Why doesn’t chlorine penetrate biofilms?

Posted on 14 Jan 2016 by Valerie




Direct measurement of chlorine penetration into biofilms during disinfection


Transient chloride profiles measured in biofilms during disinfection.

Chlorine is ineffective for biofilm removal as it has difficulity penetrating into the biofilm matrix and is partially neutralised inside.  While effective for suspended cells, biofilms are much more resilient.

At normal doses the chlorine only manages to penetrate 0.1 to 0.2 mm within the biofilm matrix. Neutralising ability of cells may explain the rapid regrowth of highly resistant biofilm cell groups

Only 20%-30% of bulk concentration affects the cell matrix.

This can be compared to an effective oxidising agent like CIO2 which diffuses much more easily being a dissolved gas which can then oxidise cells and inhibit reproduction via chlorite formation.