Groundwater Quality: Impact Of Pollution And Its Reach

Groundwater is a major source of freshwater for much of the global population, used for drinking, agriculture, and industry. However, it is susceptible to pollution from both natural and human-induced sources. Natural groundwater is generally considered safe for consumption, but today, it is difficult to find groundwater that has not been contaminated in some way.

Groundwater pollution occurs when pollutants are released into the ground and make their way into groundwater. This can happen due to on-site sanitation systems, landfill leachate, leaking sewers, petrol filling stations, hydraulic fracturing, or the over-application of fertilizers in agriculture. Human-induced sources of groundwater pollution include industrial discharges, urban activities, agriculture, groundwater pumpage, and the disposal of waste.

Contaminants in groundwater can include inorganic and organic chemicals, bacteria, viruses, and radioactive materials. These contaminants can have serious health effects, including diseases such as hepatitis and dysentery, and long-term effects such as cancer.

The impact of groundwater pollution extends beyond human health, as it can also affect the quality of land and forests, and lead to socioeconomic issues. Given the challenges of remediating contaminated groundwater, prevention is key, and this involves implementing and enforcing environmental regulations and educating individuals and businesses about their role in keeping groundwater sources clean and safe.

Industrial waste

The production of industrial goods generates wastewater that can be contaminated with toxic substances. This wastewater is often released into nearby public waters, such as rivers and lakes, especially in emerging countries like China, India, Africa, and South America, where environmental policies are not as stringent. Even in countries with stricter regulations, like the US and Europe, industrial wastewater can still find its way into public waters, either through illegal dumping or inadequate treatment before discharge.

The effects of industrial waste on water systems are devastating. Many hazardous substances from industry are difficult to biodegrade and accumulate in water sediments. This contamination can have severe ecological impacts, killing fish, crustaceans, and other aquatic creatures, and reducing biodiversity. These contaminants can also enter the groundwater, which serves as a source of drinking water for millions of people.

One of the most common groundwater contaminants is PCE (perchloroethylene or tetrachloroethylene), a suspected carcinogen. Other contaminants include toxic chemicals from manufacturing, such as lead, arsenic, mercury, and chromium, as well as pesticides, fertilizers, and waste from landfills. These contaminants can have serious health effects, including various types of cancer, liver and kidney damage, and nervous system disorders.

To address the issue of industrial waste and its impact on groundwater, proper waste management and treatment facilities are crucial. While most major industries have treatment facilities for their effluents, small-scale industries often lack the necessary resources for pollution control equipment. Additionally, regulations and enforcement vary across regions, with emerging countries facing challenges in consistently implementing and monitoring environmental legislation.

Agricultural chemicals

Fertilisers and pesticides do not remain stationary; they are transported into local streams, rivers, and groundwater through runoff and infiltration. When land is converted for agricultural use, it is modified to optimise production, which can have unintended environmental impacts on receiving waters and their ecosystems.

The US Geological Survey (USGS) has found that agricultural contaminants are widespread in surface water and groundwater across the US. Their studies detected pesticides in about 94% of water samples and over 90% of fish samples from streams across the nation, as well as in nearly 60% of shallow wells sampled.

To reduce the impact of agricultural chemicals on groundwater, it is essential to implement protective actions in areas with vulnerable aquifers and promote sustainable agricultural practices that minimise the use of chemicals and reduce nutrient transport through runoff.

Poorly constructed wells

Wells with structural issues located near agricultural land are particularly vulnerable to pesticide or chemical seepage. These chemicals can originate from agricultural or industrial waste and end up in wells that are not properly regulated. This can have serious health consequences for those who rely on well water for drinking or irrigation.

In addition, improperly constructed wells can also lead to subsurface leakages, which can impact nearby groundwater sources. This is a particular concern for hydrocarbon wells, including shale gas wells, where well integrity failure is considered the main cause of such leakages.

To prevent groundwater pollution from poorly constructed wells, it is crucial to ensure that wells are properly designed, located, and maintained. This includes considering the surrounding environment and taking steps to prevent contamination from nearby sources. Regular testing of well water for contaminants is also essential to identify any issues early on.

Furthermore, when wells are no longer in use, proper decommissioning and sealing are necessary to prevent them from becoming conduits for contamination. Abandoned wells can become dumping grounds for industrial waste, oil, and other contaminants, indirectly polluting water sources even if they were properly constructed during their operational lifespan.

Natural sources

Arsenic

Arsenic is one of the most serious inorganic contaminants in drinking water worldwide, according to the World Health Organization (WHO). It occurs naturally in groundwater, particularly in Asia, including China, India, and Bangladesh. Arsenic is often found in groundwater in areas with mining operations or mine waste dumps. It can also be released from volcanic rocks and dispersed volcanic ash. Arsenic in groundwater can cause severe health issues, including dermal, neurological, reproductive, and cognitive problems, and even cancer.

Fluoride

Natural fluoride in groundwater is a growing concern, especially as deeper groundwater sources are being used. High levels of fluoride in groundwater pose serious health risks, including dental and skeletal fluorosis. Volcanic rocks and dispersed volcanic ash are common sources of fluoride in groundwater.

Nitrates

Nitrate is the most common chemical contaminant in groundwater and aquifers globally. Elevated nitrate levels in groundwater can be caused by on-site sanitation, sewage sludge disposal, and agricultural activities. Drinking water with high nitrate levels can cause "blue baby syndrome" (acquired methemoglobinemia).

Iron and Manganese

As groundwater flows through the ground, it can dissolve metals such as iron and manganese, which may later be found in high concentrations. These metals can affect the taste, colour, and odour of water, and may require treatment before the water is suitable for domestic use.

Pathogens

The lack of proper sanitation measures and improperly placed wells can lead to drinking water contaminated with pathogens carried in faeces and urine. Such waterborne diseases include typhoid, cholera, and diarrhoea.

Volatile Organic Compounds (VOCs)

VOCs are dangerous contaminants of groundwater and are typically introduced through careless industrial practices. They include aromatic hydrocarbons such as BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) and chlorinated solvents like tetrachloroethylene (PCE) and trichloroethylene (TCE).

Human waste

Furthermore, human waste can also contain harmful chemicals, such as household chemicals, that can contaminate groundwater. This can occur when septic tanks are not properly maintained or when there is a leak in the septic system. These chemicals can have toxic effects on both human and wildlife health.

The impact of human waste on groundwater is particularly relevant in the United States, where over 50% of the population depends on groundwater for drinking water. Improperly managed human waste can lead to the contamination of this vital water source, posing risks to human health and the environment.

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