September, 2006 Vol. 31 No. 3
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Water Resources Research Center

Manoa Department of Oceanography

Published September 2006

After the Spill

Researchers work to determine when sewage contaminants make the ocean unsafe

by Jeela Ongley
illustration of a surfer girl looking at waves but thinking of sewage being dumped
Illustration by Kelly Hironaka

From the air, the reddish-brown rings that encircle the islands after a heavy rain give the impression that the land is bleeding into the ocean around it. Yet heavy rainfall is beneficial for the environment, it replenishes fresh water supplies, clears debris from steams and moves nutrients to offshore reefs.

Unfortunately, runoff inevitably also contains human waste products such as pesticides, garbage and, perhaps most disturbing, raw sewage from overburdened sanitation systems.

By most accounts, spring 2006’s record rainfall was a state disaster. The chaotic six-week weather pattern included a deadly dam breech on Kauaʻi, severe flooding, mudslides, evacuations, toppled utility poles, even a small tornado and short hailstorm. Popular Waikīkī beaches were closed as 48 million gallons of raw sewage were diverted into the Ala Wai Canal, an effluvium containing billions of pathogenic bacteria, protozoa and viruses.

The horrific death of Oliver Johnson, who fell into the Ala Wai Harbor two days after the spill stopped, was attributed to a waterborne bacterium—news that dramatically increased public interest in ocean water quality.

Testing the waters

At University of Hawaiʻi at Mānoa’s Water Resources Research Center, microbiologist Roger Fujioka leads a team concerned with determining risk and preventing waterborne diseases. Fujioka developed the newly adopted state standard for water quality tests, which measures the prevalence of Clostridium perfringens instead of usual E. coli and enterococci bacteria used by the Environmental Protection Agency as indicators of fecal contamination. E. coli and enterococci levels are not a valid guide in Hawaiʻi since these species multiply naturally (and harmlessly) in tropical soil.

Fujioka’s team sampled water three times during and after the Ala Wai spill looking for new alternative fecal indicators, such as bacteroide species and certain bacterial viruses specific to human intestines as the most sensitive and specific indicator of human sewage contamination. They determined that beaches were clear of sewage contamination four days after the spill stopped, and that the decision by Department of Health personnel to reopen Waikīkī beaches two days later based on concentrations of C. perfringens was a sound one.

Next they tested the sand at Ala Moana and Kūhiō beaches, where they determined that concentrations of all the fecal indicators were similar to levels before the sewage spill. In fact, the indicators were at higher concentrations in sand farthest from the water, indicating that sewage-polluted ocean water had not measurably contaminated the beach.

Thankfully, there are numerous natural physical, chemical and biological factors that prevent the accumulation of pathogens and many chemical contaminants in the environment. Salt, sunshine, acidity and microorganisms comprise an ecological clean-up crew that breaks down and kills sewage-borne pathogens in the water.

Ironically, the problem was also part of the solution

"Rain was the cause of the sewage spill, but persistent rain also helped to dilute and transport the sewage out of the canal and out to sea, away from populated areas," Fujioka explains.

"To be sure, some of the sewage in the Ala Wai Canal contaminated nearby beaches—Magic Island, Ala Moana, Waikīkī—but the rain and ocean current helped to limit the contamination at these beaches, especially once the sewage contamination stopped."

So although the spill seemed to coincide suspiciously with Johnson’s death, physicians determined that the culprit was Vibrio vulnificus, not a sewage-borne pathogen. The somewhat sinister-sounding V. vulnificus is a marine bacterium whose natural habitat is warm brackish waters in Hawaiʻi and other parts of the world. Infection through ingestion or via open sores leads to deaths, primarily in susceptible people with liver disease, every year across the country, including a 2001 case on the Big Island.

In Mānoa’s Department of Oceanography, Assistant Professor Grieg Steward and another team of scientists looked specifically for the presence of Vibrio bacteria in the surface waters of the Ala Wai Canal and nearby beaches in the weeks after the spill. They found that the levels were not unusually high. The data cannot be compared over time, however, since no continual monitoring processes are in place.

Planning for better data

"The real problem in determining water quality after an event like this, is that the spill is going out in a plume and it is moving," Steward says. "A site determined to be contaminated one day could be clean the next, and vice versa."

The School of Ocean and Earth Science and Technology is working toward ocean-observing systems—autonomous instrumentation mounted to moorings with sensors at various locations, collecting and uploading data, he says. The database created by this technology could better predict when water quality in certain areas might be compromised and monitor water quality in near real-time.

Then, just as surfers check buoy readings for signs of incoming swells, beachgoers could check results after heavy rainfall or sewage spills to determine when it is safe to go to the beach.

Jeela Ongley (BA ’97 Mānoa) is web content coordinator in External Affairs and University Relations


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