Beach showers pollute the ocean

This article originally appeared on Hakai magazine, an online publication about science and society in coastal ecosystems. Read more such stories at hakaimagazine.com.

At 49 Black Sand Beach, in Honoka’ope Bay, Hawaii, lies a strange, moated hillside in the middle of the beach. This little island, made of sand piled up about half a meter high, built by a beach shower. Every time a beachgoer steps in the shower to rinse off, water spills out of the base and carves gullies in the sand.

But while the obvious effect of the shower on the beach is usually benign, it belies a more subtle and potentially more destructive consequence.

As new research shows, the water flowing from the shower to the nearby surf is laden with a toxic mix of contaminants, including UV filters, microplastics and parabens. Scientists who have tested the water say this beach shower, like the thousands of others scattered along coastlines around the world, is a source of pollution that pours chemicals into the ocean in concentrations high enough to cause serious damage to life. cause in the sea.

The problem, says Craig Downs, an ecotoxicologist at the Haereticus Environmental Laboratory in Virginia who co-authored the new paper, is that most beach showers don’t connect to the local wastewater system. Instead, the runoff flows onto land and into the ocean.

Swimmers throw large amounts of sunscreen and other contaminants into the ocean, and scientists have accumulated ample evidence that these contaminants can harm marine life. But the concentrations of contaminants pouring out of beach showers, Downs explains, are shockingly high. Beach showers, Downs says, are point sources of pollution that can create concentrations of pollution that pose a serious threat to local corals, crustaceans and fish. Royal tides and monsoons can push these concentrations even higher when all the contaminants that have accumulated in the sand are released in one giant pulse.

Because the showers are point sources of pollution, Downs and his colleagues argue that their owners and operators — mainly municipalities — can be sued for violating the U.S. Clean Water Act.

However, Downs would like to see the situation resolved more proactively. “We don’t really want to get rid of the showers,” he says. Instead, “what we can do is apply technologies or legislation to end it” [the showers] be a source of pollution.”

However, fixing the showers will not be easy. The plumbing of beach showers in municipal sewers is not working: beach sand can clog traditional wastewater treatment systems. Municipal systems are also not built to remove such high levels of these contaminants.

However, there are technologies that will work.

One possibility to address the high levels of contaminants in beach showers, says Ranil Wickramasinghe, a chemical engineer at the University of Arkansas who was not involved in the research, is to use a membrane bioreactor. This all-in-one wastewater treatment system uses a thermoplastic or ceramic membrane to trap contaminants and allow clean water to flow through. Microbes absorb the contaminants, rendering them harmless. But there are a few catches: Installation costs are high, and the microbes must be tuned for each contaminant.

Another option, says Carlos Martinez-Huitle, an environmental electrochemist at Brazil’s Federal University of Rio Grande do Norte, who was also not involved in the research, is to use advanced oxidation processes (AOP). There are two modes that can be used with the showers, he says: direct AOP, where electricity is applied to the AOP cell, which allows the material on the inside of the surface to break down pollutants; or indirect AOP, where the flow draws pollutants to one end while forming oxidants at the other. The oxidizing agents then convert the pollutants into benign compounds. Municipalities could collect wastewater from the shower, filter the sand out and then apply an AOP device to remove pollutants before discharging the water into the ocean, Martinez-Huitle suggests.

However, AOP is an energy-hungry technology, so the key is to pair it with a renewable energy source. In their lab, Martinez-Huitle and his team have developed a system that uses AOP to clean industrial wastewater with electricity supplied by solar panels or wind turbines.

But even the most cost-effective wastewater treatment technology will put the meager municipal budgets to the test. Deciding which one to use and then implement it also takes time.

In the meantime, the researchers hope that consumer education, wider use of UV protection factor (UPF) clothing and regulations, such as Maui’s incoming ban on chemical sunscreens, will help curb the flow of pollutants into the environment.

For Downs, now that we know that beach showers can be powerful sources of pollution that can threaten marine life, the next steps are obvious. “If you can identify a point source of pollution,” Downs says, “then you have a… responsibility to reduce that pollutant.”