SOLID PHASE BIOTREATMENT TECHNOLOGY STUDY USING MANUFACTURED GAS PLANT TARRY WASTES

摘要

Research was co-sponsored by EPRI, Cytec and CH2MHill to evaluate the feasibility of remediating soil contaminated with coal tars using a solid-phase bioremediation technology patented by Cytec. This technology targets PAHs typically found in tarry sludges such as coal tars. In previous studies, greater than 90% of the PAHs have been successfully removed in highly contaminated materials with concentrations of VOCs and PAHs in the percent range. In the EPRI study, the bench- and pilot scale treatability trials achieved 90% or better removal of total PAHs. Individual PAH concentrations in this moderately contaminated soil ranged from several 100 mg/kg up to 500 mg/kg. Compound reduction was determined on a weight basis, with the reduction of individual PAHs ranging from 76-98%. For solid phase biotreatment, the important material characteristics are physical properties, organic concentrations, and pH. Preliminary evaluation of the contaminated soil indicated a pretreatment step was required to bulk the material to facilitate handling and mass transfer processes during treatment. The Cytec microorganisms were added to the preconditioned material and the material was then placed in a reactor operated under negative pressure and monitored for VOC and PAH. Moisture content and pH were maintained throughout the bench-scale and pilot trial with nitrogen and phosphorus added as needed. For the pilot trial, previously treated material containing Cytec microorganisms was recycled into the preconditioned material as inoculum. The patented solid-phase treatment technology proved to be viable for use in removing both VOCs and PAHs during the four week treatment period. As expected, 2-3 ring compounds (such as naphthalene and anthracene) were removed preferentially over 4-5 ring compounds (such as fluoranthene, pyrene, and benzoanthracene). In addition, these results indicate that in a full-scale system, recycling a portion of the treated material provides an effective source of inoculum for remediating contaminated soils.