In response to the growing water demand in the northern portion of the Des Moines metropolitan area, Des Moines Water Works (DMWW) is in the final phase of constructing a new water treatment plant on NW 26th Street, just south of NW 66th Avenue. The plant is nearing completion and should be in service this fall.
The Saylorville water treatment plant will use technology different than the two current water treatment plants. The treatment process will include ultra filtration (UF) membranes followed by split treatment through reverse osmosis (RO) membranes. The first treatment step will be oxidation to precipitate the dissolved iron and manganese in the shallow groundwater. The water will then go through the UF membranes which will filter out all of the particulate (undissolved) material in the water.
After filtration, part of the water will go through the RO membranes and some of the water will bypass the RO membranes. The RO membranes have smaller pores than the UF membranes and are able to filter out dissolved material in the water. The primary removal targets for the RO membranes are hardness (calcium and magnesium ions) and nitrate.
The ratio of water that is sent through versus around the RO membranes will be set to match the hardness of the water treated at the two existing water treatment plants and to ensure the nitrate concentration in the finished water is below the limit for drinking water. DMWW is excited to begin utilizing membranes for water treatment to compare with the operation and maintenance of a membrane plant with the two current lime softening plants.
The treatment capacity will be 10 million gallons per day (MGD) and the plant can be expanded in steps to 20 MGD by adding additional UF and RO membrane units.
Check back with us here on the blog for more updates.