Simultaneous dissolved methane and nitrogen removal from low-strength wastewater using anaerobic granule-based...

Area of Science:

• Environmental Microbiology
• Wastewater Treatment Engineering
• Biogeochemistry

Background:

• Anaerobic wastewater treatment offers bioenergy benefits but faces challenges with limited organics for nitrogen removal and dissolved methane emissions.
• Dissolved methane emissions and insufficient nitrogen removal hinder the widespread adoption of anaerobic wastewater treatment plants (WWTPs).

Purpose of the Study:

• To develop a novel technology for simultaneous removal of dissolved methane and nitrogen from wastewater.
• To investigate the microbial competition and kinetics involved in coupled anammox and anaerobic methane oxidation processes.

Main Methods:

• A laboratory granule-based sequencing batch reactor (GSBR) was developed and operated to treat wastewater mimicking effluent from mainstream anaerobic treatment.
• The GSBR coupled anammox (anaerobic ammonium oxidation) and nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) microorganisms.
• Microbial community structure, functional gene abundance and expression, and apparent microbial kinetics were analyzed.

Main Results:

• The GSBR demonstrated high nitrogen and dissolved methane removal rates and efficiencies (> 99% total nitrogen removal, > 90% total methane removal).
• The type of electron acceptor (nitrite or nitrate) significantly impacted removal efficiencies and microbial community dynamics.
• Kinetic analysis revealed higher nitrite affinity in anammox bacteria compared to n-DAMO bacteria, and higher methane affinity in n-DAMO bacteria compared to archaea.

Conclusions:

• The developed GSBR technology effectively achieves simultaneous nitrogen and dissolved methane removal, overcoming limitations of conventional anaerobic wastewater treatment.
• Nitrite is a preferred electron acceptor over nitrate for combined ammonium and methane removal, driven by microbial kinetic preferences.
• The study provides crucial insights into microbial cooperation and competition in granular systems for enhanced wastewater treatment and bioenergy recovery.