Effect of equilibrium models in the simulation of heavy metal biosorption in single and two-stage UF/MF membrane reactor systems

Abstract

In this paper heavy metal biosorption in an UF/MF (ultrafiltration/microfiltration) membrane reactor was simulated outlining the effect of different equilibrium models on the predicted performances of the bioreactor. In particular using Langmuir, Freundlich and Redlich–Peterson isotherms slightly different simulated profiles were obtained evidencing the adequacy of all the equilibrium models in representing a common dynamic behaviour. Experimental data of copper biosorption onto Sphaerotilus natans cells obtained using an UF membrane reactor system, were compared with theoretical profiles obtained from the combination of mass balances with adsorption equilibrium properties. This comparison outlines the necessity of considering a partial cell degradation (as confirmed by permeate flux decline) which was taken into account in the modelling phase introducing a time depending biomass concentration, function of the copper retention coefficient. The simulated dynamic behaviour of a single reactor was also compared with a series of two reactors (with the same total volume and biomass amount) in order to optimise the operative configuration to use.