DESIGN AND PERFORMANCE OF A TRICKLING AIR BIO-FILTER FOR CHLOROBENZENE AND O-DICHLOROBENZENE VAPORS

From contaminated industrial sludge, two stable multistrain microbial enrichments (consortia) that were capable of rapidly utilizing chlorob enzene and o-dichlorobenzene, respectively, were obtained. These conso rtia were characterized as to their species composition, tolerance ran ge, and activity maxima in order to establish and maintain the require d operational parameters during their use in biofilters for the remova l of chlorobenzene contaminants from air. The consortia were immobiliz ed on a porous perlite support packed into filter columns. Metered air streams containing the contaminant vapors were partially humidified an d passed through these columns. The vapor concentrations prior to and after biofiltration were measured by gas chromatography. Liquid was ci rculated concurrently with the air, and the device was operated in the trickling air biofilter mode. The experimental arrangement allowed th e independent variation of liquid flow, airflow, and solvent vapor con centrations. Bench-scale trickling air biofilters removed monochlorobe nzene, o-dichlorobenzene, and their mixtures at rates of up to 300 g o f solvent vapor h(-1) m(-3) filter volume. High liquid recirculation r ates and automated pH control were critical for stable filtration perf ormance. When the accumulating NaCl was periodically diluted, the tric kling air biofilters continued to remove chlorobenzenes for several mo nths with no loss of activity. The demonstrated high performance and s tability of the described trickling air biofilters favor their use in industrial-scale air pollution control.