Bacteria and micro-organisms involved in water treatment

What are they used for?

The biological method purifies wastewater and is still the most widely used treatment method in the world. This technology uses different types of bacteria and other micro-organisms to decontaminate and clean polluted water. In microbiology, these organisms play a crucial role by using organic waste as a source of food and energy to grow and reproduce.

The importance of wastewater treatment is crucial to both human health and environmental protection. Indeed, the use of these bacteria accelerates the treatment of pollution on a small surface: the purification plant. A river, for example, has its own purification process, similar to what happens in nature. However, atmospheric pollution levels are currently too high and can disrupt the natural cycle. By cultivating these micro-organisms, wastewater treatment plants help to prevent the eutrophication of watercourses and the spread of disease.

Domestic wastewater and industrial effluent are the main sources of grey water requiring treatment. The use of micro-organisms in this context enables wastewater to be recycled efficiently, contributing to a healthier environment. These micro-organisms, or microbes, are in fact the biological cleaners essential to this process.

You got it, bacteria are the heart of the process. A wastewater treatment plant can thus be compared to a farm where micro-organisms are cultivated on a large scale to decontaminate and recycle wastewater, illustrating their importance in modern society.

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Where are bacteria present?

Everywhere, from the water arriving at the treatment plant to the water leaving it. The operating parameters defined in the treatment basins influence the development of various microbial structures and the species of which they are composed. This species-rich ensemble of microorganisms achieves a higher level of biodegradation on a wide range of substrates, unlike the use of single cultures. This is the main factor affecting the quality of treated wastewater.

Usually, these organisms swarm and agglutinate into a flake-like mass in free cultures, called the floc. These flocs, visible to the naked eye, contain living and dead cells of bacteria, fungi, protozoa and metabolic products. They agglomerate around the suspended organic matter on which they feed. This is the case, for example, with activated sludge. In addition, in fixed cultures, similar biofilms develop on contact surfaces. For example, biofilters and biological discs are fixed cultures.

Some plants have UV reactors to decontaminate the water and eliminate any remaining microbes. Others inject chlorine before discharging the water into the river. This is the case in Australia and New Zealand, for example.

bactéries sur site 2 x 1m3 bacteries bacteria - 1H2O3
Culture batch bacteria on site 2 x 1m3 bacteria - 1H2O3

Who are these micro-organisms?

Production bactéries mésophiles 1 souche pure par bouteille bacteries bacteria - 1H2O3
Mesophilic bacterial production 1 pure strain per bottle bacteries bacteria - 1H2O3

Parameters influencing the growth of micro-organisms

First of all, before we can understand the different types of micro-organisms, we need to understand the parameters that influence their growth. In microbiology, we study how bacteria and microbes react to these factors, which are important for their effective development. Firstly, geographical location plays a crucial role in the composition of the polluted water treated by the plant. Secondly, the type of tank in which the cleaning bacteria are grown has a significant impact on their growth. Thirdly, the characteristics of the domestic wastewater influence the microbial composition and the decontamination processes required. Finally, the operating parameters of the system, such as aeration and agitation, modify the growth of the micro-organisms. These factors cause quantitative changes between autotrophic and heterotrophic bacteria, influencing the extent of treatment. For example, grey water recycling depends on the effectiveness of these well-balanced and controlled microbiological processes. It is useful to outline the names of the methods used to better understand their specific application.

Bacteria present in wastewater treatment plants

In municipal wastewater treatment plants, Gram-negative bacteria, particularly proteobacteria, predominate, accounting for between 21 and 65% of micro-organisms. Microbiology shows how the abundant Betaproteobacteria class plays a major role in the elimination of organic elements and nutrients. Other important phyla include Bacteroidetes, Acidobacteria, Chloroflexi, and contribute to the decontamination of polluted water. The most numerous types of bacteria, considered to be microbial cleaners, are Tetrasphaera, Trichococcus, Candidatus Microthrix, Rhodoferax, Rhodobacter, and Hyphomicrobium. Each name of these bacteria illustrates their importance and crucial role in the recycling of domestic wastewater. These examples show how micro-organisms contribute to the purification of grey water, demonstrating their usefulness for the environment.

Other micro-organisms: fungi and archaea

Among the fungi studied in microbiology, Ascomycetes are the most abundant, accounting for 6.3 to 7.4% of micro-organisms. It is interesting to note how these fungi react to polluted environments. Archaeobacteria, often seen as natural cleaners, particularly Euryarcheota, make up around 1.5% of the micro-organisms present. The importance of these micro-organisms is crucial in different environments and during decontamination processes. These microbes play a vital role, especially in the presence of ammonia and oxygen, where Nitrosomonas is very present. Among the examples of specific micro-organisms, the name Nitrosomonas often comes up because of its key role in recycling. These micro-organisms also contribute to the treatment of grey and domestic water in a variety of contexts. It is useful to outline these processes to better understand their ecological importance.

The impact of temperature and location

Temperature influences the presence of certain species, and geographical location also affects species composition. In microbiology, it is important to understand how these factors influence polluted water and its treatment. In industry, the dominance of specific micro-organisms is explained by their ability to biodegrade components of industrial wastewater. These micro-organisms act as natural cleaners, which are crucial to the decontamination of polluted water. Their ability to adapt to different environments enables these microbes to recycle grey water effectively. Domestic species exposed to these conditions are proving their usefulness in the treatment of industrial wastewater. For example, understanding the names of adapted species can improve decontamination processes.

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Classification of bacteria according to how they obtain oxygen

In microbiology, bacteria are classified according to how they obtain the oxygen they need to survive in polluted water. In wastewater treatment, there are three types of bacteria: aerobic, anaerobic and facultative. These bacteria act as biological cleaners, essential for effective decontamination and recycling of domestic grey water. Their importance lies in their ability to adapt to different environments to eliminate harmful microbes. Among the examples of these bacteria, each name reflects their specific function in the purification process. It is useful to outline these processes to better understand their crucial role in wastewater purification.

Impact of microbial imbalances on treatment systems

The presence of bad bacteria or the absence of good strains can cause problems in polluted treatment systems. These problems include:

  • Low biogas yield from the anaerobic digester: Bad bacteria can reduce the efficiency of biogas production, compromising the recycling of organic matter.
  • Poor flocculation and sedimentation: This can lead to poor separation of solids and liquids, affecting the overall decontamination of the system.
  • Excess of filamentous bacteria: Can cause flotation problems and equipment clogging, exposing installations to the risk of breakdown.
  • Excess phosphorus: Can lead to eutrophication of receiving waters, compromising the importance of environmental prevention measures.
  • Low nitrogen removal efficiency (NH4, NO3) : Causes water pollution with high levels of nutrients, affecting treated grey and domestic water.
  • Production of unpleasant odours: Generated by undesirable bacteria, illustrating how a microbial imbalance can impact the environment.
  • Excess consumption of chemical reagents: To compensate for microbial imbalances.
  • Production of foam in an anaerobic digester: Can lead to malfunctions and loss of capacity, limiting the treatment of domestic wastewater.

Solutions for restoring effective treatment

There are generally three ways to restore good treatment:

  1. Modification of operating settings: By adjusting the parameters, we can allow the right strains to naturally recolonise the polluted environment.
  2. Complete elimination of micro-organisms in place: When the first solution fails, this method can be considered. However, it is not recommended, as the biomass will take several days to develop, delaying treatment.
  3. Injection of selected bacteria: This solution involves introducing bacteria that have been cultivated and multiplied to take advantage of the undesirable bacteria present. This decontamination process is essential to guarantee the effectiveness of treatment systems and environmental protection.
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Frequent applications

Microbial biotechnology offers innovative scientific applications of great ecological and economic interest. It makes effective use of natural decontamination processes to treat polluted water. This method is much less costly than conventional physico-chemical or mechanical techniques, demonstrating the importance of sustainable solutions.

How bacteria differ from conventional treatment methods lies in their ability to use simple natural processes. They act as natural cleaners, treating pollution without creating new contamination. Most of the time, they require a bioreactor and the nutrients they need to multiply in large numbers. Dosage is easy and requires only a short operating time, useful for rapid treatment of domestic wastewater. These systems can also be adapted to recycle grey water, thus preventing future contamination problems. Explaining these advantages is essential to understanding the importance of integrating such technologies into modern infrastructures.

Accelerate plant startup / Get a quick start on bacterial seeding for a mobile plant

The colonization of a medium by the necessary bacteria and microorganisms required for depollution generally takes between 4 and 8 weeks. Once again, it is the temperature that has the greatest impact on this growth time.

There are some solutions to reduce this delay to about a week, thanks to the seeding with selected and multiplied bacteria. There are two major benefits here:

  • Reduce the start-up time of a wastewater treatment plant
  • Accelerate the start-up of a mobile processing unit (e. g. in case of accident at the main plant)

The technique is based on the recirculation of a clever mixture of adapted substrate and bacteria selected so that they settle in very quickly. Under these favorable conditions, bacteria rapidly form flocs or biofilms. After a few days, the environment is ready for wastewater discharge.
We’ve selected a range of bacteria to get your plant up and running in a week under normal conditions, with water temperatures between 12 and 30°C.

The design is available on the microbiological optimization page.

Solving the presence of undesirable bacteria

In activated sludge plants, the presence of filamentous bacteria is a real problem. First, the solution is to remove as much mud as possible, and to increase aeration. The recuperation of the environment by the good bacteria can put back several days. If this does not work, then it is possible to destroy these bacteria with chlorine. The problem is that this kills all the bacteria. Und dann wird es ein paar Wochen dauern, bis wieder normale Bedingungen herrschen.

While most operators continue to inject chlorine, we suggest the injection of dedicated bacteria. Like accelerated factory starting, the massive addition of these good populations quickly restores the balance in the ponds.

For example, here is an illustration of the removal of floats in a clarifier.

The design is available on the microbiological optimization page.

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Elimination of pathogenic germs

The microbiological quality of treated water is crucial to public health and environmental protection. When treating wastewater, the elimination of pathogenic germs, such as bacteria, viruses and protozoa, is an essential step in ensuring that the water is safe for reuse or discharge into the environment.

Pathogenic germs in waste water can cause serious illness if the water is not treated properly. Here are some of the methods commonly used to eliminate these dangerous micro-organisms:

  • Chlorination: Adding chlorine to water destroys pathogenic germs. However, this method can leave behind chemical residues and generate potentially harmful by-products.
  • UV disinfection: The use of ultraviolet (UV) light is an effective method of destroying micro-organisms without leaving chemical residues. UV disinfection systems, such as those offered by 1h2o3, use the germicidal effect of UVc rays to eliminate microbes, viruses, bacteria, fungi and algae present in water.
  • Ozonation: Ozone is a powerful oxidising agent that destroys micro-organisms by oxidation. This method is effective but requires complex management and higher operating costs.

How to improve treatment efficiency:

By eliminating the fats and oils responsible for the habitat degradation

Lipophilic bacteria are specialized in the degradation of animal and vegetable fats and oils in urban WWTPs and industrial treatment plant. These bacteria are easily adaptable to all current treatment systems.

On the market, there are products such as completely natural bacteria and enzymes, designed and selected for their ability to solubilize and digest grease and mud. Some bacteria are so specialised in fat degradation that they are capable of degrading high loads, up to 300,000 mg/L of COD.

The design is available on the microbiological optimization page.

By increasing the presence of good bacteria

As expected, the technique of injecting a mixture of suitable substrate and selected bacteria is still the most effective. Therefore, the rapid adsorption of these products in the environment allows to improve the efficiency of the following systems:
  • Activated sludge (fine-bubble aeration)
  • Natural and artificial lagoons and ponds
  • Biofiltres
  • Thrickling filter
  • Rotating biological contactors
The design is available on the microbiological optimization page.

By adding bacteria for the treatment of cold or hot water

The majority of micro-organisms generally develop more rapidly at high temperatures, up to 38°c max. However, their development becomes very slow below 12 ° C, or almost nul below 5 ° C. These low temperatures are often reached when sewage treatment plants are located in geographic areas such as Canada or northern Europe. When the snow melts, these bacteria have to deal with the pollution in cold water. The main solution is to significantly increase the size of the plant to compensate for the lack of microbial activity. However, this solution, which is still widely practiced, is very expensive. On the contrary, some industrial processes generate water temperatures in excess of 38°C. The most common bacteria cannot survive in these conditions. That’s why there are mixtures of bacteria that are effective in treating different types of water. In this way, before a cold event for example, it is possible to inoculate the biological reactor with bacteria specially selected for these conditions. They will then overtake the existing populations, and ensure effective treatment of these difficult conditions. We have a selection of bacteria for these difficult conditions:
  • cold waters (between 1°C and 12°C),
  • warm waters (between 30°C and 50°C or more)
The design is available on the microbiological optimization page.

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