Cold Climate Surface Water Membrane Water Treatment Plant Operation Considerations

The City of Fargo owns and operates a 15 million gallons per day (MGD) integrated membrane water treatment plant (MWTP), which is the largest and most sophisticated surface water membrane treatment plant in North Dakota, and potentially the upper Midwest. The MWTP has been a demonstration site since it was constructed. Fargo MWTP’s major treatment process consists of three-stage flocculation/coagulation/sedimentation, ultrafiltration (UF), reverse osmosis (RO), ozone, and GAC filtration (RO bypass). The City blends the finished water from the MWTP and its 30 MGD lime softening WTP to serve three cities with a combined population of more than 175,000 people. The 15 MGD MWTP has been a great asset to the City of Fargo since its commissioning because it allows the City to continue using the Sheyenne River as the primary source water during times of drought, which Fargo experienced in 2021; improve the finished water quality; and address unexpected water quality changes in the Red River. Fargo MWTP treats one of the most difficult surface waters in the nation and the membrane systems have been challenged since the first day of commissioning: pretreatment upsets (poor settling during cold water season), high operating pressures in winter and spring, severe organic/bio fouling, and rapid differential pressure (DP) rising in summer. The plant staff has been constantly optimizing and improving the plant operation to consistently produce high quality and safe drinking water. This manuscript documents several unique optimization trials to share the knowledge and experiences with the field.

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