Better understanding of the activated sludge process combining fluorescence-based methods and flow cytometry: A case...

Area of Science:

• Environmental microbiology
• Environmental biotechnology
• Wastewater treatment technologies

Background:

• Activated sludge processes in wastewater treatment plants (WWTPs) are complex and not fully understood.
• Conventional physicochemical analyses provide limited insight into the microbial dynamics governing these processes.

Purpose of the Study:

• To validate fluorescence-based methods and flow cytometry as complementary tools for activated sludge process control.
• To monitor bacterial viability and oxidative stress in WWTP activated sludge.

Main Methods:

• Utilized fluorescence staining with SYTO 9, propidium iodide, and carboxy-H2DFFDA.
• Employed flow cytometry to analyze bacterial populations in activated sludge.
• Correlated flow cytometric data with conventional physicochemical parameters (SST, COD, ammonia).

Main Results:

• Identified unstable periods characterized by >75% non-viable bacteria.
• Observed elevated oxidative stress in bacterial populations (up to 9%) during specific unstable periods.
• Found correlations between flow cytometry data and effluent quality parameters (SST, COD, ammonia), clarifying instability origins.

Conclusions:

• Fluorescence staining and flow cytometry provide a simple, rapid, and reliable method for monitoring bacterial dynamics in biological wastewater treatment.
• This approach enhances the understanding and control of activated sludge processes in WWTPs.