Biological treatment

A key to successful wastewater filtration

Biological wastewater treatment is an ecological and effective method of purifying water using natural processes. This technique involves the transformation of dissolved and suspended organic pollutants into :

  • biomass
  • and emitted gases (CO2, CH4, N2 and SO2), separated from the treated water.

These gases can then be separated from the treated water, guaranteeing cleaner, less polluted water. In addition, it is designed to break down the pollutants dissolved in the effluent by the action of micro-organisms. These micro-organisms then use these substances to live and reproduce with the pollutants as nutrients.

So not only do they purify water, they also contribute to a healthy aquatic ecosystem.

What is the purpose of biological treatment?

First of all, you need to know the meaning of the acronym MBBR. It is the Moving Bed Biofilm Reactor.

It is a biological process for the treatment of pollutants through a modular system of fixed cultures. Therefore, this process will be classified as our digestive system, in order to act step by step on the water to be treated.

These steps include:

  • denitrification
  • carbon elimination

MBBR purification in various stages is based on the distribution of bacteria in different compartments. In addition, MBBR can be used for the treatment of carbon and nitrogen pollution in :

  • municipal environments
  • and industrial settings

How does biological treatment work?

MBBR is a simple, effective technique for treating municipal or industrial wastewater from :

  • biological matter (BOD)
  • ammonia and nitrogen

Biological treatment is advantageous because it optimizes treatment capacity while using less energy. The consequence is that not only the environmental impact but also the price of such an operation is reduced.

This technology will use a separating system to treat the water in a fragmented way:

  • Micro-organisms (often bacteria) transform chemical pollutants in water.
  • The water passes through a raw sewage grate system, which filters out any heavy pollutants.
  • Once the wastewater has been removed, it is sent to an equalization tank.
  • In this tank, water is mixed to a uniform consistency. This facilitates rapid processing in subsequent stages, thanks to the bacteria present.

Biological treatment operating step 1

Once the water has been thoroughly mixed, it is directed into the first tank. This is where the key micro-organisms in MBBR technology come in. are involved.

Moreover, to be active and functional, these micro-organisms require three essential needs.


A support or substrate will serve as a medium for the bacteria where they can survive and grow. Also called media, this support can be of several natures.

At 1h2o3, we prefer activated carbons, as they offer many advantages.

This is because they can support many bacteria and therefore have a faster action at large scales. In addition, these charcoals provide energy space savings, but also money.

Food requirement

They also need food to ensure their survival and development. This will be the organic matter present in the water.

This is because it will be consumed by our bacteria in order to proliferate and have a more efficient action, while guaranteeing a purification of the water to be treated.

Oxygen demand

To ensure the degradation of organic matter (BOD), it is essential that aerobic bacteria have access to a source of oxygen. This is in order to achieve the right chemical reaction. This means aerobic cellular respiration. There is therefore a “blower” capable of sending air into tank 1. His action will have a double purpose. It will :

  • renew the oxygen present in the treated water
  • allow the bacteria to carry out their purification
  • promote the agitation of the water inside the tank
  • increase the interactions of bacteria with their environment.

The quantity of air injected into the tank must be correctly evaluated and will depend on the number of active bacteria and therefore on the quantity of water to be treated.

Biological treatment operating step 2

After prolonged exposure to the action of the bacteria in tank 1, the bacteria will be transferred to tank 2. This tank n°2 will then have a very similar action to that of tank n°1. The water then passes through a lamella column, separating sludge and water for final purification.

After treatment, the sludge is transferred to a special tank. If they meet certain standards, they can be recycled as soil improver or land application sludge. If not, they are incinerated, and the treated water then passes through a sand filter to eliminate any remaining residues.

The treated water will be sent to a sand filter under pressure to remove the last residues

It will be sent directly to an activated carbon filter. The activated carbon will then absorb a wide variety of pollutants present in the wastewater.

To ensure optimal water purification, a final filtration process targets key elements such as :

  • DCO and DBO
  • mineral oils
  • hydrocarbons
  • pesticides
  • persistent organic pollutants, etc.

To remove any pathogens that may be in the water, a UV disinfection unit is used. These rays destroy the DNA of germs, neutralizing them.

Following this last step, the water will be stored in a tank to be reused. The major advantage of this method is its flexibility. It adapts to the growing need for treatment in the face of increasingly polluted water.

What is bioremediation

Bio-remediation is a technology based on the use of micro-organisms to purify various media. It has proved effective time and again in a variety of situations and fields. Actually, it allows to decontaminate :

  • soils
  • groundwater
  • environmental disasters in the oceans

The micro-organisms used in the bio-remediation process can be of several kinds, in order to ensure the widest possible range of action.

What are the two types of bioremediation?

Microbial bioremediation uses microorganisms to break down contaminants using them as a food source.

  • Phytoremediation uses plants to capture and eliminate various pollutants, such as pesticides or metals.
  • Mycoremediation uses fungi to break down harmful substances with their enzymes.

There are several organizations that specialize in the remediation of environmental pollutants.

As we explore bio-remediation further, it is important to note that the domains affected are not limited to the environmental domain, but also to the health and safety domain.

Which bacteria are used for bioremediation

Biodiversity offers a variety of micro-organisms that can treat a wide range of pollutants using biological treatment. Substances such as arsenic, cadmium and mercury lose their harmfulness thanks to these organisms. It’s the power of nature at the service of pollution control.

However, it is first necessary to identify these different organizations and find the function they perform. Their function varies according to environmental conditions, such as temperature or pH. Drawing up a complete list of these organisms is a challenge, given their diversity and adaptability.

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