Water treatment
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Legionella loves the ‘new normal’
Ian Wedd, from Guardian Water Treatment, explains the importance of secondary disinfection as we navigate the new working from home normal
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any office spaces across the UK continue to remain empty, or at least underused, as working from home becomes a widespread
hangover of the pandemic. While some businesses and their employees are benefitting from this situation, so too is bacteria, such as legionella, which is more freely able to proliferate thanks to underused water outlets. We have quickly accelerated into a new working
culture that ordinarily would’ve taken many years to materialise. Until the pandemic, working from home wasn’t a widespread phenomena for employed people. The speed at which this change has happened means that our buildings are having to catch-up quickly. Large commercial spaces, designed to be occupied by hundreds of people are now undreused and in some cases empty, in fact according to a survey by real-estate broker, Lambert Smith Hampton, 75% of workers only go into the office three days a week or less. When buildings are designed, they are created
with footfall in mind, where this footfall decreases, essential building services can suffer. For water- based services, underusage can potentially lead to bacterial proliferation, including the dreaded Legionella. During the lockdowns of the last three years we commonly saw maintenance teams resorting to regular flushing through (of taps and other water outlets) as a means of keeping bacteria at bay, but unfortunately this is not enough. Our own data collection from the buildings we managed during 2020 and 2021 show that, compared with pre-Covid, there was a 50%
increase in bacteria, demonstrated by a rise in Total Viable Count (TVC), which gives an estimate of the concentraton of microorganisms. There was also an increase in failure rates and poisitive legionella samples, which rose by 20%. Almost all of these buildings favoured manual flushing regimes as their main method to manage water systems.
A secondary line of defence
To keep all buildings, but particularly underused ones, bacteria free, building managers, maintenance teams and FMs, should consider secondary disinfection, which will maintain water quality and prevent future issues. Delivered by biocides, historically, secondary
disinfection was effective but dangerous. Powerful chemicals, such as chlorines, chlorine dioxides and monochloramines, have been chosen due their robust anti-microbial properties. Issues lie in the fact that they require careful handling and storage; chlorine dioxide, for example, one of the most commonly used biocides, can reduce in efficiency if exposed to light, temperature differences and fluctuations in flow. Thankfully, there is a new, safer, more sustainable and cost-effective approach to secondary disinfection, swapping hazardous substances for hypocholorous acid (HOCI), a naturally occuring, chemical-free, non-toxic solution which fights bacteria without the danger. Commonly found in hosptial settings, we are championing its usage within the water treatment industry, as, not only is it safe, so no need for safe
Legionella prevention tips
As there is an increased risk of legionella in underused buildings, facilities managers and responsible parties must review their Legionella Risk Assessment ensure compliance with ACoP L8. Following a risk assessment, legionella control and treatment measures can be implemented, including chemical and non-chemical options, where required.
Steps to prevent the risk of legionella might include: ¡ Implement system cleaning regime, including flushing and chemical dosing ¡ Proper control of any water spray ¡ Temperature control – keeping water cool or hot to prevent favourable conditions for legionella ¡ Removal of redundant pipework and re-design of any other locations where water can stagnate ¡ Avoidance of materials that encourage legionella growth as detailed by WRAS ¡ Replacing water-based HVAC plant, such as a wet cooling tower with a dry, air-cooled system ¡ Water testing and monitoring to check any remedial works have been effective ¡ Record keeping of the risk assessment itself and where maintenance and repair work has taken place – if you have five or more employees you must record any significant findings by law.
handling and storage, it is also far less effected by changes in condition, such as exposure to sunlight and fluctuations in flow. Lower CO2 emissions, less wastage and low production costs, also make it a more sustainable option.
A change needs a new approach
Whatever the reasons behind a buildings change of use, where systems are no longer meeting the potential of what they were designed for, a review should take place. For water systems, secondary disinfection is now a relatively simple and much safer solution, that ensures bacterial proliferation is kept at bay and that workplaces are ready for a return to work, or a completely new chapter, as the way we use our commercial spaces continues to evolve.
16 October 2022
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