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Study: Wastewater treatment improves fish health

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Courtesy of Fluence Corporation

A decade-long study by Canadian researchers concludes that improved water treatment benefits fish populations.

University of Waterloo researchers found that within a year after an upgrade to one of the area’s municipal wastewater treatment plants, there was a 70 percent decrease in the occurrence of intersex fish in Ontario’s Grand River. Within three years there was a full recovery of the fish population.

The researchers, who have been monitoring male rainbow darter fish in the river since 2007, found male fish were developing female characteristics at a rate that at one point was the world’s highest. The rate is now less than 10 percent.

Improved Wastewater Treatment

The upgrade of the Kitchener Wastewater Treatment Plant, one of two major wastewater treatment plants on the Grand River, started in 2012. The upgrade gave the scientists a unique opportunity to assess whether conditions could change technology updates.

The improvements to the plant included changes in aeration with the addition of diffused air systems to treat sludge and encourage the growth of nitrifying bacteria. The aim was reducing the amount of ammonia in the water, researchers said, but the microorganisms also reduced the levels of endocrine disruptors in the water. With the reduction in these chemicals, the rate of intersex fish in the river was reduced within a year.

Endocrine-disrupting chemicals are found in waters worldwide. Trace amounts of substances such as estrogen in birth control pills and chemicals that mimic natural hormones can affect fish health. They can be affect by even one part per trillion, much less than the amount conventional wastewater treatments can typically remove.

Working With Available Technology

Mark Servos, a professor of biology from the University of Waterloo who served as lead researcher on the project, said:

Having long-term data of the fish population, before and after the wastewater treatment upgrades, makes this a truly unique study. […] The changes to Kitchener’s wastewater treatment system have had a much larger positive impact then we had anticipated.

Servos said these findings are particularly exciting because they demonstrate what researchers can do with technology that’s available now. Some water treatment plant operators, notably in Europe, have been using tertiary treatment to address the problem, but these treatments typically are expensive.

Deborah Roberts, an engineer who working on microbial decontamination systems at the University of British Columbia, Canada, called the study an “important contribution” to the field. She told Chemistry World “I am not aware of another study that has documented this finding.”

Watershed Concerns

The Grand River in southern Ontario empties into Lake Erie. Concern about its watershed is tied to regional population growth. The population, which was 780,000 residents in 2001, is forecast to grown to 1.2 million people by 2031. Managing that growth while protecting the environment is a particular concern.

Another masters’ thesis study of the Grand River watershed, published by the University of Waterloo in 2010, observed that the two primary wastewater treatment concerns for the watershed were:

Inadequate treatment, with Kitchener’s facility provided as an example
Minimal dilution prior to discharge, which was observed at the Guelph outfall

Endocrine Disruptors

To better understand how municipal wastewater treatment affects fish populations — both upstream and downstream of wastewater outfalls — the study examined the two most abundant fish species in the river, the greenside darter (Etheostoma blennioides) and rainbow darter (E. caeruleum).

An intersex fish with both male and female characteristics. Scientists tie the condition directly to exposure to hormones or endocrine-disrupting chemicals put in the water by industrial processes or through contaminants in wastewater discharges.

These “chemicals of emerging concern” include veterinary antibiotics in agricultural runoff, and human pharmaceuticals.

Interest in studying endocrine disruption and intersex fish is not confined to Canada. The United States Geological Survey, for example, is among the agencies that have been studying the condition for years.

Bryan Cole’s post-doctoral research at the University of California Davis examined fish in the Sacramento-San Joaquin Delta. Cole explained in a 2013 interview with California Sea Grant’s news service that endocrine-disrupting compounds are unusual because they are more harmful at lower concentrations than higher ones. Cole said:

Fish physiology is set up to react to low concentrations of hormones. This means that some endocrine disruptors are most potent to fish at low exposures. It’s very counter-intuitive, and it has significant implications for meeting environmental water quality objectives.

Such exposure can significantly damage fish populations. The U.S. Geological Survey explained:

Exposure to low-levels of some contaminants can cause disruption of endocrine functions in animals, such as reproduction. This is done by modulating, mimicking, or interfering with normal hormonal activity. Examples of endocrine-active contaminants are chemicals such as synthetic hormones, certain pesticides, some pharmaceuticals, detergents degradation products (nonylphenol), and many others.

Servos said he and the researchers are examining other fish characteristics that may be influenced by wastewater, including behavior, genetic expression, and steroid hormone production. They will also look at data to “determine to what level of treatment we need to go to ensure protection and sustainability of our ecosystems and water resources.”

There has been some concern about whether the presence of these substances, even in trace amounts, could affect the health of large vertebrates (including humans) and other animal that consume water containing endocrine-disrupting chemicals.

The study’s findings — “Reduction of intersex in a wild fish population in response to major municipal wastewater treatment plant upgrades” — were published in the journal Environmental Science & Technology.

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