The COVID-19 pandemic prompted closure and low occupancy of many buildings, raising water quality concerns, especially around Legionella. The Source looks at the issues highlighted in a recent IWA webinar.
The unprecedented challenges created by the COVID-19 pandemic include an important water-related issue connected with the significant number of large buildings that have been uninhabited, or had low occupancy, for a number of months while workers were on lockdown. While it is not unprecedented for buildings to be left in this way, and all new large buildings will have a commissioning period, the scale at which this has occurred, and the global focus, is new.
The IWA COVID-19 Task Force, chaired by Professor Joan Rose, recognised the need for this issue to be addressed proactively. An IWA webinar was held in July, chaired by Professor Stuart Khan of the University of New South Wales, Australia, and a member of the Task Force. “We know that unused or under-utilised water supply systems can produce many water quality problems, relating to both corrosion and microbial growth,” says Khan. “With so many sparsely inhabited buildings during COVID-19 lockdowns, elevated in-building water quality risks would certainly be many times greater than normal.”
What has happened
In terms of buildings closing or moving to low occupancy, Professor Andrew Whelton of Purdue University in the US explained in the IWA webinar that there was an awareness from the start of lockdown of the potential effects of building closure. “In March, when we moved towards shutting down buildings and having people go home from schools, offices, daycare centres and manufacturing facilities, the issue of building water safety was raised.”
In March, Purdue University received a $200,000 grant from the US National Science Foundation, the country’s premier agency for science, with a view to providing help to the public health and plumbing sectors, as well as building owners and others involved in building water safety. “In March 2020, there were no guidance documents about what building owners should do to rid buildings of stagnant water in the US,” said Whelton.
Some 60 documents had been issued by July, both in the US and other countries, and there is significant information available about how to handle large building water systems after a long shutdown.
Dr Susanne Lee of UK-based Legionella Ltd added that a European study group on Legionella infections published a report at the beginning of April, for those owning, managing or advising businesses large and small on the actions to take to ensure the buildings are safe for when their occupants return.
Professor Michele Prevost of Polytechnique Montreal in Quebec, Canada, noted that her team has been conducting validation studies for recommissioning industrial and municipal sites, carrying out intensive field testing and laboratory monitoring to assess whether the recommissioning procedures being undertaken are making the buildings safe.
She explained that the team was testing three large buildings: one a modern institutional building with 250 devices, mostly sinks, toilets, urinals and fountains, and just two showers; the second, a much older building with 350 similar devices. The third building is a large sports centre with 130 showers. Sampling was conducted at the end of the stagnation period, on the day of commissioning, and again two weeks after commissioning to determine whether the benefits were retained.
What issues have been raised
The webinar consensus was that the water systems of these buildings would have suffered deteriorating water quality and may even have been colonised by bacteria or experienced high levels of metals such as lead or copper. Professor Whelton noted that the first concern was that individuals returning to school or work would be exposed to these pathogens and contaminants.
He observed a further issue regarding conflicting guidance: “One of the challenges is that a lot of people weren’t working off the same script, so you may see guidance from one organisation that says ‘flush your faucets for one minute once a week’, then see another guidance document from another organisation that says ‘flush your faucets once a week completely and drain the plumbing system’.”
Another concern that Indiana’s Department of Health had publicised is that there may be cases of misdiagnosis of Legionnaires’ Disease as COVID-19. “The symptoms can be similar, and we already have confirmed waterborne illness in the US during the pandemic,” Whelton said. “One of the questions is, was it caused by the pandemic?”
Studies have reported conflicting evidence regarding Legionella infection rates, Lee said. She highlighted a report of a case of co-infection of Legionella and COVID-19. “It suggests we need to be aware of the risks when diagnosing.”
She warned that “in systems that contain drinking water or other non-sterile water and operate within the range of 28 to 45oC (68-130oF) in any part of the system where there is a potential for aerosol production, then it is a high-risk system.” Legionella is tough, she added. “Legionella within amoebal cysts has been shown to survive even when treated with chlorine overnight at 50ppm.”
The long period of water stagnation during lockdowns has increased the likelihood of opportunistic pathogens growing to levels that can cause infections, including Legionella. Subsidiary systems and specialist equipment may pose a particular risk, for example in the leisure and beauty sectors, where Pseudomonas aeruginosa is a recognised waterborne pathogen, and also in construction, commercial, industrial and healthcare settings.
Lee noted: “The presence of scale gives an increased opportunity for attachment and growth, as rough surfaces are preferentially colonised, and iron also acts as a Legionella growth factor.” Films can form in any part of a system, including outlets, washers, flexible hoses, and surfaces, and in any complex component. Even small lengths of ‘dead leg’ pose a significant risk, she warned.
Advice for dealing with the issues
Purdue University has worked with Professor Prevost and other experts to put together a ‘state of the science’ understanding about water quality in large buildings – what happens under stagnation conditions, and the main health risks, Whelton said. This is available as a free download.
One common message from several speakers was for the need to address all water outlets rather than just a few. Whelton noted: “You really need to think about all these outlets, cleaning the areas, taking these devices off. You’ll see debris often – this is great real estate for biofilm growth, which is something that we need to address and control.”
The speakers stressed the importance of cleaning all devices, such as taps and showers, cooling towers, and other equipment such as ice makers. Lee advised that for Legionella, temperature is the primary control factor. “At 50oC it takes approximately two hours to kill 90% of the Legionella; at 55oC, it takes approximately 12 minutes, and at 60oC, it takes around two minutes.”
When monitoring, it is important to take representative temperatures from all parts of a building, particularly when recommissioning after lockdown, and to make sure there is flow across all areas of the system and that it is properly balanced, Lee added. All water-using systems need to be identified and assessed, which means checking the asset register. “It may be provident to avoid the use of complex equipment until you can have those risk assessed and dealtÊwith following professional advice – get help where needed,” she advised.
Risk assessment is needed, and water safety plans should be adopted, with World Health Organization (WHO) advice on water safety in buildings and a new document from the Health and Safety Executive in the UK also seen as good places to start.
Prevost explained that the Quebec guidance advocates a tiered approach to recommissioning, starting by flushing main branches and risers, then bringing in fresh water and rinsing every system outlet. The guidance also emphasises occupational health and safety. “When you are flushing these devices that can have high levels of pathogens, it is quite important to ensure personnel conducting these operations are well protected.”
Prevost’s work provides suggestions: preventive actions such as flushing and disinfection should be selected based on feasibility and demonstrated efficacy; monitoring will identify water quality issues that may have been present before the pandemic; and there is a need to measure the impact of recommissioning.
Lessons for the future
Many of the lessons to be learned will come from the huge amount of research being undertaken. “We have a lot going on here in the US. There are 15 different universities working on building water safety and hopefully in the next year or so you’ll start hearing about their work,” Whelton said. One of the research projects has looked at a three-building school where the campus was left in March for three months with no movement, so the scientists carried out extensive sampling and characterised the entire water system, flushed it and sampled again, and were waiting on the results of that work. That looked at everything, from pathogens to heavy metals, testing many different hypotheses.
Lee noted that “insurance companies really need to look at the liability issues arising from the role of poor water management during this time, so it is essential for businesses in future that risk is effectively managed so as not to negate liability insurance in future.” She warned of a need to continue to guard against Legionella, given the number of survivors of COVID-19 who have damaged lungs and possibly other issues that might make them vulnerable.
The intensive sampling proved that while short periods of flushing may resolve issues in many parts of a system, in some distant points it did not, and relying on chlorine and flushing to bring this to remote points was not really practical. Also, for temperatures, short (1.5 minute) bursts of flushing were not sufficient to bring temperatures up to the required level and it was found that for risers and large branches more than 30 minutes of flushing were required.
Repeat testing after two weeks found very low levels of Legionella and P. aeruginosa, and testing for total coliforms and E. coli was found to be unnecessary extra effort, despite this being advocated in some guidance documents. “Faecal indicators are not really giving you a lot of information and are quite a bit of work,” she observed.
For metals, even flushing will not eliminate issues if the baseline level is high, Prevost added. “What you had there before is still there,” she said. These trials revealed a basic need for better planning, with an absence of drawings and specifications of systems and devices, unavailability of key staff and yet a need for quick recommissioning. The information gathered from such work will be of great value in improving water quality in green/LEED buildings and managing future seasonal closures.
Following the webinar, Khan emphasised that “it is more important than ever to understand the underlying risk factors and the best practice procedures for ensuring ongoing safe drinking water”. He argued that ongoing active risk management is an essential component of the Water Safety Plan approach to water quality risk management, as promoted in the WHO Guidelines for Drinking-water Quality, and should never be approached as a “set and forget” activity. He said: “COVID-19 should remind us that risk management is an ongoing active task in which water quality managers must always remain alert and responsive to new challenges and unanticipated circumstances.”
Article based on: COVID-19: Ensuring Safe Water in Sparsely Occupied Buildings
IWA webinar held 13 July 2020