Biofiltration of Chloroform in a Trickle Bed Air Biofilter Under Acidic Conditions

In this paper, the application of biofiltration is investigated for controlled removal of gas phase chloroform through cometabolic degradation with ethanol. A trickle bed air biofilter (TBAB) operated under acidic pH 4 is subjected to aerobic biodegradation of chloroform and ethanol. The TBAB is composed of pelleted diatomaceous earth filter media inoculated with filamentous fungi species, which served as the principle biodegrading microorganism. The removal efficiencies of 5 ppm_v of chloroform mixed with different ratios of ethanol as cometabolite (25, 50, 100, 150, and 200 ppm_v) ranged between 69.9 and 80.9%. The removal efficiency, reaction rate kinetics, and the elimination capacity increased proportionately with an increase in the cometabolite concentration. The carbon recovery from the TBAB amounted to 69.6% of the total carbon input. It is postulated that the remaining carbon contributed to excess biomass yield within the system. Biomass control strategies such as starvation and stagnation were employed at different phases of the experiment. The chloroform removal kinetics provided a maximum reaction rate constant of 0.0018 s^-1. The highest ratio of chemical oxygen demand (COD)_removal/nitrogen_utilization was observed at 14.5. This study provides significant evidence that the biodegradation of a highly chlorinated methane can be favored by cometabolism in a fungi-based TBAB.