Assessment of activated sludge viability with flow cytometry

Area of Science:

• Environmental Microbiology
• Biotechnology
• Analytical Chemistry

Background:

• Activated sludge processes are crucial for wastewater treatment.
• Assessing microbial viability and activity is essential for process optimization.
• Current methods for biomass assessment can be time-consuming.

Purpose of the Study:

• To evaluate fluorescent dyes and multiparameter flow cytometry for rapid, direct assessment of activated sludge viability and activity.
• To develop a reliable procedure for sludge floc disaggregation and cell analysis.
• To apply these methods for estimating key activated sludge process parameters.

Main Methods:

• Utilized SYBR Green I and Propidium Iodide for membrane integrity (viability).
• Employed FDA and BCECF-AM for enzymatic activity assessment.
• Developed a floc disaggregation technique for accurate bacterial recovery and minimal cell damage.
• Applied flow cytometry for multiparameter analysis.

Main Results:

• A reproducible procedure for sludge floc disaggregation was established.
• High bacterial recovery rates with good accuracy and repeatability were achieved.
• The method enabled estimation of endogenous decay and specific growth rates.
• Preliminary data show promise for investigating bacterial dynamics in wastewater treatment.

Conclusions:

• Fluorescent dyes and flow cytometry offer a rapid and direct approach for activated sludge assessment.
• The developed method accurately quantifies biomass viability and activity.
• This technique can enhance the monitoring and optimization of wastewater treatment plants.