Effect of oxygen dosing point and mixing on the microaerobic removal of hydrogen sulphide in sludge digesters

• Published in: Bioresource technology 2011-02, Vol.102 (4), p.3768-3775
• Main Authors: Díaz, I., Pérez, S.I., Ferrero, E.M., Fdz-Polanco, M.
• Format: Article
• Language: English
• Subjects: Anaerobiosis; Applied sciences; Bacteria; Biofuel production; Biogas; Biological and medical sciences; Bioreactors; Biotechnology; Biotechnology - methods; Chromatography, High Pressure Liquid - methods; Digesters; Dosing; Energy; Equipment Design; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Gases; Hydrogen sulfide; Hydrogen Sulfide - chemistry; Hydrogen-Ion Concentration; Industrial applications and implications. Economical aspects; Microaerobic; Oxidation; Oxygen - chemistry; Pollution; Sewage; Sludge; Sludge digestion; Sulfides; Sulfides - chemistry; Sulfur; Sulphide; Sulphide-oxidising bacteria; Temperature; Time Factors; Waste Disposal, Fluid - methods; Wastes
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2010.12.016

► Microaerobic removal of H2S achieved an efficiency higher than 98%. ► Headspace was found the optimal dosing point. ► Dissolved sulphide was removed with biogas recirculation. ► The main result of H2S oxidation was S0, partly accumulated in the headspace. ► Sulphide-oxidising bacteria developed in the headspace. Limited oxygen supply to anaerobic sludge digesters to remove hydrogen sulphide from biogas was studied. Micro-oxygenation showed competitive performance to reduce considerably the additional equipment necessary to perform biogas desulphurization. Two pilot-plant digesters with an HRT of ∼20d were micro-oxygenated at a rate of 0.25 NL per L of feed sludge with a removal efficiency higher than 98%. The way of mixing (sludge or biogas recirculation) and the point of oxygen supply (headspace or liquid phase) played an important role on hydrogen sulphide oxidation. While micro-oxygenation with sludge recirculation removed only hydrogen sulphide from the biogas, dissolved sulphide was removed if micro-oxygenation was performed with biogas recirculation. Dosage in the headspace resulted in a more stable operation. The result of the hydrogen sulphide oxidation was mostly elemental sulphur, partially accumulated in the headspace of the digester, where different sulphide-oxidising bacteria were found.