Performance and microbial mechanism of eletrotrophic bio-cathode denitrification under low temperature

Area of Science:

• Environmental Microbiology
• Environmental Biotechnology
• Wastewater Treatment

Background:

• Biological nitrogen removal is often limited by low temperatures and insufficient carbon in wastewater.
• Autotrophic denitrification using electrotrophic cathodic microbes offers a novel approach, utilizing electrical current as an electron source.

Purpose of the Study:

• To culture and acclimatize cold-tolerant electrotrophic cathodic microbes at low temperatures (10°C).
• To investigate the effectiveness of simultaneous nitrification and denitrification (SND) using integrated and open-circuit microbial fuel cells (MFCs).
• To elucidate the microbial mechanisms underlying cold-tolerant autotrophic denitrification.

Main Methods:

• Staged culturing and acclimatization of microbial communities in integrated MFC (R_W) and open-circuit MFC (R_O) systems at 10°C.
• Evaluation of ammonia-nitrogen (NH4+-N) removal and SND efficiency under specific conditions (DO, current, pH).
• High-throughput sequencing to analyze microbial community composition and gene abundance.

Main Results:

• The R_W system successfully enriched cold-tolerant electrotrophic cathodic microbes.
• R_W achieved 75.50% NH4+-N removal and 81.91% SND, significantly outperforming R_O (40.47% and 54.01%).
• Key cold-tolerant bacteria (Thauera, Pseudomonas, Hydrogenophaga) and enriched genes related to energy, metabolism, and denitrification were identified in R_W.

Conclusions:

• The integrated MFC (R_W) system effectively cultivates cold-tolerant electrotrophic cathodic microbes for efficient autotrophic denitrification at low temperatures.
• Optimal SND performance in R_W was achieved at specific dissolved oxygen, current, and pH levels.
• The enhanced abundance of specific genes in R_W explains its superior performance in ammonia and total nitrogen removal under cold conditions.