Biofouling is the uncontrolled growth of organic matter in a technical environment. Biofouling develops on existing biofilm and spread the biomass with the fluid downstream.
Development of Biofilm
Biofilms form at interfaces. At the water / air interface, which is an open water surface. Or in our case at the water / pipe – boundary surface.
Biofilms are usually gelatinous, slimy films of microorganisms. If mature biofilm can develop undisturbed in a pipe or a system, it soon will spread in all directions. Horizontal along the pipe, vertical in the height. Plateaus are forming. If such plateaus reach a certain height, parts of the biomass are torn off by the current. And then transported with the water in flow direction. This is called biofouling.
The illustration shows very clearly how this process takes place.
First, some microorganisms accumulate (1). They become more (2) and then form a protective film (3), they continue to grow into a plateau(4) and when the plateau becomes too big, it bursts (5) and sprays the occupants in all directions. When the water flows, it migrates and spreads out in the direction of flow. This is an endless process as long as the environmental parameters are right.
We talk in this article not about biofilm infections caused by bacterial biofilms in catheters or other medical devices. This is an issue in the medicine, but Merus concentrates on water systems only. Even if technical speaking, these two things are be related. As both are pipes, a catheter and a water line.
Biofilm formation is not only found in drinking water, but increasingly in technically water used in the industry or agriculture. This means in cooling circuits, cooling towers, heat exchangers, water tanks or water lines for drip irrigation. Bacterial biofilms even occur in water used for production. Having biofilm in food or beverage, is not acceptable. The higher the requirements on the purity of the water, the higher the effort to avoid such biofilms or at least to control them.
It is one thing to have biofilm in a cooling tower. But having biofilm in the process equipment of a pharmaceutical company is really serious.
We also are confronted with cases where the biofilm contained microorganisms, which released very aggressive secretions. These in turn led to considerable corrosion damage in the system. This phenomena is called MIC – Microbiological Induced Corrosion.
Technically it can become problematic, if whole „plates“ of biofilm are loosened and pressed through the pipe. This can result in a plug that can lead to blockages in tight places in the system. Like blocking valves or the inlet of a heat exchanger.
Or even lead to the formation of biofilm and biofouling in parts of the system that have not been contaminated since.
Solution against biofilm formation
The common way in the industry to avoid biofilm is the use of biocides. Biocides are chemicals that combat all types of living organisms in a water system. The results achieved through the use of biocides do not always make customers happy. It’s the same as with all chemical dosages, you have to reach every corner of a water system. And this task is very difficult to solve with large and complex pipe constructions.
In order to remove already existing biofilms, the classic method is heat or acid treatment. However, this is very complex and therefore expensive. One of the main problems with classical rehabilitation is to ensure that all areas of the pipe network are flushed. As explained above, this is very difficult to impossible.
As an example, if you have to make heat sanitisation in a hospital or hotel, you have to ensure that no guest is using the tap point during this sanitisation. To ensure to kill biofilm bacteria the water has to have minimum 60°C. If you like to achieve 60°C on the 10th floor of a building, the water have to have at the boiler in the basement, usually more then 80°C.
However, if not all microorganisms are killed during this remediation, biofilm formation begins again after a short time.
Merus against biofouling
Merus has developed special bio rings for the treatment of different biofilm composition. With these Bio Rings we can achieve very good results in infested systems. The mode of action is to be compared with that against the legionella. However, the removal of the biofilm is even more demanding. This is mainly due to the fact that the bacterium or other microorganism living in it have developed strategies for self-protection.
This slimy film, for example, offers good protection against thermal remediation. Some spores are even more resistant to heat than the bacterium itself. This means that problems with a biofilm structure cannot be solved overnight. With the Merus Ring we can prevent the biofilm even in sewage systems. And stop biofouling.
Today, we have numerous applications in which the biofilm has been minimized so that it no longer causes any problems. In some applications the biofilm was even completely removed.
Even if the chemical dosage has been completely discontinued, the results obtained are very stable and satisfactory. Long-term results and measurements also speak for us. Some projects show excellent and stable results for more than ten years.
Before – After comparison
The picture above shows a piece of pipe cut lengthwise. The Merus Ring was previously installed in the middle of this pipe section. The left section shows many small and medium white dots. In the middle, where the ring was installed, there is almost no biofilm. And in the right section behind the ring there are even fewer, smaller dots.
Unfortunately, the complete system is not biofilm-free in this application. In untreated sections, the biofilm can continue to grow undisturbed. With very large systems, the range of effect is limited. This means that in order to completely control the biofouling process, the entire pipeline system must be equipped with several Merus Bio rings.
If only one Merus Bio Ring is installed on a pipe string, the spread is only restricted. It is also difficult if the feed water is contaminated.
However, the biggest advantage is still that the Merus oscillations spread even in stagnant water. This means that they also reach the dead legs*. It is precisely in these pipeline sections that the biofilm usually settles undisturbed.
*Dead legs, from the English, for a part of a line through which there is no flow. This can be a branch line with a valve at the end, which is rarely or never opened.