Performance assessment, kinetics and modelling of biofilm membrane bio-reactor for the treatment of dairy wastewater

Abstract

Aim : The present study investigated the performance of a bench scale Biofilm Membrane Bioreactor (BFMBR) and determined relevant biokinetic coefficient for subsequent kinetic modelling and simulation studies for evaluating the feasibility of BF-MBR for treating dairy wastewater. Methodology : The bench-scale BF-MBR was devised by combining conventional aerobic membrane bioreactor with a moving bed biofilm reactor. The bioreactor was operated at varying Hydraulic Retention Times (HRT) of four, six, and eight-hour to determine the optimum HRT and thereby, enhance reactor performance. Kinetic studies were also performed on the BF-MBR treated dairy effluent to determine the biokinetic coefficients like yield coefficient and other rate constants. Subsequently, kinetic modelling and simulation studies which incorporates the obtained biokinetic coefficients were performed using BioWin, a simulation software, used to optimize system design and performance. Results : The results revealed that the Biofilm MBR that operated at an optimum HRT of six hours produced treated effluent with the following physico-chemical properties: Chemical Oxygen Demand= 60.90 mg l-1 , Total Nitrogen = 9.61 mg l-1 and Total Phosphorus = 6.26 mg l-1 corresponding to removal efficiency of 97.25%, 91.8% and 64.8% respectively. The obtained average value of biokinetic coefficients were Yield Coefficient = 0.617 mg mg-1, Decay rate = 0.1387 per day, maximum specific growth rate = 2.5189 per day and saturation constant = 888.917 mg COD l-1. Also, the simulated effluent characteristics were found to be closely related with those of an experimental investigation showing R2 values of 0.9586, 0.8394 and 0.8362 for various concentrations of COD, TN and TP, respectively. Interpretation : It was observed from the laboratory bench-scale performance and modelling studies that biofilm-membrane bio reactor is a suitable system for removal of organic and nutrient pollutant from dairy wastewater to meet the discharge standards.