biological and chemical oxidation of the chemicals of concern through the slow release of oxygen. ORC has been shown to be effective in the treatment of petroleum hydrocarbons (Koenigsberg et al., 1995) as well as some chlorinated hydrocarbons such as vinyl chloride (Dooley et al.,1998). Two mini-barriers, each 90 feet long, were installed at the site in January, 1999. Monitoring points were installed along the centerline of the barriers. Data was collected in two baseline sampling events prior to installation of the system. Data will be collected over an eight month period. Additionally, a companion study will be performed to investigate the viability of a reinjectable point system to reduce on-going operating costs. Data will be gathered to determine life expectancy for such a system.

INTRODUCTION

Contamination of groundwater from landfill leachate is a common problem that plagues many former landfill operations. Conventional treatment techniques include groundwater collection and treatment coupled with landfill capping to reduce further problems. This approach requires a large investment in the construction of the collection and treatment system plus on-going operation and maintenance cost associated with the decades of system operation. Typical contaminants include volatile organics such as benzene and toluene, solvents such as methyl ethyl ketone and acetone, chlorinated hydrocarbons such as vinyl chloride, dichloroethylene and trichloroethylene , as well as soluble heavy metals. A new alternative treatment technology is the use of passive bioreactive barriers that promote accelerated in-situ bioremediation of the groundwater. To promote aerobic treatment slow release magnesium peroxide (ORC®) has been successfully used for a wide variety of compounds (Koenigsberg et al.,1995). Several small scale pilot tests have also demonstrated ORC®’s applicability for vinyl chloride (Dooley et al., 1998). This field demonstration was designed to confirm the application of this innovative technology for much larger projects such as a cut-off barrier at a landfill.

Objective. The objective of the field study is to quantify the concentration reductions for the chemicals of concern and heavy metals by the construction of the ORC bioreactive barrier in a Flank Area, and in the Central Area where there are higher concentrations. The field study will also confirm delivery of oxygen immediately downgradient of the ORC barriers. In addition, if the process is technically feasible, a detailed engineering cost estimate to refine ORC usage estimates (ORC mass and changeout interval) for a full-scale implementation will be developed to determine comparative long term project costs as compared to a conventional pump and treat system coupled with an upgraded landfill cap. ORC would serve as a permeable containment barrier at the edge of the landfill, with multiple treatment cycles required to maintain the effectiveness of the barrier. The pilot study will allow the Site-specific performance of ORC to be evaluated for incorporation into a revised Feasibility Study (FS). The revised FS will consider a new range of groundwater remedial measures.

Site Description. The site is a former municipal landfill that closed in 1986. It is located in New Jersey adjacent to a creek and associated wetlands. Capping of the site was performed as part of the closure process. The site is approximately one mile long and one half mile wide. A site map is depicted in Figure 1.

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