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Wastewater discharge harms reefs, study finds

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    Remnants of an invasive algal bloom, Hypnea musciformis, above, cover a beach and rocks at Kuau Bay in Paia, Maui.

A team of University of Hawaii scientists has completed an intensive study of nearshore ecosystems around Maui that paints a clear picture of the impact of discharged treated wastewater.

And the picture isn’t pretty.

Results from the study were published in the Nov. 3 edition of PLOS ONE, a scientific journal.

Led by botanist Daniel Amato, scientists representing the UH Botany Department and the Department of Geology and Geophysics based their investigations on field experiments and chemical analysis of water and algae at six locations around Maui, including Kahului Bay, which is adjacent to Maui’s highest-volume sewage treatment plant.

The facility has used wastewater injection wells to dispose of treated wastewater, releasing the discharge deep into the ground.

A study of nearshore areas in nearby Kahului Bay found high nutrient levels in marine surface waters and a “thick, fleshy mat” of colonial zoanthids, a coral-like organism, according to a UH news release.

In the published study, the authors noted that the presence of such concentrations of zoanthids is associated with areas close to wastewater injection wells; such concentrations were not found anywhere else during the team’s study.

The authors said the study supports the rarely investigated hypothesis that submarine groundwater discharge is a significant source of harmful nutrients in coastal ecosystems.

The study also found that agriculture has a significant impact on coastal ecosystems, particularly with regard to nitrogen levels.

“By comparing the spatial distribution of (nitrogen) in both water and algal samples among locations with various potential nitrogen sources, the role agriculture and wastewater have in coastal regions has become more clear,” the study reported.

“These land use practices are the most likely sources of excess nitrogen in Maui’s coastal waters.”

Overall, reefs near plantations and wastewater injection wells had the most seaweed, the lowest diversity and the highest nitrogen concentrations in algal tissues, coastal groundwater and marine surface waters, according to the study.

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      • The EPA is pressuring the State to put more chemicals with secondary treatment and will cost Billions to do. They are their own worst enemy.

        Raw sewerage is best for environment. I was told ogo 2 feet long at the outfall. In the old days Humans were stronger or got treatment for infections. No need to treat the sewer.

  • They cannot dump all this “treated waste water” into a clean environment and expect it not to degrade. The waste water needs to be treated (cleaned) more thoroughly.

  • Sewage discharge concentrations into the ocean at an out fall or via an injection well may change the dilution of damaging chemicals but they are damaging all the same. The City of Honolulu paid millions in damages when Fasi was mayor for near shore out fall pollution. this is not new and it probably goes on at the tail end of all mans waste streams to some extent. Treated water does not mean clean H2O. There are still plenty of chemicals in there. Also be aware of the agro/chemical activities in your area as it relates to drinking water. Is the Conservation Plan being followed ? Are Best Management Practices [BMP] being practiced? The lag time may be decades …

    • Actually many years ago the EPA falsely accused San Diego of ocean contamination due to an underwater treated sewage discharge line way out into the ocean. EPA said the discharge was an environmental disaster.

      San Diego’s Scripps Institute of Oceanography, the Gold Standard, stepped in and slammed the EPA to the ground with decades of credible research showing there was no problem at all, the EPA was just spreading unfounded lies.

      Nothing unusual there. Lets not forget the EPA is directly responsible for releasing toxins into a river when an EPA bureaucrats opened a drain line. Lets not forget the EPA was aware of the Flint water issues and did what they do best, nothing.

  • I checked out the study. It correlates submarine groundwater discharge (SGD) to nutrient levels in nearby ocean waters. SGD is where water in the soil and rock leak into ocean at the coast. This study only pertains to Maui’s wastewater injected into the ground and not Oahu’s outfalls which discharge into deeper water away from the coast. Also, agricultural fertilizer was a more significant source of nutrients via SGD in some areas.

    “…of the six locations studied here, we find Ku’au Bay as the most impacted study location… imply that synthetic fertilizer applied to adjacent sugarcane fields was the most likely source of nutrients to this area…”

    “…although shallow wastewater injection wells (relatively small facilities associated with individual condominiums at Ma’alaea) may be a source of nutrients in the nearshore zone of Ma’alaea Bay, fertilizer applied to adjacent sugarcane farms is the dominant source of N to this reef…”

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