Background:
Sink drains can be a significant source of microbial contamination in healthcare settings, from aerosolization and splash-back of pathogens caused by flowing water.

Aim:
To demonstrate a method of ozone disinfection of drains using a novel generation process that suppresses pathogen growth in the drain sump, whether planktonic or dwelling in biofilms.

Methods and Results: Highly biocidal ozone was generated in-situ in the drain, using the ambient air sealed between the drain water-trap and a portable cold plasma device. Safety mechanisms in the device ensured that the operator was not exposed to ozone. Subsequent bacterial recovery illustrated an approximate bioburden reduction of 5log10 for biofilms in the drain itself, and 6log10 for biofilms located in the sink.

Conclusions:
Plasma-generated ozone is a safe and effective method for controlling bioburden in periodically wetted, otherwise inaccessible pipework and drains.

Significance and Impact of Study:
The portable ozone disinfection system described has demonstrated potential for controlling the escape of pathogens from drains.

Compared to conventional liquid-based disinfection techniques we find the following advantages: (a) a gaseous biocide can reach all surfaces inside the treatment target, without any restriction from orientation or surface tension; (b) ozone is effective in reducing planktonic and biofilm bacterial counts; (c) the ozone is generated at the point of use from air, using only minimal electrical power, requiring no chemical delivery or storage, and producing no toxic residues.