WATER HYGIENE AND SAFETY Trial at North Tees and Hartlepool Trust
The DCW water disinfection system has already been installed successfully in countless hospitals, schools, leisure centres, hotels, and even luxury cruise liners, throughout the world. At the University Hospital of North Tees, operated by the North Tees and Hartlepool NHS Foundation Trust, Stuart Watkin, head of Engineering, Compliance, and Energy, carried out a comprehensive six-month trial to determine whether the system would be suitable for the hospital. At the end of the trial period, estates and facilities/engineering personnel and an independent consultant were impressed by the system’s efficacy and lack of ‘side-effects’. Stuart Watkin, BEng (Hons), MSc, CEng, MIHEEM, said: “After carrying out extensive trialling of the DCW
UK, and the one with the longest and best-established heritage, is chlorine. What makes chlorine so valuable in water-based processes is that it is exceptionally good at killing waterborne germs. When pure chlorine gas or a chlorine compound such as sodium hypochlorite are mixed with water, they form hypochlorous acid, which penetrates cell walls and destroys protein in many pathogens, parasites, and viruses. It literally kills these waterborne germs by the trillions, more efficiently, effectively, and permanently, than just about anything else on the planet. More on hypochlorous acid later, however. Controlling Legionella and other pathogens in the hospital water system is unfortunately not as simple as turning the temperature up or down to avoid the dangerous 20-45˚C zone; cold spots and areas where heat leaches into cold water will still cause problems. For really
‘‘
disinfection system, I have absolute confidence in its ability to control Legionella. When we installed the DCW unit, we not only reduced the bacterial count in the water to zero, but also succeeded in maintaining that level, something we had not been able to achieve consistently until then. I was also impressed by the remarkably low running costs of the DCW system compared with ClO2
. I firmly believe that
hypochlorous acid, as produced in the DCW unit, is the most effective way to control Legionella. When you take into account costs, efficiency, ease of use, maintenance, and, of course, the fact that it neither uses nor produces toxic chemicals, it is clear that this system works on every level, and I wouldn’t hesitate to recommend it.”
effective and ongoing management, an in-water solution is needed too. There are various options out there, including ozone and UV radiation, but none of these alternatives is a ‘drop-in replacement’ for what chlorine does – continuous disinfection throughout a system.
A flawed solution?
Historically, chlorine in the form of chlorine dioxide (ClO2
) has been the most widely
used option. However, it is a flawed solution; although effective, chlorine dioxide is hazardous, since it is highly flammable and reactive, and presents a dangerous fire and explosion risk. It is also difficult to handle, especially in its most popular form for water treatment – compressed gas. It does not occur naturally, and Public Health England’s document on incident management involving chlorine dioxide states, very clearly: ‘Hazardous to the environment’.
When pure chlorine gas or a chlorine compound such as sodium hypochlorite are mixed with water, thay form hypochlorous acid, which penetrates cell walls and destroys protein in many pathogens, parasites, and viruses
Hypochlorous acid – a real alternative to chlorine dioxide Hypochlorous acid (chemical formula HClO or HOCl) is a weak acid that is created by the electrolysis of ordinary water and sodium chloride – common salt. Although it kills every pathogen (viruses, bacteria, fungi, and mould, etc) known to cause harm to humans, unlike chlorine dioxide, hypochlorous acid is non-toxic and non-irritating – it’s actually the same substance that white blood cells produce to keep humans healthy in the phagocytosis process.
Hypochlorous acid is a highly effective way to disinfect water in man-made water systems. It achieves outstanding results by launching a two-pronged attack on bacteria: n Attack and invade – A key property that makes hypochlorous acid lethal to microbes is its neutral electrical charge. Legionella and Pseudomonas bacteria are Gram-negative, meaning they have an impenetrable cell wall with a net negative charge that repels other negatively charged particles in the water. Hypochlorous acid, however, being neither positively nor negatively charged, can make contact with, and invade, bacterial cells.
n Destroy – Hypochlorous acid is a strong oxidiser with a very high ‘redox
February 2019 Health Estate Journal 45
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