Fine-screen retrofit saves a Hawaiian MBR facility space and money
Hawaii typically conjures up images of azure seas, swaying palms and pristine beaches. Behind the romance of this tropical paradise is a reality that faces most wastewater treatment professionals today—a rising population placing increased demands on treatment facilities and tougher regulatory requirements.
To preserve Hawaii’s natural beauty, keep up with growth and ensure regulatory compliance, the U.S. Army Schofield Barracks, Hawaii’s largest Army post, recently upgraded its wastewater treatment facility located 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 following a contract with the Army to privatize the facility. Key to the project’s ultimate success was technology from JWC Environmental, Costa Mesa, Calif., and GE Water and Process Technologies.
Wayne White, Aqua Engineer’s plant engineer for Schofield, explained that goals for the upgrade were specific as well as challenging.
“We needed to upgrade the plant from R2-quality effluent to R1-quality effluent suitable for reuse in agriculture and irrigation applications,” White said. “We also needed to increase plant capacity by roughly 30%, from 3.2 to 4.2 million gal per day (mgd). An additional requirement to provide surge capacity of 15 mgd to handle Oahu’s frequent rainstorms further increased the design challenge. And, the total project was to be completed without major capital expenditure.”
Aqua Engineers recommended GE’s ZeeWeed membrane bioreactor (MBR) technology to achieve the R1-quality effluent desired. This advanced wastewater treatment system combines rugged, hollow-fiber ultrafiltration membranes with biological processes, resulting in high-quality effluent and reduced chemical consumption. As specified by the membrane manufacturer, the MBR required 2-mm screening in front of the membranes in order to protect them from clogging and damage.
“Protecting the membrane is critical in these types of MBR systems,” said Kenny Oyler, director of Monster separation systems for JWC Environemntal. “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 completely new separate screening facility downstream from the existing installation to accommodate the new screens. But in working with JWC, the need for a separate screening structure was eliminated.
“With JWC’s help, we found a different way of using the existing infrastructure, which enabled us to replace the old 6-mm screens with the new 2-mm ones in the same channel,” White said. “This was a significant design change that saved about $1 million in infrastructure and screen costs.”
Aqua Engineers selected JWC Environmental’s Bandscreen Monster and Screenings Washing Monster as the equipment most suitable for the project.
“JWC’s Monster screens could handle the 15-mgd-per-screen requirement for storm-surge capacity and were priced less,” White said. “The stainless steel material is also more desirable for the humid environment. Ultimately, though, it was the fact that JWC’s screens could fit the existing channel like a glove that really won out. Other companies offered custom capabilities up to a point, but were still too large and required channel improvements.”
“The screen’s retrofit ability was key to the installation success,” Oyler said. “It was absolutely critical that we fit the screen into the existing envelope without making any changes to the concrete or any other structure. When the equipment arrived at the scheduled time, we were able to put it right into the channel without any modifications. The smooth operation pleased everyone involved.”
The Bandscreen Monster offers high capture rates and is able to remove a wider variety of solids, particularly small solids, trash and hair. It is frequently specified to protect high-tech MBRs so they can run more efficiently and with less maintenance. 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.
This self-contained, hopper-fed system grinds, washes, compacts and dewaters screenings. The removed solids contain up to 50% dry solids, are 80% compacted and are significantly lighter and cleaner than typical screened solids. This unique process of grinding prior to solids separation removes virtually all of the soft organics (fecal) from the discharged product, which reduces odor and landfill costs.
In comparison to the previous screens used prior to the upgrade, which only dewatered, the combined equipment collects, washes and grinds the screenings to produce a product that is relatively dry and free of organic products. Not only did the screens reduce the size of materials passing through the screen from 6 mm to 2 mm, but they also eliminated the odor, resulting in a better quality of waste product going to the landfill.
Using the latest water treatment technologies available from GE and JWC Environmental, Aqua Engineers improved the local water quality and made more than 1 billion gal of high-quality, recycled water a year available for beneficial nonpotable uses.
The Schofield Barracks plant upgrade enabled the plant to provide premium-quality recycled water to irrigate lawns, golf courses, parks and other sites on base, positively affecting the nearly 28,000 military personnel, their families and civilians who work on the base and nearby.
Aqua Engineer’s President and Chief Executive Officer Eassie Miller praised the team effort involved in completing the upgrade, which has turned the plant into an asset and made it the largest privately owned R1 facility in Hawaii. “The upgrade enables the military to conserve water, decrease pollution and contribute to sustainability goals,” Miller said.
U.S. Army Garrison, Hawaii (USAG-HI), was also enthusiastic about the project goals and results. “We’re committed to doing the right thing for the right reason,” said Col. Howard J. Killian, former commander, USAG-HI. “Everything has value, even wastewater; it’s just a matter of figuring out how to use that value. The wastewater treatment facility is just one example of how we’re trying to capture that lost value.”
The Schofield Barracks wastewater treatment facility upgrade was awarded a 2007 Global Ecomagination Leadership Award for employing the latest technology to achieve significant environmental and operating improvements to meet community needs.