Missouri River water from Lake Sakakawea is the primary water source for residents of Dickinson, North Dakota. Due to increasing demand in this community, an expansion of their existing water treatment plant was needed. The Southwest Water Authority made the decision to upgrade their overall system with a 6 MGD plant expansion. This would also allow for a phase-out of the existing treatment equipment. The current water treatment plant was using conventional treatment through clarification and filtration. The expansion applies membrane ultrafiltration (UF) rather than conventional media filters, utilizing up to date water treatment technology to better position the system for the future. Tonka Water, a U.S. Water brand was selected as the manufacturing partner on the project, providing a U-Flex™ ultrafiltration system.
Treatment begins with clarification and lime softening supplied by others. Water then flows through six membrane trains of thirty-six DOW Integrapac IDP-77 UF modules for removal of any remaining solids, while also providing a pathogen barrier. Assembled on-site into a self standing frame, this compact design does not require factory skid assembly of UF modules, providing additional cost savings. The membrane modules are packed with hollow fiber membranes, with water flowing from the outside to the inside and through the hollow fibers, while the rejected solids accumulate in the module. A secondary ultrafiltration system consisting of two trains, each with eighteen modules, is utilized for backwash recovery, where backwash water is treated and then blended with the incoming raw water. This reduces overall waste volumes and increases efficiency. Designed for redundancy, both UF systems allow for treatment of peak flow with one train out of service. Membrane filtration with UF provides a consistent barrier that rejects fine solids as well as pathogens and even viruses. Frequent integrity testing ensures a sound barrier in accordance with membrane module certification log removal.
The Tonka Water, a U.S. Water Brand treatment system has been effectively delivering high quality water. We are proud to have assisted the Southwest Water Authority in achieving its treatment goals.