Evaluating the Biological Health of Your ETP & STP

Biological wastewater treatment, also known as secondary wastewater treatment, is one of the key components of any effluent treatment plant. In this process, the microbial population acts on the sewage or industrial effluent and helps in the degradation of harmful substances and pollutants.

The main aim is to protect the environment and public health from the negative effects of untreated or substandard effluent.

Given the importance of this process, a comprehensive understanding and regular evaluation and monitoring are critical to keeping maintain the efficiency of the biological system.

General evaluation methods for assessing a system’s health include monitoring BOD removal, oxygen uptake rates, MLSS/ MLVSS ratio, etc, but these methods fail to evaluate biomass at a more cellular level.

In order to provide an indication of how efficiently the biomass of the system is operating at a cellular level, various common tests for evaluation include a microscopic exam consisting of 4 primary categories: the flocs, filaments, high life forms, and the quality of the bulk water.

Most industrial effluents contain inhibitory substances that might compromise the overall stability of the microbes, and hence, it is important to understand biomass health, growth pressures, toxicity, and inhibition.

Microscopic Analysis

Microscopic analysis using advanced tools can help in determining the wastewater treatment system’s health at any given time.

Moreover, the relevant information can help better understand BOD, COD, TSS, and TOC parameters, which will assist in making predictions about plant performance and the need for additional supplements.

This can help in daily monitoring and evaluation of the biomass, preparing and protecting plants from upsets, and sending warning signs to the operation teams working in such plants.

There are four key components of a wastewater biomass analysis: Flocs, Filaments, Higher Life Forms, and Bulk Water, which help to understand the state of biomass and its performance.


In a biological wastewater treatment system, the bacterial population aggregates and forms floc. The flocculation process enables bacteria to form a protective weighted mass and settle.

With polysaccharide coating, the floc is capable of adsorbing contaminants present in the effluent and later degrading it to consume as food.

A simple microscopic observation of the different floc characteristics can help in assessing the health of the system.

  • Floc Shape: Floc shape can vary from being distinctly irregular to more or less round. When irregularly shaped, there is a reduction in the settling velocity. In most treatment plants, flocs observed are more or less round.
  • Floc Structure: These could include either compact flocs or open flocs (water can flow through these flocs. Settling is faster in the case of compact flocs.
  • Floc Strength: Microscopic evaluation can help in making a distinction between ‘firm’ and ‘weak” flocs. Weak flocs show loosely bound cells to the edges of the flocs, while with firm flocs, there is a clear visible distinction observed between the floc and the surrounding liquid.


The microscopic examination will evaluate the shape and size of the flocs. Uniform floc structure and smooth outer surfaces signify stable operation, whereas poor floc formation shows poor settling in a treatment tank.

Microscopic Image of FlocsMicroscopic Image of Flocs


Filaments can be defined as long strands of bacteria that interlock with each other and form a mesh. This helps in holding the floc together to form a larger entity in the biological wastewater treatment system.

Different types of filamentous bacteria present indicate different characteristics of the system, such as DO concentration and nutrient availability.

Filamentous bulking can also be a possible cause of poor settling. Thus, microscopic analysis helps determine each type of filament, which in turn helps in better effluent system evaluation.

Higher Life Forms

A wastewater biomass analysis shows the number of higher life forms in the biological wastewater treatment system. Additionally, you can learn about different types of higher life forms.

These observations help determine the health and age of the sludge present in the system.

When a system is malfunctioning, these higher life forms, also called indicator organisms, are the last to form and the first to be eliminated.

Thus, the presence of these organisms is a great method to assess the condition where bacterial growth occurs.

For example, Rotifers may indicate a mature and stable system, Flagellates can be observed in heavily BOD loaded systems as they can survive in low oxygen, and high content of ciliates shows a settled and freely floating system.

Organica Biotech is one of the leading companies that offer advanced solutions for biological wastewater treatment.

Choosing the right microbial consortium plays an essential role in the effective breakdown of pollutants, and in order to properly assess the biomass health and efficiency of your bioreactor, Organica Biotech offers two analysis services.

BioCheck is an in-depth bacteriological study that analyzes the current health and status of your wastewater treatment plant.

BioSure helps you identify and test the efficiency of Organica’s microbial solutions on your effluent under simulated treatment plant conditions.

Also Read:

Post by Karen Sam