Deodorization of contaminated air by immobilized microbes

Abstract

Biological removal of odorous volatile fatty acids (VFAs) in the gas stream of a trickling biofilter was studied. The column reactor was packed with spirally wound fibrous sheet material on which a consortium of microorganisms selected from activated sludge was immobilized. The bioreactor was operated under counter‐current flow of gas and liquid streams. Odorous VFA, butyric and valeric acids were introduced into the bioreactor at various inlet concentrations and flow rates. The effects of inlet VFA concentration and gas empty bed retention time (EBRT) on bioreactor performance were investigated. The effect of inlet concentration was studied by increasing the gaseous VFA concentrations at fixed EBRTs of 90, 60, 45 and 30 s. While the effect of EBRT was investigated by increasing the gas superficial velocity or shortening EBRT, at different inlet VFA concentrations of 0.08, 0.2, 0.4 and 0.7 g/m3. The bioreactor was effective in treating odorous VFA at mass loadings up to 32 g/m3/h, at which VFA started to accumulate in the recirculation liquid indicating the biofilm was unable to degrade all the VFA introduced. Although VFA accumulated in the liquid phase, the removal efficiency remained above 99%, it implies the biochemical reaction rate rather than gas‐to‐liquid mass transfer rate was the rate limiting step of this process. The bioreactor was stable for long‐term operation; relatively low and steady pressure drop, no clogging and degeneration of the packing medium occurred during the 4‐month period studied.