Microfiltration Water Treatment Facility
Location: Westminster, Colo.
Client: City of Westminster
Burns & McDonnell/Garney LLC was selected to provide design-build services for the new 15 MGD City of Westminster Microfiltration Water Treatment Facility. The process utilizes enhanced conventional treatment with plate settlers prior to the microfiltration membrane units with the flexibility to bypass pretreatment and utilize the raw water pressure for direct treatment during periods of low turbidity raw water. By providing pretreatment, the allowable flux of the membrane units was increased by 50 percent.
With cost rising substantially, the City of Westminster decided to pursue a design-build procurement option and solicit proposals from prequalified firms. The Burns & McDonnell/Garney team was selected to design and construct the facility. The unit price per gallon was reduced from $2.70 per gallon to less than $1.33 per gallon.
The City of Westminster Northwest WTP is sized for a hydraulic capacity of 20 MGD and allows space to accommodate future process equipment. The membrane system is designed to utilize one skid for either secondary recovery or to recycle membrane backwash water to the front of the pretreatment process. This allows the city to operate either in a high recovery mode or higher process flow mode incorporating flexibility into the system. The project also includes a 2 MG clearwell with a 15 MGD high service pump station (expandable to 20 MGD).
The city took an innovative approach to their new Water Treatment facility by utilizing:
- The design-build procurement process:
- Overall project costs are at a competitive unit cost per gallon $1.33/gallon for a membrane treatment facility.
- Expediting project schedule to include a design and construction schedule of 20 months.
- Enhance project quality by selecting a contractor based on qualifications and selecting a strong engineer/contractor team, Burns & McDonnell/Garney.
- Providing a single-source accountability and responsibility of the design-build team to the City of Westminster.
- Enhanced conventional pretreatment with membrane filtration:
- By using settled water in lieu of raw water, membrane flux capacity increased by 50 percent.
- Pretreatment provides maximum operational flexibility including flexibility to treat changing water quality, enhancing flux, providing a buffering zone prior to the membranes, and enhancing TOC removal capabilities.
The city's approach reduced costs, expedited the schedule and provided the innovation, quality, reliability and excellence on the new Northwest Water Treatment Plant.
- Increased capacity with pretreatment
- Secondary recovery to greatly minimize wash water loss
- Membrane cleaning enhancements to minimize cleaning downtimes and enhance cleaning performance
- Beta testing of the Hach Medusa laser turbidimeter to allow nearly continuous online membrane integrity testing and possibly reduce downtime associated with pressure decay tests
- Providing for the future installation of ultraviolet light to provide an additional barrier for microbiological protection
"The design-build team of Burns & McDonnell and Garney Construction is building a 15 million gallon per day (MGD) plant for 75 percent of what we had originally anticipated spending on a 10 MGD facility."
— City of Westminster