WATER SYSTEMS


Importance of risk assessment, testing, and monitoring


1: Risk assessment To implement a correct scheme of control for Legionella and other waterborne pathogens, a risk assessment must be undertaken of the water distribution system, water components, and the area within which individuals could be exposed to water, including water aerosols. Legionella risk assessment must be by a qualified and competent person(s), who must factor in the physical aspects (i.e., water source, water components, and water distribution system), the environmental aspects, and the channels via which the waterborne pathogens can affect patients / the public. The most serious form of disease caused


by Legionella is Legionnaires’ disease, predominantly caused bv L. pneumophila bacteria. Legionellae are opportunistic pathogens, and normally inhabit warm, moist, or aquatic environments, growing there in association with other organisms. Legionella bacteria transmission to humans only occurs via breathing in particles remaining in the air, when water in a droplet evaporates, leaving airborne matter such as Legionella bacteria held within the aerosols. The bacteria can also be inhaled into the lungs, and via aspiration.2


environments – such as sinks, water baths, hot water systems, showers, and spa pools. P. aeruginosa can be transferred from person to person via hand-to-hand and hand-to-surface contact.


2: Testing and monitoring Water sampling is a starting point in understanding water quality at a specific time / place. However, to ensure that quality is properly monitored / maintained, we must take specific steps – including temperature testing to ensure that domestic hot and cold water are stored and distributed at the correct temperature. Cold water should be stored and distributed at below 20 °C, while the hot water flow temperature from the calorifier should be kept at a minimum 60 °C. The temperature should be at a minimum of 55 °C on flow and returns to all outlets (in healthcare), and at the start of the hot water return, and at a minimum of 50 °C at the final connection to the calorifier. Temperature monitoring is key in Legionella control. Where Legionella bacteria in water


Person-to-person transmission


does not occur. When addressing Pseudomonas aeruginosa bacteria, risk assessments must include aspects of hygiene / hygiene control. Work with potable water requires scrupulous personal hygiene to prevent system contamination. P. aeruginosa can be found in faeces, soil, water, and sewage. Able to multiply in aquatic environments, and on the surface of suitable materials in contact with water, the bacterium has been isolated from a range of moist


systems are difficult to control, a biocide may be added. Biocides must, however, be monitored at the frequency stipulated by the HSE’s Technical Guidance HSG 274 Part 2: The control of legionella bacteria in hot and cold-water systems, with levels not exceeding the allowed drinking water parameters.


pH-sensitive processes While chlorine dioxide is unaffected by water pH or hardness, the copper and silver ionisation processes are pH- sensitive, and dosing levels may need increasing for pH levels over 7.6. Tests for pH levels should be undertaken at the time of monitoring for copper and silver levels in domestic hot and cold water systems when used as a biocide. To


ensure accurate testing and monitoring of temperature or biocide chemical levels, all equipment requiring calibration must be calibrated by an accredited calibration service, at the manufacturer-specified intervals. Where concerns over drinking water quality exist, testing should be regular. Such water should not contain pathogenic microorganisms, or bacteria indicative of faecal pollution.


Keeping water in a clean environment To minimise contamination, it is important to keep water in a clean environment protected from outside contaminants (i.e. dirt, dust, rust, scale, and animal faecal contamination), and to keep it moving. Regular water system monitoring, cleaning, and disinfection, are essential, together with monitoring of low-use outlets. HTM 04-01: Safe water in healthcare premises: Part B: Operational management, recommends establishing a multidisciplinary Water Safety Group to develop and manage a Water Safety Plan (WSP), and advise on remedial action when water systems or outlets are found to be contaminated.


Microorganisms of significance – Pseudomonas and Mycobacteria Microorganisms of significance are those falling under the category of antibiotic- resistant bacteria. Pseudomonas aeruginosa is a multi-drug-resistant pathogen recognised for its ubiquity; it has no need for organic growth factors, and is able to harness over 75 organic compounds for growth, making it highly resistant to many antibiotics.3


An aerobic,


gram-negative, rod-shaped bacterium (very similar to the Legionella bacterium in shape) with polar flagellum, its shape helps it swim in any water system, even against the flow. Found in soil, water, skin flora, and most man-made environments, it thrives both in normal and hypoxic atmospheres, and can colonise many natural and artificial environments. It uses a wide range of organic material for food, but does not rely entirely on a food supply (the bacteria have been observed to grow in distilled water).


The corroded internal surface of a cold water tank, where biofilm will likely grow.


P. aeruginosa bacteria biofilm starting to colonise a tap’s flow straightener.


A risk to the immunocompromised The bacterium almost never infects healthy tissue, yet there is hardly any tissue it cannot infect where host defences are compromised. P. aeruginosa infections are increasingly antibiotic-resistant, and the organism may acquire resistance during therapy. Infection can be found on and in medical equipment. The wide-ranging areas it affects, and its impacts, include: n The urinary tract. n Respiratory systems. n The skin. n Soft tissue. n Bacteraemia and septicaemia. n Bones and joints.


February 2023 Health Estate Journal 35

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