Effect of superficial gas velocity and ratio of bed volume to reactor volume of inverse fluidized bed biofilm reactor on the removal of ammonia-nitrogen from wastewater

Hydrodynamic parameters of an inverse fluidized bed biofilm reactor (IFBBR) have been studied using spherical polypropylene (PP) particles having average diameter and density of 5.63 mm and 920 kg/m3 respectively. Gas-phase holdup (g) was analyzed for various ratios of settled bed volume to reactor volume (Vb/Vr) and superficial gas velocities (Ug) with a liquid recirculation velocity (Ul) of 0.0021 m/s. The g values were found to increase with Vb/Vr ratios up to a certain limit and then decrease with further increase of Vb/Vr ratios. The effect of Ug, Vb/Vr ratios, and initial concentration of ammonia-nitrogen (NH4 +-N) on the removal of NH4 +-N from synthetic wastewater were studied. The optimal values of Vb/Vr ratio and Ug were found to be 0.380 and 0.0085 m/s respectively for all initial NH4 +-N concentrations. Complete removal of NH4 +-N was achieved in 8 to 44 hours for different initial NH4 +-N concentrations. It was also observed that with the increase in initial NH4 +-N concentrations, the nitrification decreases