Fine Screen Retrofit Cuts Upgrade Costs for New MBR Facility
Hawaii typically conjures up images of azure seas, swaying palms and pristine beaches.
By Cynthia Guardia
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 the natural beauty, keep up with growth and ensure regulatory compliance, the Schofield Barracks, one of Hawaii’s largest military bases at 17,000 acres, recently upgraded the 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 spear-headed by Aqua Engineers of Kauai following a contract with the Federal government to privatize the Barracks’ treatment plant. Key to the project’s ultimate success was technology from JWC Environmental, Costa Mesa, CA, and GE Water and Process Technologies, a unit of General Electric.
Wayne White, Aqua Engineer’s Plant Engineer for Schofield, explained that goals for the upgrade were specific and challenging.
“We needed to upgrade the plant from R2 to R1 quality effluent suitable for re-use in agriculture and irrigation applications,” White said. “We also needed to increase plant capacity by roughly 30% – from 3.2 to 4.2 million gallons per day. 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 General Electric’s ZeeWeed® Membrane Bioreactor (MBR) technology to achieve the R1 quality effluent desired. This advanced wastewater treatment system combines hollow-fiber, ultrafiltration membranes with biological processes resulting in superior effluent quality and reduced chemical consumption. As specified by the manufacturer, the MBR required 2mm 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, the manufacturer that 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 screening facility downstream from the existing installation to accommodate the new screens. However, 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.”
While a number of screen manufacturers were considered, 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 million gallons per screen requirement for storm surge capacity and were priced less than competitive screens,” 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,” he said. “Other companies offered custom capabilities up to a point, but were still too large and would require channel improvements.”
A pair of Bandscreens remove rags, trash and hair as small as 2 mm in order to protect the membrane bioreactor.
The Bandscreen Monster offers high capture rates and is able to remove a variety of solids, particularly small solids, trash and hair. It is frequently specified to protect Membrane Bioreactors. 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.
Once removed the captured trash is then cleaned, compacted and dried before dropping into a dumpster.
The self-contained, hopper-fed cleaning 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. The process of grinding prior to solids separation removes virtually all of the soft organics from the discharged product, which reduces odors and landfill costs.
Using the latest water treatment technologies available from General Electric and JWC Environmental, Aqua Engineers improved the local water quality and made more than one billion gallons of high quality, recycled water a year available for beneficial non-potable uses. The Schofield Barracks’ wastewater treatment plant upgrade enabled the plant to provide premium recycled water of R1 quality to irrigate lawns, golf courses, parks and other sites on base, positively affecting the nearly 28,000 military personnel and their families, and civilians who work on base and nearby.
Aqua Engineer’s president and CEO, 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 R-1 facility in Hawaii. “The upgrade enables the military to conserve water, decrease pollution, and contribute to sustainability goals.”
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.
About the Author:
Cynthia Guardia is the owner of Cia Communications Inc., a business-to-business communications firm based in Anaheim Hills, CA. She may be contacted at cynthiaguardia@