Mathematical prediction of COD removal using interrelation of operating variables of the aerobic inverse fluidized bed biofilm reactor (AIFBBR)

Abstract

The present study aimed to develop a mathematical model for predicting COD removal using the interrelation of operating variables. The model for predicting COD removal is named the dimensionless number for COD removal (DNC). The DNC was formulated based on the critical variables of the AIFBBR process for the rice mill wastewater treatment. HRT, OLR, and biomass concentration (M_b) are considered for the generation of DNC for the AIFBBR system. In the present attempt of framing such a dimensionless number DNC, many experimental runs were conducted by varying the COD strength of 0.8–3.2 kg/m³, OLR of 0.80–6.40 kg/m³.d, and M_b of 0.90–7.43 kg/m³. The developed DNC was subjected to sensitivity analysis, and biomass concentration in the system was observed to be the most sensitive among other parameters incorporated in the model. In addition, from the sensitivity analysis, it was also revealed that the removal efficiencies were observed to increase with the increase in DNC values in the COD range of 0.8–3.2 kg/m³. In addition, the plot between the reported removals from the literature on biofilm processes for wastewater treatment and DNC values yielded an R² value of 0.79.