Wastewater Researchers Find Answer to Intersex Fish Problem

Researchers say that upgrading wastewater treatment plants to improve effluent quality may lead to a reduction in the kind of water pollution that causes fish to become intersex — meaning they have both male and female sex organs — which hinders reproduction.

A 10-year study, published in the journal Environmental Science and Technology, examined the effects of upgrading equipment at a wastewater treatment plant situated along Ontario's Grand River. The researchers from the University of Waterloo found that the upgrades “led to a 70 percent drop in fish that have both male and female characteristics within one year and a full recovery of the fish population within three years,” according to a statement from the university.

The upgrades included “the conversion from a carbonaceous activated sludge to nitrifying activated sludge treatment process,” the study said.

“This study demonstrated that investment in [wastewater infrastructure] upgrades improved effluent quality and was associated with an immediate change in biological responses in the receiving environment. This is an important finding considering the tremendous cost of wastewater infrastructure,” the study said.

The fish studied by the researchers were rainbow darters. "[They] are the Grand River's canary in the coal mine," said Mark Servos, one of the researchers. "They're extremely sensitive to the concentration of estrogens and other hormone disrupters in the water. Still, we didn't expect them to recover so quickly."

Researchers are finding that even in some of the cleanest waters in the U.S., pollution appears to be altering the sex functions of fish and making them intersex, according to National Geographic.

In a separate effort to target contaminants that affect the reproductive functions of fish, researchers discovered a new way to remove traces of human birth control pills from municipal wastewater during treatment.

In a paper published in Scientific Reports, a research team helmed by Carnegie Mellon University Chemist Terrence Collins argues that a group of catalysts known as TAML activators “could be a viable option for large-scale water treatment,” according to a press statement from the journal. TAML activators are small molecules that behave much like oxidizing enzymes.

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