How Clean Water Can Become Polluted

Water pollution is a pressing issue that jeopardizes human health and safety. It occurs when harmful substances contaminate water bodies, rendering them toxic and unsafe for human use. Clean water can become polluted through various sources, including agricultural and industrial practices, improper waste disposal, and natural processes. This pollution has severe consequences, including the transmission of diseases, ecological damage, and economic burdens. Restoring water quality is challenging and costly, requiring behavioral changes, technological interventions, and collaborative efforts.

Industrial and agricultural pollution

Industrial agriculture is one of the leading causes of water pollution, particularly in the United States. According to the 2017 National Water Quality Inventory of the Environmental Protection Agency (EPA), 46% of the nation's rivers and streams are in "poor biological condition", and 21% of lakes are "hypereutrophic", meaning that high levels of nutrients and algae are degrading water quality.

Sources of Water Pollution from Agriculture

Industrial Animal Agriculture

Concentrated animal feeding operations (CAFOs), also known as factory farms, house thousands of animals, generating billions of gallons of animal waste per year. This waste is stored in pits or open ponds, known as lagoons, which often leak and can rupture during large storms. Animal waste can include pharmaceutical residues, heavy metals, and harmful bacteria, which can leach into water supplies.

Industrial Crop Production

The excessive use of synthetic fertilizers and pesticides in industrial crop production contributes to water pollution. When applied at high volumes, excess nitrogen makes its way into the atmosphere and can become nitrous oxide, a potent greenhouse gas, or nitrogen oxide, which contributes to ground-level smog.

Negative Effects of Water Pollution from Agriculture

Eutrophication and Dead Zones

High levels of nutrients in water from industrial crop fertilizers and animal waste cause excessive aquatic plant growth, a process known as "eutrophication". This leads to "hypoxia", or water that is low in oxygen, and the formation of "dead zones" where aquatic life cannot survive.

Contamination of Drinking Water Supplies

Excessive nutrient runoff in waterways can impact drinking water supplies and cause severe health problems. For example, elevated levels of nitrates in drinking water can cause low oxygen levels in infants ("blue-baby syndrome") and low birth weight.

Harmful Algal Blooms (HABs)

Some types of HABs produce biotoxins that can kill fish and other aquatic life and cause human illnesses. Algal blooms can also block sunlight, disrupting the ecosystem below the water surface that relies on sunlight for energy.

Heavy Metal Contamination

The use of heavy metals like copper and zinc in CAFOs can contaminate water supplies and have negative effects on human health and the environment. Copper toxicity can cause gastrointestinal and liver disorders, while zinc pollution can cause fish kills and damage to algae and crustaceans.

Pathogen Contamination and Disease Outbreaks

Animal waste contains high levels of pathogens that can cause human diseases. When lagoons leak, contaminated water can end up in waterways and groundwater, posing risks to human health.

Addressing Water Pollution from Agriculture

Policies and Incentives

Implementing policies and incentives that encourage more sustainable and healthy diets can help moderate increases in food demand. Financial incentives such as taxes, subsidies, and consumer coupons can positively influence dietary choices.

On-Farm Practices

Adopting management measures to reduce the risk of water pollution due to fertilizers and pesticides, such as limiting and optimizing the type, amount, and timing of applications to crops. Establishing protection zones along surface watercourses and buffer zones around farms can also help reduce pollution migration into water bodies.

Efficient Irrigation Schemes

Implementing efficient irrigation schemes can reduce water return flows and mitigate the migration of fertilizers and pesticides into water bodies.

Integrated Farming Systems

Integrated farming systems, where crops, vegetables, livestock, trees, and fish are managed collectively, can increase production stability, resource use efficiency, and environmental sustainability. By ensuring that waste from one enterprise becomes inputs for another, integrated farming optimizes resource use and reduces pollution.

Sewage and wastewater

According to the United Nations, more than 80% of the world's wastewater flows back into the environment without proper treatment or reuse, and this figure rises to over 95% in some less developed countries. In the United States, wastewater treatment facilities process approximately 34 billion gallons of wastewater daily. These facilities work to reduce the amount of pollutants such as pathogens, phosphorus, nitrogen, heavy metals, and toxic chemicals in industrial and agricultural waste before discharging the treated water back into waterways. However, aging and overburdened sewage systems in the US also release over 850 billion gallons of untreated wastewater annually, according to EPA estimates.

Sewage pollution is not just a problem in the US. In the UK, for example, water companies have been criticized for their inadequate investment in protecting coastal and river environments. Instead, they rely on discharging raw sewage into rivers and the ocean through a network of licensed sewer overflows. This has led to the UK ranking last in Europe for bathing water quality, with only 14% of its rivers meeting good ecological standards.

Oil pollution

Oil spills can occur during the transportation of oil by ships, pipelines, or trucks, or during drilling operations. When oil is released into the ocean or other water bodies, it forms a slick on the surface, preventing sunlight from penetrating and reducing dissolved oxygen levels. This has severe consequences for aquatic life, as it disrupts the natural balance of the ecosystem. Oil-coated birds and marine animals, such as sea otters and whales, can suffer from hypothermia as the oil destroys their insulating properties. Additionally, ingested oil can cause toxic effects, including heart damage, stunted growth, and immune system dysfunction.

Oil spills also negatively impact coastal habitats and wildlife species. Coral reefs and marine organisms, particularly juveniles, are at risk from toxic substances in the oil and suffocation. Oil can soak into sand and gravel on beaches, killing mangrove trees and marsh grasses. The economic repercussions of oil spills can be significant, including decreased tourism, closure of recreational areas, and disruption to fisheries and seafood industries.

The cleanup and restoration of oil-spill sites are challenging and time-consuming. While various methods exist, such as using floating booms and skimming techniques, no entirely satisfactory solution has been developed. The long-term impact of oil spills on affected areas can be challenging to assess, and restoration projects are often necessary to bolster the environment and accelerate the recovery of species and habitats.

Overall, oil pollution poses a severe threat to marine life, ecosystems, and human activities. Preventative measures and effective response strategies are crucial to minimising the detrimental effects of oil spills on the environment and local communities.

Radioactive substances

Radioactive contamination is the presence of radioactive substances where they are not intended or desired. Radioactive contamination can be natural or man-made.

Natural Sources of Radioactive Contamination

Radioactive elements such as uranium and thorium are found in the earth's crust. These elements and their decay products are present in rock and soil. Radioactive radium and uranium, for example, can be found in small amounts in almost all rock and soil and can dissolve in water. Radon, a radioactive gas created through the decay of radium, can also naturally occur in groundwater.

Man-made Sources of Radioactive Contamination

Radioactive contamination can also be caused by human activity. Nuclear weapon testing, nuclear power plants, and the dumping of radioactive waste are major sources of contamination. The application of radioactive elements in nuclear weapons, X-rays, and medical equipment also exposes humans to radioactive elements, which can then be released into surface water bodies. Mining activities for radioactive elements like uranium and thorium can pollute surface and groundwater.

Health Effects of Radioactive Contamination

Radioactive contamination can have serious health impacts. When radionuclides break down, they create radiation. Coming into contact with too much radiation can cause health problems, including cancer, leukemia, genetic mutations, osteonecrosis, cataracts, and chromosomal disruption. Ingesting radioactive elements through drinking contaminated water is a major risk pathway for human exposure to radiation.

Preventing and Monitoring Radioactive Contamination

Containment is the primary way to prevent radioactive contamination from being released into the environment or coming into contact with humans. Public drinking water systems in the United States, for example, regularly test and filter out contaminants, including radionuclides, to ensure that the water meets federal, state, and local drinking water standards. Treatment methods such as aeration, reverse osmosis, ion exchange, and granule carbon adsorption are also effective in treating radioactive contaminated water.

Natural presence of chemicals

Clean water can become polluted through the natural presence of chemicals. Natural waters contain a broad range of total dissolved solids (TDS), which vary depending on the source. For instance, seawater has a TDS concentration of about 35g/kg, while some freshwater mountain streams have TDS concentrations of less than 250mg/kg.

The presence of dissolved solids in natural waters is due to the interaction of flowing water with rocks and soils, which leads to the slow dissolution of their chemical constituents. The rate of dissolution and solubility of these chemical species are determined by the pH of the water.

Some of the most common inorganic substances found in natural waters include carbon dioxide, nitrogen, and trace metals such as iron, manganese, lead, and arsenic. These substances can have both natural and pollutant sources. For example, carbon dioxide dissolves in water through atmospheric interactions, while lead can be released from rocks and soils by rainfall.

Additionally, natural waters contain dissolved gases, such as carbon dioxide and oxygen. The solubility of these gases is influenced by factors like temperature and TDS concentration. For instance, the amount of oxygen that freshwater can hold decreases by nearly 50% as the temperature rises from near freezing to 35°C.

Furthermore, human activities can introduce organic chemicals into water sources. These include pesticides, gasoline, dry-cleaning solvents, and degreasing agents, which can contaminate groundwater and drinking water supplies if improperly stored, disposed of, or spilled.

The presence of these chemicals in drinking water can have adverse health effects, particularly after extended exposure. For example, consuming water with high levels of certain volatile organic compounds (VOCs) has been linked to an increased risk of liver problems, cancer, and reproductive difficulties.

It is important to prioritize and regulate the presence of chemical contaminants in drinking water to ensure its safety for human consumption.

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