Determinação de parâmetros cinéticos em biomassa granular no tratamento de drenagem ácida de minas

Abstract

The use of bioreactors containing immobilized cells is a viable alternative for the treatment of acid mine drainage, liquid effluent from mining activities. However, in this type of reactor the substrate may find it difficult to diffuse inside the bacterial granule and affect the kinetics of the reaction. Based on this finding, the main objective of this work is to find the intrinsic kinetic parameters in granular biomass and to evaluate if there are effects of resistance to internal mass transfer. For this, temporal profiles were plotted at sulfate concentrations of 500 and 250mg.L-1 for different surface velocities. These phases were operated in differential reactors in batch mode, temperature of 30±1°C, cycle time of 48h and ethanol as carbon source. The COD/sulfate ratio was maintained equal to 2. The input pH varied between 3.2 and 3.3 and the iron, zinc and copper concentrations corresponded to 25, 20 and 5mg.L-1, respectively. In order to find the best condition to perform the profiles, preliminary tests were performed under various operating conditions. The observed Thiele modulus was used to evaluate the effect of internal mass transfer. The results showed that the kinetic model of the first order is representative to describe the sulfate reduction. The values ​​of the kinetic constants k1, for superficial velocities between 0.07 and 1.05cm.min-1, varied in the range of 0.0098 to 0.0136 for sulfate concentration of 500mg.L-1, and 0.0200 to 0.0648 for sulfate concentration of 250mg.L-1. The observed Thiele modulus showed that the resistance to internal mass transfer could be neglected, with the rate of substrate consumption being limited to the kinetics of the reaction.