LOS ANGELES — Onja Davidson Raoelison, a doctoral candidate in environmental engineering at UCLA, has been working to keep waterways safe.
Her research and studies focus on green infrastructure and how wildfires impact water systems.
“I think we all hear about air quality all the time,” she said. “Even at UCLA, we receive a lot [of news] about the air quality being bad when you’re not supposed to go outside. I never knew that the impact of wildfires on water quality would be an issue and how it impacts aquatic ecosystems and human health.”
Raoelison was born in Madagascar, where water-borne diseases are common. They drove her passion for protecting rivers, lakes, groundwater and surface water.
“I go there [to Madagascar] every three years. I know how unsafe the water is. Fifty percent of the population doesn’t have safe water. If you go to remote areas in Madagascar, you can be sure it’s unsafe water,” she said. “I want the country to have sustainable development.”
While Madagascar sparked Raoelison’s interest in water, California’s water ways are where her research is focused for now. In her lab, which is overseen by assistant professor of engineering Sanjay Mohanty, she is working with biofilters — a collection of sand, compost, gravel and other naturally occurring materials that can help absorb pollution before it enters waterways.
Specifically, Raoelison has been looking at how biofilters can protect water from debris and toxic pollutants such as heavy metals.
“I’m interested in natural based solutions that can remove contaminants in the environment, and in my case, I’m interested in green infrastructure — a sustainable solution to mitigate the impacts of wildfires on water quality,” she said.
As wildfires become more frequent in California, their impacts are felt more broadly. The ash and debris from fires can end up being washed into rivers, lakes, streams, groundwater and the ocean.
“The post-fire runoff can end up in surface water,” Raoelison said. “It will impact aquatic life, the ecosystems in the water. We want to avoid that.”
In the lab, Raoelison has built small scale biofilters to test their efficacy. Other classmates are working on research related to wildfires collected debris created after the Palisades fire in 2021.
Raoelison uses the ash to create a water-based solution that mimics rain water mixing with the ash. She then runs different versions of the solution through different versions of the biofilters.
“What we have found is that, metals can be absorbed by the stormwater biofilters compost, and nutrients as well, because there is no significant leaching of nutrients,” Raoelison explained.
While the biofilters in her lab are micro in scale, Raoelison said they can be built and created on larger scales that could have significant impacts for fire prone areas.
“That means we can implant these biofilters in any place in Los Angeles. We know we can protect the surface water,” she said.
Mohanty explained why Raoelison’s research and biofilters could be an important part of California’s water conservation efforts.
“We don’t have enough water. We spend a lot of money to get water from elsewhere, and then we discharge it to the ocean. We cannot continue to do that. We do not have enough water. We have to use the water we get, and so one of the things is stormwater. It rains here. Every time it rains, we can capture that stormwater.”
Mohanty added that biofilters designed to absorb pollutants could allow Californians to repurpose stormwater — rather than see it drained into the ocean.
Raoelison’s research is still ongoing, and while she’s focused on California for now, she hopes she can bring her research back to Madagascar too.
“You can see the impact [in Madagascar] on people’s lives every day. If they want to drink, if they want to cook, if they want to wash themselves, they can get diseases because of unsafe water. It’s important to me that everyone in the world has access to clean and safe water.”