Long Term Performance Comparison: Side by Side Pressure & Submerged Ultrafiltration Plants Treating Surface Water

The Town of Erie (Town), Colorado operates a water treatment plant with both pressurized and submerged ultrafiltration systems side by side. There are few facilities world-wide that have side by side systems limiting the ability for actual operational comparisons. This paper will provide a comparison of the pressure and submerged systems operating on the same pretreated surface water sources since the module replacement on both systems in 2014 and 2015. Operating regimes will be compared including backwash efficiency, cleaning protocols and efficiencies, and integrity results. In addition, permeability will be compared for each system along with a characterization of the differences in electrical and chemical operating costs per year. The Town recently expanded the 9.9 million gallons per day (mgd) Lynn R. Morgan Water Treatment Facility (WTF) to 16.65 mgd. The WTF was originally constructed in 1999 with Memcor (Evoqua) pressure microfiltration units followed by granular activated carbon contactors for occasional taste and odor control, disinfection, and high service pumping. In 2001, larger pressure microfiltration skids were added to expand the facility to a capacity of 5.4 mgd with six total pressure skids. In 2006, the facility was expanded to 9.9 mgd with the addition of rapid mix, four-stage flocculation and sedimentation using plate settlers to pretreat the original pressure microfiltration along with new submerged ultrafiltration. This submerged system consists of six 2.25 mgd cells of Memcor (Evoqua) ultrafiltration membranes. The three additional submerged cells were expanded in 2020 to achieve a total WTF capacity of 16.65 mgd, with the largest train out of service. The original pressure and submerged membrane modules were replaced in 2014 and 2015, respectively. Aluminum sulfate is used as the primary coagulant, powdered activated carbon and potassium permanganate are added for seasonal taste and odor control upstream of the pretreatment system.

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