Hollow fiber membrane biofiltration for removal of gaseous VOCs

Two membrane biofiltration systems that overcome many limitations of conventional compost biolfilters were investigated. A single natural rubber latex tubing and three polysulphone hollow fiber membrane modules (HFMM) were used to examine the biofiltration of gaseous benzene and butanol. Poor mass closures of benzene (60-80%) were observed in the HFMM systems. The maximum abiotic mass flux attained was 0.01 mg min-1 m-2 (0.004 mg min-1). Operated as a biofilter, the mass closure was close to 100% while removal was not observed. It was determined experimentally that polysulphone was not chemically compatible with benzene, probably due to sorption of benzene into the membrane. A 95% or greater mass closure was observed with butanol. The highest abiotic mass flux was 1.6 mg min-1 m-2 (0.48 mg min-1). The HFMM was operated for 46 days as a biofilter and achieved removals of 99%. A theoretical model was developed to predict the observed trends in biological removal of butanol due to changes in gas concentrations. The natural rubber latex tubing was operated with benzene as a bioreactor for 68 days. The maximum removal observed was 40%, with a mass flux of about 0.4 mg min-1 m-2 , higher than the abiotic mass flux of about 0.15 mg min-1 m-2 under the same operating conditions. However, compared with the removal of 80% achieved previously by Neemann (1998) with the same tubing, the removal in this work appeared much lower, possibly due to aging of the tubing --Abstract, page iii