Effects of NH4+-N and NO2--N on carbon fixation in an anaerobic ammonium oxidation reactor.

Inorganic carbon (IC) is used as a carbon source of the anaerobic ammonium oxidation (anammox) microorganisms during the anammox process. Meanwhile, anammox microorganisms possess a certain carbon fixation capacity. In this study, the effects of NH4+-N and NO2--N on carbon fixation in an anammox reactor were investigated. The carbon fixation content had a positive correlation with the amount of NH4+-N and NO2--N. A high carbon sequestration of 6.52 mg-C and relatively low CO2 emissions of 1.00 mg-C were caused by a high amount of influent nitrogen. The microbiology analysis showed that there was a significant relevance between the abundance of the cbbLR1 gene and the carbon fixation content. The results revealed that the Calvin cycle pathway for carbon fixation was used by the anammox bacteria, which may be uncultured Bacillus sp. clone TA_17 or uncultured Methylobacterium sp. clone LA8_13.