The Navajo Tribal Utility Authority has agreed to bring six wastewater treatment facilities into compliance with the federal and Navajo laws in...
England’s wastewater system dates from the Victorian era, but in recent decades has undergone significant overhauls. The industry put in place advanced new treatment technologies in order to meet higher government standards. Yorkshire Water and its Wakefield-Calder Vale treatment plant are a stunning example.
The facility has undergone major overhauls and in September 2002 the plant’s headworks was significantly upgraded with three Finescreen Monsters® to reduce the amount of solids entering the system.
“Prior to the construction, the works consisted of two bar screens with 25 mm thickness between the bars,” said Andy Poyner, the plant’s senior engineer. “Installation of the finescreens has reduced the amount of screenings found downstream of the headworks. The primary tanks and the sludge pumps have been able to operate more efficiently.”
Two of the screens handle 48 mgd of flow with one acting as a back-up. The Finescreen incorporates an endless band of stainless steel screening panels with 6mm perforations. A 3mm perforation is also available Panels are securely fastened to two heavy duty chains, each with a 15,000 lb capacity and driven by an electric motor and gear unit.
Under water, the chain tracks in high density plastic shoes, eliminating problems associated with sprocket designs, and it is available in a variety of materials, including stainless steel. The heavy duty roller chain features an eight inch pitch.
A two-stage cleaning process, which includes a modular brushing system and spray jets at six inch centers, each projecting four gallons per minute, ensures that panels remain free flowing and clean. Debris collected on the panels is sluiced to a compactor.
“The bar screens obviously let far more material through,” said Poyner. “The Finescreens have been working just fine.”
The Finescreen Monster’s® advanced design incorporates unique side frame cutouts and results in low head loss, a result confirmed by testing at the U.K. Water Industry Research group. Each panel is fitted with an Ultra High Molecular Weight plastic seal plate, which correspond with fixed side seals in the side frames, providing clearance of less than 1mm, thus ensuring maximum capture efficiency. The Finescreen Monster can accommodate channel widths to eight feet and depths to over 30 ft.
The upgrades at Calder Vale are part of a multi-million dollar environmental improvement program run by England’s private water companies. Local rivers, including nearby River Calder, are benefiting from the advanced wastewater treatment, which also includes UV disinfection. Yorkshire Water reports that the region’s coastal bathing water is the cleanest it has been in decades and the company is exceeding the strict standards set by the European Union.
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]