Morris's New Water Treatment Provides Clean Water for Cheaper; Cut's Chloride Pollution in PDT

This past summer, a German intern from the University of Applied Science in Munster stayed in Morris and conducted an in depth study of the new water treatment plant to find out whether or not it was having the predicted impact. His report came out at the end of last year and I will summarize it here. If you are interested in the full report, you can find it and more information about our water under the News and Announcements tab on the City website

As many people may remember, Morris used to have a problem with its water. The water was exceedingly hard when it came out of the ground requiring people all over Morris to have water softeners in their houses to soften the water at the source of consumption. Water coming out of the ground in Morris has around 45 grains of hardness per gallon making it some of the hardest water in the country, for reference, 10 grains of hardness per gallon is considered to be very hard water. Reducing this hardness has a couple of goals. While hard water is not considered un healthy to drink it can cause issues with our water distribution systems. Buildup of calcium and magnesium in underground pipes can cause falling water pressure and even water main breakages. And harder water leaves white spots on surfaces that come into contact with the hardened water. All of the softening required for a city the size of Morris lead to a major problem though with our wastewater too. Chloride, which is considered toxic to many aquatic ecosystems, was being introduced into our water in massive quantities in order to soften it and it was having adverse effects on our ecosystems in the Pomme de Terre river and beyond. In order to limit the amount of chloride going into our water resources, the MPCA, or Minnesota Pollution Control Agency, introduced stricter guidelines for how much chloride could be in municipal discharges of wastewater to rivers around the state. These guidelines required set a limit of 400mg of chlorine per liter. Before the new water treatment plant was built, Morris’ wastewater exceeded this number by double, regularly registering 800-1000 mg/Liter of chloride. The city was faced with two choices, fight the MPCA’s new requirement and risk years of legal battles, or take action to build a centralized water treatment system that doesn’t use chloride as a softening agent.

Morris chose to embark on a project to build this new and modern water treatment plant that used soda ash and lime to soften water instead. By centralizing the water treatment for the entire city, a different technique was able to be employed to soften the water. The plant, which cost roughly $19 million dollars to construct was covered partially by grant funding. The grant covered $12 million dollars of the construction of the plant. The process reduces the hardness of our drinking water by precipitating out the magnesium and calcium by introducing the soda ash and lime. This is done through a process where raw ground water is pumped from 6 60-80 ft deep wells which access the aquifer that our city sits atop. Then this raw water is aerated with unfiltered outside air. This accomplishes two goals. By mixing the raw water with air, It adds oxygen to the water which helps to diminish the rotten egg smell. It also oxidizes dissolved iron and manganese for further extraction. Next the water comes into contact with a solid contact filter. This brings the water into contact with the soda ash and lime allowing the agents to react with the magnesium and calcium in the water and cause them to form solid flakes which can then be filtered out. The calcium reacts with the soda ash and lime to create calcium carbonate (CaCO3) and the magnesium reacts to form magnesium hydroxide (Mg(OH)2). This water then flows to sand filters which will filter out the solid flakes of magnesium hydroxide and calcium carbonate. The lime sludge that is formed at the bottom of the contact filters is pressed of all of its water and dropped into a semi-truck which twice per week sends the lime cakes to be spread on fields as a fertilizer. The plant produced 45 tons of this lime cake each week. The treated water then flows to a ph balancer which bubbles CO2 through the filtered water. This helps to reduce the ph from 11.5 to 9.5. Then the water flows through sand filters to remove the precipitated flakes of calcium carbonate and magnesium hydroxide. After this step, some chloride is added to the water, around 1 mg per liter. This small amount helps to kill any bacteria in the water. Fluoride is also added to the water which helps to make teeth stronger and more resilient to cavities. From here the water flows to one of three clear wells at the WTP which can store around 500,000 gallons of water. The plant, which process around 1,000 gallons of water each minute, would need to run for 9 hours to fill this capacity. From the clear wells, water flows to the water tower. The water tower serves two purposes. It holds an additional 750,000 gallons of water storage. It also increases the pressure of the water to make sure it reaches all areas of Morris. In fact, it raises the water pressure so much that this clean water will flow from Morris all of the way to Alberta without any additional pumps.

The plant costs around $500,000 dollars to operate each year. This figure can be broken down even further, around $300,000 is spend on the chemical inputs for the plant. This includes the fluoride, chloride, soda ash and lime. A little over $95,000 is spent each year to pay the operators of the plant and $65,000 is spend on electrical energy. This third cost is one that we are hoping to further reduce in the future through renewable energy installations.

So, did it all work? All signs point to yes. The new water treatment plant has lowered the concentration of chloride in our wastewater from over 800 mg/Liter to around 200 mg/Liter which has continues to drop as we have continued testing. Because the plant did what it was supposed to do, reduce chloride in the water and softening the water in a central plant, Morris is safe from financial and legal challenges from the MPCA and all of Morris is able to benefit from clean and soft water.

My position with the City of Morris is funded through a grant from the ENRTF. To learn more, head to https://www.legacy.mn.gov/environment-natural-resources-trust-fund

First published in Stevens County Times 1/24/2023.