Use of biological activated carbon to treat mixed gas of toluene and benzene in biofilter.

The biodegradation of toluene and benzene in a biofilter filled with cylindrical activated carbon was studied. Three various gaseous flow rates, i.e. 0.25, 0.50 and 0.75 m3 h(-1), corresponding to empty bed gas residences of 75, 37.5 and 25 s, respectively, and total organic load lower than 400 g m(-1) h(-1) were tested. The biofilter proved to be highly efficient in biodegradations of toluene and benzene, and toluene was more easily degraded than benzene. When each inlet load of toluene and benzenewas lower than 150 g m(-3) h(-1), removal rate increased with inlet loads and reached maximum values of 150 and 120 g m(-3) h(-1) for toluene and benzene, respectively. For inlet load higher than the maximum removal capacity conditions, the removal rate decreased with inlet load. The carbon dioxide concentration profile through the biofilter revealed that the mass ratios of carbon dioxide produced to the toluene and benzene removed were 2.15 g CO2 g(-1) toluene and 1.67 g CO2 g(-1) benzene. Model predictions for toluene, benzene and carbon dioxide concentration gradient profiles were in agreement with experimental data for the tested conditions. The observation of biotic community demonstrated that the microbes consisted of bacillus, spore bacillus and fungi, of them spore baxillus was dominant.