Enhancing TCE Biodegradation by Using Agricultural Byproducts in Biobarrier System

This study was conducted to evaluate the efficiency of eucalyptus mulch (EM) and corncobs (CC) for their use in a permeable biobarrier system (PBS) to remediate trichloroethylene (TCE) under highly reduced conditions. Between the tested amendments EM was the most effective at supporting the reductive dechlorination of TCE. Although partial conversion of TCE to cis-1,2-DCE was detected before the bioaugmentation, inoculum addition accelerated the biodegradation and temporarily increased the molar recovery of the TCE and its byproducts almost three times as high as the inlet TCE molar concentration. This suggests that the previously adsorbed TCE was accessible to the TCE-degrading bacteria. The cellulose in EM slowly decomposed providing a long-lived source of carbon. The CC column initially leached high concentrations of soluble organic substances, with total organic carbon (TOC) concentrations as high as 1335 mg/L; however, low pH and relatively high ORP values prevented the development of conditions that permit TCE degradation. Calcium carbonate addition to the corncobs column neutralized acidic pH and sustained ORP values appropriate for TCE dechlorination, and resulted in rapid conversion of TCE to cis-1,2-DCE and VC and then slowly to ethylene. The results of the study showed that eucalyptus mulch could be used as an effective PBS material to remediate the TCE. Corncobs can also be used as an amendment if enough limestone or CaCO₃ is added to neutralize the acids produced by its fermentation.