[Microbial Community Structure of Activated Sludge for Total Nitrogen Upgrading Project]

Area of Science:

• Environmental microbiology
• Wastewater treatment technologies
• Molecular ecology

Background:

• Municipal wastewater treatment plants (WWTPs) employ various units to manage effluent quality.
• Advanced denitrification units (WLK_AD) are designed for enhanced removal of total nitrogen (TN).
• Understanding the microbial ecology of these units is key to optimizing treatment efficiency.

Purpose of the Study:

• To compare the microbial community structure and function between a biochemical unit (WLK_OD) and an advanced denitrification unit (WLK_AD).
• To identify key microbial players and environmental factors driving differences in microbial communities within a WWTP.
• To elucidate the microbial mechanisms responsible for achieving low effluent TN concentrations (<1.5 mg·L⁻¹).

Main Methods:

• Collection and analysis of activated sludge from WLK_OD and WLK_AD units.
• 16S rRNA gene high-throughput sequencing for microbial community structure analysis.
• Principal Coordinate Analysis (PCoA) and Redundancy Analysis (RDA) to assess community structure and environmental impacts.
• Functional gene prediction to infer metabolic capabilities.

Main Results:

• Microbial evenness was lower in WLK_AD compared to WLK_OD due to environmental selection.
• Proteobacteria were enriched in WLK_AD, with genera like *Thauera* and *Flavobacterium* identified as dominant denitrifying bacteria.
• Removal efficiency of chemical oxygen demand (COD) correlated with WLK_OD bacteria, while TN removal correlated with WLK_AD denitrifying bacteria.
• Specific bacteria in WLK_AD (*Novosphingobium, Dokdonella, Thauera, Sphingomonas*) synergistically removed TN, achieving effluent concentrations below 1.5 mg·L⁻¹.
• WLK_AD showed a higher proportion of genes encoding denitrification enzymes.

Conclusions:

• Wastewater treatment environments significantly influence microbial community structure and function.
• Advanced denitrification units harbor specialized microbial consortia essential for efficient total nitrogen removal.
• The removal of COD and TN are key environmental drivers shaping distinct microbial communities in different WWTP units.