Removal of xylene by a mixed culture of Pseudomonas sp. NBM21 and Rhodococcus sp. BTO62 in biofilter.

Xylene (a mixture of o-, m-, p-xylenes and ethylbenzene) gas removal was conducted in the a biofilter inoculated with a mixture of the m- and p-xylene-degraders, Pseudomonas sp. NBM21 and an o-xylene degrader, Rhodococcus sp. BTO62 under non-sterile conditions at 20 degrees C. Elimination capacities of o-, m-, and p-xylenes obtained were 180 g/m(3)/h at 20 degrees C and 100 g/m(3)/h at 10 degrees C, which were significantly higher than the 60-78 g/m(3)/h of previously reported biofilters, indicating that the two bacteria inoculated exhibited an almost total ability to remove xylene although only present in low numbers in the biofilter. In the sterile biofilter, carbon mass balance showed that 11.6% of the removed xylene was converted to cell mass. Among the xylene components, o-xylene was the most resistant to microbial degradation in spite of the low component ratio.

Removal of o-xylene using biofilter inoculated with Rhodococcus sp. BTO62.

Rhodococcus sp. BTO62 was isolated from activated sludge from a wastewater treatment plant as an o-xylene-degrading microorganism. BOT62 degraded not only o-xylene, but also benzene, toluene, ethylbenzene, m- and p-xylenes and styrene (BTEXS). A laboratory scale biofilter packed with Biosol as packing material, which is made from foamed waste glass mixed with corrugated cardboard, was inoculated with strain BTO62 and operated to remove relatively high loading of o-xylene at different space velocities under non-sterile and sterile conditions. The o-xylene elimination capacity to maintain more than 90% removal efficiency was 41g/m3/h under sterile condition, but it enhanced to 160g/m3/h under non-sterile condition. This indicates possibilities of the role of other contaminants for degradation of o-xylene and the degradation of intermediate products of o-xylene by contaminants. Quick recovery of o-xylene degradation was observed after shutdown of o-xylene gas supply and mineral medium circulation for 10-30 days.

Removal of p-xylene with Pseudomonas sp. NBM21 in biofilter.

As a p-xylene (p-Xyl)-degrading microorganism, Pseudomonas sp. NBM21 was isolated from an activated sludge of a wastewater treatment plant. NBM21 degraded p-Xyl, m-xylene, benzene and toluene, but not o-xylene, ethylbenzene (Eb) and styrene. NBM21 was inoculated to a biofilter with Biosol as a packing material and p-Xyl removal was operated for 105 d under sterile and nonsterile conditions. The maximum elimination capacities for p-Xyl at higher than 90% removal efficiency were 160 g/m3/h and 150 g/m3/h under nonsterile and sterile conditions, respectively. A high load of Eb adversely affected to the removal of xylene.