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people collecting sewage samples
Nicolas Storie (left) collects water samples in Keaukaha. Shayla Waiki (center) records data and Joseph Crispin Nakoa (right) measures water quality.

A newly published University of Hawaiʻi at Hilo study confirms that wastewater from cesspools and the Hilo sewage treatment plant is reaching nearshore waters, impacting coral reefs and potentially human health. The findings are the result of two years of research by UH Hilo marine scientists and students, who used dye tracer tests to track sewage movement.

“We found dye emerge at the shoreline every time,” said Steve Colbert, UH Hilo associate professor of marine science. “And the water moved fast, one to two football fields [in length], including end zones, each day.”

‘Pilau meter’

sewage map
(A) Red dots mark onsite sewage disposal systems in Hilo. (B) Zoomed in area of Keaukaha.

The project began after Keaukaha residents raised concerns about strong sewage odors and possible health risks from pollution. Lead researcher Shayla Waiki, a former UH Hilo graduate student, focused her thesis on tracking sewage in Keaukaha. Waiki is now a natural resources specialist with the Army National Guard and plans to apply to UH Mānoa’s law school this year.

Using water samples and the “Pilau-meter,” a public reporting tool for bad smells at Puhi Bay, researchers confirmed what the community suspected—sewage is present, and it’s traveling through groundwater quickly. Pilau is the Hawaiian word for stink, rotten, foul.

UH Hilo researchers found that sewage in Keaukaha’s coastal waters is moving faster than previously recorded in Hawaiʻi. They stress that Hilo should be a top priority for cesspool conversion to prevent further contamination.

Health and environmental risks

Keaukaha, home to Hilo’s sewage treatment plant, also has numerous cesspools near the shoreline. Wastewater from these systems can introduce harmful bacteria and pollutants into coastal waters, raising concerns about infections such as methicillin-resistant Staphylococcus aureus (MRSA) among residents.

The study’s findings are already driving action.

“Results from this research have been shared with the community and Hawaiʻi county, and are being used by the county to help prioritize locations for sewer line expansion in Hilo as part of the statewide effort to transition away from cesspools,” said Tracy Wiegner, a marine science professor at UH Hilo who co-authored the study.

Team effort

The study was a collaboration between UH Hilo faculty and students, including former graduate students Joseph Nakoa and Devon Aguiar, and marine science undergraduates Nicolas Storie and Ashlynn Overly. Today, they are continuing environmental work in doctoral programs and conservation efforts across Hawaiʻi.

UH Hilo marine science undergraduates Darienne Kealoha, Kaitlin Villafuerte, Finn Reil and Brooke Enright, and tropical conservation and environmental science graduate student Walter Boger also contributed to the study. Other co-authors include Karla McDermid (marine science professor, UH Hilo), Noe Puniwai (Hawaiian studies associate professor, UH Mānoa) and Craig Nelson (oceanograohy professor, UH Mānoa).

For more go to UH Hilo Stories.

By Susan Enright

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