Carbon recovery and the impact of start‐up conditions on the performance of an unsaturated Pseudomonas putida biofilm compared with soil under controlled environmental parameters in a differential biofilter

BACKGROUND: Microbial functionalities deciphered from batch/microcosm studies often do not truly represent the environmental conditions microbes are exposed to in a traditional column biofilter. Investigations under biofilter conditions with pure culture of active communities along with the fate of degraded pollutants is needed. This work explicitly tracked and quantified the various carbon end‐points, CO₂, EPS (extracellular polymeric substances) and soluble microbial products of an unsaturated Pseudomonas putida biofilm degrading airborne toluene using a unique differential biofiltration system under controlled environmental conditions. Further, the impact of start‐up conditions on the degradation rates was evaluated under two bed configurations (biofilm vs soil). RESULTS: Carbon balance closure was achieved to 97% ± 5%. The percentage of toluene converted to CO₂ ranged from 90% to 50% and dropped as toluene concentrations in the air increased over a range of 20 to 140 ppmv toluene. Scanning electron microscopy and confocal microscopy with lectin binding stain WGA‐647 demonstrated carbon accumulation as EPS, further validating the quantitative data. Start‐up at an inlet toluene concentration of 75 ppmv before increasing to 120 ppmv, approximately doubled toluene removal rates for both the pure culture biofilm and soil compared with starting at 120 ppmv—surface elimination capacity (SEC) increased from 0.040 to 0.080 g m⁻² h⁻¹ and elimination capacity (EC) from 55 to 80 g m⁻³ h⁻¹. CONCLUSIONS: The carbon end‐point pattern provided valuable insights to the metabolic response linked to the operating parameters. Optimized start‐up conditions can help improve process efficacy and address operational problems like clogging. © 2018 Society of Chemical Industry