Fig. 1.
Microbial functional groups and processes that dominate the nitrogen cycle and O2 consumption in a combined nitrification/anammox reactor with a high COD/NH4+ ratio. AHB primarily live by aerobic respiration and utilize organic matter as an electron donor and carbon source. Inorganic nitrogen (NO3−, NH4+) may be taken up as a nutrient but is not involved in catabolic processes. DNB live mostly or exclusively by anaerobic respiration using nitrate or one, several, or all of the intermediates of the denitrification pathway as electron acceptors. NOB are suppressed by low O2 in the study system.