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 for the treatment and cleaning of polluted water.

Wastewater treatment is as essential to human health as it is to environmental protection. Indeed, the use of these bacteria accelerates the treatment of pollution on a small surface: the purification plant. It’s better than letting the river handle it, because even though it’s the same purification process that occurs in nature, the quantities of pollution discharged today are too high to keep the natural cycle intact. Thus, sewage treatment plants can prevent eutrophication of rivers, for example, but also prevent the diffusion of diseases.

Municipal and industrial effluent is the main source of wastewater. And thanks to the use of micro-organisms, we are able to degrade the content of these organic wastes as they are used as a source of food and energy to grow and multiply.

You got it, bacteria are the heart of the process. And finally, a wastewater treatment plant is a kind of farm where micro-organisms are grown on a large scale.

Where are bacteria present?

Everywhere, from the water arriving at the treatment plant to its outlet. The operating parameters set in the treatment ponds influence the development of various microbial structures and the species that compose them. This set of microorganisms, rich in several species, reach 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 mud. In addition, in fixed cultures, similar biofilms develop on contact surfaces. For example, biofilters and biological disks are fixed cultures.

Some factories have UV reactors or chlorine injection to eliminate the bacteria still present in the output water, before it is discharged into the river. This is the case in Australia and New Zealand.

bactéries sur site 2 x 1m3 bacteries bacteria - 1H2O3
Culture batch bacteria on site 2 x 1m3 bacteria - 1H2O3
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Mesophilic bacterial production 1 pure strain per bottle bacteries bacteria - 1H2O3

Who are these micro-organisms?

First of all, before knowing who they are, we must understand the parameters that influence their growth. First, the geographical location. Secondly, the type of pond in which bacteria will be grown. Thirdly, the characteristics of the wastewater entering the plant. Finally, the operating parameters of the system, such as aeration, agitation, chemical injection. All these factors generate quantitative changes between autotrophic and heterotrophic bacteria. In municipal wastewater treatment plants, for example, gram-negative bacteria of the proteobacteria type predominate (21-65%) of which Betaproteobacteria is the most abundant class, largely responsible for the removal of organic elements and nutrients. The other phyla are Bacteroidetes, Acidobacteria and Chloroflexi (Nielsen and al., 2010; Nguyen and al. 2011; Wan and al., 2011; Hu and al., 2012; Wang and al., 2012 ). The most numerous types of bacteria are Tetrasphaera, Trichococcus, Candidatus Microthrix, Rhodoferax, Rhodobacter, Hyphomicrobium (McIllory et al., 2015).

Among the fungi, the Ascomycetes are the most common, accounting for 6.3 to 7.4% of micro-organisms. Then come the archaeobacteria, with the Euryarcheota (1.5% of microorganisms, Wang et al., 2014b ). In addition, in the presence of ammonia and oxygen, Nitrosomonas is very present. Finally, a high mud age allows protozoa and rotifers to colonize the environment.

Temperature affects the presence of certain species. Thus, the effect of geographic location affects species composition. On the other hand, in industry for example, the presence of well-defined microorganisms is explained by their ability to biodegrade specific components of industrial wastewater.

Bacteria are further categorized by how they get oxygen. In wastewater treatment, there are three types of bacteria used to treat wastewater entering the treatment plant: aerobic, anaerobic and facultative.

Their impacts and the treatment solutions

The presence of bad bacteria (or the absence of good ones) can cause in particular:

  • Low biogas efficiency of the anaerobic digester
  • Poor flocculation and sedimentation
  • An excess of filamentous bacteria
  • Excess of phosphorus
  • Low nitrogen removal efficiency (NH4, NO3)
  • The production of unpleasant odours
  • Excess consumption of chemical products
  • In an anaerobic digester, foam production

There are generally three ways to restore an effective treatment. First, by changing the operating settings, and waiting for the right species to colonize the environment again. 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 several days to develop, so the water will not be properly treated during this period. The third solution consists in injecting specially selected, cultured and multiplied bacteria in order to recover the advantage over the undesirable bacteria present in the environment.

Frequent applications

Microbial biotechnology offers innovative scientific applications of great ecological and economic interest. It optimally exploits natural degradation processes and thus eliminates pollution at significantly lower costs than conventional physical-chemical or mechanical treatment techniques.

The use of bacteria is different from current treatment techniques because it uses simple and natural means whose final result allows the elimination of pollution without generating new pollution. Most of the time, their installation requires the use of a dedicated bioreactor, as well as the nutrients necessary for their multiplication in large numbers. Dosing is easy and requires little operating time.

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. Thus, in these favorable conditions, bacteria develop flocs or biofilms very quickly. Finally, after several days, the environment is ready and the wastewater can be discharged.
We have selected a range of bacteria to start your installation in one 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 mud 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. And then it will take a few weeks for normal conditions to be reached again.

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.

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 specialized in fat degradation that they are able to degrade 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 mud (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. During the snow melting, these bacteria must treat the pollution while living 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.

In contrast, some industrial processes generate water above 38 ° C. The most common bacteria cannot survive in these conditions.

That’s why there are effective bacterial mixtures for the treatment of different waters. 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 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

In the Toolssection, you will find all the mathematical and cost information that will allow you to estimate a project.

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