Screening System Eliminates Clogging from Membrane Bioreactor

In order to keep up with the rising population, increased demands and tougher regulatory requirements, the U.S. Army Schofield Barracks, Hawaii’s largest Army post, recently upgraded its wastewater treatment facility. 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, California, and GE Water and Process Technologies, a unit of General Electric Company.
PROJECT GOALS
The goals for the facility upgrade were both specific and challenging. The plant needed to go from R2 quality effluent to R1 quality effluent suitable for reuse in agriculture and irrigation applications, and the crew also needed to increase plant capacity by roughly 30 percent — from 3.2 to 4.2 million gallons (12.1 to 15.9 million liters) per day. Another requirement was providing a surge capacity of 15 million gallons (56.7 million liters) per day to handle Oahu’s frequent rainstorms, which further increased the design challenge. On top of that, the total project needed to be completed without major capital expenditure.
SOLUTION AND RESULTS
Aqua Engineers recommended General Electric’s ZeeWeed® Membrane Bioreactor (MBR) technology to achieve the R1 quality effluent desired. This advanced wastewater treatment system uses rugged hollow-fiber, ultrafiltration membranes in order to protect the system from clogging and damage.
JWC Environmental recognized that protecting the membrane is critical in these types of MBR systems. The Bandscreen Monster was used because it provides excellent membrane protection, since the entire screening operation is done on the inside of the screen. This prevents any debris from passing 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. However, in working with JWC, the need for a separate screening structure was eliminated, enabling the facility crew to replace the old 0.23 inch (2 millimeter) screens with the new 0.07 inch (2 millimeter) ones in the same channel. This significant design change saved about one million dollars in infrastructure and screen costs.
MONSTER SCREENS AT WORK
While a number of screens were considered, Aqua Engineers selected the Bandscreen Monster and Screenings Washing Monster from JWC Environmental as the most suitable for the project. The screens are well-equipped to handle the 15 million gallons (56.7 million liters) per day per screen requirement for storm surge capacity and were priced less than competitive screens. The stainless steel construction is also more desirable for the humid environment. However, one of the largest benefits is the fact that the Monster screens could fit the existing channel without modification, something other competitors were not able to offer.
This retrofit aspect of the screen systems was key to the installations success, as it was absolutely critical that the screen fit into the existing envelope without making any changes to the concrete or other structures. The equipment arrived at the scheduled time, and the crew was able to put it directly into the channel without any modifications. This smooth transition also was a large time-saving benefit.
The Bandscreen Monster offers high capture rates and is able to remove a wider variety of waste solids, particularly small solids, like trash and hair, better than traditional screens. The product is particularly specified to protect high-tech Membrane Bioreactors so they can run more efficiently and with less maintenance. Unwanted solids are captured on the UHMW plastic panels with 0.07, 0.11, or 0.23 inch (2, 3 or 6 millimeter) openings and lifted to the discharge level where a spray system washes solids into the Screenings Washer Monster, used for washing, dewatering and compacting.
Used in conjunction with the Bandscreen Monster, the Screenings Washer Monster was also employed at the Schofield Barracks wastewater treatment facility. This self-contained, hopper-fed system grinds, washes, compacts and dewaters screenings. The removed solids contain up to 50 percent dry solids, are 80 percent compacted and are significantly lighter and cleaner than typically screened solids. This unique process of grinding prior to solids separation removes virtually all of the soft organics from the discharged product, which reduces odors and landfill costs.
A THOROUGH UPGRADE
In comparison to the previous screens used prior to the upgrade, which only dewatered the material, the combined Monster systems 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 the materials passing through from 0.23 to 0.07 inch (6 to 2 millimeter), they also eliminated the odor, resulting in a much better quality of waste 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 gallons (3.7 billion liters) of high-quality, recycled water a year available for non-potable uses.
The Schofield Barracks wastewater treatment 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 base and nearby.
The upgrade has turned the plant into the largest privately owned R-1 facility in Hawaii, and enables the military to conserve water, decrease pollution and contribute to the sustainability goals of the facility. After the upgrade was completed, the treatment facility was awarded a Global Ecomagination Leadership award for employing the latest technology to achieve significant environmental and operating improvements to meet community needs. ■
About The Author
Kevin Bates is the global marketing director for JWC Environmental based in Costa Mesa, California. JWC Environmental is a world leader in solids reduction and removal for the wastewater industry with its Muffin Monster grinders and Monster screening, compaction and washing systems. Bates has more than twenty year of experience working with global industrial leaders to solve challenging technical problems spanning a wide range of markets including wastewater, construction and mining. For more information, visit www.jwce.com.