Current intensity and hydraulic retention time play differential roles in functional gene expression or electron transfer pathways in a pyrite-filled three-dimensional biofilm electrode reactor (P3DBER)

Abstract

This study developed a pyrite-filled three-dimensional biofilm electrode reactor (P3DBER) to treat nitrate wastewater with a low carbon/nitrogen ratio. Meanwhile, the joint effect of current intensity (CI) and hydraulic retention time (HRT) on the performance of the P3DBER was investigated. Results indicated that under the optimal conditions (CI = 30 mA, HRT = 4.9 h), the total inorganic nitrogen removal efficiency (TINRE) reached a maximum of 93.5 ± 1.4%, with a low electrical consumption of 0.075 kW h/g TIN. Increasing CI under different HRTs significantly enhanced the nitrogen removal capacity of the P3DBER. However, at high CI (30 mA), prolonging HRT did not further improve the nitrogen removal efficiency. The introduction of pyrite not only increased the types of electron donors but also could effectively maintain the stability of pH in the P3DBER. Variation partitioning analysis (VPA) showed that CI had a greater impact on the microbial community/functional genes than HRT. In addition, network analysis demonstrated a strong interconnection among microorganisms/functional genes within the P3DBER. This study offers valuable information for optimizing the operating parameters of the P3DBER.

Key findings

• ▸Current intensity and hydraulic retention time have differential effects on functional gene expression in a pyrite-filled 3D biofilm electrode reactor.
• ▸Electron transfer pathways in the reactor are influenced by the interaction between current intensity and hydraulic retention time.
• ▸The study highlights the importance of considering both current intensity and hydraulic retention time in the design and operation of biofilm electrode reactors.

Keywords

Identifiers

DOI

10.1016/j.envres.2025.121040

PubMed

39909094

Journal

Environmental Research

Year

2025