What is Biofilm?
Biofilm is a complex network of microorganisms that attach themselves to surfaces for the purpose of reproduction and survival. Once attached, they form extracellular polymeric substances (EPS) which are very tough polysaccharides that protect the bacteria from degradation. When formed, they can be extremely difficult to remove due to the EPS, and are known to cause a wide range of problems. Biofilm is commonly found on any solid surface that is exposed to a liquid, and can be typically found in irrigation systems, cooling and heating equipment, and food and beverage processing facilities.
Biofilm formation and dispersion
Why is it a problem?
Biofilm formation causes a number of significant problems. Firstly, the bacterial matrix can provide a home for far more dangerous pathogens such as Legionella which may pose a risk to human health. Biofilms are also known to cause blockages in small tubing such as those commonly utilised for nursery drippers, which can result in dehydration and death of the plants. Furthermore, the presence of biofilm increases energy costs and can cause corrosion in equipment, resulting in lost production and spoiled product.
An example of a dripper system prone to blockages from biofilm.
The Structure of chlorine dioxide.
What can be done about it?
The only known effective treatment for biofilm removal is chlorine dioxide, which is a broad spectrum biocide that is effective over a wide pH range. It is proven to eliminate biofilm in nursery irrigation lines, heat exchangers, cooling towers, and breweries. Chlorine dioxides exceptional effectiveness is a product of two properties; its physical state and mode of action. It is a highly selective oxidant that is present as a gas within water, which allows it to penetrate into the biofilm and attack the bacteria attached to the surface, causing the complete removal and destruction of the whole structure. To achieve optimal results, chlorine dioxide should be continuously applied at a very low dosage (0.2ppm) to ensure that the biofilm is not given a chance to reattach to the surface and proliferate.
A heat-exchanger before and after chlorine dioxide treatment.
Why choose chlorine dioxide over other disinfectants?
- It is the only chemical capable of completely removing biofilm as it is present as a gas in the water, which allows it to penetrate into the biofilms and attack them at the point of attachment
- It is effective over a very wide pH range (4-11)
- It will eliminate biofilms at very low concentrations (approximately 0.2ppm), which ensures that it is both cost-effective and safe to use
- It will not react with ammonia or organic compounds, so the chemical is not wasted
- Unlike chlorine, it will not form carcinogenic by-products like THM’s. This is because it is an oxidant that operates by accepting electrons to destroy biofilms, not by donating chlorine atoms
- It can remove iron and manganese from the water by precipitating them out
- It is non-corrosive
- It is capable of destroying a wide range of bacteria, viruses, fungi and spores