Design and Performance of a Toluene-Degrading Differential Biotrickling Filter as an Alternative Research Tool to Column Reactors

Abstract

A differential biotrickling filter (DBTF) was developed as a research tool to minimise radial and longitudinal gradients, which hinder analysis in integral (column) reactors. The main design modifications were a very high gas recycle rate and a low, uniform liquid addition rate via an aerosol generator. The elimination capacity (EC), uniformity of biofilm formation and long-term reliability of the reactor were evaluated. The maximum toluene elimination capacity was approximately 430 g/m 3 h, which was higher than the EC in most previous reports. The high EC was potentially due to the thin liquid film over the biofilm generated by low liquid trickling rates. Moreover, the high gas recycle rate (2.5 -100x the feed flow rate) allowed uniform substrate and nutrients distribution throughout the bed hence promoting favourable growth and performance of the microbes. These findings can serve as a guide in improving performance of industrial biotrickling filters. Substrate inhibition was observed at loading rates (LRs) higher than 513 ± 27 g/m 3 h. Despite operational issues that affected its long-term reliability, such as: (1) unwanted growth of microbes on the pipes and in the aerosol reservoir; (2) decline in the performance of the aerosol generator; and (3) limited fan capacity, the DBTF is a promising tool that can improve biofiltration research.