Biodegration of high concentration isopropanol vapour in a biofilter inoculated with a solvent-tolerant microbial consortium

The aerobic biodegradation of high vapour-phase concentrations 2-propanol (IPA) by a previously enriched solvent-tolerant bacterial consortium within a 1.91 biofilter was investigated. Successful biofiltration of solvent vapour concentrations of up to 10,500 ppm_v was implemented. The aforementioned solvent-tolerant bacterial cells were immobilized onto porous glass cylinders as a means of bioprocess intensification. Biofilter start-up and acclimation were studied and acetone concentration tracked as an indicator of IPA utilization, as the sole carbon source within a minimal salts medium (MSM). Removal efficiencies of up to 100% for both IPA and acetone were successfully demonstrated by this biofiltration system during steady state operating conditions. IPA vapour feed concentrations were varied between 6500 and 10,500 ppm_v during biofilter start-up and acclimation, where the lowest removal efficiency obtained was 47% during the initial 48 h of operation. It is also proposed that metabolic lag within the biofilm occurs during the acclimation period, due to the presence of the dual substrate system of IPA and acetone and also mass transfer limitations. Analysis of the biofilm throughout the bed demonstrated that most dense growth occurred at the top of the biofilter, with minimal growth present in close proximity to the inlet. The results demonstrate the potential of a previously enriched solvent-tolerant bacterial consortium in biofilter systems, for the aerobic treatment of concentrated VOC gases at levels up to 2 orders of magnitude higher than other studies dealing with gas phase IPA biofiltration.