Scottish Water, the U.K.’s fourth largest water treatment organization, recently installed three Bandscreen Monsters® at their Hawick treatment plant to handle inorganic solids found in wastewater and stormwater. The Bandscreen, sold in North America by JWC Environmental, is an easy-to-install automated system designed for fine screening applications.
Prior to installation of the Bandscreens with six millimeter perforations the plant had simple bar racks with one and one-half inch spacings, which let too many solids enter the plant. The spacing did not comply with government regulations.
“For our discharge consent with the Scottish Environment Protection Agency we have to screen every flow to 6mm,” said Douglas Donald, an engineer with Scottish Water. “So we had to look at various options and the screen that was most suitable for the site was the Bandscreen. They readily retrofitted to the works that was here.”
The Bandscreen Monster’s in-to-out configuration eliminates carryover or bypass, making it ideal for sensitive applications, such as in membrane plants. Screen panels are manufactured from six millimeter to nine millimeter thick high density plastic, ensuring strength and rigidity, while virtually eliminating hairpinning. Panels are easily replaced and are available in two millimeter, three millimeter or six millimeter diameter openings.
“(The new screens) enabled us to replace the old screens and the bypass screen, which was hand raked,” said Donald. “We have vastly improved the screening potential of the works.”
The heavy duty roller chain is available in eight inch, twelve inch or eighteen inch pitch, to suit a wide range of flow and channel requirements. Under water, the chain runs in high density plastic guide shoes, avoiding the many problems associated with underwater sprockets, and it is available in a variety of materials, including stainless steel.
Each panel is fitted with a stainless steel seal plate, which correspond with fixed ultra high molecular weight plastic side seals in the side frames to provide clearance of less than one millimeter, thus ensuring maximum capture efficiency. The high pressure spray bar system features self-cleaning nozzles spaced at six inch centers, each projecting seven gallons per minute.
The Bandscreen Monster® system can accommodate widths to 14 ft and depths to 45 ft. At Hawick, two screens handle wastewater, while the third handles stormwater overflow. Screenings are channeled to a compactor.
JWC also offers the Screenings Washer Monster as a screenings compactor. The SWM’s unique grinding, washing, screening, compacting and dewatering system generates the industry’s cleanest discharged screenings. This can help reduce odors and lower transportation and landfill charges. The combined screen and washer-compactor package is called the Monster Separation SystemTM.
The new Bandscreens also improved the plants handling of stormwater which previously went unscreened. This upgrade is part of Scottish Waters overall effort to improve its 643 treatment plants. The upgrades were made to meet higher standards, including the Scotland Urban Waste Water Treatment Regulation of 1994 which directed authorities to ensure by 2005 that all discharges receive the appropriate treatment before flowing to the sea.
About the author: Fritz Egger is the director of marketing for JWC Environmental, Costa Mesa, Calif. He can be reached at 714/428-4610 or by e-mail at [email protected]
