Coming soon: softer water
Fort Dodge prepares to turn on reverse osmosis system
Towering racks full of white tubes fill the new wing of the John W. Pray Water Treatment Plant in Fort Dodge, where the mechanical roar of operating pumps can make having a conversation tough.
Those noisy pumps push water through membranes inside the tubes at high pressure. When the water comes out of those tubes, it is free of the calcium, magnesium and other substances that make water hard.
The end result: The water coming out of every faucet in Fort Dodge will not be as hard as it once was. It will not be true soft water, but residents will not have to use their water softeners as much after all of this new equipment is fully operational in early May.
All of the tubes, filters and pumps make a water treatment process called reverse osmosis possible.
Construction of the new reverse osmosis setup in Fort Dodge began in April 2019. After multiple delays caused by the COVID-19 pandemic, the system is expected to start running next month.
How does it work?
Inside each of the white tubes is a plastic membrane filled with many microscopic holes. City Engineer Tony Trotter said each hole is smaller than a virus.
He said when water is pumped into the tubes, only water molecules can pass through the holes. The molecules of calcium, magnesium, chloride and other substances are prevented from passing through, creating water with reduced hardness.
How will it impact residents?
The hardness of water is measured in grains. The water in Fort Dodge now has 26 to 27 grains of hardness, according to Trotter.
He said when the reverse osmosis system is running, the water will have about 7 grains of hardness.
Trotter said residents who have water softeners will use a quarter of the salt that they do now.
He said they will have to reset their water softeners.
”It is essential for customers to do that because that is the whole point of this project to reduce the chlorides,” Trotter said.
He said water bills will increase, but that will be offset by the savings realized by not having to buy as much salt for the softeners.
He added that everything from water heaters to coffee pots will last longer after the softer water starts flowing
Why do this?
The Iowa Department of Natural Resources directed the city to reduce the amount of chlorides in treated water discharged into the Des Moines River from the wastewater treatment plant. There is no practical way to get the chlorides out during the wastewater treatment process.
Engineers determined that the chlorides come from salt used in water softeners. The reverse osmosis system was devised to reduce the need for that salt.
How much did this cost?
Woodruff Construction LLC, of Fort Dodge, had a $19,970,000 contract to build the addition to the plant.
The reverse osmosis machinery was purchased from Harn RO Systems Inc., of Venice, Florida, for $3,343,500.
Paying for the new system will add about $7 a month to residential water bills. A portion of that increase has already been added to water bills.
How the plant works now
Step 1 Water coming into the plant from wells goes through aerators to add oxygen to it. That oxidizes iron in the water, making it easier to remove the iron.
Step. 2: Water trickles through eight-foot deep filtration basins filled with sand, gravel, and river rock. Oxidized iron and other materials stick to the sand and rock.
”This is a very tried and true method of filtering water,” City Engineer Tony Trotter said.
Step 3: Add a small amount of chlorine to the water to kill any bacteria, then pump it out into a closed reservoir and eventually, the water mains.
How the plant will work with reverse osmosis
Step. 1: Aerators
Step 2: Filtration basins
Step 3: Force water through plastic membranes in reverse osmosis system.
Step 4:Add a small amount of filtered water that hasn’t gone through reverse osmosis. Trotter said that will prevent the reduced hardness water from leaching materials from the water mains.
Step 5: Add substances called chloramines to kill bacteria, and pump into reservoir.