Risk assessment of Legionella in water systems

Purpose

Legionella is found naturally in soil and water. It currently causes between 100 and 150 cases annually in Sweden and is a growing problem. Outbreaks of Legionella are often linked to aerosol-forming water systems, e.g. cooling towers, showers, fountains, hot tubs and humidification facilities. In order to deal with Legionella in a water installation, the risks for growth, survival and spread need to be mapped and an action plan drawn up.

The new Drinking Water Directive states that there must be a risk assessment of Legionella in water systems in society important and prioritized buildings. According to the directive, prioritized buildings mean large properties that have many users who may be exposed to water-related risks. More specifically, it can, for example, be:

• Premises related to health care and social care
• Teaching premises
• Airports and ports
• Hotels
• Sports facilities
• Swimming facilities
• Multi-apartment buildings
• Assembly premises
• Premises for correctional facilities

In addition, a risk assessment should be carried out in premises and facilities that previously had problems with Legionella.

Method

The projects are structured as a traditional risk analysis according to Codex Alimentarius/FAO, 2014 (or equivalent) with the steps:

1. Hazard identification 
2. Hazard characterization 
3. Exposure estimation 
4. Risk characterization

The risk assessment can be done theoretically and/or with the support of measurements. For this, RISE offers, among other things, sampling of the customer's water system, microbiological analysis, as well as tests in labs and pilot systems.

The focus of the work is adapted to the current issue and the customer's needs. The risk assessment can be expanded and supplemented with action analysis and action proposals.

Delivery

The risk assessment is summarized in a report and presented in a meeting with the customer.