Effect of periods of non-use on biofilter performance

A biofilter does not operate as a true filter, but removes chemicals from gases by sorption and biologically degrades them. The objective of the research reported in this paper was to investigate the effect of periods of non-use on biofilter performance. The concept of non-use had two meanings in this research: ''no chemical loading,'' which indicated that humidified air was passing through the biofilter with no chemicals, and ''stagnant,'' which reflected that no flow at all was passing through the biofilter. Both instances of non-use can require the microorganisms in the biofilter to re-acclimate to differences in loading and type of chemical when a chemical load is re-applied. Acclimation time was compared with three different chemicals, initial acclimation was compared with re-acclimation following different periods of non-use, and the effect of humidification during the period of non-use was examined. Bench scale testing produced results indicating that acclimation times ranged from several hours to longer than a day. Longer periods of biofilter non-use resulted in longer re-acclimation periods and transition between different chemicals resulted in acclimation periods shorter than initial acclimation periods. Stagnant periods produced longer re-acclimation periods than periods of no chemical loading.