Synergy of potential and reduced graphene oxide enhances anaerobic nitrogen removal at 10°C: performance and mechanism.

Abstract

Stable NO 2 - supply and low-temperature inhibition represent two major bottlenecks for anaerobic ammonia oxidation (anammox) in mainstream wastewater treatment. It was reported that applied electric fields enable anaerobic ammonium-oxidizing bacteria (AnAOB) to directly oxidize NH 4 + to N 2 . Whereas, low-temperature inhibition primarily stems from impaired electron transfer and subsequent metabolic suppression. Enhancing these processes through applied potential and conductive materials offers a strategy for this study. A single-chamber microbial electrolysis cell with 0.6 V anodic potential and 10 mg L -1 reduced graphene oxide (RGO) was developed. Results showed that the system achieved nitrogen removal rates of 7.4 ± 0.5g N m -3 d -1 and 74.2 ± 4.8 mg N m -2 d -1 at 10°C. NH 4 + -N and total nitrogen removal efficiencies increased by 116.6% and 147.0%, respectively. The applied potential upregulated pili/cytochrome expression, while the RGO network provided a low-resistance conductive matrix. As a result, synergic system effectively intensified electron transfer, which increased anode current density by 1.9-fold and reduced resistance by 67.7%, supporting both conventional anammox via enhanced nitritation and the electric-anammox pathway. Furthermore, it also promoted the enrichment functional genes, such as hzs and hdh (107.6%-238.1%), and enhanced cold adaptation marked by increased in extracellular proteins and polysaccharides (44.8%-18.9%). This work demonstrates coordinated electron transfer enhancement and metabolic activation through potential-RGO integration provides an innovative solution for energy-efficient nitrogen removal in cold-region wastewater treatment.

Keywords

Identifiers

DOI

41581479

PubMed

41581479

Journal

Bioresource technology

Year

2026