Adaptive regulation of activated sludge's core functional flora based on granular internal spatial microenvironment

Area of Science:

• Environmental Microbiology
• Biotechnology
• Wastewater Treatment

Background:

• Activated sludge microbial communities are influenced by external factors.
• The internal granular microenvironment plays a crucial role in microbial interactions and material transfer.
• Understanding granular microenvironments is key to optimizing biological wastewater treatment.

Purpose of the Study:

• To investigate the effects of granular microenvironment on microbial community structure and function in activated sludge.
• To correlate granular characteristics with biological treatment performance, specifically carbon and nitrogen removal.
• To elucidate the role of extracellular substances and granule size in shaping microbial colonization.

Main Methods:

• Characterization of granule sizes (0.5-1.5 mm, 1.5-3.0 mm, 3.0-5.0 mm) and their physical properties (pore volume, average pore size).
• Analysis of extracellular protein and polysaccharide content, cell hydrophobicity, and viscosity.
• Microbiological analysis using scanning electron microscopy (SEM) and fluorescence in situ hybridization (FISH) to determine microbial community composition and spatial distribution.
• Enzyme activity assays (dehydrogenase and nitrogen invertase) to assess microbial activity.

Main Results:

• Granule size influences the content of extracellular proteins and polysaccharides, affecting granule structure and porosity.
• Distinct microbial communities were observed in different granule sizes, with specific bacteria associated with aerobic and anaerobic zones.
• Granules of 1.5-3.0 mm (GM) exhibited higher enzyme activity and superior carbon and nitrogen removal efficiency compared to smaller (GS) and larger (GL) granules.
• The formation of alternating aerobic and anaerobic zones within granules was confirmed, supporting diverse microbial consortia.

Conclusions:

• The granular microenvironment is a critical factor in the adaptive regulation of activated sludge microbial communities.
• Granule size and associated microenvironmental characteristics directly influence pollutant removal performance.
• Optimizing granular characteristics holds potential for enhancing the efficiency of biological wastewater treatment processes.