Process to convert bisulphide to elemental sulphur

A control method for a process to convert bisulphide to elemental sulphur in an aqueous solution comprising sulphide-oxidising bacteria wherein the control method comprises

• providing an electrochemical cell comprising a cathode electrode, an anode electrode and a reference electrode,
• wherein the electrodes are in contact with the aqueous solution,
• wherein a potential is applied, the applied potential, between the anode electrode and the cathode electrode or between the anode electrode and the reference electrode resulting in a current between the cathode electrode and the anode electrode and wherein reduced sulphide-oxidising bacteria transfer electrons to the anode electrode,
• wherein the current is measured running between the cathode electrode and the anode electrode at anaerobic conditions while maintaining a constant potential between the anode electrode and the cathode electrode or while maintaining a constant potential between the anode electrode and the reference electrode,
• wherein the measured current is a measure of the bioactivity of the sulphide-oxidising bacteria to convert bisulphide to elemental Sulphur, and
• adapting the process in response to the measured current.