Groundwater Pollution: Sources And Entry Points

Groundwater contamination occurs when pollutants are released into the ground and make their way into groundwater. These pollutants can be human-induced, such as gasoline, oil, road salts, and chemicals, or natural, such as metals like iron and manganese that dissolve as groundwater flows through the ground. Human activities such as industrial discharges, urban activities, agriculture, and the disposal of waste can all negatively impact groundwater quality.

Accidental or deliberate spills

Accidental spills can occur in a variety of settings, from fast-food restaurants storing cooking oil to farms using fuel and agricultural chemicals. For instance, hazardous leaks and spills can happen at businesses that work with liquids, such as mechanics storing oils and fuel, or offices storing cleaning products. These spills can be difficult and expensive to clean up and may render groundwater unusable for decades or even thousands of years.

Deliberate dumping of chemicals and waste into drains or on the ground can also contaminate groundwater. This includes illegal dumping by manufacturers, refineries, or wastewater treatment facilities, as well as improper disposal of chemicals, oils, and non-biodegradable items by consumers. Additionally, sewage treatment systems can release untreated wastewater, which can find its way into groundwater.

To prevent groundwater pollution from accidental or deliberate spills, it is essential to properly store and dispose of chemicals, fuels, and waste. Regular inspection of high-risk areas, such as underground fuel tanks, is crucial, as well as implementing pollution prevention plans and supporting protection legislation.

Improperly treated wastewater

One of the main issues with on-site wastewater treatment systems is that they are prone to malfunction and failure if not properly maintained. This can result in the release of untreated or partially treated wastewater into the environment, including groundwater. Wastewater contains a variety of contaminants, such as bacteria, viruses, and household chemicals, which can pose serious health risks if they find their way into groundwater sources.

Another issue with improperly treated wastewater is that it can introduce excessive nutrients, such as nitrogen and phosphorus, into the groundwater. This can lead to eutrophication, algal blooms, and fish kills in surface water bodies that are fed by groundwater. High levels of nitrogen, in particular, can be harmful to human health, with elevated nitrate levels posing a risk to infants and causing a condition known as methemoglobinemia or blue baby syndrome.

To prevent groundwater contamination from improperly treated wastewater, it is crucial to ensure proper maintenance and management of on-site wastewater treatment systems. Regular inspections, maintenance, and upgrades can help identify and address any issues before they lead to system failure. Additionally, the use of alternative treatment methods, such as centralized wastewater treatment plants, can help reduce the risk of groundwater contamination.

Industrial operations

Volatile Organic Compounds (VOCs)

Volatile organic compounds (VOCs) are dangerous groundwater contaminants often introduced through careless industrial practices. Many VOCs, such as aromatic hydrocarbons (BTEX compounds like benzene, toluene, ethylbenzene, and xylenes) and chlorinated solvents (tetrachloroethylene, trichloroethylene, and vinyl chloride), were not known to be harmful until the late 1960s. Regular groundwater quality monitoring has since identified these substances in drinking water sources.

Polycyclic Aromatic Hydrocarbons (PAHs)

Polycyclic aromatic hydrocarbons (PAHs) are another type of organic pollutant derived from industrial operations. They are generally produced as byproducts of incomplete combustion of organic matter and have complex molecular structures. This complexity determines their water solubility, adsorption capacity, and mobility in the groundwater system, with some types of PAHs being more mobile and, thus, more likely to reach drinking water sources.

Chlorinated Solvents

Chlorinated solvents, such as PCE and TCE, are used in various industrial practices, including dry cleaning and metal degreasing. PCE, for example, is a highly utilised solvent in the dry cleaning industry due to its effectiveness and relatively low cost. These solvents have densities higher than water, and once they reach the aquifer, they accumulate on top of low-permeability layers, becoming a long-term source of contamination.

Metals and Metalloids

Industrial activities such as mining, metallurgy, solid waste disposal, and paint works can lead to elevated concentrations of toxic metals and metalloids in groundwater. This includes elements like lead, cadmium, chromium, and arsenic. The mobility of these contaminants in groundwater is influenced by several factors, particularly chemical reactions that determine the partitioning of contaminants among different phases and species.

Pharmaceuticals

Trace amounts of pharmaceuticals from treated wastewater can infiltrate aquifers and contaminate groundwater. Popular pharmaceuticals like antibiotics, anti-inflammatories, antidepressants, and tranquilizers are often found in treated wastewater, which is then discharged from treatment facilities and can make its way into groundwater sources.

Other Organic Pollutants

Other organic pollutants found in groundwater due to industrial operations include organohalides, petroleum hydrocarbons, chemical compounds found in personal hygiene and cosmetic products, and drug pollution involving pharmaceutical drugs and their metabolites.

Septic tank leaks

Septic tanks are commonly used for wastewater treatment in homes and buildings that are not connected to a city sewer system. They are designed to slowly drain human waste underground, allowing contaminants to be broken down and destroyed. However, if a septic tank is not properly maintained or is damaged, it can leak bacteria, viruses, household chemicals, and other harmful substances into the groundwater.

Improperly designed, located, constructed, or maintained septic systems can cause serious problems. For example, if a septic tank is placed too close to a well, the groundwater may flow from the septic drain field and contaminate the water flowing into the well. Similarly, if there are multiple septic systems operating in close proximity, the combined concentration of contaminants can overwhelm and contaminate the groundwater.

To prevent septic tank leaks and potential groundwater contamination, it is crucial to ensure proper maintenance and installation. This includes regular pumping, typically once every 3-5 years, and maintaining a safe distance between wells and septic systems. By taking these precautions, we can help protect our drinking water sources and mitigate the health, environmental, and economic risks associated with groundwater contamination.

Atmospheric deposition

The environmental impact of atmospheric deposition is significant. It is a primary source of pollutants, including gases, particulates, metals, and nutrients, to both terrestrial and aquatic environments. Pollutants can be transported over long distances and distributed into broad uncontaminated areas. For example, urban pollutants may reach rural areas through atmospheric deposition. The deposition of sulfur and nutrients contributes to the acidification and eutrophication of various water bodies, which can have adverse effects on human health, wildlife, and the ecosystem.

Overall, atmospheric deposition is a significant pathway for pollutants to reach aquatic and terrestrial ecosystems, including groundwater. The complex interplay of various processes and the long-range transport of pollutants make it a critical factor in the contamination of groundwater and other water sources.

Frequently asked questions