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Biofilm and Its Formation in Water System

Know about the biofilm formation in pipelines of water distribution system and methods to remove it.

Biofilm is a well known problem of water systems in pharmaceuticals. It is produced by the bacteria and other organisms of various species. Bacteria and other microbes are attached to the inner surface of the water pipelines and starts colonizing.
Sometimes pathogens can also participate in the formation of biofilms in the water distribution system. E.coli and Salmonella are more likely to be found in bilfilms.

Biofilm Formation

Formation of biolfilm in water system starts with the attachment of free floating bacteria to the inner surface of water supply pipeline. Polymucosaccharides, secreted by bacteria helps to attach to the surface and cannot be detached with gentle rinsing. If these initially attached cells are not removed, these cells grow on surface forming colonies and permanently attached to the surface with the help of pili and flagella. These cells are embedded in a self prepared matrix known as slime layer or EPS (Extracellular Polymeric Substance) which protects them from external environment. Slime layer is an initial stage of biofilm formation and produced by the byproducts secreted by these attached microorganisms. These slime layers are hydrophobic in nature that helps the microorganisms remain attached with the surface.
After the maturation of biofilm it starts releasing microorganisms spreading in water which cause continuous contamination in water system.

Biofilm forms in a very short period if water remains stagnant in water distribution system.  Dead legs and rough surface also cause the biofilm formation. Therefore, water system should always remain in continuous recirculation having smooth surface and no dead leg. These biofilms cannot be disinfected easily and re-colonize again in very short time period after the removal of disinfecting agent. Most of the biofilms are resistant to weak disinfectants as chlorine, ozone etc.

Biofilm associated microorganisms are also resistant to low concentrations of antibiotics then free living microbes. E.coli in biofilms requires 500 times more concentrate amphicillin to get 3 log reductions and Staphylococcus aureus requires 10 times more concentration of vancomycin to get 3 log reductions.

The properties of biofilm associated bacteria may completely differ from the free living bacteria of same species. The growth of microorganisms remain slow then the free living probably because of the availability of the nutrients available in the biofilms.

These biofilms also damage the pipes because of the presence of sulfate reducing bacteria those produce hydrogen sulfite as byproduct. This hydrogen sulfite reacts with the iron of pipes causing leakage and break down.

Biofilm Removal from Water System
Removal of biofilm from water system is not an easy task. It is always much better to prevent the system from the occurrence of biofilm then its removal. But when occurred it is first treated with strong acid i.e. nitric acid followed by strong base i.e. sodium hydroxide. By these both inorganic and organic compounds associated with the biofilm are removed very effectively resulting its separation from the surface. Now whole system is disinfected with the strong disinfectants as hydrogen peroxide. Use of UV light in water system is an effectve way to prevent the formation of biofilm.

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Sakthi Vel said...

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