Being prepared for toxic algae season

As climate conditions continue to shift, Colorado has seen increasingly warm and nutrient-rich waters during the summer months — conditions that remain ideal for toxic algae to form in standing or slow-moving water. Toxic algae or harmful algae blooms (HABs) are made up of cyanobacteria, commonly known as blue-green algae. Although these organisms naturally occur in Colorado waters, they become a problem when they multiply rapidly, resulting in a dense cyanobacteria concentration or “bloom.” In drinking water sources, cyanobacteria blooms can cause the water to taste or smell bad. Taste and odor in drinking water is not regulated but creates customer concerns about water quality and safety. Most complaints that water utilities receive are about taste and odor, and these issues can last for prolonged periods. In addition to taste and odor problems, the blooms can become harmful and create a public health risk when they produce toxins. Removing toxins in a safe and cost-effective way can be a challenge for treatment facilities, and not all water providers are equipped to do so. 

Drinking water providers can contact the Water Quality Control Division at 303-692-3500 with questions about toxic algae. We can help water providers who experience taste and odor problems and toxins. This includes ideas about customer communication and steps that utilities can take to monitor and manage toxic algae and best treat their drinking water. If you detect microcystins above 0.3 μg/L and/or cylindrospermopsin above 0.7 μg/L (EPA’s cyanotoxin health advisory values), call the CDPHE 24-hour incident reporting hotline at 1-877-518-5608 so the division can provide you with immediate assistance.

We have resources to help drinking water providers and recreational water managers with toxic algae monitoring, response and public education and created a map to show recent toxic algae conditions for select waterbodies in the state. 

This 2019 AquaTalk article remains especially relevant today as cyanotoxins still pose a public health concern, even without being formally regulated. While EPA is continuing to evaluate the need for national regulation, the core takeaways from past events like Salem, Oregon’s microcystin advisory remain vital reminders for proactive communication, monitoring, and response. Whether you manage a public drinking water system or recreate on Colorado lakes and reservoirs, this piece offers timeless lessons for navigating toxic algae season safely.

The Increasing Threat of Toxic Algae

Scientists predict that climate change will have various effects on freshwater environments. This includes catalyzing harmful algal blooms to occur more often in more water bodies, and to be more intense when combined with nutrient loading. This summer, due to increasing temperatures and drought conditions, we saw harmful algae blooms impact many of our water bodies in Colorado. Harmful algae blooms or toxic algae are made up of cyanobacteria, commonly known as blue-green algae. These types of algae in drinking water sources can cause the water to taste or smell bad. Taste and odor are not regulated under the primary drinking water regulations but certainly can create customer concerns about water quality and safety. In addition to taste and odor problems, toxic algae can create a public health risk when they produce toxins.

This summer, between June and August, the Water Quality Control Division coordinated with local water body managers to test lakes and reservoirs suspected of experiencing toxic algae. The following water bodies had detectable levels of toxins: DeWeese Reservoir, Barr Lake, Sloan's Lake, Pikeview Reservoir, Jumbo Reservoir, Prewitt Reservoir, Jackson Reservoir, Joe Moore Reservoir, Summit Reservoir, Windsor Lake, Milavec Reservoir, Pelican Pond (St Vrain State Park), Smith Reservoir, Willow Creek Reservoir, North Sterling Reservoir. The division is not aware of any treated drinking water having detected toxins. 

The only way to be certain if an algae bloom is toxic is to run specific water tests. The Colorado Laboratory Services Division is one lab that can complete these tests. Removing toxins in a safe and cost-effective way can be a challenge for treatment facilities and not all of them are equipped to do so. Drinking water providers can contact the Water Quality Control Division at 303-692-3500 with questions about toxic algae. We can assist water providers that experience taste and odor problems and toxins. This includes ideas about customer communication and the appropriate steps utilities can take to monitor and manage toxic algae and effectively treat their drinking water. Our toxic algae webpage has resources to help drinking water providers and

recreational water managers with toxic algae monitoring and response.

➽ David Dani, Emerging Contaminants Coordinator

Program Manager Message

Looking Ahead to the 2020s

A few months ago, we republished an Aqua Talk article I authored in late 2009 entitled “Perspectives on a New Decade.” It looked back on what happened in the 2000s and attempted to look forward to what might happen in the 2010s. Then, in December we published an article titled “Perspectives on the 2010s” reviewing what actually happened in the 2010s. Now let’s  look forward to the 2020s. I know this is coming out a year late, but considering what happened in 2020, that worked out for the best as no one could have predicted the start to this decade that we actually experienced. 

In the 2020s we will not take our eye off the ball in terms of focusing on preventing waterborne disease outbreaks. We intend to continue vigorous implementation of our rules regarding disinfection waivers, storage tanks, backflow prevention and cross connection control, disinfectant residual in distribution, hand pumps, and water haulers. We hope to see a continued positive track record of no waterborne disease outbreaks and only rare E. coli violations in drinking water. However, new challenges will arise on this front as well. Pathogens present in biofilms have recently been shown to cause most of the serious health problems and health care costs related to waterborne disease in the United States. As EPA reviews the suite of Microbial/Disinfection Byproducts Rules in the early to mid-2020s, they will be considering these pathogens like Legionella and also more disinfection byproducts and different health endpoints, such as fetal development.

The 2020s will involve continued focus on lead and PFAS. EPA just finalized the Lead and Copper Rule Revisions (LCRR). The new administration is going to review this rule, and once it is truly finalized, Colorado will have two years to adopt the federal rule. Adopting this rule will involve a thorough stakeholder process, and of course our final rule must be at least as stringent as the federal rule. However, once the rule is final it will take years of effort to fully implement the rule, especially for systems with lead service lines. The revised rule will include efforts to sample at schools and daycares, and we will be able to provide some support in that area using a federal grant program. 

EPA also finalized their regulatory determination for PFAS compounds and indicated that they will move forward with MCLs for PFOA and PFOS. Again, the new administration may revise this approach. Additionally, many more PFAS compounds must be included in the fifth Unregulated Contaminant Monitoring Rule (UCMR5) sampling efforts under federal law. Fortunately, the sampling that we have done proactively in the late 2010s shows that we likely do not have a large number of water systems with high PFAS levels, but only about half of the community systems have been sampled so far.

As climate change continues to impact Colorado’s water supplies and the temperature of state waters, we could also see more harmful algae blooms and the threat of cyanotoxins being present in drinking water sources and possibly tap water. We have good programs in place to try to address underlying nutrient pollution and monitor for blooms, but these programs are not comprehensive so we are at some risk.

During the 2020s, we also intend to develop a regulatory framework including regulations, policies and guidance to assist water systems in planning and implementing direct potable reuse if needed. Direct potable reuse can help Colorado move forward with our State Water Plan. The framework for direct potable reuse is intended to have flexibility and ensure safe drinking water and help with public support. But we also intend to prevent communities without adequate technical, managerial, and financial capacity from undertaking such a serious effort.

While drinking water in Colorado is safer today than ever before, the world is not necessarily safer. In 2020 we saw considerably more vandalism and cyberattacks against drinking water infrastructure than normal. I hope that trend does not continue, but unfortunately I believe that this will be an added pressure on all of us for the foreseeable future.

It will take resources for water systems to continue their track record of improving water quality and for the Safe Drinking Water Program to enhance our services in support of those efforts. I am hopeful the recently increased federal funding will continue and be increased further to help us with implementing the expected new LCRR and PFAS rules plus help us support security needs.

Even with all these expected challenges ahead and those that we cannot anticipate as well, I am not losing sight of the fact that, as mentioned before, our tap water is safer than ever and that is something to celebrate and be proud of. We launched a Culture of Health, and I believe it is catching on. We will continue our partnership with water systems, EPA, local health departments and operators to foster a Culture of Health throughout the community of water suppliers. With a Culture of Health firmly entrenched in all of us, we will be ready to face challenges and succeed! I cannot predict what the drinking water world will look like in 2030, but hope we have some fun this decade on that journey!  

➽Ron Falco, Drinking Water Program Manager

New Toxic Algae Resources

It's the Season for Toxic Algae!

During summer months, most water treatment professionals are well aware of the challenges of algae in surface water bodies. They cause a myriad of issues relating to lake management and water aesthetics. Algal blooms cause many customer complaints and public outcry about water quality. However, in recent years, more awareness has been raised about possible immediate health risks from certain types of algae.

New Resources!

We have published a webpage with guidance on harmful algal toxins and what a utility can do about it. As we approach the height of algae season - please stay diligent in monitoring lakes and reservoirs for signs of harmful algae.

Preparing for Harmful Algal Bloom Season

Water that is warm, slow moving and high in nutrients can cause harmful algal blooms to form in waters above ground like reservoirs. With the weather warming up, managing these waters to prevent these blooms becomes critical for water safety. Certain types of cyanobacteria, also known as blue green algae, produce unpleasant taste and odors in water. Some blue green algae are also capable of producing cyanotoxins which can create health risks for humans and animals. The toxins can be problematic for anyone that ingests them or is exposed through recreational activities. Currently, cyanobacteria is not a regulated contaminant but EPA has published non-regulatory drinking water 10-day health advisories for the cyanotoxins microcystin and cylindrospermopsin based on studies showing that these two strains cause liver, kidney and reproductive toxicity.

Responding to situations where an unregulated contaminant measures above a health advisory is very difficult because there is not a playbook with available instructions like there is with regulated contaminants. In May 2018, Oregon’s capital and second-largest city, Salem, made national headlines by declaring a state of emergency after issuing a “Do not drink” advisory due to elevated microcystin levels in their treated water. Here are a couple of the lessons learned Salem shared after the event:

Do not wait to notify your customers

After receiving initial sample results showing levels above the health advisory, the system spent a couple of days making operational changes to try and lower toxin levels before taking more samples. Because Oregon didn’t have any labs capable of cyanotoxin analysis, they had to ship samples to an out-of-state lab, causing a long turnaround time for receiving results. The system believed it was okay, since they were still responding within the 10-day health advisory window. However, those follow-up sample results came back high and the system issued a “Do-not drink” advisory. The customers and local papers were outraged because they weren’t notified sooner.

Knowing when to lift the advisory is tricky 

After receiving sample results showing microcystin levels were below the health advisory, the city lifted the initial “Do not drink” advisory. The city then issued another “Do not drink” advisory four-days later after receiving additional results showing elevated toxin levels. They waited to lift the second advisory until they had levels below the health advisory for 12 consecutive days.

Between 2018 and 2020, all drinking water systems nationwide serving over 10,000 individuals, as well as a random selection of other systems, are required to sample for cyanotoxins as part of EPA’s Unregulated Contaminant Monitoring Rule (UCMR). EPA will use the test results to see where cyanotoxins are occurring and determine whether or not to regulate them in the future. There are over 100 Colorado drinking water systems required to perform this additional testing and they have been notified. As of May 2019, there have not been detections of any UCMR cyanotoxins in treated water.

Online resources

Learn more about cyanotoxins and how to monitor and prepare for them by reviewing these resources:

• Monitoring guidance created by the Colorado Harmful Algal Bloom Workgroup.
• EPA's  toolkit and webinar Preparing for HABs season. 

➽ David Dani, Local assistance unit