Abstract: The invention is directed to a process to convert carbon dioxide to methane by contacting an aqueous solution comprising dissolved carbon dioxide with an electron charged packed bed comprising of a carrier, suitably activated carbon granules, and a biofilm of microorganisms under anaerobic conditions, wherein more than 90 mol % of the dissolved carbon dioxide in the aqueous solution is present as a bicarbonate ion and/or as a carbonate ion.

Abstract: The invention is directed to a continuous process to treat a hydrogen sulphide comprising gas comprising the following steps: (a) contacting the hydrogen sulphide comprising gas with an aqueous alkaline solution further comprising sulphide oxidising bacteria thereby obtaining a loaded aqueous solution comprising sulphide compounds and sulphide oxidising bacteria. (b) contacting the loaded aqueous solution with an oxygen comprising gas to regenerate the sulphide oxidising bacteria to obtain a liquid effluent comprising regenerated sulphide oxidising bacteria which is partly used as the aqueous alkaline solution in step (a). (c) separating elemental sulphur as prepared by the sulphide oxidising bacteria in steps (a) and (b) from the loaded aqueous solution of step (a) and/or from the liquid effluent of step (b) and wherein the consumption of oxygen in step (b) is measured and wherein the supply of oxygen in step (b) is controlled by the measured consumption of oxygen.

Abstract: The invention is directed to a control method for a process to convert bisulphide to elemental sulphur in an aqueous solution comprising sulphide-oxidising bacteria wherein the process is controlled by applying a potential between the anode electrode and the cathode electrode or between the anode electrode and the reference electrode of an electrochemical cell resulting in a current between the cathode electrode and the anode electrode, measuring a current as measured by an electrochemical cell and adapting the process in response to the measured current. The process to convert bisulphide may comprise the following steps: (a) contacting bisulphide with oxidised sulphide-oxidising bacteria in the aqueous solution and elemental sulphur, (b) oxidizing the reduced sulphide-oxidising bacteria, (c) using the oxidised sulphide-oxidising bacteria obtained in step (b) in step (a) and (d) isolating elemental sulphur from the aqueous solution obtained in step (a) and/or step (b).

Abstract: The invention is directed to a process to prepare elemental sulphur by (i) contacting an aqueous solution comprising bisulphide with oxidised sulphide-oxidising bacteria under anaerobic conditions wherein elemental sulphur is produced and a reduced sulphide-oxidising bacteria is obtained and (ii) wherein the reduced sulphide-oxidising bacteria are oxidised by transfer of electrons to an anode of an electrochemical cell to obtain the oxidised sulphide-oxidising bacteria.

Abstract: The invention is directed to a process to convert a sulphur compound to bisulphide by direct or indirect transfer of electrons from a cathode of a bio-electrochemical cell to the sulphur compound under anaerobic conditions and in the presence of mixed culture comprising methanogens and suitably also a anaerobic or facultative anaerobic bacteria. The sulphur compound may be a thiol like methanethiol or ethanethiol or a polysulphide, like dimethyl disulphide.

Abstract: The invention is directed to a process to convert a sulphur compound to bisulphide by direct or indirect transfer of electrons from a cathode of a bio-electrochemical cell to the sulphur compound under anaerobic conditions and in the presence of mixed culture comprising methanogens and suitably also a anaerobic or facultative anaerobic bacteria. The sulphur compound may be a thiol like methanethiol or ethanethiol or a polysulphide, like dimethyl disulphide.

Abstract: The invention is directed to a control method for a process to convert bisulphide to elemental sulphur in an aqueous solution comprising sulphide-oxidising bacteria wherein the process is controlled by applying a potential between the anode electrode and the cathode electrode or between the anode electrode and the reference electrode of an electrochemical cell resulting in a current between the cathode electrode and the anode electrode, measuring a current as measured by an electrochemical cell and adapting the process in response to the measured current. The process to convert bisulphide may comprise the following steps: (a) contacting bisulphide with oxidised sulphide-oxidising bacteria in the aqueous solution and elemental sulphur, (b) oxidizing the reduced sulphide-oxidising bacteria, (c) using the oxidised sulphide-oxidising bacteria obtained in step (b) in step (a) and (d) isolating elemental sulphur from the aqueous solution obtained in step (a) and/or step (b).

Abstract: The invention is directed to a process to prepare elemental sulphur by (i) contacting an aqueous solution comprising bisulphide with oxidised sulphide-oxidising bacteria under anaerobic conditions wherein elemental sulphur is produced and a reduced sulphide-oxidising bacteria is obtained and (ii) wherein the reduced sulphide-oxidising bacteria are oxidised by transfer of electrons to an anode of an electrochemical cell to obtain the oxidised sulphide-oxidising bacteria.

Abstract: A process to treat a gas comprising hydrogen sulphide and mercaptans is described. The following steps are part of this process: (a) contacting the hydrogen sulphide and mercaptans comprising gas (1) with an aqueous solution (3) comprising sulphide-oxidising bacteria thereby obtaining a loaded aqueous solution (5) and a gas (4) having a lower content of hydrogen sulphide and mercaptans, (b) contacting the loaded aqueous solution with mercaptan reducing microorganisms immobilized on a carrier under anaerobic conditions, (c) separating the aqueous solution obtained in step (b) from the mercaptan reducing microorganisms to obtain a first liquid effluent (7), and (d) contacting the first liquid effluent (7) with an oxidant (9) to regenerate the sulphide-oxidising bacteria to obtain a second liquid effluent (11) comprising regenerated sulphide-oxidising bacteria. The sulphide-oxidising bacteria as present in step (a) are comprised of regenerated sulphide-oxidising bacteria obtained in step (d).

Abstract: The invention is directed to a process for the biological conversion of bisulphide into elemental sulphur, comprising the following steps: a) converting bisulphide as dissolved in an aqueous solution to elemental sulphur in the presence of sulphide-oxidizing bacteria and under anaerobic conditions to obtain a first liquid effluent comprising elemental sulphur and used sulphide-oxidizing bacteria; b) regenerating the used sulphide-oxidizing bacteria as obtained in step (a) and as comprised in an aqueous solution in the presence of an oxidant to obtain a second liquid effluent comprising regenerated sulphide-oxidizing bacteria; c) separating elemental sulphur from either the first and/or the second liquid effluent; d) using the regenerated sulphide-oxidizing bacteria in step (a) as the sulphide-oxidizing bacteria.

Abstract: A process to treat a gas comprising hydrogen sulphide and mercaptans is described. The following steps are part of this process: (a) contacting the hydrogen sulphide and mercaptans comprising gas (1) with an aqueous solution (3) comprising sulphide-oxidising bacteria thereby obtaining a loaded aqueous solution (5) and a gas (4) having a lower content of hydrogen sulphide and mercaptans, (b) contacting the loaded aqueous solution with mercaptan reducing microorganisms immobilized on a carrier under anaerobic conditions, (c) separating the aqueous solution obtained in step (b) from the mercaptan reducing microorganisms to obtain a first liquid effluent (7), and (d) contacting the first liquid effluent (7) with an oxidant (9) to regenerate the sulphide-oxidising bacteria to obtain a second liquid effluent (11) comprising regenerated sulphide-oxidising bacteria. The sulphide-oxidising bacteria as present in step (a) are comprised of regenerated sulphide-oxidising bacteria obtained in step (d).

Abstract: The invention is directed to a process for the biological conversion of bisulphide into elemental sulphur, comprising the following steps: a) converting bisulphide as dissolved in an aqueous solution to elemental sulphur in the presence of sulphide-oxidising bacteria and under anaerobic conditions to obtain a first liquid effluent comprising elemental sulphur and used sulphide-oxidising bacteria; b) regenerating the used sulphide-oxidising bacteria as obtained in step (a) and as comprised in an aqueous solution in the presence of an oxidant to obtain a second liquid effluent comprising regenerated sulphide-oxidising bacteria; c) separating elemental sulphur from either the first and/or the second liquid effluent; d) using the regenerated sulphide-oxidising bacteria in step (a) as the sulphide-oxidising bacteria.