Controlling Legionella in Drinking Water Systems

Photo Credit: CDC Public Health Image Library ID #11148 by Janice Haney 2009; Edited with cropping.

The prevalence of Legionella bacteria in drinking water and distributions systems has gained notice over the past several years due to its increasing rate of infection in the United States. Inhalation or aspiration of small aerosolized Legionella bacteria from water can cause Pontiac fever and Legionnaires’ disease most frequently in sensitive or immunocompromised populations. Between 2000 and 2015, the National Notifiable Diseases Surveillance System (NNDSS) reports that the incident rate of Legionnaires’ disease in the U.S. increased from approximately 0.42 cases per 100,000 persons to 1.89 cases per 100,000 persons. According to the Ohio Department of Health, potential reasons for this change in rate might include increased monitoring and awareness, higher population susceptibility, climate change, water-saving fixtures, and/or aging infrastructure. As of 2019 Legionnaires’ disease is reported to afflict and kill more people in the U.S. than any other waterborne disease.

Existing research indicates that, though Legionella bacteria can be found in all parts of the water treatment system, they amplify best inside protozoan hosts and near the biofilm typically found within premise plumbing or drinking water systems. The resiliency of biofilm to disinfection acts as a protective barrier for Legionella while creating an environment abundant in nutrients. Protozoan hosts also offer defense against extreme temperatures and treatment technologies. A 1994 study by Kramer and Ford found that hundreds of Legionella bacteria can be contained within a single amoeba vesicle. L. pneumophila, the species responsible for most human infections, can also differentiate into various life cycle forms that alter susceptibility to water treatment. This symbiotic relationship with other microorganisms complicates Legionella disinfection.

Hot spots for growth include showerheads, faucets, plumbing systems, cooling towers, hot tubs, fountains, and distribution systems where water stagnation, insufficient disinfectant residual, warm temperatures (77-124°F), or excess nutrients foster biofilm formation. As a result, the most frequent outbreaks from Legionella have been documented in hotels and healthcare facilities. Management of outbreaks can start at the site of these impacted buildings as well as the treatment plant. Drinking water utilities can participate in prevention by understanding the conditions that favor propagation and the methods to control growth.

The U.S. EPA established a Maximum Contaminant Level Goal (MCLG) for Legionella at zero microorganisms. While this is not an enforceable limit, the Agency believes that if Giardia and other viruses are removed or inactivated as required under the Surface Water Treatment Rule, Legionella will also be controlled. Requirements to manage bacterial contamination under the Revised Total Coliform Rule and Ground Water Rule also contribute to Legionella management. Though some systems may routinely monitor for Legionella bacteria, testing methods can often yield both false positives and false negatives. Given the complications of environmental monitoring as well as the cost, management generally starts in response to outbreaks or sporadic cases.

Ongoing research has identified that potential drinking water treatment methods for Legionella include chlorination, copper-silver ionization, ultraviolet (UV) light, ozonation, and thermal disinfection. Among these technologies, chlorine, chlorine dioxide, chloramine, and ozone are the most widely used disinfectants. A combination of these techniques offers the most effective defense against recolonization and biofilm formation. To inactivate individual bacteria as well as those contained within biofilm, operators should also pay attention to the contact time and concentration of disinfectant used during treatment. Equally important to contact time is the maintenance of disinfectant residuals throughout distribution. The National Academy of Sciences’ Management of Legionella in Water Systems details the recommendations for proper disinfection using free chlorine, chlorine dioxide, monochloramine, and technologies more commonly used by building water systems.

To effectively manage Legionella in drinking water, utilities must also collaborate with impacted buildings. Facilities that have experienced outbreaks can develop their own management plan using the Center for Disease Control’s (CDC) Developing a Water Management Program to Reduce Legionella Growth & Spread in Buildings and the World Health Organization’s Legionella and the Prevention of Legionellosis. This literature, along with the CDC training on Legionella Water Management Programs and the other resources linked within this guide will ensure that your community members, especially those at greater risk to illness, are protected from Legionella.

What Operators Should Know about PFAS in 2019

In February of 2019, the EPA released an action plan to manage the contamination of poly- and perfluoroalkyl substances (PFASs) in water. The plan will propose an MCL regulatory determination for perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) detected under the UCMR3 by the end of 2019 and will continue environmental cleanup.

The UCMR3 found that areas with affiliated industrial sites, military fire training, and wastewater treatment plants were associated with PFOA and PFOS detection. Once released, PFASs can persist in the environment for the long periods of time, bioaccumulating in humans and animals that consume contaminated drinking water. A new health advisory for these chemicals has set the maximum recommended concentration in drinking water at 70 ppt. Exposure above this threshold may cause developmental defects, cancer, liver damage, immune issues, metabolic effects, and endocrine changes. 

Unfortunately, a health advisory is not enough to protect consumers from PFAS in drinking water as it does not legally require utilities to take action against unsafe levels. In the absence of necessary regulatory authority, several states have pushed forward with their own policies. These states have struggled with how to implement a standard without clear federal guidelines. Despite this, many states are working to set or have already set their own maximum contaminant levels. 

Options for reducing exposure to elevated PFAS contamination include changing sources, closing off contaminated wells, alteration of blending rates, or implementation of treatment. Studies have found that granular activated carbon (GAC), ion exchange, or membrane separation can treat PFAS. The removal efficiency can reach 98-99%, but it will ultimately depends on the length of the PFAS chain and the treatment method used. Installing a new treatment method is financially devastating for many systems. Alabama’s West Morgan East Lawrence Water and Sewer Authority (WMEL) estimates that the costs to install a permanent R.O. filter will reach $30-50 million. The authority has filed a lawsuit that could assist with funding the necessary upgrades.

There is currently no standardized analysis approved for PFAS testing in drinking water, however laboratories have modified the EPA groundwater detection method 537 for systems in need of monitoring. When using this method, the EPA recommends that systems “evaluate its appropriateness relative to your goals for the data.” In some locations PFAS regulators and manufacturers have also set up programs to monitor groundwater contamination. You can contact your state primacy to learn about these types of resources. 

If test results repeatedly indicate water concentrations of 70 ppt or greater for either contaminant, systems should follow any existing state regulations and promptly notify their primacy and customers. In absence of regulations, customers should be informed of the health effects and advised to consume bottled water until a better option is available. Download a consumer-friendly fact sheet from CDC.

An Overview of Drinking Water Fluoridation

With cost efficiency community fluoridation overcomes disparities in oral health regardless of community size, age, education, or income level. A dental health study found that the savings from fluoridation in communities of 1,000 people or more exceeded program costs by $20 per every dollar invested. When Juneau, Alaska voted to end fluoridation in 2007, a study found that children six years and under had an increase of one dental cavity per year, roughly equivalent to $300 in dental costs per child annually. Juneau’s increase in cavities was also reflected in adults.

All water contains some levels of naturally-occurring fluoride though these levels are often too low for health benefits. In untreated water, fluoride levels vary considerably with geology and land practices. Fluoride is introduced to water when dissolved from the Earth’s crust into groundwater or discharged from fertilizer and aluminum factories. Systems with fluoridation should set final levels near 0.7 mg/L as suggested by the Department of Public Health. This concentration factors for other sources of consumer fluoride exposure such as toothpaste. Fluorosilicic acid (FSA) is most commonly used in water treatment. Though fluoridation decisions are left to a state or local municipality, the EPA has established federal standards for the upper limits allowed in drinking water.

At high levels fluoride can cause the development of bone disease and tooth mottling. As a result, the EPA has set both the Maximum Contaminant Level Goal (MCLG) and the MCL for fluoride at 4 mg/L. Levels higher than 4 mg/L can lead to increased rates of bone fracture, Enamel Fluorosis, and Skeletal Fluorosis. If systems find fluoride concentrations higher than the MCL, they are required to notify customers within 30 days and potentially install treatment methods such as distillation or reverse osmosis to remove the excess fluoride. 

The EPA has also set a secondary standard for fluoride at 2.0 mg/L. The secondary standard is intended to be used as a guideline for an upper bound level in areas with high levels of naturally occurring fluoride. Below this level, the chance for tooth mottling and more severe health impacts are close to zero. Even if the secondary standard is reached, systems must notify customers. In the U.S. very few systems have exceeded the fluoride MCL at all. Where violations have occurred, the concentrations are generally a result of natural, geological conditions. 

Even with this track record, some concerned customers are still weary of fluoridation. When customers broach fluoridation concerns, operators can offer educational materials and refer customers to consumer confidence reports. The CDC and the EPA offers a variety of consumer-friendly educational material that operators can reference in addition to the resources linked in this blog post. Remember that good customer service starts by establishing a trusted relationship with your community.

What's on the Drinking Water Radar for the Year Ahead: 2019

Being a small-town water operator is not easy; it is up to you to ensure the quality of your community's water day-in and day-out, often with very limited resources. Let WaterOperator.org help you meet the challenge head-on with this list of tools and resources to put on your radar for the year ahead:

• Have you gotten in the groove yet with the new RTCR requirements? Here are two new documents from the USEPA designed to help small public water systems: Revised Total Coliform Rule Placards and a Revised Total Coliform Rule Sample Siting Plan with Template Manual. Additional compliance help, including public notification templates, a RTCR rule guide, a corrective actions guidance and more can be found here.
• While we know your hands are full just getting the job done, there are new and emerging issues you may have to deal with in the year ahead. For example, this past year many communities have been dealing with PFAS contamination issues. This ITRC website provides PFAS fact sheets that are regularly being updated on PFAS regulations, guidance, advisories and remediation methods. Especially of interest is this excel file that has begun to list the different state standards and guidance values for PFAS in drinking water as they are developed. Be sure to check back often for updates.
• Your utility may also have to adjust to new compliance rules in the coming year. In Michigan, for example, a new Lead and Copper Rule arising from the water crisis in Flint has gone into effect, making it the strictest in the nation. Other states, such as Ohio, have also adopted tougher standards, or are now requiring schools to test for lead. Oregon has established temporary rules that will require drinking water systems in the state using certain surface water sources to routinely test for cyanotoxins and notify the public about the test results.
• With a warming climate, these incidences of harmful algal blooms in surface water are on the increase, causing all sorts of challenges for water systems that now have to treat this contaminant. This cyanotoxin management template from the EPA can help assist you with a plan specific to your location.
• Worker turnover and retirements will still be an issue in 2019. According to this article, the median age for water workers in general (42.8 years) and water treatment operators specifically (46.4 years) are both above the national average across all occupations (42.2 years). You can keep transitions as smooth as possible by using EPA's Knowledge Retention Tool Spreadsheet and/or this Electronic Preventive Maintenance Log.
• New Tech Solutions: A UMass lab focusing on affordable water treatment technologies for small systems will be rolling out its Mobile Water Innovation Laboratory in 2019 for on-site testing. In addition, the facility is testing approaches to help communities address water-quality issues in affordable ways. "Early next year, in the maiden voyage of the mobile water treatment lab, UMass engineer David Reckhow plans to test ferrate, an ion of iron, as a replacement for several water treatments steps in the small town of Gloucester, MA.

But even without all these challenges and new ideas for the future, simply achieving compliance on a day-to-day basis can be tricky - if this sounds familiar, you may want to check out our recent video on how operators can approach the most common drinking water compliance issues.

Featured Video: The Future of Water

Water is a scarce resource for many communities around the globe, and this scarcity is becoming more and more widespread. Our featured video this week from Quartz Media looks out how one locality half a world away has addressed this challenge, and how the rest of us can learn from systems like these where the "future of water" has already arrived.

While this video focuses on a larger metropolitan area, there are some interesting takeaways for smaller systems as well such as:

•  Solutions to water challenges are best solved at the individual and/or community level. 
•  Water reuse is most likely already happening in your community and efforts can be made to change public perceptions. For example, a wastewater pipe enters the Mississippi River every 8 miles - meaning almost every community using the river as a water source is already drinking someone else's wastewater!     

Focus on Chemical Feed Control

Chemical dosing at the water treatment plant is a critical, but often underrated step in producing safe drinking water. Historically, process control points have focused on the hazards present in incoming source water - with emphasis on the filtration and disinfection steps to minimize microbial risks. But while many hazards do indeed enter the plant with the raw water, it is just as important to identify the multiple risks associated with treating this raw water.   

Spooky Sewers and Things That Go Bump at the Treatment Plant: 2018 Edition

Featured Video: Using Powdered Activated Carbon to Remove Cyanotoxins

In May of this year, the city of Salem, Oregon discovered the state's first-ever algae breach in finished drinking water. Since then, there has been quite a bit of soul-searching, as well as a third-party assessment of exactly what happened and the effectiveness of the water utility's response after the event. In the end, the assessment concluded that the city was not prepared to deal with the public relations fallout, or the more practical matter of helping citizens access emergency water supplies. 

In the meantime, the Oregon Health Authority responded by creating almost unprecedented new cyanotoxin monitoring regulations for systems across the state, and the city of Salem was left to figure out how to cope with what may turn out to be a long-standing threat.

As an emergency measure, the utility started using powdered activated carbon (see video below from Statesman Journal reporter Dick Hughes) but it can cause clogging of the filtration plant.  The city is now also looking into ozone filtration, as well as other improvements including hazard response and crisis communication planning in order to be better prepared to handle future events.  

Featured Videos: Small Communities Benefit From Shared Resources

The Small Communities Environmental Infrastructure Group assists small Ohio communities in finding resources to help solve their infrastructure and funding problems. These two videos feature water and sewer district officials and staff discussing the benefits of participating in SCEIG regional partnerships in order to better serve their communities. 

The Disinfection By-Product Challenge

Staying in compliance with Stage II DBP testing can be a challenge for many small systems. Moreover, when preventing DBP formation becomes a pressing need, it is easy to get overwhelmed by the range and cost of options out there, especially if you are trying to keep up with new technologies. Then there is the fact that solutions to DBP problems often involve several different actions or multiple steps, giving the situation an extra level of challenge.

However, before planning a remediation strategy it might be valuable to initiate a DBP profile study - testing from the source water through the treatment process, and continuing into the distribution system. Why? Because, as Justin Spears in a recent H2Outlook (Kentucky Water & Wastewater Operator's Association) article found out, sometimes the problem isn't where you think it is!

According to his article, he was all set to add a mixer to his storage tank when results from his DBP profile study showed that most of his DBPs were forming in the plant's clearwell. His problem was at the treatment plant, not in the tank! In the end, Justin solved his DBP problem quickly by using chlorine dioxide, made on site by mixing chlorine gas, which he had already in place, with sodium chlorite. However, every treatment plant and source water is different, and what worked for him might not be the best for you.

Interested in finding out more about options for DBP control? Check out this video or this website or this manual. In addition, you can choose Disinfection and Disinfection By-Products as a category in WaterOperator's document or event database to find all sorts of resources.