In September 2023, Moshe Harel watched the waters of Mantua Reservoir, a lake that supplied water to Brigham City, Utah, turn from pea-green to a clear blue. The reservoir had been choked with cyanobacteria, leading to public health advisories that warned people not to touch or swim in the water and putting financial stress on the local public works department. But over the course of a single day, Harel and a team of workers poured bags of white powder into the water, killing the bacteria and letting local residents access the lake again.

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