Why Chlorides?

Chloride harms aquatic life and vegetation and is corrosive to infrastructure. As the chloride concentrations increase and our waters become saltier, aquatic and plant biodiversity decreases and native species are overtaken by salt tolerant invasive species. One teaspoon of salt can pollutant five gallons of water. It is cost prohibitive and very difficult to remove chloride through current treatment options available; whereas, proactive measures to reduce the amount of chloride discharged can help reduce the impacts from chloride on receiving waterways and the environment. Even chloride that ends up at wastewater treatment facilities is discharged back into the environment. The processes at wastewater treatment facilities do not remove chloride from the water.  

Chlorides are commonly found in fertilizers, water softeners, and road salt. Chlorides, commonly Potassium Chloride, in fertilizers leech through the soil, polluting the groundwater. Water softeners use salt to replace heavy minerals like calcium and magnesium with sodium to reduce the hardness of the water. For those using groundwater as their primary source of drinking water without a water softener, hard water can lead to mineral build up in pipes and make hot water heaters less efficient over time.  

In the Chicago area and Northern Illinois, road salt used in winter road, parking lot, and sidewalk maintenance is one of the primary sources of chloride. Road salt, commonly made up of rock salt as sodium chloride, lowers the freezing point of water causing ice to melt when the temperature is below freezing. When the road salt dissolves, the sodium and chloride ions split apart and help disrupt the hydrogen and oxygen ions of water from forming into the crystal structure of ice. Other materials used in winter maintenance commonly include Magnesium Chloride and Calcium Chloride. Both of these materials also contribute to chloride pollution. 

Road salt used for winter maintenance is a primary source of chlorides in the Chicago area.

Chlorides Impact the Environment

According to local work done by other watershed groups in the Chicago Region, chloride impacts aquatic life at concentrations as low as 150 mg/L. This is even lower than EPA’s secondary drinking water standard of 250 mg/L and Illinois’ water quality standard for chloride at 500 mg/L. 

Many of our aquatic species are not salt tolerant and can’t survive well in salty water. As the chloride concentrations from salt increase, and our waters become saltier, biodiversity will decrease as chloride inhibits aquatic life from successfully reproducing and surviving in our waterways. Macroinvertebrates and plankton are impacted by chloride and unable to survive at chloride concentrations below the current water quality standards set by Illinois and the US EPA. This impacts fish and other aquatic life that rely on macroinvertebrates or plankton for food disrupting the naturally occurring food chain. Amphibians that lay their eggs in our waterways can be impacted by chlorides with malformation, reduced hatching, and reduced survival rates. Native aquatic species tend to impacted more by chlorides as they haven’t adapted to the saltier water.  

Chlorides Damage Plants

Chlorides can impact local vegetation as well. As native salt intolerant plants die off in our wetlands, they are replaced by salt tolerant invasive species that don’t provide good habitats for native wildlife. Plants along roads, sidewalks, and parking lots are also impacted by excessive road salt. Salt spray from roads or parking lots, can damage vegetation planted alongside roadways and parking lots. Salt applied to sidewalks can runoff and damage plants and soil along sidewalks. Salt can burn foliage on roadside plants or kill grass along sidewalks. The salt draws the moisture out of the plants. This kind of salt damage is commonly seen in evergreens as brown or yellow foliage or in deciduous trees as dense clusters of twigs at branch tips, called “Witches Broom”. High sodium and chloride levels from road salt can make the soil more compacted reducing the amount of oxygen available to plant roots, thus decreasing plant growth. 

Drinking Water

Chlorides aren’t just a problem for plants and aquatic wildlife. Humans are impacted too. High concentrations of salt in the water we source for drinking water can be a problem. We taste salty water when the concentrations of chloride is above 250 mg/L. Too much sodium in drinking water can lead to health problems for those who need low sodium diets. Additionally, salt is corrosive. High chloride concentrations in drinking water can damage metal pipes. 

High levels of chlorides can make drinking water taste salty.

Chlorides Corrode Infrastructure

Because salt is corrosive, our infrastructure and vehicles can be damaged by overusing road salt. Salt can damage concrete, bridges, roads, and sidewalks. Salt can corrode the metal on our cars. All of this leads to more costs in future years as the infrastructure needs to be repaired or replaced due to damage from road salt. 

What Can We Do About It?

But we can do something about chlorides in our waterways. Transportation agencies and communities follow industry accepted best practices for winter maintenance operations. These best practices keep roads safe while using less salt. This saves money, time, and reduces the impact of chlorides on the environment. Adding liquid salt brine to dry salt can help speed up how quickly the salt works to melt snow and ice while reducing how much salt is needed. Pretreating roads, bridges, overpasses, parking lots, or sidewalks with liquid salt brine ahead of a winter storm, called “Anti-Icing”, can make it easier for plows to remove the snow and ice and use less salt after plowing. Many agencies that have added liquid salt brine and anti-icing to their operations have saved over 32 pounds of salt for every gallon of liquid salt brine they use. 

Incorporating techniques like anti-icing can save salt and make it easier for plows to remove snow and ice.


Simple Changes You Can Make at Home

At home, you can help by shoveling snow before it gets walked on and compressed down. This reduces the amount of ice that forms on your sidewalks or driveways. Before reaching for the salt, use an ice scraper to break up any compacted snow or ice. Use only the salt you need, a 12-ounce cup of salt is enough to cover 10 sidewalk squares or about a 20-foot driveway. If you use fertilizers for your plants or lawn, follow the instructions on the bag and don’t use more than you need. Plants can only take up so many nutrients and too much fertilizer can be harmful to plants. Sweep up any fertilizer that falls on hard surfaces like driveways or sidewalks so that it doesn’t wash into our local waterways. If you have well water, aging water softeners can be replaced with more efficient models that use less salt reducing the amount of chloride going to wastewater treatment facilities. If your community relies on well water for the public drinking water supply, they may already soften the water and you may not need to have a water softener at your home.  

Learn more about salt and how you can help at www.saltsmart.org. Members of the Chicago Area Waterways Chloride workgroup have access to any of the public outreach materials available at www.saltsmart.org for use in their communities.