Contaminants In Drinking Water: Sources And Causes

Water is an essential resource for all living beings and is crucial for social and economic development. However, water pollution poses a significant threat to this vital resource, endangering the health of millions worldwide. Pollutants can enter drinking water through various pathways, including industrial waste, agricultural runoff, sewage, and natural sources. These contaminants range from toxic chemicals and heavy metals to microorganisms and pathogens, all of which can have detrimental effects on human health and ecosystems. With less than 1% of the Earth's freshwater accessible, protecting our water sources from pollution is of utmost importance. This introduction will delve into the various ways pollutants infiltrate drinking water, the consequences they bring, and the actions needed to safeguard this precious resource.

Human activity and waste

Water pollution is caused by the release of substances and energy into bodies of water, making the water unsafe and disrupting aquatic ecosystems. Human activities that generate domestic sewage and toxic waste are significant sources of water pollution. Sewage and wastewater, even when treated, can contain harmful chemicals, bacteria, and pathogens. These contaminants breed disease and cause health issues in humans and animals.

Improper disposal of solid waste is another major source of water pollution. Solid waste includes garbage, trash, electronic waste, and construction and demolition debris. Inadequate infrastructure, resources, or regulations in some regions contribute to the improper disposal of solid waste, with intentional dumping into bodies of water occurring in certain places.

Industrial sites also produce toxic waste and pollutants, and while regulated, some lack proper waste management systems. Industrial waste can be dumped into nearby freshwater systems, contaminating the water with poisonous substances and making it unsafe for human consumption. Additionally, agricultural practices involve the use of chemicals and pesticides, which can be carried into water sources through rainfall runoff or snowmelt, contaminating lakes and streams.

Other human activities, such as felling forests, can exhaust water resources and create organic residues that become breeding grounds for harmful bacteria. Rising global temperatures caused by CO2 emissions heat the water, reducing its oxygen content. Oil spills, often accidental, are another significant source of water pollution, with leaks and spills originating from oil drilling operations or ships transporting oil.

Industrial and agricultural sites

Industry accounts for about 20% of freshwater withdrawal worldwide. This water is used in production and becomes polluted. In some cases, it is cleaned by industrial wastewater recycling systems and is sometimes reused or disposed of in an environmentally friendly way. However, in some areas, it is discharged untreated into nearby public waters. As a result, rivers and lakes become polluted and unsafe for swimming, fishing, and drinking.

The production of industrial goods generates wastewater contaminated with toxic substances. These include heavy metals like arsenic and mercury, oils and greases, and industrial salts. In the production of pharmaceutical and chemical substances, wastewater is contaminated with active pharmaceutical ingredients, especially from cleaning the production facilities.

Oil refineries, chemical and plastics manufacturers, and fertilizer plants are among the biggest culprits of industrial water pollution. In the US, oil refineries discharge nearly half a billion gallons of wastewater into waterways every day. In 2021, refineries discharged 60,000 pounds of selenium, which causes mutations in fish, and nearly 16 million pounds of nitrogen, which creates algae blooms that kill fish.

Agricultural sites are also major contributors to water pollution. Agriculture accounts for 70% of water withdrawals worldwide. Farms discharge large quantities of agrochemicals, organic matter, drug residues, sediments, and saline drainage into water bodies. Increased fertilizer and pesticide use have led to changes in water quality and the health of stream ecosystems. High levels of nitrates in water from fertilizer runoff can cause "blue baby syndrome", a potentially fatal illness in infants.

Veterinary medicines, such as antibiotics, vaccines, and growth promoters, have emerged as a new class of agricultural pollutants. These medicines move from farms through water to ecosystems and drinking water sources. Fish excreta and uneaten feeds from fed aquaculture also diminish water quality.

Sewage and wastewater

Wastewater can also contain chemical pollutants, such as nitrates and nitrites, which are present in human sewage and can contaminate private wells through groundwater movement and surface water seepage. High levels of nitrates and nitrites in drinking water can cause methemoglobinemia, or "blue baby syndrome," which reduces the blood's ability to carry oxygen and can be life-threatening for infants.

Additionally, wastewater can be contaminated with heavy metals from household plumbing, mining operations, petroleum refineries, and municipal waste disposal. These heavy metals can leach into drinking water, posing risks of nervous system or organ damage, developmental or reproductive issues, and long-term health conditions such as cancer.

To address these concerns, wastewater treatment processes are crucial. Treatment plants employ various methods, such as filtration, reverse osmosis, and biological filtration, to remove solids, large particles, and harmful contaminants. The treated wastewater is then mixed with natural water supplies and undergoes further filtration before being distributed to communities through water lines and pipes.

While the idea of recycling wastewater into drinking water may be unappealing to some, it is a safe and effective way to ensure water availability, especially in areas facing water scarcity. By properly treating and cleaning sewage water, communities can become self-sufficient and self-sustaining, reducing the risk of water shortages.

Accidental oil spills

Oil spills are a significant threat to our drinking water sources. While some oil seepage occurs naturally, accidental oil spills from human activities can have devastating effects on the environment and drinking water sources. Oil spills can occur during industrial or domestic operations, such as spills in fuel depots, oil leaks in vehicles, or non-accidental pouring of paint or oil down storm drains. These spills can be washed down storm drains and carried into water sources through runoff, especially from asphalt.

The impact of oil spills on drinking water sources is not limited to the immediate spill location. Currents and wind can carry the oil, causing damage to vegetation, birds, and marine animals along its path. Oil spills can also have long-lasting effects on the environment. While cleanup activities can help, they may never remove 100% of the spilled oil, and some methods can cause additional harm.

Furthermore, oil spills contribute to air pollution, as the burning of oil during cleanup releases hydrocarbons into the atmosphere. These hydrocarbons can mix with water vapour and fall as acid rain, causing damage to water sources, plants, and even buildings and statues.

To protect drinking water sources from accidental oil spills, it is crucial to understand the potential sources of contamination and take preventive measures. This includes proper management of oil-based products and prompt response to spills to minimize their impact on the environment and drinking water sources.

Natural sources

Rivers, lakes, and other surface-level freshwater sources can be easily contaminated by dirt or plants in or near the water simply due to their presence. Animals that defecate in or near the water can contaminate it with bacteria, viruses, and other potentially harmful microbial organisms. Groundwater, such as underground aquifers, rivers, or wells, can be contaminated by minerals and elements in the earth. While some substances in the earth that can enter groundwater, like calcium and magnesium, tend to improve the taste of the water, other substances, such as arsenic, lead, radon, or uranium, pose a great threat.

Human and animal waste from sewage and septic systems can carry harmful microbes into drinking water sources, as can wastes from animal feedlots and wildlife. Major contaminants include Giardia, Cryptosporidium, and E. coli. Human waste in the form of both over-the-counter and prescription drugs flushed down the toilet can end up in cesspits or directly in the sewer system. Overflows or leaks from either destination can seep into the ground, where potential contaminants eventually end up in the groundwater.

Sources of chemical contaminants include poorly designed or poorly maintained subsurface sewage-disposal systems (e.g. septic tanks), industrial wastes disposed of in improperly lined or unlined landfills or lagoons, leachates from unlined municipal refuse landfills, mining and petroleum production, and leaking underground storage tanks below gasoline service stations. In coastal areas, increasing groundwater withdrawal (due to urbanization and industrialization) can cause saltwater intrusion: as the water table drops, seawater is drawn in.

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