Exclusive microbially driven autotrophic iron-dependent denitrification in a reactor inoculated with activated sludge

• Published in: Water research (Oxford) 2020-03, Vol.170, p.115300-115300, Article 115300
• Main Authors: Tian, Tian, Zhou, Ke, Xuan, Liang, Zhang, Jing-Xiao, Li, Yu-Sheng, Liu, Dong-Feng, Yu, Han-Qing
• Format: Article
• Language: English
• Subjects: Activated sludge; Autotrophic iron-dependent denitrification (AIDD); Autotrophic Processes; Bioreactors; Denitrification; Gallionellaceae; Iron; Kinetic modeling; Nitrates; Nitrogen; Sewage; Wastewater treatment
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2019.115300

Autotrophic iron-dependent denitrification (AIDD) is arising as a promising process for nitrogen removal from wastewater with a low carbon to nitrogen ratio. However, there is still a debate about the existence of such a process in activated sludge systems. This work provides evidence and elucidated the feasibility of autotrophic Fe(II)-oxidizing nitrate-reducing culture for nitrogen removal by long-term reactor operation, batch experimental verification, unstructured kinetic modeling and microbial community analyses. A relatively stable nitrate removal rate was achieved coupled with the oxidation of ferrous ions in 3-month operation of reactor. The kinetic modeling suggests that the iron oxidation was a growth-associated process in AIDD. Utilization of extracellular polymeric substances (and/or soluble microbial products) as electron donor for denitrification by heterotrophic denitrifiers was not mainly responsible for nitrogen removal in the reactor. After long-term operation of the reactor with activated sludge as inoculum, the enrichment culture KS-like consortium, dominated by Fe(II) oxidizer, Gallionellaceae, was successfully acclimated for autotrophic Fe(II)-oxidizing nitrate reduction. This work extents our understanding about the existence of such an autotrophic Fe(II)-oxidizing nitrate-reducing culture in both natural and engineered systems, and opens a door for its potential application in wastewater treatment. [Display omitted] •Exclusive iron-dependent denitrification seeded with activated sludge was confirmed.•An average NRR of 0.33 kg-N m−3d−1 and FeOR of 6.46 kg-Fe m−3d−1 were achieved.•Batch tests and kinetic modeling validated autotrophic Fe-oxidizing nitrate reduction.•The enrichment consortium was dominated by Gallionellaceae.