Tucked into Makiki Valley State Recreational Area, near leafy hiking trailheads and the Hawai'i Nature Center, an unassuming structure recycles wastewater into irrigation water, using decades-old yet still innovative environmental ideas.

The Green Machine, a tank-based wastewater treat-ment facility, simulates the action of wetlands to recycle about 50 gallons of wastewater daily from the nature center's septic tank system.

"We use native Hawaiian plants, fish, insects and micro-organisms — primarily bacteria — to clean water, using a natural process that's found in our coastal and inland wetlands," said Chad Durkin, a program manager for Partners in Development, the nonprofit foundation operating the Green Machine — given the Hawaiian name Ho'oma'ema'ewai (to clean the water).

"This is nature's way of cleaning water. If you think of our natural wetlands as the 'livers' of the earth, you can think of our constructed wetlands as the future of sustainable Hawai'i," Durkin said.

The water produced in the machine's tanks is odor-free and irrigation-ready.

After processing, the water is funneled underground to a nearby field, which serves as a garden laboratory for Hālau Kū Māna Public Charter School students. They study the workings of wetlands and related environmental issues, sharpening their science and math skills along the way.

The Green Machine itself is a recycled apparatus. Designed by Ocean Arks International, a nonprofit research organization that builds energy-efficient water-cleansing "living machines," it started out as a demonstration structure in San Francisco, and was moved on-island about 12 years ago to treat pigs' waste at an 'Ewa Beach slaughterhouse. In 2004, the hydroponic-hybrid model was refurbished and installed in Makiki.

USE IN Hā'ENA

Wetlands-based technology hasn't been tapped for a large-scale wastewater recycling effort in Hawai'i, but it is a workable option.

The wetlands concept is being incorporated underground, for example, at Kaua'i's Hā'ena State Park, where workers found a Hawaiian burial site, bones and artifacts while installing a septic tank and drainfield near a park restroom.

The iwi were moved to a graveyard. In response to Hawaiian community concerns that leaching wastewater would further desecrate the area, park officials agreed to construct an artificial wetlands to drain cleaner effluent into the ground.

When the original Hā'ena restroom was constructed in 1979, its wastewater was discharged into a large cesspool — a disposal method outlawed five years ago by the U.S. Environmental Protection Agency.

"The nitty-gritty to understand is that they're basically holes that receive raw sewage," Hawai'i EPA spokesman Dean Higuchi said of cesspools. "There's a huge potential for the waste to end up impacting near-shore waters" as well as inland areas.

Shortly before the federal ban took effect, the EPA estimated that there were 1,500 large-capacity, nonresidential cesspools statewide. Since then, most owners have switched to more environmentally friendly septic tanks, which store solid waste and filter liquid waste into the ground.

Constructed wetlands are even friendlier, in that they filter out more contaminants before releasing the water.

LOCAL RESILIENCY

A glimpse of the sustainable wisdom tied to the Green Machine's model of using small or neighborhood-sized systems to clean wastewater rather than relying on a large and centralized wastewater treatment was presented to O'ahu residents in March 2006. That's when a Waikīkī sewer-line break sent some 50 million gallons of wastewater into the Ala Wai Canal, triggering a $45 million repair and replacement project.

"When that pipe burst, it wasn't just the wastewater from Waikīkī," Durkin said. "It was the wastewater from upper Kaimukī and Mō'ili'ili and lower Mānoa.

All of that was coming down the track on its way to Sand Island Wastewater Treatment Plant, where about 85 percent of the Ho-no-lulu area's wastewater is processed — about 60 million gallons daily.

Durkin concedes that installing scores of small constructed-wetland operations under Hawai'i's high-priced land is not a cheap proposal. But, he said, in addition to eliminating the threat of a massive pipeline spill, a gravity-fed or "stepped" system — following the old Hawaiian mountain-to-sea ahupua'a land-use design — could yield huge operational energy savings, as little pumping and machinery would be needed to maintain such an operation .

Looking further into the future, Durkin points out that using more recycled water in our backyards, parks and fields would ease Hawai'i's ongoing demands on its diminishing underground aquifers.

About 60 percent of the fresh water we siphon from aquifers is tagged for irrigation purposes, he said.

The vision of a sustainable water supply in the Islands, Durkin said, ought to come with the "idea of local resiliency — having a system in place so that you're not dependent on other areas for getting or treating water."