Surface Water Pollution: Impacting The Purity Of Groundwater

Groundwater is a vital source of freshwater, with around one-third of the global population depending on it for drinking water. However, human activities such as urbanization, agricultural practices, industrial activities, and climate change pose significant threats to groundwater quality. Contaminated groundwater can have detrimental effects on both human health and the environment.

Surface water, including lakes, streams, and rivers, can be a source of groundwater contamination. When surface water is polluted, contaminants can infiltrate and compromise groundwater quality. This occurs when harmful substances from industrial processes, agricultural practices, or improper waste disposal seep into the soil and reach the groundwater.

For example, pesticides, fertilizers, and road salts can be washed into the ground by rainfall, eventually finding their way into the groundwater. Similarly, drainage wells used for water removal in wet regions may contain agricultural chemicals and bacteria, which can also contaminate the groundwater. Atmospheric contaminants, such as industrial emissions and acid rain, can also reach the groundwater, rendering it unfit for consumption and irrigation.

The consequences of consuming contaminated groundwater can be severe, including waterborne diseases, toxic poisoning, and an increased risk of certain types of cancer. Additionally, contaminated groundwater can harm local wildlife and ecosystems, disrupting ecological balances and potentially leading to the decline of certain species.

Therefore, it is crucial to implement measures to prevent and mitigate groundwater contamination, such as proper storage and handling of hazardous materials, adequate septic system maintenance, responsible disposal of hazardous waste, and landfill management and monitoring.

Poorly constructed wells

For instance, wells with structural issues located near agricultural land are susceptible to pesticides or chemicals seeping in. The space between the casing and the sides of the hole in poorly constructed wells provides a direct channel for surface water and pollutants to reach the water table. This can be mitigated by sealing the well from anything that might enter it from the surface.

In addition, the well driller fills the space with grout, such as cement, concrete, or a particular type of clay known as bentonite, to prevent pollutants from seeping into the well. However, if the well is poorly constructed, it may be unable to keep out contaminants, leading to groundwater pollution.

Improperly abandoned wells

When wells are no longer in use, they must be properly sealed off from large water sources, such as aquifers, to prevent contamination of the water people use for drinking. However, there are many cases in which wells are not properly abandoned and this can have serious consequences for the environment and human health.

Wells that are improperly abandoned often become dumping grounds for industrial waste and oil, which can leak into and contaminate groundwater. In addition, old wells may have degraded well casing or cement that can allow oil, gas, or salty water to leak into freshwater aquifers. This can have severe ecological, economic, and public health impacts, including jeopardising drinking water sources and local ecosystems.

In the US, there are estimated to be over 3.7 million abandoned wells, with many more internationally. In the late 1980s, the US Environmental Protection Agency estimated that 200,000 of 1.2 million abandoned wells may not have been properly plugged. While efforts have been made to plug these wells, the exact number of improperly abandoned wells is unknown, especially as older wells drilled before the 1950s are particularly likely to have been improperly abandoned and poorly documented.

The process of well abandonment involves permanently sealing a well that is no longer in use to prevent the migration of fluids and contaminants between subsurface formations and the surface environment. This process is essential for protecting the environment and ensuring regulatory compliance. Downhole plugging is the primary method used to seal the wellbore, with cement or specialised sealing materials pumped into the wellbore under pressure to create a permanent barrier.

The risks of improperly abandoned wells include not only contamination but also accidents, as these sites can become hidden traps for people, livestock, or wildlife. In addition, landowners may be held responsible for any injury or groundwater contamination caused by an abandoned well that was not properly decommissioned.

Septic systems, sewers, and pipelines

Septic systems are commonly used in rural areas and on boats, where no sewer system exists. They are enclosures that store and treat wastewater through bacterial decomposition, resulting in what is called sludge. However, if they are not properly maintained, located, or constructed, they can leak bacteria, viruses, household chemicals, and other contaminants into the groundwater. Poor placement of septic leach fields can also allow partially treated wastewater to infiltrate and contaminate drinking water sources.

Sewer pipes carrying waste can sometimes leak fluids into the surrounding soil and groundwater. When leaking sewer lines are located deep underground, the sewage can directly enter groundwater, introducing chlorides, microorganisms, organics, trace metals, and other chemicals that may cause diseases and foul tastes or odours in drinking water.

Pipelines carrying industrial chemicals and oil brine are also susceptible to leaks, especially when transporting corrosive materials. This can result in the release of harmful substances into the environment, including the groundwater.

To prevent contamination from septic systems, sewers, and pipelines, proper maintenance and construction are crucial. Regular servicing and pumping of septic tanks are necessary to ensure they are functioning correctly. Systematic inspection of sewer lines and adherence to modern construction and maintenance specifications are essential for protecting groundwater sources from sewer leaks. Additionally, the safe disposal of industrial chemicals and proper waste management practices can help reduce the risk of contamination from these sources.

Landfills

Inadequate landfill management can lead to fires, explosions, vegetation damage, unpleasant odours, soil contamination, and air pollution. The organic fraction of landfill waste also contributes to greenhouse gas emissions, especially methane.

The primary mechanism by which landfills contaminate groundwater is through leachate formation. When precipitation infiltrates a landfill, it percolates through the waste, collecting a variety of inorganic and organic compounds. This contaminated water, known as leachate, can then permeate the surrounding soil and migrate into nearby groundwater sources.

The age of the landfill is a critical factor in determining the degree of groundwater pollution. Older landfills tend to have higher concentrations of pollutants, and the contaminants can migrate further over time. Additionally, the specific composition and quantity of leachate produced can vary depending on the type and amount of waste present in the landfill.

The effects of landfill contamination on groundwater quality can be severe. Studies have found that landfills can negatively impact both physical and chemical water quality characteristics, rendering the water unwholesome and unsafe for consumption. For example, landfills can increase turbidity, reduce pH levels, and introduce toxic heavy metals, such as cadmium, into the groundwater.

To mitigate the risks associated with landfill contamination, proper management and control measures are essential. This includes regular monitoring, implementing protective liners, and adopting leachate collection systems. Additionally, waste should be adequately treated before disposal, and landfills should be located away from aquifers and other sensitive water sources.

Uncontrolled hazardous waste

One of the primary sources of uncontrolled hazardous waste is landfills. While landfills are designed with protective bottom layers to prevent contaminants from leaching into the groundwater, these liners are not always effective. In rare cases, toxic leachate can seep through cracks or holes in the landfill lining. More commonly, contamination occurs through indirect means, such as transportation leaks, stormwater runoff, and animal activity.

Another source of uncontrolled hazardous waste is septic systems, particularly those that are improperly designed, located, constructed, or maintained. These systems can leak bacteria, viruses, household chemicals, and other contaminants into the groundwater, causing serious health issues for those who rely on nearby private wells for drinking water.

Atmospheric contaminants, such as nitrogen oxides released from the burning of fossil fuels, can also contribute to groundwater pollution. These contaminants can be carried by air currents and deposited onto land, where they are then washed into nearby water bodies and groundwater sources.

Additionally, there are an estimated 10 million storage tanks in the US that contain gasoline, oil, chemicals, and other liquids. Over time, these tanks can corrode and develop leaks, allowing contaminants to reach the groundwater.

The consequences of uncontrolled hazardous waste are far-reaching and detrimental. Drinking contaminated groundwater can lead to various diseases, including hepatitis and dysentery, as well as long-term health issues such as cancer. Contaminated groundwater also poses a danger to wildlife and can negatively impact soil and forest quality. Furthermore, groundwater contamination can lead to socioeconomic issues, including water shortages and conflicts among citizens.

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