What dissolves biofilm?

Breaking Down Biofilm: What Works Best?

Biofilm—those stubborn, slimy layers formed by bacteria in water systems—can be a persistent problem, especially when it comes to pathogens like Legionella. Once established, biofilms are tough to remove and can shield harmful microbes from conventional cleaning methods. So, what actually dissolves or destroys them?

Strong oxidising agents are the most effective solution. Substances like chlorine and peroxoacetic acid have proven track records in breaking down biofilm structures. These chemicals don’t just kill surface-level bacteria—they penetrate the extracellular matrix that holds the biofilm together, disrupting its integrity at a deeper level.

Chlorine, in particular, is widely used in water treatment systems because of its dual ability to disinfect and degrade biofilm. Studies, including Green (1993), have shown that chlorine outperforms nonoxidative biocides such as quaternary ammonium compounds or biguanides when it comes to eliminating Legionella biofilms. While nonoxidative agents may work on free-floating bacteria, they often fail to penetrate the protective layers of biofilm effectively.

Peroxoacetic acid is another powerful oxidiser gaining traction, especially in sensitive environments like food processing or healthcare, where residue and safety are major concerns. It combines strong biofilm-dissolving action with fast decomposition into harmless byproducts—making it both effective and environmentally friendlier.

The key takeaway? When tackling biofilm, oxidation is essential. Simply using standard disinfectants isn’t enough. A targeted approach using proven oxidisers like chlorine or peroxoacetic acid offers the best chance at long-term control and prevention—especially in complex water systems where biofilm can quietly undermine hygiene efforts.