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Iron-doped biocarriers enhanced nitrogen removal from saline wastewater in an unplanted constructed wetland-microbial electrolytic cell system

Year: 2025

Type: article

Abstract: Enhanced nitrogen removal by an iron-doped biocarrier (IDBC) in an unplanted constructed wetland-microbial electrolytic cell (UCW-MEC) system was investigated. The results showed that the UCW-MEC with IDBC achieved efficient nitrogen removal from saline wastewater. IDBC had excellent physicochemical properties and had a significant effect on UCW-MEC for nitrogen removal ( p < 0.05). The system with IDBC achieved optimal performance at 1.4 V (Current density 0.154 A/m 2 ) for efficient nitrogen removal, with removal efficiencies of 70.9 %, 84.2 % and 87.2 % for ammonia (NH 4 + -N), total nitrogen (TN), and total organic carbon (TOC), respectively. The nitrate (NO 3 − -N) and nitrite (NO 2 − -N) concentrations were reduced from 14 mg/L and 1 mg/L in the influent to 0.78 mg/L and 0.06 mg/L in the effluent, respectively. The relative abundances of denitrifiers such as Xanthomarina , Sedimenticola , Marinicella , and Marinifilum significantly increased in the system ( p < 0.05). The results indicated that iron promoted the enrichments of denitrifiers such as Sedimenticola on the IDBC and cathode, and Marinifilum and Xanthomarina on the IDBC. The voltage of 1.4 V increased the abundances of the denitrifiers, Marinicella and Oceanospirillum . Additionally, Iron-redox microbes colonized both biocarriers and activated carbon cathodes. A mechanism framework for the iron-enhanced nitrogen removal in the UCW-MEC with IDBC was proposed. This study provides insights into saline wastewater treatment using IDBC-enhanced UCW-MEC technology.

Source: Journal of Environmental Management

DOI: 10.1016/j.jenvman.2025.127939