Gas-liquid mass transfer studies in inverse fluidized bed biofilm reactor for the biodegradation of industrial effluent rich in phenolic compounds

Gas-liquid mass transfer studies were carried out in inverse fluidized bed biofilm reactor (IFBBR) for the biodegradation of phenol. Studies were done to analyze the effect of superficial air velocity (U-g), gas holdup ((g)), and biofilm characteristics such as biofilm thickness, biofilm dry density, suspended and attached biomass concentration, and bioparticle density on oxygen transfer rate (OTR) and gas-liquid volumetric mass transfer coefficient (k(L)a) for different superficial air velocities and various particle sizes (2.9, 3.5, and 3.8 mm). Average OTR and k(L)a was found to be high [(OTR)(avg.)=0.0159 min(-1); (k(L)a)(avg.)= 1.8823 g/(Lmin)] for the particle size of 3.5 mm at the optimum superficial air velocity (U-gm) of 0.220 m/s which created high turbulence with smaller bubble size. Higher volumetric mass transfer coefficient and OTR resulted in higher percentage of Chemical Oxygen Demand (COD) removal (98%) and phenol degradation (100%) in IFBBR. The gas holdup dominated over the smaller size bubbles resulting in higher mass (oxygen) transfer rate. Thin, dense, and stable biofilm was produced at U-gm. Above U-gm, thickness of the biofilm was increased where the detachment force did not control the outgrowth of biofilm anymore and thus the k(L)a was found to be decreasing. (c) 2015 American Institute of Chemical Engineers Environ Prog, 35: 433-438, 2016