Growth and metabolism characteristics of anaerobic ammonium-oxidizing bacteria aggregates

The present study reported the growth and metabolism characteristics of anaerobic ammonium-oxidizing (anammox) bacteria aggregates in an expanded granular sludge bed (EGSB). The results showed that the anammox bacteria aggregates presented starvation, growth, and inhibition phase along with the increase of substrate supply. The substrate conversion rates for survival were 0.05 kgNH ₄ ⁺ –N/(kgVSS·day), 0.07 kgNO ₂ ^? –N/(kgVSS·day), and 0.12 kgN/(kgVSS·day); the substrate conversion rates for maximum growth were 0.21 kgNH ₄ ⁺ –N/(kgVSS·day), 0.24 kgNH ₄ ⁺ –N/(kgVSS·day), and 0.45 kgNH ₄ ⁺ –N/(kgVSS·day), respectively. In the growth phase, the yield of anammox bacteria aggregates was 0.14 gVSS/(gNH ₄ ⁺ –N), 0.12 gVSS/(gNO ₂ ^? –N), and 0.70 gVSS/(gNO ₃ ^? –N); the yield of extracellular polymeric substances (EPS) was 0.11 gEPS/(gNH ₄ ⁺ –N), 0.09 gEPS/(gNO ₂ ^? –N), and 0.55 gEPS/(gNO ₃ ^? –N), respectively. The EPS contents in anammox bacteria aggregates were high compared to that in anaerobic granular sludge. Speculated from the cell yield, the energy for anammox bacteria growth was not only from nitrite oxidation, but also from anammox reaction.