WATER-CONTENT DYNAMICS IN BIOFILTRATION - THE ROLE OF HUMIDITY AND MICROBIAL HEAT-GENERATION

Mass and energy balances were performed on a compost biofilter to iden tify the mechanisms for water content change in the compost bed materi al. Three mechanisms were identified: humidity fluctuations at the inl et and outlet, heat generation from microbial oxidation, and gradients in the water potential. Microbial oxidation and humidity fluctuations were the dominant mechanisms for water content changes. Time domain r eflectometry was used to estimate on-line volumetric water content in the bed material. Biofiltration experiments demonstrated a moving fron t of temperature increase and water evaporation associated with the mi crobial oxidation of toluene. The localized microbial heat generation evaporated sufficient water from consecutive sections of the bed, even tually impairing degradation throughout the entire column.