Soil vapor extraction and bioventing of contaminated landfill mixed waste

Disposal of chemical waste at a landfill facility in Ohio resulted in release of chemicals into the groundwater. Fluctuation of the groundwater table extended the contamination throughout the landfill. Waste excavated at the Site as part of source removal activities needed to be treated to acceptable levels so it could be disposed. The waste consisted of a non-homogenous mixture of municipal and industrial waste, including rubber strips, putrescible garbage, wood, metal, and other solids. The compounds of concern (COCs) in the waste included benzene, toluene, ethylbenzene, and xylenes (BTEX), trichloroethene (TCE), tetrachloroethene (PCE), and vinyl chloride monomer (VCM). Soil vapor extraction (SVE) followed by bioventing as a polishing step was identified as a potential treatment alternative for the remediation of this waste. A bench-scale treatability study (Phase I of USEPA remedial action) was conducted to assess whether this technique could be applied to effectively treat the waste and reduce the contaminant concentrations. The treatability study was conducted in phases: SVE to remove the TCE, PCE, and VCM, followed by bioventing to enhance biodegradation of the BTEX compounds. The SVE treatment was 99.3 percent effective in removing the TCE. The toxicity characteristic leaching procedure (TCLP) regulatory limit for TCE is 0.5 mg/L. All of the rubber and waste samples were below this limit with greater than a 99 percent confidence level after 6 weeks. Bioventing resulted in greater than 78 percent removal of the BTEX from the soil and greater than 99 percent removal from the rubber material. Based on the successful results of the treatability studies, a pilot test is being conducted.