Anaerobic methane oxidation for biological sulphate reduction
03 / 2004 - 06 / 2009
[Introduction] Emission of sulfate containing wastewater results in an increased salinity of the environment. To prevent this techniques are used by which gypsum is produced. However in the metal industry, the produced gypsum is heavily polluted with metals. This gave rise to an alternative technique, in which sulfate is biological reduced to sulfide. Sulfide precipitates with metals to form metal sulfides or is oxidized to elemental sulfur. Both products are reusable. For sulfate reduction an electron donor is required. For this hydrogen is being used, which is produced from methane in natural gas or biogas. However, this process requires a high temperature and pressure. In addition, the efficiency of the conversion to hydrogen is low, only 0.53 mol sulfate can be reduced with one moll methane. Therefore, the emission of the greenhouse gas CO2 and the costs of the wastewater treatment would be greatly reduced if methane could be used directly as electron donor for biological sulfate reduction: CH4 + H2SO4 ¿ CO2 + H2S + 2H2O [Research] The research aims to develop a sulfate reduction process in a high-rate bioreactor with methane as electron donor. The research focuses on: Screening of marine sediments, anaerobic reactor sludge fs and pure cultures for sulfate reducing capacity with methane as electron donor. Enrichment of the responsible organisms in a membrane reactor. Development of a suitable bioreactor process. Immobilization or augmentation of the methane oxidizing organisms in a bioreactor. Optimization of the process and characterization of the bioreactor.