Chloride's Impact: A Serious Water Pollutant?

Chloride is a serious water pollutant that poses a threat to freshwater sources and aquatic life. It enters water bodies through various natural and anthropogenic sources, such as road salt, water softeners, industrial wastewater, and seawater intrusion. Once in the water, chloride does not break down or settle, making prevention the only solution. High levels of chloride are toxic to fish, amphibians, and other aquatic organisms, and it can also contaminate drinking water sources, affecting both taste and healthfulness. With increasing awareness of the environmental and health impacts of chloride pollution, communities are working to reduce salt use and minimize its presence in local water resources.

Chloride in drinking water

The issue of chloride in drinking water is multifaceted. Firstly, chloride occurs naturally in water bodies, and many organisms require it to carry out basic life functions. However, elevated levels of chloride can be harmful. For instance, chloride levels above 250 mg/l are associated with negative effects on aquatic life, including fish, aquatic bugs, and amphibians. High chloride concentrations can cause cells to lose water and become deprived of nutrients, ultimately leading to the death of these organisms. Additionally, chloride can harm plants and trees along roadsides and alter plant community structures in streams, lakes, and wetlands.

The sources of chloride in water are diverse. Naturally, water can flow through chloride-containing soil layers or be affected by seawater during high tides, leading to increased chloride content. Anthropogenic sources, such as industrial wastewater discharged from various industries, also contribute significantly to chloride pollution in surface water. De-icing salt used on roads, parking lots, and sidewalks during winter can contaminate local water bodies and groundwater when the snow and ice melt.

To address the issue of chloride in drinking water, various strategies are being implemented. In Minnesota, organizations are encouraged to use less salt for de-icing through programs like Smart Salting, which has helped reduce salt use by 30-70%. The Minnesota Pollution Control Agency (MPCA) also offers grant funding to communities to help reduce chloride pollution by identifying chloride sources and decreasing salt use. In Missouri, recommendations include using the right type of deicer, such as calcium chloride, and sweeping up extra salt to prevent it from being washed into water bodies.

Chloride's impact on fish and aquatic life

Chloride is a serious threat to freshwater lakes and streams, and by extension, the fish and aquatic life that depend on these ecosystems. Chloride does not break down or settle out of water, so prevention is the only solution. As a result, lakes and streams are becoming saltier over time.

At elevated levels, chloride is toxic to fish and other aquatic life. One teaspoon of salt pollutes five gallons of water. Chloride occurs naturally in lakes and streams, and many organisms need it to carry out basic life functions. However, elevated levels can cause cells to lose water and become deprived of nutrients, ultimately killing fish, amphibians, plants, and other aquatic organisms.

Chloride ions in water can have a range of harmful effects on fish and other aquatic life. They can cause skin damage, hypoxia, gill tissue necrosis, and neurological issues, including trouble swimming and incorrect body positioning. In some cases, chloride exposure can lead to sudden death.

In addition to the direct impact on fish, chloride can also affect the structure and diversity of aquatic communities. It can alter the plant community structure in lakes and streams, impacting the availability of food and habitat for fish and other organisms. High chloride levels can also affect the survival, growth, food intake, and behaviour of fish.

To address the issue of chloride pollution, organizations in some areas are working to reduce salt use and identify chloride sources. For example, the Minnesota Pollution Control Agency offers grant funding to communities to help reduce chloride pollution and protect local water resources.

Chloride's impact on plants

Chloride is an essential micronutrient for plant growth and health. It is one of the 16 essential elements for plant growth and is needed in small quantities (about 50–100 μM in the nutrient media) for healthy plant development. It is easily dissolved in water and enters the plant through the soil and air.

Chloride is necessary for the chemical reaction that allows the opening and closing of the plant's stomata—tiny pores that facilitate gas and water exchange between the plant and the surrounding air. This exchange is vital for photosynthesis. Chloride also promotes cell elongation, resulting in larger leaf cells with a higher ability for ion compartmentalisation and higher turgor. This leads to increased water storage capacity in plant cells.

However, excessive chloride accumulation in sensitive organs under salt stress conditions can be toxic to plants. High levels of chloride in water sources, such as lakes, streams, and wetlands, can harm aquatic vegetation and alter the plant community structure. This toxicity may result in symptoms similar to salt damage, including scorched leaf margins, smaller and thicker leaves, and overall reduced plant growth.

The adverse effects of chloride on plant growth are rare due to the element's availability through various sources and the ability to easily leach away excesses. Nevertheless, it is crucial to maintain optimal chloride levels to ensure the health and growth of plants, as well as to prevent ecological damage.

Sources of chloride in water

Chloride is a naturally occurring ion that is present in both fresh and saltwater. It is a major component of dissolved solids and is derived from dissolved salts such as sodium chloride or magnesium chloride. It is also a common anion found in tap water, where it combines with calcium, magnesium, or sodium to form various salts.

There are several natural sources of chloride in water. Firstly, it is present in rainwater, streams, groundwater, and seawater. Additionally, it occurs naturally through the natural weathering of bedrock and soils, as well as volcanic activity.

However, human activities have also led to increased chloride levels in water sources. One major contributor is seawater intrusion, which occurs in coastal areas when saltwater seeps into freshwater aquifers. This contamination can dramatically increase chloride concentrations in groundwater. Another significant source is road salt runoff, particularly during winter when municipalities use sodium chloride to de-ice roads. As snow and ice melt, the salt can wash into local streams and groundwater, significantly increasing chloride levels.

Other human-influenced sources of chloride in water include wastewater discharge, certain industrial processes, fertilizers, detergents, water softeners, and urban runoff. These activities can lead to elevated chloride levels in both surface water and groundwater, particularly in urban and agricultural areas.

While small amounts of chloride are essential for normal cellular function in plants and animals, higher concentrations can cause significant problems. Elevated chloride levels can have indirect health risks, such as exposure to copper, lead, and other corrosion by-products. Additionally, it can cause plumbing issues, damage to water distribution systems, and harm to aquatic life.

Reducing chloride pollution

Chloride is a serious water pollutant that threatens freshwater lakes and streams. It does not break down or settle out of water, so prevention is key. Once in the water, there is no feasible way to remove it. It takes only one teaspoon of salt to permanently pollute five gallons of water.

Water Softening

Water softeners are a source of chloride pollution, as the salty brine they produce often drains into municipal wastewater treatment plants that are not equipped to remove salt from wastewater. Before installing a water softener, it is important to test the hardness of your water and only install a softener if necessary. If a water softener is required, consider a demand-initiated version that is more salt-efficient and operates based on how much water is used. These can reduce salt use by up to 60%.

De-icing

Salt used for de-icing roads, parking lots, and sidewalks can flow into storm drains and contaminate local lakes, streams, and wetlands. To reduce the environmental impact of de-icing, it is recommended to:

• Apply a liquid deicer before it snows to prevent snow and ice buildup
• Shovel, snow blow, plow, and sweep early and often to reduce the amount of salt needed
• Use a handheld spreader that applies salt consistently
• Use the right deicer—Calcium chloride works at much lower temperatures than sodium chloride
• Sweep up extra salt that is visible on dry pavement to prevent it from being washed into water

Agriculture and Industry

Chloride also gets into the environment through fertilizer use, livestock waste, dust suppressants, and industrial wastewater. To reduce chloride pollution from these sources, it is important to:

• Optimize fertilizer use and properly manage livestock waste to minimize chloride runoff
• Find alternatives to chloride-containing dust suppressants
• Implement better wastewater treatment practices in industries such as chemical, petrochemical, pharmaceutical, paper, and textile to reduce chloride discharges

Education and Community Action

Educating communities about the impacts of chloride pollution and providing resources to help them reduce their salt use can be effective in preventing water pollution. The Minnesota Pollution Control Agency, for example, offers grant funding to communities to help reduce chloride pollution. They also offer Smart Salting training to organizations that apply road salt, which has been shown to reduce salt use and prevent chloride contamination in bodies of water. Similar programs can be implemented in other regions to raise awareness and promote best practices for reducing chloride pollution.

Frequently asked questions