Pollution's Pathways: Surface And Groundwater Contamination Sources

Water pollution is a pressing issue that affects both surface water and groundwater. Surface water pollution is caused by pathogens, nutrients, plastics, chemicals, pesticides, antibiotics, industrial waste discharges, and individuals dumping harmful or benign substances into waterways. Groundwater, which starts as precipitation, can be contaminated by human-induced chemicals, leaking fuel tanks, toxic chemical spills, and agricultural activities. Both types of water pollution have significant environmental and health impacts, and understanding their sources is crucial for effective pollution prevention and water protection measures.

How does pollution enter surface water and groundwater?

Industrial waste and agricultural pollution

Industrial Wastewater Pollution

Industrial activities generate large volumes of wastewater, which can contain various toxic pollutants. These pollutants include plastics, pesticides, herbicides, oils, chemicals, heavy metals, and pathogens. Improper waste disposal and dumping practices by manufacturing, mining, and waste disposal companies have contaminated drinking water sources across the United States. For instance, in Ringwood, New Jersey, Ford Motor Co. dumped toxic paint sludge, poisoning groundwater in an area occupied by the Turtle Clan of the Ramapough Lenape tribe. Similarly, the now-defunct Diamond Alkali Co. in Newark, New Jersey, polluted the Passaic River, a drinking water source for millions, with chemicals used to make Agent Orange.

Industrial wastewater is also released during manufacturing, cleaning, and other commercial activities. The nature of the contaminants in this wastewater depends on the specific industry and factory. For example, the manufacturing processes of Anaconda Aluminum in Montana contaminated local water sources with lead and chromium. In Louisiana, Gulf States Utilities discharged toxins, including benzene, into marshlands, damaging the local water bodies.

Stormwater runoff is another significant source of industrial water pollution. During heavy rainfall or flooding, water flows above the ground and collects various pollutants from streets, industrial sites, and construction sites. This polluted water eventually discharges into nearby natural waterways, including ponds, rivers, streams, and lakes, without undergoing any treatment. As a result, stormwater runoff poses a severe threat to aquatic life and the entire environment, as all life forms rely directly or indirectly on these natural waterways.

Agricultural Water Pollution

Agriculture is the single largest user of freshwater resources, accounting for about 70% of surface water usage globally. It is both a cause and a victim of water pollution. Agricultural practices discharge pollutants and sediments into surface and groundwater through poor land management, net soil loss, and the salinization and waterlogging of irrigated land. Intense cultivation and livestock operations contribute to the accumulation of nitrogen, phosphorus, and pesticide residues in water bodies, leading to nutrient pollution. This type of pollution is the number one threat to water quality worldwide and can trigger algal blooms that are harmful to people and wildlife.

Agricultural wastewater, also known as irrigation tailwater, occurs when excess water runs off fields during surface irrigation. This runoff carries sediments and nutrients, such as fertilizers, pesticides, herbicides, crop residues, and animal wastes, into nearby water sources. The expansion of aquaculture, especially in Asia, has further exacerbated this issue, with fish excreta and uneaten feeds from fed aquaculture diminishing water quality.

On-farm practices in crop production, livestock, and aquaculture play a crucial role in preventing agricultural water pollution. Implementing efficient irrigation schemes, establishing protection zones, and adopting proper farm management techniques can help reduce the migration of pollutants into water bodies.

Sewage treatment plants

The construction of centralised sewage treatment plants began in the late 19th and early 20th centuries, primarily in the United Kingdom and the United States. Today, most homes and businesses in developed countries send their wastewater to treatment plants. In the US alone, approximately 34 billion gallons of wastewater are processed daily.

Wastewater contains various impurities, including nitrogen and phosphorus from human waste, food, and certain soaps and detergents. These nutrients, when released into water bodies without proper treatment, can cause nutrient pollution, which is the leading type of contamination in freshwater sources. Excess nitrogen and phosphorus can lead to algal blooms, which are harmful to people and wildlife. Therefore, sewage treatment plants employ various technologies and approaches to remove these nutrients and other pollutants from wastewater.

However, it is important to recognise that sewage treatment plants can also contribute to water pollution under certain circumstances. For example, during heavy storms, combined sewer and stormwater systems can overflow, resulting in untreated sewage being directed into waterways. Additionally, sewer leaks can occur due to various factors such as tree root invasion, seismic activity, or flooding. These leaks can contaminate both surface water and groundwater with untreated sewage, posing a significant threat to water quality and human health.

To address these challenges, preventative measures such as systematic inspections, exclusion of hazardous waste, and adherence to modern construction and maintenance specifications are crucial for protecting groundwater sources from sewer leaks. Additionally, newer technologies and approaches are being developed to improve the efficiency of energy, nutrient, and chemical recovery from treatment plants, transforming them from mere pollution mitigation entities to resource recovery facilities.

Radioactive waste

Radioactive materials, also called radionuclides, are both naturally occurring and human-made. Radionuclides from naturally occurring sources can get into groundwater and surface waters. For example, radioactive radium and uranium are 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.

In some cases, human activities can lead to increased levels of radionuclides in water sources. For example, the Fukushima Daiichi NPS nuclear meltdown in 2011 released large amounts of radionuclides into the environment, including radiocesium, which was released into the North Pacific through direct discharge of radioactive water and atmospheric deposition. Radioactive waste can persist in the environment for thousands of years, making disposal a major challenge.

To address radioactive pollution in water, it is important to identify the source of the pollution (point source or non-point source) and the type of water body impacted (groundwater, surface water, or ocean water). Containing the source and removing the pollutants are critical steps in mitigating the issue. This may involve implementing strategies such as walls containment, bores abstraction, infiltration control, and the use of tanks for the temporary storage of contaminated waters.

Additionally, preventing radioactive waste from entering water sources in the first place is crucial. Drinking water suppliers play a vital role in this by identifying potential contamination pathways and preparing for emergencies that could threaten the drinking water supply. Public education and business guidance on proper waste disposal are also important preventive measures.

Rain and erosion

Rainfall can have a significant impact on water pollution, particularly when it comes to surface water. When rain falls, it can pick up and wash away various pollutants, carrying them into nearby water bodies. This is known as runoff, and it is a significant contributor to water pollution. For example, rainwater can wash away pesticides, fertilisers, and animal waste from farms, carrying them into rivers, streams, and other waterways. This type of pollution is known as nutrient pollution and is caused by excess nitrogen and phosphorus in the water. It is a significant threat to water quality and can lead to harmful algal blooms.

The impact of rainfall on water pollution is particularly notable in agricultural areas. With the increasing population and the corresponding rise in agricultural activities, the use of chemicals in farming has also increased. These chemicals often contain heavy metals and other toxic substances. When it rains, these chemicals are leached from the soil and washed into nearby surface waters, contaminating them. This is a significant issue in regions like the Niger Delta, where agricultural fields are often located close to rivers and other aquatic ecosystems.

Additionally, rainfall can also contribute to groundwater pollution. When rain seeps into the ground, it can fill cracks and porous spaces, eventually reaching underground water stores known as aquifers. While this process naturally filters the water, it can still be polluted by various contaminants. For example, rainwater can pick up pollutants like pesticides and fertilisers from the surface and carry them into the groundwater. Additionally, improperly disposed of waste, such as leaking underground storage tanks or poorly maintained septic systems, can also contaminate groundwater.

Erosion also plays a crucial role in water pollution. It can carry pollutants from the soil into water bodies, contributing to both surface water and groundwater pollution. Sediment resulting from soil erosion, construction activity, or mining can be transported by runoff into lakes, rivers, and oceans. These sediments can contain heavy metals and other toxic substances, further degrading water quality. Additionally, erosion can expose previously buried contaminants, such as buried waste or contaminated soil, to rainwater and runoff, facilitating their transport into water bodies.

Natural and human-induced chemicals

Agricultural activities, such as the excessive use of nitrogen-based fertilisers, pesticides, and the spreading of animal waste, contribute significantly to water pollution. These chemicals seep into the ground and contaminate groundwater, making it unsafe for human consumption. In regions with intensive agriculture, like California's Tulare Lake Basin and Salinas Valley, nitrate contamination of groundwater has become a pressing issue.

Urban storm water runoff is another significant source of surface water pollution, potentially impacting groundwater as well. Residential areas, for example, often contribute high levels of pesticides to runoff, while retail and commercial areas introduce trash and bacteria. Additionally, contaminants carried by wind can settle on the ground, further polluting the runoff that eventually finds its way into water bodies.

Industrial activities also play a role in water pollution. Toxic chemical spills, leaking fuel tanks, and discharges from manufacturing units can introduce a range of harmful chemicals into water sources. These include organic pollutants, such as pharmaceutical products, pesticides, hydrocarbons, and plasticizers, which can have long-lasting effects on the environment and pose risks to human health.

Furthermore, conventional sewage treatment plants only partially remove micropollutants like hormones, pharmaceutical residues, and other contaminants in urine and faeces. The remaining pollutants are discharged into surface water and can eventually reach groundwater. This issue is particularly concerning as the population grows and more reclaimed wastewater is used for municipal water supplies.

Frequently asked questions