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May, 2005 Vol. 30 No. 2
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Dangerous watersMay 2005

Riverbank Filtration November 2003

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Water Resources Research Center

Pacific Research Center for Marine Biomedicine

Board of Water Supply, City and County of Honolulu


Rainwater Catchment Systems

HAPPI-Home series

Managing Hawaiʻi’s Watersheds (pdf)

Published May 2005

Water in Peril

Human activity, natural disasters, even terrorism create threats

by Jennifer Crites (AA ’90 Windward, BA ’92 UHWO)

There’s something magical about Hawaiʻi’s water. Evaporated from the ocean and mixed with sunshine, it tumbles from the skies creating rainbows, replenishing streams and nourishing the ʻaina. Then it vanishes into lava rock—a natural filtration system—reappearing 10–20 years later in underground lakes known as aquifers, cleansed of impurities and ready to drink.

Lately, though, some of that magic has been flushed down the drain. Overuse and droughts shrink the underground lakes. Agricultural pesticides, lead, arsenic and leptosporosis bacteria show up in wells, streams or estuaries. Terrorism brings threats of malevolent contamination.

Problems with water are not limited to the islands, of course. The tsunami in Asia is one recent reminder that supplying people with clean water is a worldwide concern. University of Hawaiʻi researchers, most affiliated with the interdisciplinary Water Resources Research Center, are responding by seeking solutions at home and abroad.

Trouble in river cities

"Many cities in India use river water for drinking because groundwater is scarce or undrinkable. Yet mega-cities dump their wastes into these rivers," says Chittaranjan Ray, an associate professor of civil and environmental engineering.

Ray received a Fulbright award to study the potential for riverbank filtration in India and Nepal. Water is drawn through sand and alluvial (clay, silt or gravel) deposits beside or beneath a river, removing many of the pathogens and chemicals. Ray also works with scientists in Seoul to clean up Korea’s Han river, as well as officials in Louisville, Cedar Rapids, Santa Rosa and other U.S. cities that use riverbank collectors.

A 1993 outbreak of Cryptosporidium in Milwaukee killed 20 people and sickened 400,000 when the protozoa, carried in cow feces, washed into rivers feeding Lake Michigan. The public water utility’s chlorination procedure proved ineffective.

Ray says the U.S. Environmental Protection Agency (EPA) now takes a very aggressive approach in favor of riverbank filtration for any public utility drawing its water from the surface or surface-influenced wells.

Drugs in the water

In addition to fecal bacteria, substances turning up in the world’s water supplies include antibiotics, pain medication, tranquilizers, caffeine, cholesterol drugs and birth-control hormones.

"Drugs we take are only partially metabolized; the rest goes into wastewater," explains Associate Professor of Civil and Environmental Engineering Roger Babcock.

Pharmaceuticals aren’t removed by conventional wastewater treatment, which eliminates organisms that cause disease. Babcock is helping evaluate the ability of microfiltration systems known as membrane-bioreactors to remove pharmaceuticals and provide high-quality recycled water for non-potable use.

Alternate sources

"A lot of our potable (drinkable) water goes for uses that don’t require potable water," he emphasizes. Oʻahu’s 35 golf courses each guzzle close to one-million gallons a day—enough for 9,000–10,000 people.

Wastewater could even be put through reverse osmosis (a process that pushes water through a very fine membrane, trapping unwanted particles on the membrane) to make ultra-pure potable water, he adds.

Fellow engineer Clark Liu is studying reverse osmosis to desalinate water. "We might have major water shortages as population and economic development increases. That’s why we have to find other sources," he cautions.

Scientists around the world are looking at reverse osmosis as desalination’s magic bullet, but it’s an expensive procedure that requires power to produce the necessary water pressure, he says. "Some people are using the wind to generate electrical power. Our system is more efficient and cheaper. We’re bypassing the need for electricity and using wind directly to raise the water pressure."

When enough is too much

Liu is also evaluating an aquifer’s sustainable yield: how much water can be pumped out without negative consequences. Land subsidence occurs when overpumping causes the pressure to drop inside a groundwater source and the surrounding soils collapse. Luckily, it’s not a problem for Hawaiʻi’s sturdy basal rock.

Intrusion is another story, however. Oʻahu's freshwater lens sits on top of a seawater basin. "If you pump too much, seawater moves upward into freshwater—especially in coastal areas where the freshwater lens is thinner-and turns the freshwater brackish and undrinkable," Liu says.

Working with Honolulu’s Board of Water Supply and the U.S. Geological Survey, Liu monitors water and salinity levels in the Pearl Harbor aquifer and prepares a mathematical model that will predict how salinity levels change with pumping rates and quantities.

Assistant Professors of Botany Kaʻeo Duarte and Lawren Sack are working at the source, studying the effects of nonnative versus native forests on the infiltration of water.

"How are these plants using water throughout their growing cycle, how does water availability affect forest dynamics and how does the forest community affect soil moisture and infiltration?" Duarte explains. "We want to see if the different communities of plants make a difference in the net recharge of water into the ground, and from there into streams and groundwater."

The team is looking at two test sites in South Kona. The sites are at the same elevation and receive similar rainfall, but one has nonnative eucalyptus and ash, the other, native plants such as koa, ʻōhiʻa, hāpuʻu, kōlea and pilo. The ultimate goal is an accurate watershed-wide model of the interaction between plant life and hydrology that can contribute to better water resource policy decisions.

The chemical threat

Experts agree that Oʻahu’s groundwater is free of biological, disease-causing organisms, which die off during their multiyear journey through soil and lava rock. But man-made chemicals don’t die, and they can end up in the islands’ aquifers.

In 1983 agricultural pesticides DBCP and EDB were banned from Oʻahu’s sugarcane and pineapple fields after they were discovered in some Mililani-area wells. The Board of Water Supply removes known chemicals with activated-charcoal filters before they reach household taps, but there’s pressure from golf courses, diversified agriculture and termite-control businesses to import new chemicals, says Ray.

"The Department of Agriculture favors the introduction of newer chemicals but wants to make sure they won’t be harmful to our water supply. So we test and make recommendations—which ones leach into the soil after it rains, how readily they stick to different soil types (if they stick, they don’t wash down into aquifers), what secondary products are produced when they degrade and how toxic they are."

With a similar objective, engineer Ray and Associate Professor of Geology and Geophysics Aly El-Kadi locate, categorize and rank the danger of all potentially contaminating hazards near each of the state’s 450-plus drinking water sources.

"We looked at gas stations, auto repair shops, landfills, parks—any activity that could impact a water source," says Ray.

The taste of chlorine

Some chemicals are added for good reason. Honolulu’s Board of Water Supply selectively chlorinates some drinking water at a low level to prevent biological contaminants from reaching households. EPA is considering legislation to force states to disinfect most drinking water with 0.2 milligrams per liter of chlorine, a remedy Professor of Public Health Roger Fujioka calls unnecessary on Oʻahu.

"People will be able to taste the chlorine," Fujioka says. He has served on a number of EPA advisory panels and successfully argued against the excessive chlorine for many years. Environmental water-quality standards are applied uniformly to every state, even though microbes behave differently in tropical climates, he points out.

"We were able to convince the National Science Foundation and National Institute of Environmental Health Sciences to fund the Pacific Research Center for Marine Biomedicine at Mānoa, one of four Ocean and Human Health Centers across the country," he adds. Its mission includes prevention of waterborne diseases.

Fujioka also developed a monitoring plan and trains Board of Water Supply laboratory staff to rapidly detect changes in drinking water that could signal contamination by terrorists.

Other water-preservation efforts by UH faculty include safe operation of water-catchment systems in areas not hooked up to a public utility.

Ultimately, all appreciate the sentiment expressed by American anthropologist Loren Corey Eiseley: "If there is magic on this planet, it is contained in water."


Dangerous Waters

In a state where water figures prominently in recreation, concerns about biological and chemical contaminants aren’t limited to drinking water.

Researcher Roger Fujioka hopes to develop an accepted health-safety standard for Staphylococcus aureus, a bacteria that causes more infections among swimmers, surfers and paddlers in Hawaiʻi than in any other state (see Mālamalama, September 2004).

And on the Big Island, UH Hilo Assistant Professor of Chemistry Debra Weeks investigates the movement of arsenic in Hilo Bay’s Wailoa estuary.

Arsenic was introduced into the estuary between 1932 and 1962 when the Waiākea Sugar Mill operated in the area. Sugarcane bagasse, or waste, didn't break down easily, so it was treated with an arsenic solution to repel termites and processed into a building material called canec. "The arsenic solution drained into the estuary as waste," says Weeks. Arsenic sticks to particles that sink to the bottom as sediment. "There’s a concern about contamination if the bottom gets stirred up or swimmers ingest muddy water," she says.

Subsequent sediment layers could have covered those containing arsenic. Still, a graduate student working on the project won’t let her children go barefoot in Waialoa Park. "Until the distribution of arsenic has been fully studied, this level of discretion is reasonable," says Weeks.

She plans to look into the arsenic’s mobility in the food chain—algae-eating ducks, Hawaiian mud hens and bottom-feeding fish caught by recreational fishermen.

Jennifer Crites is a Honolulu freelance writer and photographer


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