It was around 20 years ago that I met Greg Bova, who at that time was working in facilities management at Johns Hopkins Hospital (JHH).
Since then, Greg and I have had many conversations, most of them on the phone and a few in person. In addition to his genuine interest in providing safe water for his employer’s patients, Greg has contributed to public health more broadly by sharing insights from his experience in managing JHH water systems.
Greg has gathered a lot of data! He has always been meticulous and thorough in testing ideas before and after implementing them. So, I was excited to find out Greg’s team was sharing 23 years of data on their water systems.
The published papers, titled “The results of chlorine dioxide use after 23 years,” parts 1 and 2, are about much more than chlorine dioxide (ClO₂). The physical system changes that accompanied chlorine dioxide treatment are a classic example of Legionella risk management: Instead of trying to pin Legionella findings on one cause and looking for a silver bullet solution, the hospital took a step-by-step approach that involved, over time, several physical and operational changes to their water systems, along with ClO₂ treatment.
Their efforts were successful. Legionella positivity (percentage of potable water system samples in which Legionella was found) and concentrations were reduced over the 23-year study period. In the last four years of the study period, no Legionella was detected. The papers provide a building-by-building breakdown of the results.
Chlorine dioxide treatment for Legionella control
The hospital began chlorine dioxide (ClO₂) treatment in 2001. For the first 10 years or so, ClO₂ was injected only into the cold-water system (near the point of building entry) with the goal of maintaining a residual throughout the potable water system, including the hot water. Around 2012, the hospital began injecting ClO₂ into the hot-water system as well as the cold. Adding the second injection point just downstream of the water heaters resulted in higher (more effective) ClO₂ residual levels in the hot water, better control of ClO₂ levels in both the hot and cold systems, and reduced Legionella findings.
0.5 ppm (mg/L) was found to be the optimum dosing concentration of ClO₂. Dosing was automated based on sensor-monitored data.
Pipe Corrosion and Investigations
After finding pinhole leaks in copper piping, the hospital sent multiple samples to laboratories to determine the cause. The leaks were found to be caused by either chlorine, chloride, pipe flux, or high water velocities. Although ClO₂ was not identified as the direct cause of the leaks, it may have contributed by removing biofilm and thereby exposing the pipes to direct contact with chlorine and chloride, accelerating corrosion.
System Changes That Made a Difference
As with other chemicals used for supplemental disinfection, the success of ClO₂ treatment in reducing Legionella and other pathogens in potable water systems depends in part on the design, operation, and maintenance of the systems. The papers report many physical and operational changes that Johns Hopkins Hospital made during the study period, including the following:
- Faucets and showers in patient bathrooms were flushed daily. This was found to be important for maintaining a ClO₂ residual through every fixture.
- Because oversized pipes led to lower water circulation velocities, inadequate temperature distribution, and laminar flow, they were replaced with smaller pipes.
- Pumps were added, and undersized diverter valves were replaced to improve hot water circulation.
- Pumps and controls were adjusted to correct high pressure and water hammer.
- Electronic faucets were replaced with manual faucets on inpatient sinks.
- Aerators were replaced with laminar flow devices.
- Twenty-micron centrifugal filters with automatic backflush (purge) were installed on water supply lines near points of building entry.
Final Thoughts
Kudos to Greg Bova and the Johns Hopkins Hospital team for sharing their lessons learned in managing water systems for Legionella control. Their efforts provide a good example for facility managers worldwide.
For the full report, see part 1 and part 2 in Health Facilities Management magazine.
What has your facility learned about managing Legionella risk or implementing supplemental disinfection? Share your experiences in the comments or reach out to continue the conversation.
Confirming what we’ve applied and learned over the years.
Thanks Anthony!
This is such a powerful example of what can come of sharing performance data – particularly folks who are still figuring things out – sometimes that “leap of faith” is a little easier when you can “see” that it has worked for others.
True! Thanks Steve
When a building-wide supplemental disinfection system is installed my understanding is that such systems become regulated as Non-transient Non-Community Public Water Supplies (NTNCPWS) under the Safe Drinking Water Act if they serve more than 25 people for more than six months in a year.
In North Carolina these NTNCPWSS are permitted through our Public Water Supply Section (PWSS) in our Department of Environmental Quality. Are the systems at Hopkins as described in your commentary and the papers considered as NTNCPWSS?
In North Carolina, the PWSS permits NCNTPWSS which includes approve the design of the system, and a management plans for operations, maintenance, and emergency action plans, monitoring and recordkeeping. In addition, there must be oversite by a North Carolina Certified Water Treatment Operator.
Does Hopkins have to comply with the SWDA requirements or the Maryland equivalent? Can you provide any idea of the costs to installation and operational costs?
Hi David. Very few states have set up a regulatory process for supplemental treatment of building water systems. Good job getting that done in NC! Maryland was one of the first states, if not the first, to set up regulations, and to my knowledge (but not certainty), JHH has complied with those regulations. I don’t have information on the installation and operating costs of the JHH chlorine dioxide systems.
Hi David, nice to meet you. Hopkins is licensed with the state of Maryland Department of Environment (MDE) as a Non-transient Non-Community Public Water Supplies. MDE construction and operating permit is required. MDE monthly and quarterly reporting is required as well as annual inspections by the MDE.
The average price to install a chlorine dioxide system (we use PureLine) is approximately $70,000. Annual cost: PureLine ClO2 generator service plan $2,500, Chlorite $10,000, maintenance, MDE testing and reporting $35,000 = $47,500
Thanks, Gregory Bova, Hopkins Medicine, Director of Engineering and Commissioning
Thanks for sharing that, Greg!
In your investigation of pipe corrosion, was residual chlorine from the municipal water supply monitored over time, and if so, was there any observed correlation between fluctuations in city water chlorine levels and the onset or severity of corrosion—particularly in conjunction with the ClO₂ treatment program?
Hi Gregory, we did not observe any changes in corrosion rates when the city’s residual chlorine rated fluctuated. City’s chlorine fluctuation was observed occurred however only for a day or so. If the city’s residual chlorine level was low to 0 our chlorine dioxide levels remained as set point and did not decrease. If the city’s residual chlorine level was high over 1.5 ppm our chlorine dioxide levels remained as set point and did not increase. This was due to having chlorine dioxide variable speed chemical pumps and we were controlling based on chlorine dioxide levels and not ORP.
Thanks, Gregory Bova
Matt, I have not had as many years of experience with secondary disinfection as Mr. Bova. I am impressed with his insights. My experience with secondary disinfection came as a result of the legionella outbreaks in NYC in 2015. Initial focus was on cooling towers, and then moved to domestic water. My company at the time was using chlorine dioxide as a disinfectant. I was more concerned with the byproducts of generating chlorine dioxide.
That company was purchased in 2018 and were told to move away from chlorine dioxide and go with hypochlorite. However, recently they purchased a competitor who preferred to generate monochloramine, which I have been told is more effective against legionella in domestic water.
I have always been concerned with the effects of injecting any oxidant into a domestic water system long term, but I do not have any specifics at this time.
Thanks for commenting based on your experience, Mitchell. As you probably know, there are pros and cons to each of the disinfectants commonly used in domestic water. In LAMPS we provide a long list of questions to consider in selecting a molecule for a particular system. Regarding disinfectant byproducts (DBPs), I don’t think chlorine dioxide would be of greater concern than chlorine or especially monochloramine, but I agree it’s important to weigh the risk of health effects from DBPs with the risk of Legionella and other pathogens.
Mitchell, chlorine dioxide byproducts are chlorite and chlorate. Chlorite is regulated by the EPA not to exceed 1.0 ppm. At no time over the 23 years using chlorine dioxide did we exceed the EPA maximum levels. This is even when we had chlorine dioxide levels at 0.7 years ago (0.8 ppm EPA maximum level). Daily chlorine dioxide and chlorite levels are reported to MDE (Maryland Department of Environment) monthly.
One of the main reasons for selecting chlorine dioxide was its fast efficacy CT rate which is a lot faster than chorine and monochloramine. Water can be utilized within 15 minutes upon entering a building and we did not have an hour to obtain the efficacy rate noted by the EPA CT rates.
Not sure that monochloramine is more effective against legionella in domestic water than chlorine dioxide. We have 2 monochloramine systems at other Hopkins hospitals which so far have not been more effective than chlorine dioxide. Mainly we do not see the efficacy EPA CT time because the water is utilized with in 15 minutes entering the buildings. Time will tell.