Thermophilic toluene biofiltration

Thermophilic biodegradation of toluene with active compost biofilters was s tudied. Thermophilic conditions were maintained either by daily substrate a ddition (semicontinuous composting) or with a heating system (batch thermop hilic composting). The semicontinuous system was designed for the treatment of cool (less than approximately 35 degrees C) gases under thermophilic co nditions, while the extended batch approach was developed for the treatment of warmer gases. When the semicontinuous system was operated at 50 degrees C (after a one-day start-up period) at an average inlet concentration of 5 .5 g m(-3), toluene was degraded at a rate ranging from 73 to 110 g C m(-3) hr(-1). Batch thermophilic treatment was somewhat less effective at the Sa me inlet concentration. Semicontinuous toluene biofiltration at 60 degrees C was also investigated, but biodegradation rates were significantly lower than at 50 degrees C. In all systems, toluene biodegradation was proportion al to the inlet concentration. Rates of up to 289 g C m(-3) hr(-1) (at an i nlet concentration of 14.7 g m(-3)) were achieved for semicontinuous and ba tch operation and 251 g C m(-3) hr(-1) (at an inlet concentration of 18.4 g m(-3)) for batch thermophilic at 50 degrees C. Semicontinuous thermophilic operation at 60 degrees C showed a maximum rate of 119 g C m(-3) hr(-1). A ctive compost thermophilic biofiltration was found to be very effective whe n concentrations are high. At lower concentrations, rates were similar to t hose obtained with mesophilic biofiltration. Mixing, humidity, and the pres ence of cosubstrate were important parameters in maintaining high degradati on rates. Biofiltration in the batch thermophilic mode could be useful when conventional biofiltration is ineffective due to elevated gas temperatures . Biofiltration in the semicontinuous thermophilic could reduce the biofilt er size necessary for treatment of cooler gases containing high concentrati ons of volatile organic compounds.