TY - JOUR
T1 - Start-up and operational strategies for side-stream nitrification reactors in a cyclic up-concentration nitrogen recovery process
T2 - Enhancing targeted nitrate conversion and deciphering nitrogen metabolism
AU - Lian, Molin
AU - Ma, Zihang
AU - Chen, Guang
AU - Xu, Xiangdong
AU - Tang, Rui
AU - Yan, Shikun
AU - Wang, Yu
AU - Zhang, Yuyue
AU - Zhou, Zhen
N1 - Publisher Copyright:
© 2025 Elsevier B.V.
PY - 2025/12/1
Y1 - 2025/12/1
N2 - Nitrogen recovery as nitrate from wastewater using mainstream ammonium separation and side-stream cyclic up-concentration and targeted conversion systems is economically and technically feasible. However, influences of hypersaline autotrophic condition featured in the side-stream cyclic up-concentration systems on nitrification performance remain unknown. Various start-up strategies of side-stream nitrification reactors (SNR) with different initial salinities and nitrogen loading rate (NLR) were evaluated to investigate nitrogen conversion dynamics and microbial evolution during long-term operation. After appropriate start-up and operational regulation, the SNR achieved stable, complete nitrification with an ammonium removal >98.0 %, a nitrate yield of 97.7 %, and a nitrogen up-concentration factor of 225 under salinities of 5.5–9.5 g Na+/L and an NLR of 100 mg/(L·d). During start-up, the combined inhibition of nitrite-oxidizing bacteria (NOB) by salinity and free ammonia or free nitrite acid was mitigated through microbial adaptation and NLR reduction, but excessive inhibition may prevent recovery even after long-term regulation. The saline and nitrogen-rich autotrophic environment enriched Nitrosomonas and halotolerant bacteria (Luteimonas, Wenzhouxiangella, Thioalkalivibrio, Truepera) and shifted the predominant NOB from Nitrospira to Nitrobacter. The relative abundance of nitrogen metabolism genes (hao, amo, nxr) and genes involved in Calvin-Benson-Bassham cycle and tricarboxylic acid cycle increased greatly in the SNRs. Additionally, Na+/H+ antiporters and antioxidant genes were enriched to maintain osmotic and redox balance in functional bacteria. These findings provide valuable insights for optimizing start-up and operational strategies for nitrification under high salinity and completely autotrophic conditions, supporting the development of cyclic up-concentration nitrogen recovery processes.
AB - Nitrogen recovery as nitrate from wastewater using mainstream ammonium separation and side-stream cyclic up-concentration and targeted conversion systems is economically and technically feasible. However, influences of hypersaline autotrophic condition featured in the side-stream cyclic up-concentration systems on nitrification performance remain unknown. Various start-up strategies of side-stream nitrification reactors (SNR) with different initial salinities and nitrogen loading rate (NLR) were evaluated to investigate nitrogen conversion dynamics and microbial evolution during long-term operation. After appropriate start-up and operational regulation, the SNR achieved stable, complete nitrification with an ammonium removal >98.0 %, a nitrate yield of 97.7 %, and a nitrogen up-concentration factor of 225 under salinities of 5.5–9.5 g Na+/L and an NLR of 100 mg/(L·d). During start-up, the combined inhibition of nitrite-oxidizing bacteria (NOB) by salinity and free ammonia or free nitrite acid was mitigated through microbial adaptation and NLR reduction, but excessive inhibition may prevent recovery even after long-term regulation. The saline and nitrogen-rich autotrophic environment enriched Nitrosomonas and halotolerant bacteria (Luteimonas, Wenzhouxiangella, Thioalkalivibrio, Truepera) and shifted the predominant NOB from Nitrospira to Nitrobacter. The relative abundance of nitrogen metabolism genes (hao, amo, nxr) and genes involved in Calvin-Benson-Bassham cycle and tricarboxylic acid cycle increased greatly in the SNRs. Additionally, Na+/H+ antiporters and antioxidant genes were enriched to maintain osmotic and redox balance in functional bacteria. These findings provide valuable insights for optimizing start-up and operational strategies for nitrification under high salinity and completely autotrophic conditions, supporting the development of cyclic up-concentration nitrogen recovery processes.
KW - Nitrate
KW - Nitrification
KW - Nitrogen recovery
KW - Salinity
KW - Start-up
KW - Wastewater
UR - https://www.scopus.com/pages/publications/105020776671
U2 - 10.1016/j.cej.2025.170348
DO - 10.1016/j.cej.2025.170348
M3 - 文章
AN - SCOPUS:105020776671
SN - 1385-8947
VL - 525
JO - Chemical Engineering Journal
JF - Chemical Engineering Journal
M1 - 170348
ER -