FARGO MEMBRANE WATER TREATMENT PLANT
Fargo, North Dakota
Source Water Quality ChallengesThe Fargo Water Treatment Plant (WTP) uses a combination of water from both the Red River and Sheyenne River, with the Sheyenne River being used nearly 40 percent of the time.
Unfortunately, changing water quality in the Sheyenne River was challenging the City’s ability to utilize this important water source because it contains high salt concentrations, including sulfates and bromide, which posed a significant treatment challenge to the existing Fargo WTP.
Date: 2010 – 2019
Client: City of Fargo
- Preliminary Engineering Report with K-T Decision Analysis
- Assisted in Securing Grant Funding
- Membrane Filtration and RO Help City Meet Water Quality Goals
Project Planning, K-T Analysis, and Preliminary DesignIn 2010, the City of Fargo retained AE2S to complete a Facility Plan to study treatment options and to conduct an extensive Pilot Testing Program, which began in 2011.
During the Facility Plan phase, a decision analysis tool referred to as Kepner-Tregoe (K-T) was used to help the City clarify the purpose, evaluate alternatives, assess risks, and decide about the future location for the new Membrane WTP.
Various “wants” such as stakeholder acceptance, treatment operations, system operations, and phasing considerations were targeted as key objectives. Each of these “wants” were weighted relative to each other and scored against a variety of alternatives to help identify the most desirable alternative.
One key factor of expanding adjacent to the current site over construction at a site located approximately nine miles from the current WTP was the staffing of the WTPs. At the current site, staff resources could easily be split between the current 30 MGD Lime Softening WTP and the 15 MGD Membrane WTP.
The Performance Score from the K-T analysis was normalized and combined with the normalized estimated construction costs to understand which alternative provided the biggest “bang for the buck.” Based on the results, the City expanded on the site adjacent to the current WTP.
Final design of the project commenced in 2013 and the Membrane WTP became operational in early 2019. The Facility Plan was submitted under the Drinking Water State Revolving Fund (SRF) program. AE2S assisted the City of Fargo with securing $30 million in grant funding, along with approximately $98 million in SRF loan funds, to help fund this project.
Treatment ProcessesThis project included the construction of a new Membrane WTP along with various improvements to the existing WTP. The Membrane WTP is capable of treating raw water from either of the City’s source waters with a treatment capacity of 15 MGD. Raw water is treated through pretreatment utilizing plate settlers to remove large suspended solids and provide the necessary pretreatment for the membrane system.
The membrane filtration consists of ultrafiltration (UF) and removes particulates and provides pathogen removal. Reverse osmosis (RO) is used to soften and reduce the sulfate concentrations, while primary disinfection is achieved using free chlorine in a contact basin with chloramines for secondary disinfection.
A portion of the UF filtrate flow can bypass the RO system and is treated for taste and odor utilizing ozone and granular activated carbon (GAC). Finished water from the Membrane WTP is blended with the finished water from the existing WTP before entering the clearwell and distribution system. A second standby generator was installed to allow the WTP to provide capacity for demands up to 25 MGD.
Regional Service Shortens Payback
Another consideration to help with the long-term capital improvements and expenses from the WTP was the installation of RO skid capacity to provide water to additional regional stakeholders. During the construction phase of the project, the City of West Fargo decided to be served water from the City of Fargo, an element that has significantly shortened the payback period of the additional skid.