HMP Addiewell - Sodexo

HMP Addiewell is a prison located near to the village of Addiewell in West Lothian, Scotland. HMP Addiewell is operated by Sodexo Justice Services under contract to the Scottish Prison Service. The prison holds adult males who have been convicted as well as those being held on remand.

The task of keeping the prison gym clean, safe, and sanitary falls on Stenia Walker and her Sodexo team. Stenia uses Stabilised Aqueous Ozone (SAO®) from Tersano to keep the gym clean, safe, and sanitary. SAO is a rapidly growing, alternative way to clean without the risks that come with traditional cleaning chemicals.


Number of residents: 700
Number of Staff: 350
Gym square footage: 1260 m²
Sector: prisons
Number of gyms: 1 plus a number of smaller wing gyms
Product: cleaning and deodorising

“The level of hygiene achieved by using Tersano is unbelievable.”

Stenia Walker
Deputy Group Head for Safety and Risk
Sodexo Justice Services Division

In 2008, the HMP Addiewell prison opened in West Lothian, Scotland between the cities of Glasgow and Edinburgh. The facility is designed as a learning prison where offenders can address their behavior, improve their prospects, and return to community productively. The prison is operated by Sodexo Justice Services – a division of Sodexo Worldwide and is under contract to the Scottish Prison Service.

In 2016, Sodexo sought to improve maintenance operations at the prison. “We’ve been looking for ways to increase safety and sustainability here at Addiewell – along with saving money, of course,” notes Stenia.

After researching opportunities, Stenia discovered one option to improvement was by reducing costly cleaning chemicals and switching to an alternative cleaning technology that harnesses the power of ozone instead of relying on hazardous chemicals: the Tersano lotus PRO®. The lotus PRO creates Stabilised Aqueous Ozone (SAO): a simple, safe, sustainable way to replace traditional chemical-based cleaners and deodorisers. SAO is an environmentally-friendly cleaning solution approved and certified by many organizations including Green Seal, HACCP, OSHA, and more.

Stenia decided to test SAO in one of the toughest areas to maintain: the prison gym – a space full of dirt, grime, and odors. She has been pleasantly surprised with the results. “The gym and the cleaning cupboard no longer have the odour you would normally expect in these spaces,” explains Stenia.


Calling SAO “energised water”, Stenia’s team has been using the SAO for nearly 12 months and is happy with the switch. “It’s very simple to use as there is no longer any change of chemicals needed,” explains Donny Wornin, team leader and a member of the British Institute of Cleaning Science training centre. “After testing each area, there is a definite downward trend of possible cleaning cross contamination using Tersano.”


Steven Bryce, a team leader in the fitness area of the prison, notes the improvement. "We use it in all areas of the gym including the equipment, the mats, and the commons. It's working well."

In addition to cleaning effectiveness, Stenia is realising other benefits from SAO. “Disposal of wastewater is more straightforward as it no longer needs to be placed in foul waste – and it cleans the drains as a bonus,” she says. “Where safety and sustainability are concerned, cleaning with SAO is definitely safer as it allows us to reduce our chemical usage.” Adds Donny:

"“The potential risks and hazards from using chemicals are eliminated."

Best of all, Stenia confirms the switch from chemicals to SAO has increased profitability. “The reduction in bureaucracy and the hard and soft costs that come with chemicals has been a positive for us,” she says.

Donny sums up SAO the best: “The place is clean.”

Today, Stenia will be adding four more Sodexo sites to the overall testing program with another two lotus PRO dispensers being installed at Addiewell.


  • SAFE FOR STAFF - Powerful enough to clean, yet safe for people, planet and animals.
  • SIMPLER TO USE - With no storing, managing, mixing, or disposing SAO is simply a quicker, easier way to clean.
  • SUSTAINABLE FOR THE ENVIRONMENT - No more pouring chemicals into drainage systems when cleaning is complete.
  • COST-EFFECTIVE - The days of buying chemicals are over.