WATER HYGIENE AND SAFETY


purpose-built water systems. They can’t be eradicated entirely, but as long as levels are controlled, and counts are kept acceptable, they present little risk. However, the problem can become serious when favourable conditions cause the bacteria to multiply. This is where biofilm enters the Legionnaires’ story. There are biofilms all around us – for example the slimy coating that is often found on rocks in streams and rivers. Made up of various microorganisms, biofilm is a microbial community – and an ideal breeding ground for bacteria – as it creates a protective slime layer or matrix that encapsulates colonies of bacteria inside the outer shell. It sticks to just about anything, from skin to a pipe, and from metal to plastic. It will not disperse naturally, and is hard to remove. The issue for hospitals and other public buildings is that biofilm thrives in a poorly maintained water system in which moisture, bacteria, and surface – the three elements essential for its existence – are all present. Just as the biofilm needs the bacteria, the bacteria need the biofilm – the Legionella and Pseudomonas bacteria attach themselves to the biofilm, and reproduce many thousands of times over, becoming part of this co-dependent unit. Keeping the water system free of slimy, sticky biofilm is essential for establishing and maintaining a safe water system.


The ‘perfect storm’


Hospitals often have complex water systems that may be old and not working efficiently, or have been added to or modified over the years, leading to some areas of the system not being monitored adequately, as happened at RUH Bath. This may create the perfect environment for the proliferation of Legionella and other dangerous waterborne pathogens, due to: n Slow-moving water or deadlegs/dead- ends in the system that allow water to stagnate.


n Water temperature that allows bacterial growth (the bacteria multiply where temperatures are between 20˚C and 45˚C, but are dormant below 20˚C, and do not survive above 60˚C).


n The presence of nutrient-rich biofilm. n The use of materials that encourage the growth of bacteria.


n Poor flushing, cleaning, descaling, and draining of cylinders and infrequently used outlets,


n Generally poor maintenance, meaning that corrosion, for example, goes unnoticed.


Once Legionella gets a hold, a cohesive, consistent plan needs to be put in place as quickly as possible to control and contain it.


44 Health Estate Journal February 2019


The Danish Clean Water T Zero dosing unit incorporates a patent-registered water softening system said to effectively remove limescale from the water used for the production of Neuthox.


Hot


water system


+


24V DC


÷


Neuthox injection


Dosing pump


Cold water supply


Softener


Brine tank / Salt solution


Neuthox tank


Figure 2: The method of operation of the DCW water disinfection unit for hot and cold water systems.


Government guidelines and Water Safety Groups


The Health and Safety Executive provides advice to control the risk of exposure to Legionella in man-made water systems. It refers healthcare estates teams to the Approved Code of Practice (ACOP): Legionnaires’ disease: The control of Legionella bacteria in water systems, and the comprehensive guidance document, HSG274 Part 2: Legionella bacteria in hot and cold water systems. In 2016, HTM 04-01: Safe water in healthcare premises (Part B), was updated to align with the ACOP document, and to


move users of the document towards a holistic management of water systems via Water Safety Groups (WSGs) and Water Safety Plans (WSPs). The WSG is a multidisciplinary team of experts that collectively has the responsibility for creating, implementing, and maintaining the WSP. It benefits from bringing together experts from different speciality areas, such as a microbiologist and a facilities manager, to share their knowledge and expertise. Wider representation gives a much greater overview of potential risks, and the pooling of information allows the hospital to develop a comprehensive, robust WSP that everyone has bought into and can adhere to. ACOP L8 also requires that a ‘Legionella responsible person’ be appointed, who will typically have day- to-day responsibility for the management of Legionella risk in their hospital. It is also interesting to note that the HSE Business Plan 2018-2019 highlights Legionella as an area of high consequence risk, alongside fairgrounds and major construction projects. HSE inspectors will be focussing much more on the control and management of Legionella risks in the workplace, with an extensive programme of proactive inspection. Clearly this is an issue that is receiving increasing attention.


Chlorine


Once any pipework, water storage, overview, and responsibility issues have been addressed, the hospital needs to install a system that continuously controls the level of biofilm, Legionella, and Pseudomonas. There are various options available, but the most widely used in the


Electrolysis cell


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