Minnesotans depend on salt to soften our water and remove ice from our roads, sidewalks, and parking lots. But we’re often using more than we need and that’s harming the environment; data show salt (chloride) concentrations increasing in both surface waters and groundwater across the state.
The MPCA and its partners have been working for some time to reduce the use of deicing salt. But we need to do more to reduce salt from water softening. Twenty-three percent of all chloride pollution comes from wastewater treatment plants. Roughly 65 percent of all chloride passing through wastewater facilities — 136,000 tons of chloride annually — comes from residential and commercial water softening processes. In rural areas, wastewater discharges are often the primary source of chloride in lakes and streams.
Softened water protects certain industrial equipment or residential appliances from scaling and mineral buildup. Older in-home softening units are less efficient than newer models, meaning they use and discharge more salt than they need to. Common industrial sources of chloride include food processing facilities, manufacturing, pipeline terminals, biofuel facilities, and groundwater treatment systems.
Some cities soften water centrally before it’s distributed to home and businesses, using processes that don’t require salt. Other communities are offering grants to residents to switch to more efficient water softeners. A key challenge is educating the public on the balance between necessity and preference with water softening practices.
Success story: City of Marshall
The City of Marshall discharges treated wastewater into the Redwood River, and as of 2016, the chloride concentration in the discharge was between 470 mg/L and 689 mg/L. The proposed limit for the City of Marshall was 261 mg/L. To address this reduction, the city hired a consultant to identify the major sources of chloride in wastewater and found that 75 percent came from residential, commercial, or industrial water softening.
Marshall Municipal Utilities evaluated options to further soften water at its water treatment plant; currently, it reduces hardness from 53 grains to 31 grains. The utility determined that updating lime slacking and providing soda ash treatment could reduce the hardness to 5-7 grains prior to distribution. The city then informed residents about the change, and a considerable number said they would turn off or reduce their use of in-home or on-site equipment if the city achieved the lower hardness levels.
Salt Symposium covers water softening, much more
The 20th annual Salt Symposium (to be live streamed this year on August 4-5) educates Minnesota professionals, including wastewater treatment operators, on ways to reduce chloride in Minnesota’s environment. Day 1 of the symposium will focus on chloride use in water softening, fertilizer, and dust suppressants. Day 2 will cover best practices and the latest developments in salt use optimization for those involved in winter maintenance. On Aug. 6, two free MPCA certification trainings will be offered online: Smart Salting for Roads and Smart Salting for Parking Lots and Sidewalks. Get more information on the Salt Symposium web page.