BACKGROUND: Hydrogen sulphide (H 2 S) present in biogas can be oxidized to elemental sulphur (S 0 ) or sulphate (SO 4 2-) using nitrate and nitrite. Both nitrate and nitrite are normally available in most wastewater treatment plants and could be used to oxidize H 2 S depending on the molar loading ratio of wastewater and biogas. A control approach is required in order to minimize the fluctuations in inlet and outlet H 2 S concentrations in biogas, and the oxidation potential of the wastewater used. RESULTS: A control scheme has been developed for biogas desulphurization using oxidation reduction potential under industrial conditions. The redox potential was maintained at about +50 to +100 mV in the activated sludge plant to monitor the performance of the nitrification process. The redox potential in the bioscrubber was related to sulphide removal from biogas. More than 90% of the hydrogen sulphide was removed from the biogas.
CONCLUSION: The oxidation reduction potential can be used as a key parameter for monitoring and controlling biogas cleaning. Fluctuations of the inlet H 2 S concentration in biogas can be compensated by manipulating the flowrates of wastewater used in order to achieve consistent and desired H 2 S concentrations in treated biogas.