Water Pollution: Power Plants' Toxic Legacy

Power plants are a major source of pollution, and while they are widely recognised as air polluters, they also cause significant water pollution. Power plants are large users of water, and they discharge billions of gallons of heated and treated water back into bodies of water every day. This heated water can starve aquatic life of oxygen, trap species in ice-free areas, and change the biodiversity of the affected locations. Power plants also discharge polluted water containing chlorine, heavy metals, and other harmful pollutants, such as lead, arsenic, and uranium. These pollutants can contaminate drinking water and cause serious health issues, including cancer. The US Environmental Protection Agency (EPA) is working to reduce water pollution from power plants by implementing the Clean Water Act and proposing stricter standards and regulations for wastewater discharges.

Coal-fired power plants

Coal combustion releases harmful pollutants, including heavy metals such as lead and arsenic, as well as carbon monoxide and hydrocarbons. Arsenic, a known carcinogen, can contaminate drinking water sources, increasing the risk of cancer for those consuming it. Additionally, the warm water plumes discharged back into rivers or seas can disrupt aquatic ecosystems by depriving them of oxygen in summer and trapping species in ice-free areas during winter.

The mining and extraction of coal also contribute to water pollution. Mountaintop removal and valley fill mining, commonly practised in regions like the Appalachian Mountains, alter the landscape and can result in water runoff containing pollutants that harm aquatic life. Underground mines, although less disruptive to the landscape, face issues with ground collapses and the drainage of acidic water.

Furthermore, coal ash, a byproduct of coal combustion, poses significant environmental risks. Coal ash impoundment ruptures can contaminate downstream environments, and improper storage or disposal of coal ash can lead to groundwater pollution. Fly ash and bottom ash, when not properly managed, can leach pollutants into the ground, further exacerbating water pollution.

To address these issues, regulatory bodies like the Environmental Protection Agency (EPA) have proposed stricter wastewater discharge standards for coal-fired power plants. The Clean Water Act and the Clean Air Act mandate industries to reduce pollutants released into water bodies and the air. Additionally, advancements in pollution control technology, such as emissions scrubbers, have been effective in capturing and reducing harmful emissions, showcasing a commitment to fostering cleaner water and healthier communities.

Nuclear power plants

One way nuclear power plants cause water pollution is through the discharge of heated water used for cooling. Nuclear power plants rely on water from lakes, rivers, or the ocean for cooling, and the heated water released back into the environment can cause thermal pollution. This can disrupt the biodiversity of the affected water bodies, as it accelerates the metabolism of cold-blooded aquatic animals, leading to malnutrition and potential species death. Additionally, the thermal plume currents generated by the heated water can extend for several kilometres downstream, impacting both the ecosystem and human communities.

Another concern is the production and improper disposal of radioactive waste. Radioactive wastes, such as uranium mill tailings and spent reactor fuel, can remain dangerous to human health for thousands of years. If not properly managed and contained, these wastes can contaminate water systems, posing a serious threat to the environment and human health. The Fukushima nuclear accident in 2011, caused by a tsunami, is an example of how radioactive materials can be released into the ocean, leading to ongoing challenges in managing contaminated water.

The mining and refining of uranium ore, the fuel for nuclear power plants, can also contribute to water pollution. Underground mining exposes workers and the surrounding environment to high levels of radon gas, a radioactive byproduct of uranium breakdown. Open-pit mining, while safer for miners, generates radioactive and toxic waste that can pollute soil and water.

While advancements in water treatment technologies, such as improved filtration methods, help mitigate the potential pollution caused by nuclear power plants, the impact of thermal and radioactive water pollution remains a critical issue that requires stringent safety measures, comprehensive monitoring, and improved waste management techniques.

Mercury emissions

Mercury is a naturally occurring element found in the earth's crust. However, when it is above ground, it can be harmful due to its neurotoxicity. Mercury is present in coal and other fossil fuels, and when these fuels are burned to generate electricity, the mercury becomes airborne and enters the atmosphere. Power plants that burn coal are the largest source of mercury emissions in the United States, accounting for about 44% of all man-made mercury emissions.

The majority of coal-burning power plants emit around 5 kilograms of mercury per year, which is considered acceptable by the EPA. However, there are clusters of lignite-burning power plants, such as those in North Dakota and Texas, that emit over 100 kilograms of mercury annually. These emissions have severe environmental and health impacts, particularly on vulnerable communities living nearby, including Indigenous communities in North Dakota.

Once mercury is emitted into the atmosphere, it can be transported over various distances, eventually depositing in soil or water. Mercury deposition is influenced by factors such as the height of release and weather conditions. When deposited in water, mercury can accumulate in fish and shellfish, leading to high mercury levels in these organisms. As a result, people who consume contaminated fish and shellfish are at risk of exposure to toxic methylmercury, which can have detrimental effects on their health, especially for children and pregnant women.

To address this issue, the EPA has proposed regulations to tighten mercury emissions from coal-burning power plants. The new standards aim to reduce mercury emissions from lignite coal plants by 70%, which is expected to significantly benefit the health of those exposed, particularly vulnerable communities. Additionally, technologies such as activated carbon injection can help reduce mercury emissions from lignite coal.

Water withdrawals and discharges

The electricity generation industry in the United States withdraws about 15% of the total freshwater flow in the country each year. In 2015, steam-electric power plants withdrew 133 billion gallons of water per day, primarily from rivers, lakes, and estuaries. The amount of water needed by power plants varies by region. In the eastern United States, where water sources are more readily available, once-through cooling systems are more prevalent. These systems withdraw large amounts of water to cool the power plant and do not reuse water like recirculating cooling systems. As a result, power plants in the eastern United States withdraw more water per unit of electricity generated than those in the west.

Thermoelectric power plants, which include coal-fired plants, require cooling water to cool and condense the steam that is used to drive steam turbines. In 2017, the total volume of water withdrawn by thermoelectric power plants in the United States was more than twice the amount that flows over Niagara Falls each year. The water is withdrawn from sources such as rivers or lakes and is either consumed (lost to evaporation or blowdown during generation) or diverted or discharged back into a body of water.

The environmental effects of these water withdrawals and discharges are significant. They include entrainment and impingement of fish and shellfish species from cooling water intakes, with resultant damage to fish populations. The cumulative damage from intake and discharge from multiple plants along a river, coastal area, or other important water bodies can be considerably more significant than the impact of a single plant.

To address these issues, there have been calls for a review and revision of the National Pollutant Discharge Elimination System (NPDES) program to ensure that all chemical and thermal discharges meet the criteria of biological acceptability. It is also important to evaluate the cumulative impacts of water withdrawals and discharges on water bodies with multiple power plants. In addition, technologies such as dry cooling, closed-cycle cooling, and hybrid cooling systems can help reduce water use and minimize harmful discharges.

Thermal water pollution

Power plants are a major source of water pollution, an issue that is less well-known than their air pollution. Water pollution from power plants can occur when large amounts of water are withdrawn from natural water bodies for use in cooling, generating steam, and other industrial processes. This water is then discharged back into water bodies at higher temperatures, causing thermal pollution.

Thermal pollution refers to the degradation of water quality by any process that changes the ambient water temperature. It is primarily caused by the use of water as a coolant in power plants and industrial manufacturing. When water is heated, it reduces the availability of oxygen for aquatic life and can be detrimental to the ecosystem. Aquatic plants, for example, exhibit reduced photosynthesis rates due to inhibited enzyme activity at higher temperatures.

Nuclear power plants, in particular, contribute to thermal water pollution. While their thermal energy efficiency is typically around 30%, lower than that of conventional thermal power plants, they release a higher proportion of their wastewater as liquid effluent streams. This wastewater is discharged at high temperatures, with coal and natural gas plants releasing wastewater at temperatures of 128.4°C and 91.1°C, respectively.

The effects of thermal pollution can be observed in both the ecosystem and human populations. A study of the Danube River in Romania found that thermal pollution from two nuclear power plants created a thermal plume current that extended up to 6km downstream, with temperature changes of up to 1.5°C. Additionally, research on Lake Stechlin in Germany revealed that industrial thermal pollution during winter persists in the deep water column until the following winter, impacting the lake's temperature and mixing regime.

To address thermal water pollution, the Clean Air Task Force has advocated for closed-cycle re-circulating systems and the assessment of dry cooling systems for existing power plants. They have also called for a review of the National Pollutant Discharge Elimination System (NPDES) to ensure that all thermal discharges meet biological acceptability criteria and are properly monitored and reported.

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