A review on hydrodynamic parameters and biofilm characteristics of inverse fluidized bed bioreactors for treating industrial wastewater

Abstract

Abstract Wastewater treatment processes play crucial role in keeping the human health and environment at proper hygiene. Currently, biological wastewater treatment methods are dominant in the effluent treatment process because of their cost-effectiveness in the treatment. However, the rapid increase in population has created a need for the implementation of highly efficient wastewater treatment methods. In the recent past, the treatment of wastewater through fluidized-bed bioreactor has proven as one of the best processes from the currently available methods of chemical and biochemical engineering fields. This review aims to explore and compile the methods of fluidization used for the treatment of wastewater in the recent past, majorly by the inverse fluidization method. In the inverse fluidization process, the density of solid particles utilized in the fluidization is lower than that of the liquid and compared to an up-flow fluidized bed bioreactor, and it is a very effective system for biological wastewater treatment. This review discusses the developments made in recent years with regard to aerobic inverse fluidized bed bioreactors, with more emphasis placed on the reported applications on treating industrial wastewaters. The influence of hydrodynamic parameters (minimum fluidization velocity, phase holdup, bed expansion, and bed height, pressure drop, superficial gas velocity, liquid velocity, hydraulic retention time, biofilm carriers and ratio of volume of settled bed to the volume of reactor) are highlighted in the discussion, and also the effect of these parameters on the biofilm and its subsequent effect on wastewater is included. Recent trends of application of aerobic inverse fluidized bed bioreactors for the removal of COD and scope of future study elements have been discussed in this manuscript.