Xylene biofiltration of polluted air: Experimental observations

A new filtering material has been tested for its biofiltration performance for the treatment of air contaminated with the three isomers of xylene. The biofilter, operated at an empty bed residence time of 68 s and for xylene concentrations up to 6.7 g.m(-3), allowed a xylene and reduction of more than 92% for concentrations up to 2 g.m(-3), and more than 65% for concentrations less than 6.7 g.m(-3). The maximum xylene elimination capacity is of 236 g.m(-3).h(-1). In general, the removal efficiency of meta-xylene is the highest whereas the removal efficiency ortho-xylene is the lowest. At high xylene concentration, the increase of biodegradation intensity leads to the accumulation of a voluminous biofilm around the filtering particles, causing the clogging of the filter bed, the progressive retention of the nutritive solution in the superior parts of the bed, and the drying of the inferior parts of the bed. These observations have showed that a biofilter operating at high elimination capacities requires a meticulous control of the humidity of the filtering bed and a regular draining of the biomass excess.