But toxins don’t have to enter the water system to cause disruption. In Utah in 2016, a massive algal bloom on Utah Lake tainted the water that residents in three counties use as untreated “secondary water” for their lawns and gardens. Officials were unable to determine if food grown with the contaminated water was safe to eat. As the algae spread, one secondary system after another opted to exercise an abundance of caution and close its valves. Residents switched to watering their lawns with drinking water, causing citywide shortages.

The lack of good treatment options has led the Water Research Foundation to recommend a multistage approach combining several methods of decontamination. That could require treatment plant renovations that run into the millions of dollars. Many states are taking aim at the algal blooms themselves, attempting to starve the cyanobacteria by reducing nutrients like nitrogen and phosphorus, present in fertilizers and discharge from sewage plants. Kansas has an annual budget of over $5 million dedicated to limiting the amount of fertilizer and wastewater in waterways used as drinking water sources.

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