Sun Prairie Village County Water and Sewer District is a community located about 8 miles northwest of Great Falls, Montana. The community is a residential development constructed in the late 1970s. Most of the water and sewer infrastructure was installed during the initial development of the community. Currently, the District is home to approximately 1,500 people.
Like many communities across Montana, Sun Prairie Village County Water and Sewer District is located in an area where access to quality drinking water is limited. For years, the community has utilized aging groundwater wells drawing water from an aquifer that yielded low-quality water. In the last several years the District has taken steps to replace their existing water supply and improve their water quality.
Today, the District has four new groundwater wells and a new reverse osmosis water treatment plant that has the capability to produce over 690,000 gallons per day of high-quality drinking water. The treatment process includes both oxidation-filtration and reverse osmosis to produce water for the community.
During the planning stage of the project, the Preliminary Engineering Report (PER) identified the recommended water source as a pre-glacial alluvial aquifer that generally lies 160 to 200 feet below ground surface in the area of the District. Unfortunately, the recommended water source has very high total dissolved solids (TDS), up to 5,400 mg/l. Due to limited options, the District ultimately selected moving their well field to a County Park located next to their office and completing the wells in the pre-glacial alluvial aquifer.
High TDS in the water source required water treatment to improve quality. Ultimately, the PER selected reverse osmosis as the preferred method of water treatment. Because reverse osmosis membranes can be fouled with iron and manganese, pretreatment to removed iron and manganese was required. The PER evaluated pretreatment and selected oxidation-filtration. During pilot testing of the preferred treatment alternative, the removal of manganese (pre-treatment) proved to be challenging. After piloting several configurations using various pretreatment methods of oxidation-filtration, pyrolusite media combined with a relatively high dose of chlorination (17 mg/l) was selected. As a result of the piloting, the treatment equipment vendor proposed pre-treatment method had to be changed from a greensand media to pyrolusite media to provide effective and long term manganese removal.
The design of the treatment system began in the fall of 2014 and in the fall of 2015 construction began on the project. In the summer of 2016, the project was substantially complete. The final water supply system provides approximately 480 gpm of high-quality drinking water to the District. The final treated water has less than 350 mg/l TDS and meets all primary and secondary maximum contaminant limits required by the EPA.
Our team is always available to answer questions. If you would like to speak with a water specialist, please contact us for more information.
Todd K. Kuxhaus, PE