Twin Cities WRS Seminar

Chloride Contributions From Water Softners and Other Domestic, Agricultural, and Industrial Sources to Minnesota Waters


Alycia Overbo
WRS Ph.D. Candidate

October 12, 2018


Elevated chloride levels in surface waters can negatively affect aquatic life, plant life, and quality of drinking water sources. With numerous water bodies in Minnesota impaired for chloride, chloride is an emerging concern across the state. Previous research has shown that use of deicing salts contributes large amounts of chloride to surface waters, but chloride discharge from household water softener use has not been quantified. A chloride budget was developed for the state of Minnesota to estimate the amount of chloride discharged from household water softeners as well as other domestic, environmental, and industrial sources. The analysis employed multiple types of data, including water quality data, spatial data, effluent monitoring data, and responses from a statewide survey of water conditioning professionals. Annual chloride mass contributions were estimated for the following sources: household water softener use; human excretions; household appliance use; background concentrations in drinking water; atmospheric deposition; deicing salt use; dust suppressant use; fertilizer application; industrial discharge; and livestock excretions. The results of the statewide chloride budget showed that household water softener use is a major chloride source, comparable to chloride from fertilizer use and livestock excretions. Domestic sources accounted for only a fraction of chloride discharged to wastewater facilities, suggesting that commercial organizations and industries may be substantial chloride sources. The results suggest that reducing chloride from water softening salt is a viable solution to decreasing chloride levels in Minnesota waters.