Abstracts Biological Sciences

Treatment of Mixtures of Methyl Ethyl Ketone (MEK) and Toluene Using Continuous and Sequencing Batch Operated Biofilters

by Jorge C. Atoche

During the past decade, biofiltration has increasingly been applied as an air pollution control technology to minimize or eliminate emissions of volatile organic compounds from industrial sources. Although of the ability of this technology to maintain high removal efficiency during relatively steady conditions has been well established for many waste streams, a limitation of this technology has been its inability to maintain high removal efficiency during transient loading conditions typical of industrial operations. In the research described herein, a conventional continuous-flow biofilter (CFB) and a sequencing batch biofilter (SBB) were operated for more than 295 days to treat a model waste gas stream containing a two-component mixture of toluene and methyl ethyl ketone (MEK). During "normal" loading conditions, the model waste stream contained toluene concentrations ranging from 28 to 30 ppmv and MEK concentrations ranging from 80 to 89 ppmv. On a regular basis, the influent toluene and MEK concentrations were temporarily increased to five times the normal influent concentration for duration of one hour to test performance during shock loading. Profile studies were conducted in both biofilters during the loading conditions tested. Biomass distribution within the biofilters and head loss was also measured. Data presented herein establish that sequencing batch operation of biofilters treating air contaminated with mixtures of toluene and MEK is not only a feasible technology, it also offers advantages over conventional CFBs in several important measures of performance, namely, minimum instantaneous removal efficiency, overall contaminant removal efficiency, and head loss. During normal loading conditions both biofilters exhibited stable long-term performance with greater than 99% contaminant removal. During shock loading experiments, the SBB was able to remove more than 99% and 87% of the influent contaminants when subjected to loading rates of 209 and 449.5 gm<sup>-3</sup>h<sup>-1</sup>, respectively. In comparison, the CFB exhibited lower overall removal efficiency. The SBB exhibited lower head loss than the CFB, likely because of a more homogeneous spatial distribution of biomass within the system. Accumulation of undegraded contaminants during the loading period and the subsequent biodegradation during the recirculation period in the SBB was demonstrated, even after long-term operation.