WATER SYSTEMS
How can chemical disinfection be used in a healthcare setting? Chemical disinfection of a water system, often called biocidal treatment, consists of contractors introducing chemicals, often chlorine dioxide, into the water system and running the taps through all the pipework within the water system. The taps are then closed to allow the chemicals to kill live Pseudomonas within the water system. However, the selection of appropriate chemicals is extremely complex and is dependent on a number of factors, of which are much more prevalent in a healthcare setting. For example, biocides introduced into hot water systems are often ‘gassed off’,5
and when they are
placed in cold water systems – more specifically drinking water systems – they must be monitored to ensure that they do not exceed prescribed concentrations for drinking water.
Is chemical disinfection more effort than what it is worth? The UK government’s Health Technical Memorandum 04-01 Part A – Design, Installation and Commissioning (HTM04- 01-Part A) suggests where biocides are used to control microbial growth in water systems ‘meticulous control and monitoring programmes should be in place if they are to be effective.’6
HTM04-
01 Part B agrees, stating the use of biocides ‘requires meticulous monitoring, and their use can have an effect on water quality including taste and odour’.7 Both these statements taken from HTM04-01 highlight the effort behind chemical disinfection and the overall impact of chemicals on the water system post disinfection. Thus, implying strenuous risk assessments needing to be completed by a WSG to corroborate the safety, as well as hygiene, of the water system. The imbalance of biocides within a water system can have a number of impacts, affecting both the components of the water system and the end-users. If a WSG selects incorrect acidic chemicals the components in that make up the water system can begin to deteriorate. HTM04-01 Part A states, ‘Within a healthcare facility, the detrimental effects of biocidal treatment, such as corrosion of metal components and deterioration of plastics and elastomers, should be taken into consideration as biocide use may shorten the lifespan of particular components.’ Proving that, no matter the quality of the components within the system, chemicals can cause the water system to completely breakdown causing additional operational issues.
Furthermore, the breakdown of such
materials creates the perfect environment for Pseudomonas to grow as it potentially can feed off these types of materials.
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TMVs are used to blend hot and cold water to a set constant outlet temperature.
Thus, a WSG is stuck in a ‘cycle’ of disinfection and bacteria growth, potentially making the system unsafe and unhygienic.
How can thermal disinfection be used in a healthcare setting? It is widely known that Legionella, and other Pseudomonas, grow in water systems where water is stored at between 20-50˚C. Thermal disinfection, however, allows water temperature to be increased to above 60˚C thus, killing the Pseudomonas. Although this has far fewer limiting factors to the chemical disinfection of a system, thermal disinfection poses a scalding risk to the end-user. For example, Health Building Notes 00-10 Part C – Sanitary Assemblies advises that outlets above 46˚C present a scalding risk and should be labelled as such.8
It also advises that thermostatic
devices, such as thermostatic mixing valves (TMVs), should be used at each outlet remove scalding risk. TMVs are used to blend hot and cold
water to maintain a set constant outlet temperature. This ensures safe and comfortable hand washing, showering and bathing temperatures, and significantly reduces the risk of scalding. Scalding of vulnerable end-users, who
would regularly be using the water outlets in a healthcare setting, should be avoided at all costs and WSGs should impose
measures to keep all end-users safe. So, could thermal disinfection keep those in a healthcare setting both safe and protected against Pseudomonas?
Is thermal disinfection the most effective method for a healthcare setting? In order to safely use water at temperatures that will thermally disinfect the system, WSGs must specify a TMV that adheres to the strict testing regime of the TMV3/NHS D08 regulatory standard to ensure the contend safety of the water supply to the end-user, i.e. predominantly the patient. The TMV3 approval scheme provides
assurance that a TMV is tested and deemed safe to use in a NHS setting. The scheme applies to thermostatic mixing valves for use in high-risk commercial healthcare applications within the UK. These valves offer a high level of protection, reacting much more quickly in shutting off the flow of water if the cold water fails, or a safe temperature is exceeded. Third-party accredited testing ensures that the valve adheres to the NHS D08 regulatory standard, which ensures stable temperature output despite varying supply pressures and temperatures. As well as allowing for thermal
disinfection, the fitting of a TMV that adheres to these standards prevents the end-user from scalding. Within a
A common area is a dead-leg where either pipework has been altered and no longer in use, where the water may sit stagnant or where there is infrequent use of the water being drawn off
IFHE DIGEST 2022
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