Biological treatment

A key to successful wastewater filtration

Biological wastewater treatment involves the transformation of dissolved and suspended organic pollutants into :

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

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

This segmented purification is possible due to the separation of bacteria in each compartment. 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, but very effective technology for the removal from municipal or industrial wastewater of :

  • biological matter (BOD)
  • ammonia and nitrogen

In addition, the biological treatment allows its operator to maximize the treatment capacity by minimizing the required energy space. 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:

  • It is based on the action of micro-organisms (often bacteria) capable of carrying out chemical transformations of the various pollutants present in the water.
  • The wastewater will pass through a system of screens (raw sewage) that will filter out large pollutants such as macro-plastics, sticks, etc.
  • Once the wastewater has been removed, it will be sent to a tank (an equalization tank.)
  • Its purpose is to homogenize the water. This means that they can be treated as quickly as possible by the following tanks and the bacteria they contain.

Biological treatment operating step 1

After being properly homogenized, the treated water is sent to tank number 1 where the micro-organisms that are at the center of the MBBR technology are found.

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 use activated carbons because they have 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. After a second treatment, the water will be sent to the lamella column. Its purpose is to allow the separation of mud and water.

Furthermore, the sludge will be sent directly to a mud tank. They can be transformed into soil improvers or mud for spreading. This is only possible if they meet certain standards, otherwise they will be incinerated. They can either be revalued or destroyed.

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 a quality of water treatment always more important, it will allow a last filtration centered on :

  • 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. Its purpose is to bombard the water passing through it in order to destroy the DNA of the pathogens making them inactive.

Following this last step, the water will be stored in a tank to be reused. The advantage of such a concept depends on its ability to adapt. It is this adaptability that allows it to respond in the most efficient way to the demand for treatment of water that is increasingly contaminated by the population.

What is bioremediation

Bio-remediation is a technology based on the use of micro-organisms to clean up various environments. It has proven its effectiveness in many areas and on many occasions. 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 bind, extract and clean pollutants such as pesticides, petroleum hydrocarbons, metals and chlorinated solvents.
  • Mycoremediation uses the digestive enzymes of fungi to break down contaminants such as pesticides, hydrocarbons and heavy metals.

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

As a result of the benefits of biodiversity, there is a range of micro-organisms capable of treating and transforming the very broad range of pollutants in biological treatment. It is so broad that each pollutant (arsenic, cadmium, copper, mercury, nickel, etc.) can be treated and lose its harmful aspect.

However, it is first necessary to identify these different organizations and find the function they perform. This function can also depend on environmental conditions (oxygen level, temperature, PH, etc.). It is therefore difficult to make an exhaustive list of all the micro-organisms used in bio-remediation.

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