Simultaneous removal of high concentrations of ammonia nitrogen and calcium by the novel strain Paracoccus denitrificans AC-3 with good environmental adaptability

The novel Paracoccus denitrificans AC-3 strain was isolated and displayed outstanding purification capability for high concentrations of ammonia nitrogen (NH4+-N) and calcium (Ca2+). Meanwhile, the strain exhibited excellent environmental adaptability within a wide pH range and high levels of NH4+-N and Ca2+. Nitrogen balance analysis demonstrated that the pathways of NH4+-N removal consisted of 80.12% assimilation and 16.60% heterotrophic nitrification aerobic denitrification (HNAD). In addition, Ca2+ was removed by forming calcium carbonate (CaCO3) with carbonate (CO32-) and bicarbonate (HCO3-). CO32-and HCO3- were obtained from carbon dioxide (CO2) hydration, which was catalyzed by carbonic anhydrase (CA) secreted by strain AC-3. The alkaline environment for carbonate precipitation was provided by CA and HNAD. The resulting CaCO3 existed in the form of calcite and exhibited a unique morphology and elemental composition.