Removal of Nonbiodegradable Chemicals from Mixtures during Granular Activated Carbon Bioregeneration

The purpose of this research was to better understand the interactions between biodegradable and nonbiodegradable synthetic organic chemicals (SOCs) during bioregeneration of biologically active granular activated carbon (GAC) columns. Continuous-flow GAC bioregeneration experiments were conducted at different empty-bed contact times (EBCTs) using mixtures of a biodegradable (benzene or toluene) and a nonbiodegradable (perchloroethylene or carbon tetrachloride) SOC. The GAC was preequilibrated with respect to each combination of SOCs to facilitate the study of bioregeneration. If no dissolved oxygen limitations occurred in the bioregeneration experiments, the effluent biodegradable SOC concentration decreased over time and then remained low, after which the effluent nonbiodegradable SOC concentration also decreased because of the increased availability of adsorption sites on the GAC. Pre- and postexperimental GAC loadings show a marked decrease in the biodegradable SOC loading as well as an increase in the nonbiodegradable SOC loading. Greater degrees of bioregeneration were found for higher SOC equilibrium concentrations and longer EBCTs. Bioregeneration ranged from 28.8 to 45.5% of the initial biodegradable SOC loading after 13-17  days. These results illustrate an increase in GAC adsorption capacity for nonbiodegradable SOCs through bioregeneration of GAC containing biodegradable SOCs.