Microscopic examination of activated sludge

The activated sludge process has been well established as the most reliable, efficient and cost-effective method for wastewater treatment. The method uses microorganisms (biomass) that feed on the organic material contained in wastewater. Activated sludge process is based on the basic principle that as microorganisms grow, they form aggregates, known as sludge flocs, which can be separated from the treated wastewater by sedimentation, thus providing a high-quality effluent. Therefore, the operational stability and performance of the process is directly dependent on the biomass composition and quality characteristics.

The physical, chemical and biological characteristics of the sludge flocs are influenced by wastewater quality, treatment method, as well as various environmental and operating parameters of the process itself. Due to this fact, sludge flocs can vary not only between different WWTPs but also within the same plant at different time periods. In addition, these parameters have a significant influence on the variety of microorganisms present in the activated sludge, as well as on the population of specific microbial species.

When collecting information on the operational level of a WWTP and the quality of the activated sludge, the microscope is a powerful tool. It can be used for the observation of certain sludge characteristics and the identification of microorganisms-indicators of plant performance. Regular microscopic examination of biomass samples also makes it possible to diagnose and prevent at an early-stage important operational problems (e.g., sludge bulking, plant overloading, toxic effects etc.).

The microscopic examination of activated sludge samples from a WWTP can give very important information with respect to:

Diagnosis/ prognosis of operating problems

Evaluation of biomass health (incl. possible inhibition by toxicity)

Control and optimization of key operating parameters (e.g., sludge retention time, level of dissolved oxygen, sludge loading, etc.)

Filamentous Index estimation

Prediction and monitoring of population rearrangements of the microbial flora