August 2020 was a strange month in the San Fransisco Bay.  As lockdowns persisted, my children were growing increasingly restless in our home. The monotony was briefly broken by an unexpected thunderstorm, a rare occurrence in August. Sitting atop a hill behind our house, my 5-year-old daughter and I marveled at the show of lightning striking a ridgeline twenty miles north of us.

“Wow, that’s what lightning looks like?! That’s so cool!” she exclaimed, just before we hurried down the hill to escape the oncoming rain.

Days later, excitement turned into apprehension as the impact of the lightning strikes became apparent. The skies turned an unforgettable shade of orange from smoke billowing from fires surrounding the area. These lightning complex fires became the third largest in California’s history, burning thousands of acres and over 3,000 structures.

On one of those spooky, orange-hued days, I got a frantic call from a longtime customer and friend. “Drop what you’re doing and meet me at our storge tank,” he said, “I’m in real trouble here.”

Racing to the site, I passed through the police cordon and arrived in a devastated neighborhood.  The air was thick with the smell of charred debris.

“We lost about 30 homes in this neighborhood,” my friend lamented, “Despite our best intentions, the efforts to manage water quality here left us defenseless against the fires. We need a solution to prevent this from happening again.” 

This harrowing experience underscored the intricate challenges faced by municipal water utilities in managing water age and water quality in their distribution systems, particularly in storage tanks. From a regulatory standpoint, municipalities are generally advised to design and operate their systems to minimize water age and ensure effective water turnover. The goal is to balance the size and configuration of a distribution system with demand patterns to minimize stagnation and ensure that the water remains within acceptable quality standards.

In tanks, water inherently ages as it is stored. Over time, reactions with naturally occurring organic matter in the water can cause taste and odor issues and form harmful disinfection byproducts, such as trihalomethane (THM).  Seasonal temperature fluctuations can also lead to thermal stratification, creating layers of water with different temperatures, especially in larger tanks. This phenomenon leads to an accelerated decay of disinfection residual in warmer water layers, causing biological growth and possible corrosion or leaching of the tank material. These issues pose serious health risks to consumers and result in difficult tank maintenance. 

In response, utilities employ a range of strategies to mitigate these challenges. Hydraulic models, water quality monitoring, and asset management practices form the basis of efforts to control water age. Operational strategies include directional flushing and tank cycling. In the case of our customer in the San Franciso Bay area, the tanks were being operated at partial volume. This is often one of the first things utilities do to fix water quality challenges, but this time, it inadvertently exacerbated the community’s vulnerability to fire. By the time the fire came over the hill in the neighborhood, there was not enough water left in the tanks to maintain distribution system pressure; and the fire trucks were unable to operate. Fortunately, there exists a better solution - tank-based water treatment.

Tank-based water treatment is a well-established practice used by thousands of utilities nationwide. By integrating appropriate equipment, operators can proactively maintain consistent water quality and keep tanks full, preventing unforeseen consequences such as the loss of a neighborhood to fire.  
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Considering the challenges posed by water age in distribution systems, it is imperative for municipal utilities to adopt innovative solutions that prioritize water quality and resilience. If your water quality management program includes practices that leave tanks less than optimally filled, consider exploring tank-based water treatment solutions.

Let us help you! As technology experts in water quality, we can work with you to evaluate options to enhance your distribution system's resilience and safeguard the communities you serve. Together, let us embark on a journey towards a safer and more sustainable water future. Good news - it starts with something as simple as adding a tank mixer.

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