Bacteria and micro-organisms involved in water treatment

What are they used for?

Biological wastewater treatment is the most common method of sanitation 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 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. Using 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.

Where are bacteria present?

Everywhere, from the water arriving at the treatment plant to its outlet. 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 reason for the quality of the 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. Some factories use UV reactors to eliminate any remaining bacteria in the water. This is the case in Australia and New Zealand, for example.

Who are these micro-organisms?

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 efficiency 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.
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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 their 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.
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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.

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.

Their impacts and the treatment solutions

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 microbiological 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.

There are generally three ways to restore an effective treatment. Firstly, by changing the operating settings and waiting for the right strains to re-colonise the polluted environment. Second, by completely removing the microorganisms in place when the first solution did not work. Be careful, this method is not recommended, because the biomass will take days to develop, delaying the correct treatment. The third solution is to inject selected bacteria, cultivated and multiplied to regain the advantage over the unwanted bacteria present. This decontamination process is useful to guarantee the efficiency of the treatment systems and the protection of the environment.

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, 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 solutions to reduce this time to about a week, through seeding with selected and multiplied bacteria. There are two main advantages 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 consists of extracting as much sludge as possible and increasing aeration. The good bacteria can take several days to recover the environment. If this does not work, then it is possible to destroy these bacteria with chlorine. The problem is that it kills all bacteria. Then it will take a few weeks for normal conditions to be reached again. While the majority of operators continue to inject chlorine, we recommend the injection of dedicated bacteria. As for the accelerated start-up of a plant, the massive addition of these good populations makes it possible to quickly restore the balance in the tanks. For example, here is an illustration of the removal of floats in a clarifier. The design is available on the microbiological optimization page.

Elimination of pathogenic germs

The microbiological quality of treated water is crucial to public health and environmental protection. When treating wastewater, eliminating pathogens 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 the 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 decomposition of animal and vegetable fats and oils in urban WWTPs and industrial treatment plants. 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 dissolve and digest fats and sludge. Some bacteria are so specialized in the degradation of fats that they are capable of degrading high loads, up to 300,000 mg/L 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 nil below 5°C. These low temperatures are often reached when sewage treatment plants are located in geographic areas such as Canada or northern Europe. During the snow melting, these bacteria must treat the pollution while living in cold water. The main parade consists in significantly increase the size of the plant to compensate the lack of microbial activity. However, this solution, although still widely practiced, is very expensive. By contrast, some industrial processes generate water above 38°C. The most common bacteria cannot survive under these conditions. This is why there are effective bacterial mixtures for the treatment of different types of water. Thus, before a cold event, for example, it is possible to pre-seed the biological reactor with specially selected bacteria for these conditions. They will then take over the existing populations, and ensure effective treatment under these difficult conditions. We have a selection of bacteria for these difficult conditions:

cold water (between 1°C et 12°C),
eaux chaudes (entre 30°C et 50°C ou plus)

The design is available on the microbiological optimization page.

Design tools

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