ENGINEERED BIOFILTER FOR REMOVING ORGANIC CONTAMINANTS IN AIR

Biofiltration is an established economical air pollution control techn ology for removing organic contaminants in air. Existing filters using natural media, such as peat and compost, were demonstrated in the fie ld for degrading up to several thousand ppm of contaminants. An engine ered biofilter using synthetic media, such as activated carbon, has be en developed that shows improvements in removal efficiency, biodegrada tion and space requirements over the existing filters. This carbon fil ter has been operated for > 11 months in a bench-top unit, accomplishi ng greater-than-or-equal-to 90 percent removal efficiency consistently in a stream containing 10 to 20 ppm of toluene. The mass transfer zon e remained stationary and extremely short (1 to 4 seconds of empty bed contact time) during the entire operating period. Compared with exist ing filters, this engineered filter showed 40 to 80 times greater biod egradation efficiency under the selected conditions, resulting in a de creased space requirement and other advantages in equipment sizing. In addition, the engineered filter allows for removal of biomass, with n o medium compaction and no replacement or excess disposal of spent med ia required. The unit, kept in a humid state supplemented with inorgan ic nutrients, offers a desirable environment for biogrowth. The extrem ely efficient bio-regeneration shown in this study indicates that the biofilter could also replace some existing carbon applications, partic ularly for removal of weakly-adsorbed, but biodegradable, contaminants or applications with strong competition by moisture.