Biofiltration of waste gases in a reactor with a split-feed

The efficiency of using different feed strategies was evaluated in the case of a gas-phase biofilter packed with an inert carrier material. During a preliminary control-period, the biofilter was first fed with a single downflow feed of toluene. Reactor performance and biomass distribution were evaluated. The feed was then split into two flows before entering the reactor. Different feed ratios were tested during a 6-month period, following the preliminary control stage. Splitting the feed into equal flow rates through the upper and middle part of the biofilter (in a 50 : 50 ratio) improved the performance compared with the single-feed period. Such a high performance could also be maintained when using a higher flow rate for the upper port than for the middle port, with a feed-ratio of approximately 70 : 30, when more biomass was formed in the upper half of the filter bed. However, performance decreased when inverting this ratio from 70 : 30 to 30 : 70, ie when the highest flow rate was fed through the middle port of the biofilter. (C) 2003 Society of Chemical Industry.