With 485 cases reported in 2015, Legionnaires’ disease continues to be a major health concern in the UK. Paul Sear, national technical manager, water hygiene, Environment & Safety Services, gives his advice on controlling the risks of legionella in the rail industry.
Legionnaires' disease is caused by the inhalation of legionella bacteria which can be present in a diverse range of water sources and systems. All organisations, including rail operators, where staff or members of the general public come into contact with water systems, have a duty of care to put in place appropriate legionella management measures to help prevent the growth of the bacteria and manage the foreseeable risk.
Legionella thrives in water at temperatures of between 20°C and 45°C, meaning that the summer months bring with them increased risk of an outbreak. As well as the correct temperature, the occurrence of limescale, sediment, rust, bio-film and organic matter in a water system can also encourage growth, reinforcing the importance of proper management of all water systems.
An updated technical guidance on the management of legionella, HSG 274, was introduced by the HSE in 2014. Together with the revised ACoP L8, it puts an increased emphasis on the responsibility of the duty holder to manage the risks associated with the bacteria. Parts two and three of the guidance are the sections most relevant for the rail industry, and clearly outline the monitoring and maintenance regimes that operators must follow to ensure the health and safety of those in their care.
Through continued work with the rail industry to manage risks associated with legionella, SOCOTEC has identified carriage wash machines and carriage tanking points (and their connected water storage systems) as being the two areas that require the most attention from railway operators. By placing a focus on these facilities, railway operators can dramatically reduce the likelihood of legionella growth, and in turn lessen the risk to staff, contractors and the public.
Carriage wash machines are commonplace at many railway depots. The design of certain carriage wash machines involves a recycled water facility to reduce water consumption and lessen the environmental impact by reducing trade effluent volume. While the water is filtered to a standard adequate for cleaning purposes, nutrients necessary for bacterial growth may remain. This, in combination with the water remaining inside the machines when not in use, can provide the conditions for multiplication of legionella. The HSE expects carriage wash machines to be managed to the similar standards of a cooling tower, with a suitable biocide dosing and monitoring programme in place, especially important if you are recycling water.
Water storage tanks and tanking facilities can also be areas of increased risk for bacterial growth in railway depots, stations and infrastructure buildings. If properly managed, water tanks are a safe and efficient method of storing and delivering water. It is important, however, to ensure water systems are in regular use and managed according to the guidance issued in HSG 274. Train tanking facilities must also be managed correctly depending on their use (potable or non-potable) to minimise bacteriological contamination and cross contamination between the two types of systems. Water supplies for onboard catering facilities should be tested for potable water quality within the rolling stock and at the tanking point facilities regularly to ensure the risk of bacteriological contamination is low at the source and throughout the fleet.
As the majority of train tanking systems are located in outside areas, during the warmer summer months they will require extra care and attention from train operators and depot staff. Warm, static water is the preferred breeding ground for legionella, and, if equipment is not used regularly, it increases the chances of bacterial growth. Solar heat gain and warmer ambient temperatures can play a role in raising the temperature of water inside water storage tanks and tanking facilities, and train operators should be conscious of the effect warm weather can have on bacterial growth.
Management of on-board water systems should be managed to an equivalent standard as required for domestic water systems to minimise the risk of bacteriological contamination in both potable and non-potable water systems. Potable water systems seen on modern rolling stock have several features to assist in reducing bacteriological contamination including UV sterilisers. Proper maintenance and monitoring of these systems is crucial to ensure water quality complies with both the standards of the train operator and national requirements.
Management of non-potable systems is also required to ensure that on-board tanks are cleaned and disinfected effectively to prevent bio-film becoming established internally on the tanks. Poor management and ineffective system disinfections can potentially lead to elevated bacteria levels within these tanks which are used by passengers and staff.
As well as full legionella risk assessments for water systems in the rail sector, SOCOTEC can also offer full management of these systems to prevent outbreaks. Services include water quality sampling and testing, disinfection of tanking facilities equipment, domestic water tanks and on-board tanks, microbiological sampling and testing, application and supply of biocides, chemical analysis of water and expert advice and consultancy relating to carriage wash systems, tanking facilities and legionella management.
To help rail operators keep their water systems in top condition this summer, the following is SOCOTEC’s advice for maintaining equipment to the highest standard:
- Ensure all systems are used or flushed regularly. Good movement of water will dramatically reduce the risk of bacterial growth
- Always treat recycled water in carriage washing machines with a suitable biocide to kill bacteria
- Carry out regular biological monitoring of carriage washing machines, including weekly dip slides and quarterly legionella sampling
- Train tanking points should be managed correctly by ensuring suitable storage facilities, kept free of residual water internally and not left lying on ballast or walkways. The end of a hose should be stored in disinfectant and flushed before being connected to any train
- If a tanking point is supplying drinking water, or water for use in food production or service on board the train, it should be regularly tested for water quality
If you would like further advice on managing legionella risk in on trains and in rail depots, please firstname.lastname@example.org
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