Influent chemical oxygen demand to nitrogen ratio regulate microbial intercellular communication influencing partial...

Area of Science:

• Environmental Microbiology
• Wastewater Treatment Engineering
• Biotechnology

Background:

• Acyl-homoserine lactones (AHLs) mediate microbial signaling in activated sludge systems, influencing nitrogen transformation.
• The precise mechanisms by which AHLs regulate nitrite accumulation in municipal wastewater remain unclear.

Purpose of the Study:

• To investigate nitrogen transformation and microbial interactions under varying chemical oxygen demand to nitrogen (COD/N) ratios.
• To elucidate the role of exogenous acyl-homoserine lactones (AHLs) in promoting partial nitrification.

Main Methods:

• Long-term cultivation of activated sludge under different COD/N ratios.
• Addition of exogenous AHLs (3-OXO-C12-HSL and C6-HSL) to assess their impact.
• Monitoring of nitrogen transformation processes and microbial community analysis.

Main Results:

• A COD/N ratio of 3 significantly enhanced nitrite accumulation (65.8%) by inhibiting nitrite-oxidizing bacteria (NOB).
• Specific AHLs, C6-HSL and 3-OXO-C12-HSL, were identified as key regulators, with C6-HSL promoting and C12-OXO-HSL inhibiting nitrification.
• AHLs demonstrated a stronger regulatory effect on NOB compared to ammonia-oxidizing bacteria.

Conclusions:

• The study identifies key microbial players and AHLs involved in partial nitrification.
• Findings provide a theoretical framework for developing self-regulating microbial communities for efficient partial nitrification in wastewater treatment.
• Optimizing COD/N ratios and understanding AHL signaling are crucial for enhancing nitrogen removal processes.