Abstract
Heterotrophic nitrification (HN) and autotrophic nitrification (AN) are the two known pathways involved in aerobic biological ammonia removal. Ammonia, a common substrate, is used by the two bacterial functional groups. However, the key factors involved in the competition and succession of HN bacteria (HNB) and AN bacteria (ANB) remain largely unknown. In this study, alkalinity was found as a key parameter influencing the microbial communities involved in aerobic ammonia removal. When a stepwise decrease in alkalinity occurred, HN was significantly enhanced with increasing contribution to ammonia removal from 56.50 ± 4.02% to 96.00 ± 2.46%. The total relative abundance of HNB increased by 105.82%, while that of ANB decreased by 84.55%. With a stepwise increase in alkalinity, the contribution of AN to ammonia removal increased by 15.84 times, while the total relative abundance of HNB decreased by 70.52%. Alkalinity induced alterations in pH and free ammonia (FA), resulting in the generation of reactive oxygen species, increasing by 216.67 ± 19.95% (200 mg/L alkalinity) and 132.15 ± 16.38% (800 mg/L alkalinity). The succession of HNB and ANB was regulated by alkalinity, pH and FA influenced by alkalinity, with pH being the most influential factor (contributing 40%). This study elucidated a potential strategy for regulating the competition between ANB and HNB, offering strategic basics into achieving more efficient heterotrophic nitrogen removal in engineered wastewater treatment systems.
NETL
NSTL
Elsevier