What are the Three Stages of Wastewater Treatment?

Biological wastewater treatment

Secondary treatment of wastewater uses the biological process to reduce and remove biodegradable organic matter, contaminants, and further act on the suspended solids that escape from the primary treatment. To achieve this objective, wastewater plants provide a suitable environment for the naturally occurring living microbes to thrive and act aggressively on the organic matter. The microbes feed on organic impurities for their growth and release by-products such as carbon dioxide, water, and energy.

The biological process is the most important part of wastewater treatment as the wastewater effluent is treated to achieve the quality that should match the standards set by the environment agencies. Once that level of purity is achieved, the effluent is released into the disposal field. Otherwise, polluted wastewater can cause great harm to human health and the environment.

Microbes perform under different sets of conditions. Secondary biological wastewater treatment can be aerobic and anaerobic based on different microbial communities used for treatment. In certain conditions, both aerobic and anaerobic are coupled together as well.


In the aerobic biological process, microbes act on organic waste and suspended solids in the presence of a sufficient amount of oxygen. The process converts waste and releases carbon dioxide, water, and other by-products. Factors like temperature, pH, oxygen available are important parameters that help microbes in the degradation of waste.


The anaerobic process uses microbes in the absence of oxygen and successfully converts contaminants and waste into carbon dioxide, methane, and other end-products. The biogas production is possible through the anaerobic process which can be further utilized for running the sewage treatment plants and systems.

Anaerobic systems should completely be closed and provided heat as it consists of different processes like hydrolysiss, acidogenesis, acetogenesis, methanogenesis where microbes act as substrates.

There are 3 biological wastewater treatment methods that are currently in use and microbes play the most important role in the success of each of the processes.

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Activated Sludge

Microbes under oxygenated conditions form biological solids called activated sludge in the activated sludge process. The microbes absorb dissolved organic matter in the wastewater and reduce the BOD. Oxygen is well supplied through the aeration system. Clean water is skimmed and released as effluent and the sludge is pumped out. A certain amount usually 30% sludge is reintroduced into the aeration tank as microbes are ready to metabolize organic waste more easily.

Tricking Filter

This biological treatment system consists of a bed of stones, rocks, gravels, etc. Wastewater is sprayed on the stones continuously which trickles down to the bottom. As it reaches the bottom, microbes come together and multiply on the stones. Thus, microbes absorb contaminants, forms a biomass layer, and lowers BOD. Air is made available in this process too.

Oxidation Pond

Oxidation pond also called aerobic lagoons are large and shallow earth basins where wastewater is treated upon by microbes, algae, and sunlight. Here, algae release oxygen during the photosynthesis process which is used by microbes.

As you can see in all the biological treatment of wastewater is possible only through powerful microbes. But due to the rapidly increasing population, industrialization, and other commercial activities, the amount of wastewater generated has increased exponentially. The excess load of wastewater entering treatment systems has stressed the normal processes. The performance of naturally occurring microbes is also affected significantly. Lack of efficient microbes has led to low-quality effluent being released into the environment which is harming the environment and humans on a large scale.

There is an urgent need to switch to innovative solutions that can maximize the productivity of secondary treatment of wastewater and the biological processes. Since setting up new plants in rural and urban areas costs too much, the solutions that can improve the treatment processes is the need of the hour.

Organica Biotech’s Cleanmaxx is one of the best wastewater treatment products which contains adaptable microbes that degrade organic waste aggressively, maximizes BOD reduction, and minimizes sludge formation. The natural and eco-friendly formulation can power the biological process involved in secondary wastewater treatment. This will ease the burden of sewage treatment plants and various treatment systems and methods too.

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Post by Priyanka Khaire