Regular Transient Loading Response in a Vapor-Phase Flow-Direction-Switching Biofilter

The principal objective of this study was determination of the response of a laboratory-scale vapor-phase flow-directionswitching biofilter to loading changes associated with normal operations such as lunch breaks, overnight shutdowns, and single-shift operation of commercial and industrial facilities. Three regular transient loading cases were considered: (a) variable flow-reversal interval lenghts, (b) variable feed-on/off interval lengths, and (c) variable inlet concentration during a repeating feed-on/off cycle. Toluene was used as the model contaminant compound. The most significant findings of the study were: (1) Relative to unidirectional mode of operation, periodic flow reversal produced a more uniform distribution of reaction capacity along the length of the packed bed; (2) a 12 h flow reversal interval was sufficiently short to maintain the toluene-degrading microbial community in a near-fully active state throughout the unit whereas a 2 day flow reversal interval resulted in diminished removal rates in the first half of the bed and (3) Increasing off-period length resulted in greater penetration of contaminant into the bed and more uniform removal rates along the length of the bed. Information developed in this study should provide a more complete basis for establishing operating protocols and monitoring regulations for vapor-phase biofiltration systems.