Groundwater Pollution: Leaking Into Surface Water?

Groundwater pollution is a serious issue that can have detrimental effects on both human health and the environment. Groundwater is highly susceptible to pollution, as contaminants can seep through the soil and find their way into groundwater supplies. These contaminants include pesticides, fertilizers, road salts, toxic substances from mining sites, and waste from septic tanks and landfills. Once polluted, groundwater can spread these contaminants over a wider area, including into surface water sources such as rivers and lakes. This can result in water supplies becoming unsafe for human consumption and harmful to wildlife. The complex interactions between groundwater and surface water mean that damage to groundwater aquifers can have far-reaching consequences. Therefore, it is crucial to implement prevention methods and management approaches to protect groundwater resources and mitigate the impacts of pollution.

Septic tank leakage

Groundwater contamination occurs when pollutants are released into the ground and make their way into groundwater. Septic tank leakage is a common cause of groundwater pollution. Here are some details on the issue of septic tank leakage and its impact on groundwater:

Septic tanks are commonly used for sewage treatment and disposal, especially in rural areas and areas without access to central sewer systems. However, when septic systems are not properly designed, installed, or maintained, they can leak and contaminate groundwater. This is a significant issue, as millions of failing septic tanks are estimated to be contaminating water resources in the United States alone.

Impact on Groundwater

Leaking septic tanks can release untreated wastewater, bacteria, viruses, household chemicals, and other contaminants into the surrounding soil and groundwater. This can lead to the spread of disease-causing pathogens, such as E. coli, which poses risks to both human health and the environment. In addition, chemicals and nutrients from septic tanks, such as nitrogen and phosphorus, can also contaminate groundwater.

Case Study: Al-Seeb, Oman

A case study from Al-Seeb, Oman, illustrates the impact of septic tank leakage on groundwater quality. In this city, rapid residential development led to the construction of many septic tanks that were old, outdated, or not built according to specifications. As a result, wastewater leaked through the soil and contaminated groundwater. Elevated levels of coliform bacteria, biochemical oxygen demand (BOD), total organic carbon (TOC), and nitrate were detected in drinking water wells, indicating possible contamination from wastewater.

Preventing and Mitigating Septic Tank Leakage

To prevent and mitigate the impact of septic tank leakage on groundwater, several measures can be taken:

• Proper design, installation, and maintenance of septic systems are crucial. Homeowners should ensure their septic systems are regularly inspected and pumped out.
• Governments and local authorities can implement regulations and standards for septic systems, including minimum standards for functioning systems and repair requirements.
• Alternative sewage treatment methods, such as pressure sewers, can be adopted in areas with high water tables or coastal locales where septic systems may be prone to failure.

In summary, septic tank leakage is a significant contributor to groundwater pollution. By understanding the causes and impacts of this issue, we can take the necessary steps to prevent and mitigate its effects, ensuring the protection of our valuable groundwater resources.

Industrial waste

• Improper Wastewater Treatment: Industrial wastewater, if not adequately treated, can contaminate groundwater. Different industries produce different types of wastewater with varying levels of contaminants. For example, the textile industry releases dyes, heavy metals, and chemicals, while the paper and pulp industry generates solid, liquid, and gaseous waste. If this wastewater is not properly treated before being discharged into water bodies, it can pollute groundwater.
• Hazardous Effluents: Many industries produce hazardous effluents that, if released directly into sewerage systems, can eventually find their way into groundwater. These effluents may contain heavy metals, chemicals, oils, pesticides, and other toxic substances.
• Landfills and Leaching: Industrial waste disposed of in landfills can leach toxic chemicals into the ground, which can then seep into groundwater. This is especially true for older landfills that may not have protective bottom layers to prevent contaminants from seeping into the water.
• Accidental Spills and Illegal Discharge: Accidental spills or illegal discharge of industrial waste can also contribute to groundwater pollution. This includes chemical spills during transport, illegal waste dumping, and leaks from storage tanks.
• Use of Groundwater for Irrigation: In some cases, industrial wastewater is used for irrigating crops. If this wastewater contains pollutants, it can contaminate the soil and eventually reach groundwater, affecting both crop quality and the food chain.
• Climate Change and Natural Disasters: Climate change has led to an increase in the frequency of natural disasters like floods and droughts. During floods, industrial waste and pollutants can be washed into water bodies, eventually reaching groundwater.
• Accumulation in Sediments: Some industrial pollutants, such as per- and polyfluorinated alkyl compounds (PFAS), are persistent and can accumulate in aquatic sediments for years. Over time, these toxins can slowly enter groundwater, especially during floods or dredging activities.
• Groundwater-Surface Water Interaction: Groundwater and surface water are interconnected. Contaminants released into surface water, such as rivers and lakes, can eventually seep into and pollute groundwater. This is particularly true for shallow, unconfined aquifers with fewer layers to filter out contaminants.

To address groundwater pollution caused by industrial waste, proper wastewater treatment and management strategies are essential. This includes implementing treatment processes specific to each industry's waste profile and adopting technologies for sustainable and economical industrial wastewater recycling. Additionally, strict environmental policies and consistent monitoring are crucial to prevent illegal discharge and ensure compliance with regulations.

Natural processes

• Climate change: Seasonal variations in temperature, precipitation, and evapotranspiration can all affect the quality of groundwater. For example, low temperatures can cause issues with the air binding of filters, and heavy rainfall can directly or indirectly charge surface water.
• Natural disasters: Natural disasters such as volcanic activities, earthquakes, hurricanes, tornados, flooding, and tsunamis contribute to water pollution. For instance, floods can destroy wells of drinking water and cause well pollution by human sewage, pollution of animals, human waste, chemicals, livestock waste, and other impurities.
• Geological factors: Geological factors such as soil types, topography slope, plant roots, dissolution of water with minerals/soils, and radioactive decay of elements can all influence the quality of groundwater. For instance, mineral dissolution is a slow process that can affect the qualitative characteristics of aquifers, such as hardness and pH.
• Soil or sediment matrix: The physical properties of the soil/sediments matrix can evaluate the pathways of water and affect the storage of groundwater aquifers. These factors also show the mean residence time along with aquifer depth.
• Hyporheic exchange: The exchange of surface water and groundwater through streambed sediments can also impact the quality of groundwater. This process can lead to physical, chemical, and biological processes that affect the quality and quantity of water resources.

Landfills

Leachate from landfills can contain many toxic and harmful substances such as heavy metals, persistent organic pollutants, and bacteria, making it one of the main anthropogenic sources of groundwater pollution. Groundwater polluted by landfill leachate can cause ecological problems such as water blooms and soil salinization, as well as various diseases in humans who are exposed to it through drinking or bathing. For example, drinking groundwater polluted by heavy metals can increase the risk of cancer and infant death, as well as induce motor and cognitive dysfunction in children.

The age of the landfill is a significant factor in determining the degree of groundwater pollution. At a landfill age of 21 years, pollutant concentrations were found to approach reference values. Closing landfills can also significantly reduce contaminant concentrations in groundwater. However, in some cases, the aquifer itself may act as a natural treatment plant, attenuating pollutants with distance and reducing the risk of environmental harm from leachate. Nevertheless, this also means that the groundwater in the area may not be safe for human use due to potential health risks.

To prevent groundwater contamination from landfills, it is essential to set up isolation distances between landfills and drinking water sources, especially in remote areas with scattered drinking water sources. The isolation distance should be determined based on specific safety requirements, taking into account factors such as the type of aquifer, the thickness of the vadose zone, and the groundwater gradient. For example, in coarse gravel aquifers, the isolation distance can range from 2.4 to 58.7 km.

Atmospheric contaminants

Atmospheric deposition is the pollution of water caused by air pollution. In the atmosphere, water particles mix with carbon dioxide, sulphur dioxide, and nitrogen oxides, forming a weak acid. As a result, water vapour absorbs more of these gases and becomes more acidic. When it rains, the water is polluted with these gases, and this is called acid rain.

Acid rain can have harmful effects on aquatic life in marine habitats such as rivers and lakes. Atmospheric pollution of the ocean also causes ocean acidification, which occurs when airborne carbon dioxide (CO2) is absorbed by seawater, causing chemical reactions that reduce seawater pH and may affect many marine organisms. The pace of ocean acidification has been accelerating, causing concern within the scientific community about its potential impacts and how those impacts may cascade through the marine food chain and affect the overall structure of marine ecosystems.

In addition to acid rain and ocean acidification, atmospheric contaminants can also include toxic chemicals from industrial practices, which can enter groundwater supplies. Volatile organic compounds (VOCs), for example, are dangerous contaminants of groundwater that are generally introduced through careless industrial practices. Atmospheric contaminants can also include trace amounts of pharmaceuticals from treated wastewater, which can infiltrate into aquifers or sources of surface water used for drinking water.

Frequently asked questions