TRANSIENT-BEHAVIOR OF BIOFILTERS - START-UP, CARBON BALANCES, AND INTERACTIONS BETWEEN POLLUTANTS

The work describes the aerobic biodegradation of volatile organic comp ound (VOC) mixtures from effluent air streams in laboratory-scale comp ost based biofilters. A rapid start-up of the system (3-5 d) was obser ved and 82% of the carbon in the influent pollutant (methyl ethyl keto ne) was recovered as carbon dioxide in the exhaust air after this peri od. Biofilter performance and carbon dioxide production were also inve stigated during and after 0.5-1-h step inputs of 2-10 g m(-3) of hexan e, acetone, 1-propanol, and/or methyl isobutyl ketone (MIBK) during st eady methyl ethyl ketone (MEK) treatment. Carbon dioxide patterns sugg est that pulsed pollutants were first sorbed onto the packing material and subsequently degraded within 2-5 h. Hexane was not sorbed, and th us not degraded to a significant extent. Little effect was observed of the step inputs on the overall MEK removal process, mainly because th e reactors were operated well below MEK breakthrough loading. However, the analysis of MEK profiles within the biofilter bed showed that sig nificant inhibition did indeed occur. An even more important inhibitio n was observed between 1-propanol, MIBK, and acetone, when such a mixt ure was injected into the reactor. Practical design of biofilters shou ld consider the possibility of reduced performances due to the presenc e of multiple VOCs in the waste air stream.