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Abstract
In a moving bed biofilm reactor (MBBR) at moderate temperature of 20°C sulfate reduction along with ammonium oxidation were established. In an upflow anaerobic sludge blanket reactor (UASBR), the same process took place at 36°C. Sulfate-reducing ammonium oxidation (SRAO) was performed using reject water as a substrate for micro-organisms and a source of , with
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/m3/d in the MBBR and 0.04 kg-N/m3/d in the UASBR.
concentrations exceeding 1000 mg/l had an inhibiting effect on the SRAO process. The stoichiometric ratio of
removal was significantly higher than that expected from the extent of
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.
Acknowledgments
The research was supported by the Estonian target-financed research project “Processes in macro- and microheterogeneous and nanoscale systems and related technological applications” (IUT 20-16), (SF0180135s08), (SLOTI08262), (SLOKT11027T), (SLOKT11119) and by the Estonian Science Foundation research project ‘‘Alternative ways of anaerobic ammonium oxidation process and the ways of its usage’’ (ETF 9370).