Dual carbon source driven metabolic coupling shapes microalgal-bacterial granular sludge stability

Area of Science:

• Environmental Science
• Microbiology
• Biotechnology

Background:

• Microalgal-bacterial granular sludge (MBGS) offers a promising wastewater treatment solution.
• Operational stability is often compromised under single-carbon conditions due to metabolic imbalances.

Purpose of the Study:

• To evaluate six dual carbon strategies for improving MBGS stability and pollutant removal.
• To understand the role of carbon source composition in regulating microenvironmental conditions and microbial communities.

Main Methods:

• Experimental evaluation of six dual carbon strategies in MBGS reactors.
• Performance monitoring for chemical oxygen demand (COD), ammonium-nitrogen (NH4+-N), and phosphate-phosphorus (PO43--P) removal.
• Metagenomic analysis to assess microbial community structure and function.

Main Results:

• Carbon source composition significantly impacted reactor performance, primarily through pH buffering.
• The acetate-glucose system demonstrated superior stability and pollutant removal (COD: 91.1%, NH4+-N: 96.8%, PO43--P: 96.9%).
• Acetate assimilation's proton consumption counteracted glucose fermentation acidification, maintaining an alkaline pH (10.0-10.2) favorable for functional bacteria and simultaneous nutrient removal.

Conclusions:

• pH buffering is a critical factor linking carbon metabolism to MBGS system stability.
• Rational pairing of carbon sources with complementary proton fluxes can enhance MBGS robustness.
• This study provides a framework for designing carbon sources in biological wastewater treatment systems.