Concerns have been raised that green building principles such as energy and water minimisation strategies may be increasing the risk of dangerous Legionella pneumophila bacteria proliferating in potable water systems. But according to critics the problem could be as much about poor facilities management and need for better co-operation between engineers and sustainability managers as it is about unintended consequences.
Attention on the Legionnaires’ disease-causing bacteria in the past has been directed towards cooling towers used for airconditioning, but the problem is now being seen in potable water supplies, where low water throughput (exacerbated by water saving devices and recycled water systems) and low hot water temperatures (due to energy efficiency practices, safety practices and solar hot water systems) may be causing an increased risk of Legionella bacteria growth.
The concern was first voiced to The Fifth Estate last year by Adam Garnys, NSW manager and senior consultant with CETEC, an industry leader in Legionella risk management and outbreak control. Mr Garnys had noticed an increase in positive test results for Legionella in potable water systems, and suspected green building practices could be playing a role. The concern has now been backed up in an article published in the Royal Society of Chemistry’s Environmental Science: Water Research & Technology journal.
Health and aged care facilities are the new battlegrounds for Legionella, because they have populations with weakened immune systems and avenues where Legionella bacteria can become aerosolised and enter the lungs – namely showers.
Legionella in a potable water supply made headlines back in 2013 when a 60-year-old patient at Brisbane’s Wesley Hospital died after contracting Legionnaires’ disease from the hospital’s hot water system. This followed a 2011 death, with the hospital also back in the paper this January following a positive Legionella test from an ice machine. In April 2015, a patient of Hervey Bay Hospital, also in Queensland, died after testing positive for Legionella.
“Legionella is popping up in potable water systems,” Mr Garnys told The Fifth Estate. “If you get Legionella bacteria in the potable system, patients who are sick have a shower and that is where the risk is.”
Following the 2013 case, the government ordered all hospitals to do testing and found “a significant number of these facilities tested positive for Legionella contamination to varying degrees”. In guidelines rushed out after the Legionnaires’ disease death in 2013, Queensland Health said healthcare facilities were at a heightened risk due to:
- increased retention time of water within the facility due to storage of potable water in tanks
- low-water-use locations further extending water retention, possible stagnation and biofilm development
- bacteria introduced by construction/renovation without proper hygienic controls
- presence of immunocompromised or immunosuppressed persons unable to normally resist infection
Mr Garnys said there had been a general increase in the number of hydraulic sanitisation jobs CETEC was engaged on due to Legionella, many of which could be attributed to sustainable design processes, including reduced hot water temperatures and reduced water throughput.
Low temperatures
Following the 2013 death, it was found that hot water temperatures at Wesley had been set to 45°C.
According to Mr Garnys, the practice of turning down hot water temperature from 60°C or above is increasing the risk of Legionella. He said there were even examples of potable water systems where the hot water system had been set as low as 42°C – a perfect breeding temperature for Legionella bacteria.
According to Deon van der Spuy, AECOM team leader – water infrastructure & treatment, setting hot water systems to 50-55°C is generally done for reasons of energy efficiency but also safety in regards to scalding.
“To limit Legionella risk, it is recommended to have hot water set to a minimum of 65°C, and preferably to 70°C,” Mr van der Spuy told The Fifth Estate.
Federal guidelines put out by the National Environmental Health Standing Committee last year recommended hot water temperatures be set at greater than 60°C for preventing Legionella growth, with thermostatic mixing valves (TMVs) employed to reduce the risk of scalding (water delivered at 45°C) in healthcare settings.
Solar hot water systems have also been identified as another potential risk for Legionella growth. The federal guidelines state solar variability may prevent temperatures from reaching 60°C if a booster is not present and operating correctly.
“Where temperatures are consistently above 60°C and the booster is operating correctly, solar water heating systems are unlikely to present a major Legionella risk,” the guidelines state. “However, if temperatures never exceed 45°C, these devices may present a growth risk, particularly if large volumes of pre-heated water are stored in the system.”
Mr van der Spuy said it would be interesting to see whether data was available on water temperatures typically achieved be solar hot water systems.
“If temperatures of 65°C and above can be achieved, the Legionella risk would not be significant.”
Low throughput
Research out of the US published at the end of last year found that green water system practices have potential consequences, including pipe corrosion, unappealing taste and microbial growth.
A report, Survey of green building water systems reveals elevated water age and water quality concerns found that high water age (water that has been sitting in pipes for a long period of time) was “inherent to some green plumbing designs”, and that chlorine disinfectant used to help control Legionella bacteria growth decayed up to 144 times faster in green systems due to high water age.
The paper looked at a range of green building types – including an off-grid office supplied only by rainwater, a LEED Gold-certified healthcare facility and a net-zero energy home. A conventional home was also included.
The levels of Legionella detected in the green buildings were high, which the authors said was expected “given the higher water age and lack of disinfectant residuals in the green buildings compared to the conventional residences”.
Lead author William Rhoads said the findings were important to consider for a construction industry where many players were looking for ways to be greener. He pointed to US Green Building Council figures stating that up to 48 per cent of non-residential buildings would be classified as “green” by 2015.
“We are at the beginning of a green building revolution where new products and approaches to water and energy conservation are coming to the market much faster than we can critically evaluate their impact,” he said.
“Design of green buildings with water conservation features should minimise overall water age and eliminate unnecessary water storage and should give special attention to avoiding conditions conducive to [opportunistic pathogens in premise plumbing],” the report found.
Mr van der Spuy said areas of low water use within buildings could be an issue for Legionella risk, however the problem could be designed out.
“Areas of low use within any facility cause problems due to creating static conditions susceptible to Legionella proliferation,” he said. “Modern design would therefore look at eliminating so-called ‘dead legs’ by ensuring adequate circulation. However, it will sometimes happen that certain areas are unused, or have low use, for a length of time, creating a need for flushing through, for example, running taps in the area of concern.”
Mr Garnys, however, said he was aware of instances where to get the appropriate throughput security staff were being instructed by facilities managers to turn on taps at night for 5-10 minutes.
“They’re using a lot more water than they’re saving,” he said. “I wouldn’t call it a water saving building.”
Mr Garnys also pointed to “unintended consequences” of greywater harvesting for things like toilet flushing, which would reduce potable water system use.
“If you draw your flushed toilet water from another source, you’re not getting same throughput,” he said.
Mr van der Spuy, though, said this would not be an issue for healthcare facilities, where strict regulations would not allow the use of recycled water.
New rating tools can help
Rating tools could play a part in reducing any tensions between green building design and health risks, Mr Garnys said.
He said that new rating tools like the WELL Building rating required comprehensive water testing regimes in order to gain certification, a lot of which involves microbial risk.
For example, on water treatment and microbial elimination the WELL standard says: “Water from all faucets, drinking fountains, showers and baths is treated with one of the following:
- UVGI water sanitation
- NSF filter rated to remove microbial cysts”
Tools like Green Star, he said, didn’t go as far. In fact, he said he knew of people who openly said that “Green Star and hospitals don’t mix”.
Green Star does, however, reference current applicable standards and guidelines.
UPDATE 3 February 2016: Robert Milagre, director sustainability services & reporting at the Green Building Council of Australia, said that Green Star has since its launch dealt with microbial control, including legionella risk management.
“The requirements refer to the Victorian Public Health and Wellbeing Act for projects in every state – considered the most stringent approach to legionella risk management nationally. We encourage people within our industry to familiarise themselves with the new generation of Green Star rating tools.”
The federal guidelines recommend a multi-barrier approach that uses:
- controls associated with the quality of the incoming water
- plumbing controls, including design, commissioning and operational controls
- disinfection systems
- regular maintenance
- exposure controls for patients based on their risk status
Can sustainability and safety co-exist?
AECOM was emphatic that green building principles and water safety were not mutually exclusive.
“It should not be concluded that green design results in increased Legionella risk, and should be avoided in the health and aged care environments,” Mr van der Spuy said.
“The heightened awareness of legionella risk in these environments does bring additional challenges and the need for changes in some areas.”
He said green design principles that continued to be valid included:
- selection of energy efficient and well insulated water heating systems
- insulation of hot water piping to prevent heat loss, thereby also ensuring that higher temperatures are maintained throughout the facility
- routing of cold water piping through well-insulated areas of buildings, to ensure that cold water does not heat up and, as a result, legionella proliferation becomes a risk
- use of water-saving taps, toilets, shower heads, provided that adequate circulation of water has been considered in the design
The holy grail
According to Mr Garnys there is a “holy grail” of sustainability and health safety, but it required a lot more work from sustainability managers, facility managers and engineers.
“The holy grail is a building that is sustainable and safe,” he said. “In order the get that holy grail of a green building with no Legionalla risk, you need to have good design, but it also has to be run in the right way. Operational practices are as important as good design.
“Facility managers and engineers have to come together.”