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Fine screen retrofit cuts upgrade costs by $1 million for Hawaii MBR
Hawaii typically conjures up images of azure seas, swaying palms and pristine beaches. But behind the romance of this tropical paradise is a reality that faces many wastewater treatment professionals—a rising population that places increased demands on treatment facilities and tougher regulatory requirements.
To preserve the natural beauty, keep up with growth and ensure regulatory compliance, the Schofield Barracks, one of Hawaii’s largest military bases, recently upgraded its wastewater treatment facility on the island of Oahu. The result was improved efficiency and water quality and decreased environmental impact on the region.
The project was spearheaded by Aqua Engineers of Kauai after a contract with the federal government to privatize the barracks’ treatment plant.
Aqua Engineers recommended GE’s ZeeWeed membrane bioreactor (MBR) technology to achieve the R1-quality effluent. According to project data, this advanced wastewater treatment system combines rugged, hollow-fiber ultrafiltration membranes with biological processes that result in superior effluent quality and reduced chemical consumption. The MBR required 2-mm screening in front of the membranes to protect them from clogging and damage.
“Protecting the membrane is critical in these types of MBR systems,” said Kenny Oyler, director of JWC’s Monster Separation Systems , which supplied the screens. “Our Bandscreen Monster provides excellent membrane protection because the entire screening operation is done on the inside of the screen. This prevents any debris from bypassing through and getting to the membrane itself. If that were to happen, the debris could go all the way through the process and wrap itself around a membrane, causing it to either plug or break.”
Originally, the project design called for building a new separate screening facility downstream from the existing installation to accommodate the new screens. But with the help of JWC , the facility used the existing infrastructure and replaced the old 6-mm screens with the new 2-mm ones in the same channel.
“This was a significant design change that saved about one million dollars in infrastructure and screen costs,” White said.
The Monster screens could handle 15 million gal per screen requirement for storm surge capacity and the stainless steel material was useful because of Hawaii’s humid environment, White said. Ultimately, the screens won out because they fit the existing channel “like a glove,” White added.
JWC’s Bandscreen Monster offers high capture rates and is able to remove a wider variety of solids—particularly small solids, trash and hair—better than traditional screens. Unwanted solids are captured on the UHMW plastic panels (with 2-, 3- or 6-mm openings) and lifted to the discharge level where a spray system washes solids into the Screenings Washer Monster for washing, dewatering and compacting.
Used with the Bandscreen Monster , the washer helped clean up and compact the heaping tons of screenings pulled out of the wastewater. This self-contained, hopper-fed system grinds, washes, compacts and dewaters screenings.
In comparison to the older screens used before the upgrade, which only dewatered, the new equipment collects, washes and grinds the screenings to produce a product that is relatively dry and free of soft organics. The screens reduced the maximum size of materials passing through the screen from 6 mm to 2 mm and eliminated the odor, resulting in a better-quality waste product going to the landfill.
Using the latest water treatment technologies available, Aqua Engineers improved the local water quality and made more than 1 billion gal of high-quality recycled water available for nonpotable uses every year. The Schofield Barracks’ wastewater treatment plant upgrade enabled the plant to provide R1-quality recycled water for the irrigation of lawns, golf courses, parks and other sites on base.
Aqua Engineer’s president and CEO, Eassie Miller, praised the upgrade, which has turned the plant into the largest privately-owned R-1 facility in Hawaii.
“The upgrade enables the military to conserve water, decrease pollution, and contribute to sustainability goals,” Miller said.