Minnesota has a growing salty water problem that threatens its fresh-water fish and other aquatic life, despite being more than 1,000 miles from the nearest ocean. Salt — from chloride — can also impact groundwater used for drinking. It takes only 1 teaspoon of salt to permanently pollute 5 gallons of water. Once in the water, there is no easy way to remove the chloride.
A Chloride Work Group, made up of volunteers from municipalities across Minnesota, presented a policy proposal to the MPCA Commissioner and Advisory Committee on April 18, 2017. MPCA is moving forward with their recommendations, including waiving the variance fee for municipalities using the streamlined approach. See the Commissioner’s signed memo and documents referenced below.
- Signed Memorandum: Chloride Water quality standard and NPDES permit implementation guidance (wq-wwprm2-47)
- Chloride Work Group Policy Proposal for Minnesota: Recommendations for addressing chloride in municipal wastewater effluent (wq-wwprm2-24)
- Alternatives for addressing chloride in wastewater effluent (wq-wwprm2-18)
- Chloride permitting decision tree (wq-wwprm2-25)
The chloride variance request form and Eligibility tool for streamlined chloride variance approach can be found on Water permits and forms.
What is the water quality standard for chloride?
Our freshwater streams and lakes naturally have low levels of chloride. High concentrations of chloride are harmful to aquatic plants and animals.
Based on guidance from the U.S. Environmental Protection Agency and the levels of chloride shown to be toxic to fish, Minnesota has a water quality standard to protect aquatic life from chloride. The standard to protect from aquatic life from impacts due to longer chronic exposure is a 4-day average of 230 mg/L, and the standard to protect from shorter term acute exposure is a 1-day average of 860 mg/L.
How does salt from chloride get into our water resources?
One major way is from salt used to deice roads during winter weather. When snow and ice melts, the salt goes with it, washing into our lakes, streams, wetlands, and groundwater. In the Twin Cities and other communities across Minnesota, local partners are addressing this problem by using sand and other strategies to keep winter roads safe while using less salt as a deicer. Find out more about road salt and water quality.
A second major way is from salt used in water softeners. People soften their water to make soaps lather more, prevent spotting on dishes from hard water, and make water heaters operate more efficiently. In most communities, these water softeners drain to municipal wastewater treatment plants, which are usually not designed to remove that much salt from the wastewater. The salt passes through the treatment system that discharges to a lake or stream.
Where in Minnesota is chloride a problem?
Road salt runoff tends be a problem in developed areas where there are many roads and other paved surfaces.
Chloride in wastewater discharge appears to be a problem in almost 90 Minnesota communities, most of them in southern and western areas of the state. Chloride flows into wastewater treatment facilities from homes and businesses that use water softeners. Treatment facilities are designed to remove particles, like grit and sand, and to biologically degrade organic waste, such as food and human waste. Once chloride is dissolved in water it cannot be removed by settling, or biologically degraded by standard treatment processes. The technology to remove chloride is available, but is costly. It would involve microfiltration and reverse osmosis, which are the same treatment processes used to produce pure water used in laboratories.
How does the MPCA know it’s a problem?
Water monitoring data also show that salt concentrations are continuing to increase in lakes, streams and groundwater across Minnesota.
The MPCA monitored several lakes and streams in the Twin Cities metro area and found that 39 have chloride levels too high to meet the standard designed to protect fish and other aquatic life. An additional 38 water bodies have chloride levels near the standard.
Chloride toxicity is a suspected stressor to aquatic life in two trout streams in the Duluth area. Road salt and other practices in high-density urban areas are the likely sources of chloride and other stressors in these streams.
The MPCA also found chloride to be stressing aquatic life in a stream in the Cannon River watershed in southern Minnesota with an upstream wastewater treatment facility the likely source of chloride.
Wastewater treatment facilities started monitoring for chloride and other salty parameters in 2009. The MPCA examined the data and found that about 100 facilities have the potential to contribute to levels of chloride higher than allowed by the standard. One common tool to reduce pollutants like chloride is to issue permits with effluent limits to control the amount of a pollutant in a facility’s discharges.
What is the MPCA doing to address the problem of salty water?
For road salt in the metro Twin Cities, the MPCA partnered with local and state experts to create a plan for effectively managing salt use to protect water resources while maintaining safe driving conditions. Other communities have also adopted plans to reduce road salt use.
For salt from softeners, the MPCA is forming a work group with community representatives to map out how Minnesota should address meeting the water quality standard for chloride in wastewater discharges.
What can citizens and businesses do to help?
- Use sand and other alternate products for deicing sidewalks and others paved surfaces.
- Use a water softener only if necessary. Water with a measured hardness of less than 50mg/l is considered soft. Generally water 50 to 150 mg/l is suitable for use in most homes and it is not necessary to use a softener. Check with your city to find out your water’s hardness level.
- Reduce the use of softener salt by softening only water used for washing and bathing.
- Calibrate softeners so they soften by demand instead of by a set timer.
What are other states doing about chloride in wastewater discharges?
Several states are developing strategies to manage chloride in wastewater discharge, ranging from regulatory (permit limits) to incentives to reduce chloride.
- California: Some cities have banned water softeners with cities providing water softening before water is pumped to homes and businesses. Some cities promote more efficient salt use in softeners, and others mandate high-efficiency softeners.
- Iowa: Research by its Dept. of Natural Resources showed that chloride toxicity is heavily dependent on water hardness and to a lesser degree, sulfate levels in the water. Iowa allows permit holders to a use a site specific standard for chloride based on water hardness.
- Indiana: This state has adopted a water quality standard similar to Iowa’s, where the protective chloride concentration is function of hardness and sulfate. Some Indiana cities also plan to switch to reverse osmosis for regional water treatment when systems need replacement.
- Wisconsin: Cities may apply for variances to the chloride standard while the state studies ways to meet the standard. Some cities are also promoting more efficient salt use and softener operation.
MPCA Watershed Project Manager, Metro
MPCA Municipal Wastewater Liaison