Hydrogen production automatic control in continuous microbial electrolysis cells reactors used in wastewater treatment

In this paper, two control laws are proposed and applied in a model for a continuous Microbial Electrochemical Cells system. The used model is based on mass balances describing the behavior of substrate consumption, microbial growth, competition between anodophilic and methanogenic microorganisms for the carbon source in the anode, hydrogen generation, and electrical current production. The main control objective is to improve the electrical current generated and thus the production of bio-hydrogen gas in the reactor, using the dilution rate and the applied potential as individual control input variables. The control laws implemented are nonlinear adaptive type. In order to demonstrate its usefulness, numerical simulation runs involving multiple set-point changes and input perturbations were conducted for each control variable. The results of these simulations show that both control laws were able to respond adequately and efficiently to the disturbances and reach the reference value to which they were subjected. Moreover, it is possible to control both the electrical current produced and the hydrogen produced. Finally, these simulations also show that the highest rate of hydrogen production can be obtained using the applied potential as a control input, but such productivity is only attainable for a short period of time.