The Principles of Medical Device Decontamination

Water Safety Group

Good teamwork with the decontamination team and Water Safety Group (WSG) is essential to monitor, control and investigate the issues of water management. Include all the relevant people and professions that can have an influence on the results and system. Ensure the water results obtained are within the desired NHS guidance and standards for use 3 .

Non-Microbial Water Contaminants

Other water contaminants can cause concern or require monitoring. Water quality varies in different parts of the UK and can also vary depending on the level of the water table, and the source of water. There are limits for contaminants in various European standards and UK guidance. However, it is worth remembering that a full chemical analysis, while no longer an absolute requirement in most parts of the UK can still be of benefit. The guidance refers to this as a subsequent test when conductivity levels are high, and it is often the only reliable method of determining the purity of rinse water for substances other than dissolved ions 3,4,5 .

Some of the water contaminants are discussed below:

Hardness

Hard water is caused by the presence of dissolved salts which have low solubilities and are released when heated to form limescale. UK guidance states: “Using hard water in the final rinse stages of an EWD cycle is one of the major causes of deposits on load items. These deposits are not only unsightly and an unwelcome contaminant but act as a focus for soiling and recontamination of the item in use. Such deposits may seriously impair the utility of the endoscope, particularly the optical system. Hard water may cause scaling on the edges of spray nozzles even when fed with only cold water. Detergent formulations intended for use only with soft water may give rise to precipitation if used with hard water. If these products are used diluted with hard water in an endoscope washer disinfector, serious damage to endoscopes may result.” Energy and detergent costs are increased with increases in hardness. Disinfectant efficacy can also be impaired.

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