Modelling of Metal Recovery using Sulfate Reducing Bacteria, Simulation in MATLAB and Aspen Plus

Abstract: This report presents a mathematical kinetic model describing the recovery of metal ions as metal sulfides, using sulfate reducing bacteria (SRB). Metal recovery from industrial waste is a potential beneficial and unused source of metals. The developed kinetic model is implemented and simulated in the computer programs MATLAB R2014b and Aspen Plus V8.8. The MATLAB simulation is performed on the bioreactor, where sulfate reducing bacteria produce hydrogen sulfide. The hydrogen sulfide can be used to precipitate metal ions as metal sulfides in which the metals can be removed and recovered from the industrial waste. The full metal recovery model with precipitation tanks and the bioreactor is simulated in the process simulation program Aspen Plus. A literature study was conducted before the simulation to develop the kinetic model. The main results from this project are a kinetic growth model for sulfate reducing bacteria implemented in the two computer programs as well as a precipitation model implemented in Aspen Plus. The kinetic model includes inhibition terms for pH and hydrogen sulfide. The models are working and calibrated according to literature data. However, in the future it will be necessary to calibrate the models according to real experimental values for the given process. It can be concluded that simulating processes in computer programs makes it possible to predict how feasible the process is in reality. It can also suggest model designs and critical steps that can be avoided in the future and other potential improvements of the process. This can save a lot of time and resources spent on the process before building it. The environmental aspects need to be considered since the process produces a lot of toxic hydrogen sulfide. It is therefore important to have an accurate and well established safety routine for this process.