Stable biofilm formation via nutrition regulation for enhancing toluene removal in gas–solid fluidized-bed bioreactors

Abstract

Gas-solid fluidized-bed bioreactors (FBRs), an innovative equipment for gaseous volatile organic compound (VOC) treatment, are used to realize efficient removal of VOCs characterized by large volumes and low concentrations and avoid clogging due to excessive biofilm accumulation. However, difficulties in biomass accumulation caused by stressful environmental pressures, especially shear force, limit their development. In this study, two laboratory-scale FBRs were built, and toluene removal was nearly twiced with saturated relative humidity and adequate nutrition supplement. Accelerated biofilm formation, activated microbial metabolism, enhanced mechanical strength, and surface smoothness were also observed. Nutrition regulation optimized cell synthesis and extracellular polymeric substance secretion through alternation of the accumulation of elements, especially C/N and Ca, which increased by 84 % and 112 %, respectively. The biofilm loss was reduced by 50–75 % under compression and collision conditions, indicating the promoted biofilm stability under shear force caused by extrusion and collision between particles. With the initial drawbacks partially mitigated, nutrient regulation during FBR operation was found to be useful. This study provides theoretical support for further applications of FBRs and efficient treatment of gaseous VOCs with large gas volumes and low concentrations.