For weeks the staff at the Clarkston Wastewater Treatment Plant battled an aggravating overpopulation of Daphnia in the secondary clarifiers.
The tiny crustaceans, often called water fleas, were reproducing in such numbers that they were clogging the screens. A team member suggested putting fish into the clarifiers to eat the Daphnia — and it worked. The Daphnia disappeared. Then, surprisingly, so did the fish.
Daphnia are an indicator of good water quality, so their presence in the clarifiers wasn’t a sign of a treatment issue. But in large numbers, they can cause problems, and that’s what was happening in 2018 in Clarkston, in the southeast corner of Washington, when
