SURFACE WATER TREATMENT PLANT
City of Thief River Falls, MN
APPLICATION
Surface Water Treatment
TREATMENT SYSTEM
Gravity filter upgrade
FEATURES
BLEU™ underdrain
Simul-Wash™ backwash system
Reduced backwash waste
State-of-the-art technology
PROJECT
The City of Thief River Falls, Minnesota was in need of a water treatment plant upgrade including the replacement of the underdrain, media, and troughs in four existing gravity filters. The plant was originally built in 1954, with a refurbishment of filters and controls in 1980. The plant had been well maintained, but the equipment had reached the end of its life. The project provided an opportunity for The City to upgrade its system with the latest technology, including stainless steel underdrains and simultaneous air and water backwash. Tonka Water proposed the BLEU™ underdrain paired with the Simul-Wash™ backwash system, which allowed for all filter components to be supplied by one manufacturer. Tonka Water was selected to supply this equipment for the gravity filter upgrade.
PROCESS
The City treats a river water source using lime softening followed by media filtration. The water flows through solids contact clarifiers, then into media filters to capture any unsettled solids. The filter is bedded with dual media, directly retained by the BLEU™ underdrain system. During backwash, water flows back through the underdrain laterals while air is applied simultaneously through separate slotted pipes between them. Adding air between the laterals ensures that the media is uniformly cleansed, eliminating dead zones. The Simul- Wash™ backwash troughs prevent media loss while sustaining a simultaneous air and water backwash. Only one trough is required per twelve-foot wide filter due to its unique design.
SIMUL-WASH™ BACKWASH SYSTEM
The treatment plant also includes Tonka Water’s value-added Simul-Wash™ backwash system. This unique backwash system uses air and water simultaneously, at sub-fluidized rates, within the collapse-pulse range for the selected media, resulting in the most effective means of backwashing granular filter media1. Tonka Water’s media rejecting Simul-Wash™ trough enables the air and water backwash cycle to continue indefinitely without media loss. This results in optimal filter cleaning efficiency and prolonged filter runs while saving approximately 50 percent of backwash wastewater compared to conventional methods.
