Siloxanes removal from biogas by a lab-scale biotrickling filter inoculated with Pseudomonas aeruginosa S240

Abstract

Removing volatile methyl siloxanes (VMSs) from biogas remains a longstanding challenge in the field of biological process due to their low bioavailability and biodegradation. To address this issue, a lab-scale aerobic biotrickling filter, packed with porous lava and inoculated with an effective strain of Pseudomonas aeruginosa, was developed and its performance for octamethylcyclotetrasiloxane (D4, selected as a model VMS) removal from an aerobic synthetic gas was monitored. The biotrickling filter exhibited a relatively high removal efficiency over 74% at empty bed residence time of 13.2min. Rhamnolipids, biosurfactants produced by P. aeruginosa, were identified in the liquid phase of the biotrickling filter by HPLC–MS and ATR-FTIR, and they were found to be the main factor of improving D4 removal. Moreover, dimethylsilanediol, methanol, silicic acid in the liquid phase and carbon dioxide in the gas phase, as the biodegradation products of D4, were determined by GC–MS, silicic acid analysis and non-dispersive infrared analysis. To our knowledge, it is the first time to report the existence of methanol in the D4 degradation products. Finally, a metabolic pathway for D4 degradation by P. aeruginosa was proposed based on our results.