Biofilm

What is Biofilm?


Microorganisms form hard-to-remove films of slime (biofilm) on surfaces permanently in contact with water.

Biofilms are made up of aerobic and anaerobic bacteria, fungi and algae (if there is sufficient light) bound together by polysaccharides secreted by the microorganisms making up the biofilm. The polysaccharides that hold the biofilm together also strongly bind the matrix to the surface on which it is growing making it extremely hard to remove. Biofilm is not a single organism but is made up of a diverse range of different species microorganisms including protozoa and rotifers as well as debris from the biofilm itself.

Why is Biofilm a Problem?


Biofilm occurs in water distribution pipes, cooling towers, filter media, storage tanks, irrigation systems, anywhere a surface is permanently in contact with water. The formation of biofilm is a well-known phenomenon. It is also well-known that, once established, biofilms are extremely difficult to remove using conventional disinfectants. In distribution systems, can reduce flow rates resulting in increased pumping costs. In irrigation systems, biofilm reduces flow rates and causes blocked filters resulting in uneven watering and high maintenance costs.

In cooling systems, biofilm reduces heat losses resulting in increased energy costs and loss of reduce flow rates resulting in increased pumping costs. In irrigation systems, biofilm reduces flow rates and causes blocked filters resulting in uneven watering and high maintenance costs. In any system employing metal component, biofilm contributes directly to corrosion as well as indirectly by harbouring anaerobic bacteria such as Desulfovibrio desulfuricans.

Biofilm can also harbour viruses and pathogenic organisms such as Legionella and serve as a reservoir of these organisms despite attempts to remove them with conventional treatments such as shock doses of chlorine.

Control of Biofilm – Conventional Methods


Chlorine is the most common disinfectant used to control microorganisms in water systems such as cooling towers and drinking water. However, in many situations, chlorine is ineffective at controlling biofilm.

Chlorine is unable to penetrate biofilm and only affects the surface layers. Chlorine is also ineffective if the level of nutrients in the water is high enough for the rate of bacterial growth in the biofilm to exceed the rate at which the chlorine can remove the surface layers. This is a common occurrence in many industrial situations.

Chlorine can provide adequate biofilm control in cooling systems if the system is relatively clean and continuous dosing is maintained. However, if biofilm is already present or continuous dosing is not rigorously maintained, continuous dosing will not control biofilm.
Bromine is comparable with or slightly better than chlorine unless the bacterial nutrient loading is high. In the latter case, bromine is a poor choice for biofilm control.

Non-oxidising biocides are generally less effective at controlling biofilm than either chlorine or bromine. If conditions for the growth of algae are present, chlorine is only effective at controlling algal growth if the chlorine is dosed continuously. Even in otherwise clean cooling systems, chlorine often fails to control algae. Bromine is generally less effective than chlorine at controlling algae. Some non-oxidising biocides control algae more effectively than chlorine and bromine, others are ineffective.

Control of Biofilm – CleanOxide 75


CleanOxide 75 controls both biofilm and algae more effectively than chlorine, bromine or non-oxidising biocides even when dosed intermittently. The reason why CleanOxide 75 is so effective at controlling biofilm is because it is a solution of pure chlorine dioxide in water. Chlorine dioxide does not react with the polysaccharides holding the biofilm together and is able to penetrate deep into the film destroying the microorganisms that are present.

In addition, CleanOxide 75 is effective over a broad pH range (4 to 10) whereas chlorine and bromine are most effective only within a narrow pH range from 7 to 7.5 and are ineffective in alkaline conditions. CleanOxide 75 does not react with ammonia or organic matter present in the water and is an effective biocide at much lower concentrations than chlorine. For these reasons, CleanOxide 75 is the superior choice for controlling biofilm and algae.

Advantages of CleanOxide 75


  • CleanOxide 75 is effective over a broad pH range (4-10).
  • CleanOxide 75 controls bacteria, bacterial spores, fungi, protozoa, viruses, biofilm and algae.
  • CleanOxide 75 does not react with ammonia and does not produce toxic compounds in contact with organic materials present in water.
  • Microorganisms do not develop resistance to CleanOxide 75.
  • CleanOxide 75 is effective at lower dose rates than chlorine or bromine.

Biofilm

Microorganisms form hard-to-remove films of slime (biofilm) on surfaces permanently in contact with water.

Biofilms are made up of aerobic and anaerobic bacteria, fungi and algae (if there is sufficient light) bound together by polysaccharides secreted by the microorganisms making up the biofilm.

The polysaccharides that hold the biofilm together also strongly bind the matrix to the surface on which it is growing making it extremely hard to remove.

Biofilm is not a single organism but is made up of a diverse range of different species microorganisms including protozoa and rotifers as well as debris from the biofilm itself.

Biofilm occurs in water distribution pipes, cooling towers, filter media, storage tanks, irrigation systems, anywhere a surface is permanently in contact with water.

The formation of biofilm is a well-known phenomenon. It is also well-known that, once established, biofilms are extremely difficult to remove using conventional disinfectants. In distribution systems, can reduce flow rates resulting in increased pumping costs. In irrigation systems, biofilm reduces flow rates and causes blocked filters resulting in uneven watering and high maintenance costs.

In cooling systems, biofilm reduces heat losses resulting in increased energy costs and loss of reduce flow rates resulting in increased pumping costs. In irrigation systems, biofilm reduces flow rates and causes blocked filters resulting in uneven watering and high maintenance costs.

In any system employing metal component, biofilm contributes directly to corrosion as well as indirectly by harbouring anaerobic bacteria such as Desulfovibrio desulfuricans.

Biofilm can also harbour viruses and pathogenic organisms such as Legionella and serve as a reservoir of these organisms despite attempts to remove them with conventional treatments such as shock doses of chlorine.

Chlorine is the most common disinfectant used to control microorganisms in water systems such as cooling towers and drinking water. However, in many situations, chlorine is ineffective at controlling biofilm.

Chlorine is unable to penetrate biofilm and only affects the surface layers. Chlorine is also ineffective if the level of nutrients in the water is high enough for the rate of bacterial growth in the biofilm to exceed the rate at which the chlorine can remove the surface layers. This is a common occurrence in many industrial situations.

Chlorine can provide adequate biofilm control in cooling systems if the system is relatively clean and continuous dosing is maintained. However, if biofilm is already present or continuous dosing is not rigorously maintained, continuous dosing will not control biofilm.

Bromine is comparable with or slightly better than chlorine unless the bacterial nutrient loading is high. In the latter case, bromine is a poor choice for biofilm control. Non-oxidising biocides are generally less effective at controlling biofilm than either chlorine or bromine.

If conditions for the growth of algae are present, chlorine is only effective at controlling algal growth if the chlorine is dosed continuously. Even in otherwise clean cooling systems, chlorine often fails to control algae.

Bromine is generally less effective than chlorine at controlling algae.Some non-oxidising biocides control algae more effectively than chlorine and bromine, others are ineffective.

CleanOxide 75 controls both biofilm and algae more effectively than chlorine, bromine or non-oxidising biocides even when dosed intermittently.

The reason why CleanOxide 75 is so effective at controlling biofilm is because it is a solution of pure chlorine dioxide in water. Chlorine dioxide does not react with the polysaccharides holding the biofilm together and is able to penetrate deep into the film destroying the microorganisms that are present.

In addition, CleanOxide 75 is effective over a broad pH range (4 to 10) whereas chlorine and bromine are most effective only within a narrow pH range from 7 to 7.5 and are ineffective in alkaline conditions.

CleanOxide 75 does not react with ammonia or organic matter present in the water and is an effective biocide at much lower concentrations than chlorine.

For these reasons, CleanOxide 75 is the superior choice for controlling biofilm and algae.

  • CleanOxide 75 is effective over a broad pH range (4-10).
  • CleanOxide 75 controls bacteria, bacterial spores, fungi, protozoa, viruses, biofilm and algae.
  • CleanOxide 75 does not react with ammonia and does not produce toxic compounds in contact with organic materials present in water.
  • Microorganisms do not develop resistance to CleanOxide 75.
  • CleanOxide 75 is effective at lower dose rates than chlorine or bromine.