Removal of xylene vapors in a biotrickling filter

Removal of p-xylene and m-xylene vapors from airstreams was studied with a small-scale biotrickling filter unit. The filter bed had a diameter of 10 cm and a height of 57 cm. The packing material was 3/4 inches ceramic Intalox saddles. The void fraction of the bed was 0.69. It was found that when all other conditions are kept constant, the removal rate increases when the inlet xylene concentration increases. However, the percent conversion of the pollutant drops when its concentration in the inlet airstream increases. At a residence time of 4 min (based on empty column) and liquid recirculation rate of 0.5 L/h conversions exceeding 95% were obtained with inlet p-xylene concentrations up to 3.2 mg/L. Under the same operating conditions, high conversions (>95%) for m-xylene were obtained with inlet concentrations up to 8 mg/L. Experiments with varying recirculation rates for the liquid medium were performed with m-xylene laden airstreams. With the given unit, it was found that removal rates and conversions increase when recirculation rate increases. Rates higher than 0.5 L/h did not affect removal rates significantly. It was also found that best results were obtained when the recirculating liquid was replenished with fresh nutrient medium every 2 days. The pH was found to remain essentially unchanged over periods of 2-3 days. The results indicate that biotrickling filters are much more efficient than classical biofilters.