Sulfate-reducing anammox for sulfate and nitrogen containing wastewaters

In a moving bed biofilm reactor ( MBBR) at moderate temperature of 20 degrees C sulfate reduction along with ammonium oxidation were established. In an upflow anaerobic sludge blanket reactor ( UASBR), the same process took place at 36 degrees C. Sulfate- reducing ammonium oxidation ( SRAO) was performed using reject water as a substrate for micro- organisms and a source of NH4+, with SO2-(4) being added as an electron acceptor. Bacterial strains belonging to the phylum Planctomycetales were detected from the biofilm of the MBBR; from the UASBR species representing phylum Verrucomicrobia were found. Average volumetric TN removal rates were 0.03 kg- N/ m 3 / d in the MBBR and 0.04 kg- N/ m(3) / d in the UASBR. HCO- (3) concentrations exceeding 1000 mg/ l had an inhibiting effect on the SRAO process. The stoichiometric ratio of NH4+ removal was significantly higher than that expected from the extent of SO2 -(4) reduction. This phenomenon can primarily be attributed to complex interactions between nitrogen and sulfur compounds and organic matter present in the wastewater. Addition of hydrazine and hydroxylamine up to 12.5 mg/ l had a positive effect on SRAO process performance, particularly in the UASBR. Hydrazine was naturally present in the reaction medium, indicating occurrence of the anammox process.