Biofouling and Biofilm

Biofouling and Biofilm

What is biofilm

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.

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.
The biofilm formation start with a small inpurity. Which came with the water or other fluids in the water lines or system. This inpurity might be, a bacterium or microbes in the feed water, or dead algaes from a cooling tower. These settle in a spot, with less flow and the process of biofilm formation start.

The biofilm structure are mostly gelatinous, glue-like, slimy films of microorganisms. It might be bacterial cells or other microbial organism. Sometimes the bacterium living in the biofilm formation are pathogen as for instance legionella, but in most cases not.

Biofilm in water lines

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. Plateus 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 torn parts of the biofouling settle somewhere else in the water system and start a new biofilm formation.

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 cathere and a water line.

 

Biofilm in a pipe

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

 

Marine Growth in seawater pipe lineThe 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.

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