This past summer, Water District 19 (WD 19), the largest drinking water supplier on Vashon Island, faced an operational crisis: A bloom of cyanobacteria, often mischaracterized as algae, developed at the water district’s treatment center recycling ponds, a vital part of its filtration system.

Though the bloom never threatened the quality of islanders’ drinking water, it disrupted the district’s water treatment process, caused a nearly two-month-long state of emergency and revealed the changing ecology of bacteria in the Pacific Northwest.

The bacterial bloom began in early July, heralded by discoloration in the water of the recycling ponds at the treatment center, located east of Vashon town on SW Bank Road. The bloom picked up with a heat wave that month and caused a noticeable drop in the treatment plant’s efficiency. By late August, unable to use the recycling ponds, WD 19 shut down the treatment plant.

“It clogged everything much faster, and our normal treatment process just wasn’t working,” said Armin Wahanik, operator in responsible charge at WD 19.

WD 19 consulted with the Washington State Department of Health (DOH) and sent water samples for analysis, but state labs were only able to test for two of the four harmful cyanotoxins listed in the DOH’s cyanobacterial management document. Lab tests for the other kinds were conducted in Florida, causing further delays in the district’s search for answers.

The test results revealed cyanobacteria levels of 5,000 colonies per 100 milliliters in one of the treatment plant’s recycling ponds, and 7,500 in the other pond — far exceeding the 2,000 threshold deemed manageable by the DOH.

The lab identified the organism as Oscillatoria, a species that can produce cyanotoxins under certain conditions. While tests later confirmed no cyanotoxins were present, the district took the plant offline as a precaution.

“Once you find that you have cyanobacteria of the kind that can produce cyanotoxins, we need to either have a treatment step in the process that will destroy the cyanotoxins, or we need to be continually sampling … to make sure that no cyanotoxin suddenly come up, and that becomes pretty difficult to sustain through time,” said Steve Deem, licensed professional engineer at the DOH office of drinking water.

The state cyanobacteria protocol primarily addresses how to manage blooms in source water systems — such as streams or lakes — not recycling ponds. The DOH had never before overseen a bloom in a treatment plant, Deem said.

“It’s uncharted territory for everybody at this point,” said John Martinak, WD 19 general manager.

WD 19 declared a state of emergency, urging customers to conserve water and placing restrictions on outdoor water use, such as irrigation and car washing. The Vashon Island School District was asked to refrain from washing school buses, and Vashon Island Fire & Rescue delayed using water for training exercises.

These efforts, coinciding with the regular decline in demand as the weather cooled, reduced water usage and allowed the district to meet customer water usage while relying solely on groundwater sources.

Clearing and cleaning the contaminated recycling pond posed its own set of challenges. The WD 19 treatment plant is a closed-loop system: the recycled water is continuously reused to clean and feed into the treatment system, but was unusable in its cyanobacterial state. This water could not simply be dumped in its entirety, however, for fear of spreading cyanobacterial to the water sources below the treatment plant.

WD 19 first discharged some of the water slowly, in accordance with the state Department of Ecology’s supervision, to ensure that no water would reach Ellis or Beall creeks.

WD 19 and Ecology worked out a contract with Vashon Sewer District to discharge the rest of the contaminated water in the recycling pond to the island’s sewage plant. The district put in place a temporary water line, connecting the recycling ponds to the sewage plant, which treated 350,000 gallons of water over the course of a month, according to Martinak.

Once the recycling ponds were cleared, contractors used vacuum trucks to remove cyanobacterial sludge that accumulated at the bottom of the ponds. Further lab testing revealed that the sludge was non-toxic, and the district finally lifted its emergency use restrictions in late October.

Though the district handled the bloom without more severe restrictions on customers, it demonstrated the future headaches that microorganisms like cyanobacteria can cause for water districts.

The science of cyanobacteria

Cyanobacteria, often called blue-green algae, are not algae at all. While both use photosynthesis like plants, they are simpler, tiny organisms that lack complex tissue structures.

Unlike algae, cyanobacteria are “prokaryotes,” or organisms without a cell nucleus. Having evolved billions of years ago, they’re one of the most ancient forms of life — believed by scientists to be the first organisms known to have produced oxygen.

Mckenzie Bomber, Water District 19 operator in training, gives a tour of the district’s Beall Creek pump station. (Alex Bruell photo)

Though often mistaken for algae because of their appearance, cyanobacteria differ significantly in structure and behavior.

These microorganisms thrive in nutrient-rich, stagnant water under warm, sunny conditions. Their ability to grow rapidly under the right circumstances often leads to harmful blooms.

This summer, the recycling ponds at WD 19’s water treatment plant provided ideal conditions for cyanobacteria growth. These recycling ponds collect backwash water from filter cleaning and accumulate soil and nutrients on which the cyanobacteria can feast.

“All that soil, it’s the perfect medium for it to grow, for it to thrive. This pond is a nice place for that [cyanobacteria] to propagate and be successful in its life cycle,” Wahanik said.

While cyanobacteria blooms are typically associated with natural water bodies like lakes or rivers, their presence in recycling ponds is a relatively new phenomenon in Washington state.

Harmful algal blooms have only recently become a concern in the region’s drinking water systems. Anatoxin-a, a potent neurotoxin, was detected in the Columbia River’s water supply in 2021 — the first discovered instance of cyanotoxins in a Washington drinking water system.

“There is no definitive answer yet as to why this happened,” Deem said, noting ongoing investigations by agencies like the Environmental Protection Agency. “The thought is that climate change may be shifting things so they have an advantage over other organisms.”

As climate change alters environmental conditions, Deem predicts these events will become more frequent.

“We will be seeing these organisms showing up more and more and more,” he said.

How the system works

WD 19 is the largest public water system on Vashon. It provides water to the eastern central portion of Vashon Island and a small area of northwest Maury Island, and its water system utilizes surface and groundwater sources to serve nearly 1,500 accounts. Source water comes from Ellis and Beall creeks and is piped to the treatment plant, where it undergoes a multi-step process.

The water is clarified, filtered through layers of material, and disinfected with chlorine. The treated water is pumped out to customers, and the excess is stored in a million-gallon tank, which provides the pressure needed to distribute water out from the system. The recycling ponds collect backwash water from the filter cleaning. This water, rich in sediment, settles and is reused.

Armin Wahanik, operator in responsible charge at Water District 19, gives a tour of the district’s treatment plant. (Alex Bruell photo)

The contamination was never a limitation of the island’s source water, but instead an issue within the treatment facility. Treated source water accounts for 60% of the district’s output, according to the WD 19 Water Quality Report. The remaining 40% comes from wells.

According to the October WD 19 report, the district spent $72,000 on resolving the summer bloom, including expenses for contractor cleanup, lab tests, and bloom drying beds.

WD 19 is developing a comprehensive plan for monitoring water quality parameters like pH, turbidity (water clarity), and temperature. The plan would act as a decision making tree, establishing the course of action for when certain water quality indicators have strayed from the normal. At the December 10 WD 19 board meeting, Martinak said he hopes to have the final design reviewed by the DOH by February.

In the wake of this summer’s bloom, WD 19 plans to take further steps and investments to prevent similar incidents.

• Pond Covers: The district plans to install covers over the recycling ponds to block sunlight, a critical factor for cyanobacteria growth. Martinak is sending off an engineer-reviewed pond cover specs to DOH for approval later this week. Martinak expects the covers will cost around $20,000, including material and installation, and hopes to have them installed by February.

• Chemical Treatment: Low doses of potassium permanganate added to recycling ponds warmer seasons would neutralize potential cyanotoxins, providing an additional layer of protection. The DOH is on board with using potassium permanganate, though WD 19 must send them a specific proposal for approval, Martinak said. The goal is to have a temporary potassium permanganate pump put in place around spring, and a permanent pump in a year.

• Infrastructure Improvements: If the treatment or prevention systems fail, the district needs a way to get rid of the waste water in compliance with the DOH and Ecology. WD 19 is considering installing a permanent water line to the Vashon Sewer District, so that they can treat contaminated waste water. WD 19 has no concrete budget or timeline for this installation, though Martinak sees it as a necessity in preventing future bloom emergencies.

Martinak believes that WD 19 can put in place all of these treatment measures without taking out a loan, relying instead on capital reserves.

The clock is ticking to make those changes while the weather is still cooperative. DOH is urging WD 19 to put these prevention measures before the summer brings about warmth that aids cyanobacterial growth, Martinak said.

“Temperature is our friend right now,” Martinak said. “As long as the water temperatures are cool, we don’t have to worry about blooms.”