Groundwater contamination is due to our everyday activities. It becomes vulnerable, especially where the population density is high and the land use is intensive. In general, any activity that releases waste or chemicals into the environment can potentially pollute the groundwater. Indeed, it is expensive and difficult to clean contaminated groundwater.
Before resolving water pollution, it is best to understand how ground and surface waters are related. Acknowledging that everything is interconnected can help you manage and fully understand it.
If a water supply is near the source of contamination, then there is a risk. If there is a stream or river nearby, then the groundwater can have a chance to become polluted.
Contaminating the Groundwater
When a contaminant is released into the environment, it may move within an aquifer, such as groundwater. This depends on the contaminant's chemical, physical, or biological properties. Some contaminants do not follow the groundwater flow because of their chemical or biological properties.
To some degree, transport within an aquifer of the substances is predictable. For example, the contaminants and water can flow in the direction of the topography. This is from the recharge areas to the discharge areas. Permeable and porous soils transport water and other contaminants easily to an aquifer found below.
The contaminants move slowly, just like the groundwater. With this movement, the contaminants become concentrated as a plume. It flows on the same path as the groundwater. The speed and size of the plume will depend on the type and amount of contaminants. Its velocity, density, and solubility determine the plume's speed.
Contaminants can flow rapidly through the rocks’ fractures. Controlling and locating contaminants in fractured rocks is problematic because the fractures are randomly spaced and do not follow the contours of the land or the hydraulic gradient.
Meanwhile, contaminants can also enter through macropores. Examples include animal burrows and abandoned wells.
The risk of contamination increases in areas near the pumping wells. This is because water from the zone of contribution is drawn into the aquifer and well.
Some water wells draw water from rivers, streams, or lakes. The contaminants in these surface waters can contaminate the groundwater systems.
Some water wells rely on artificial recharge to add water to the aquifer. This practice often uses water from irrigation, storm runoff, treated sewage, or industrial processes, which has increased the concentration of microbes, metals, nitrates, and other chemicals in the water.
In some cases, pumping can allow groundwater from another aquifer to enter the pumped water, a process known as inter-aquifer leakage. To maintain groundwater quality, you must properly identify and protect the affected areas.
In general, the greater the distance between the groundwater and the source of contamination, the more likely it is to reduce the risk of contamination. Several processes may take place in the soil layer to reduce the concentration of contaminants.
Examples include biological degradation, oxidation, and adsorption. These processes can reduce the concentration of contaminants even before they reach the groundwater.
Even when the contaminants reach the groundwater directly, they can become less concentrated through dilution, even if they do not pass through the unsaturated zone. It is the process of mixing with the groundwater.
However, since groundwater moves slowly, contaminants undergo less dilution. This is more unlikely than in surface water.
Sources of Groundwater Contamination
Human activities or natural sources can contaminate groundwater. Industrial, municipal, residential, commercial, and agricultural activities can all contaminate water.
Contaminants can also mix with water because of activities on the land surface. This can happen through spills or releases from stored industrial wastes from the sources below.
Water can be contaminated from above the land surface by leaking petroleum, septic tanks, etc.
Natural Sources of Groundwater Contamination
Substances found naturally in soils or rocks can dissolve and enter groundwater. Examples include chlorides, manganese, iron, fluoride, radionuclides, and sulfates. Other naturally occurring substances, like organic matter, can also move in the ground.
Various conditions will determine whether these substances can be found in groundwater. Some substances pose a health danger when ingested in large quantities, while others can produce undesirable color, odor, or taste.
Drinking is not recommended if the groundwater contains high concentrations of these substances. You cannot use it for other domestic uses unless treated.
Septic Tanks
Effluent from cesspools, septic tanks, and privies is one main cause of water contamination. Around 25% of homes in America use septic systems to dispose of human waste.
Indeed, each system can release only a small amount of waste. However, the system's widespread use can be a serious source of contamination. If the septic systems are improperly designed and maintained, they can contaminate the groundwater. It can release viruses, bacteria, oils, detergents, and nitrates.
Septic systems can also release cleaners containing synthetic organic chemicals, such as methylene chloride and trichloroethene. These chemicals can contaminate water supplies and interfere with the natural decomposition process.
Local and state regulators require specific distances between the septic tanks and water wells. Tools are used to calculate suitable densities and distances for installing the drinking water wells.
Improper Garbage Disposal
Take note that hazardous wastes must be disposed of properly. A licensed waste handler must handle it in your area. There are chemicals that you must not dispose of in the septic systems. Examples include oils, garden chemicals, paint, thinners, medicines, and disinfectants.
Moreover, industrial chemicals must not be disposed of in the drains at your workplace. It can only contaminate your water source. Companies must train their workers on how to dispose of the chemicals used on the site.
The different quantities and types of chemicals used at industrial locations allow proper waste disposal, which is important for protecting water.
Spills or Releases from Petroleum Products or Chemicals
Chemicals are commonly stored in aboveground or underground storage tanks. Homes have underground heating oil tanks, and some businesses store their fuel oil, diesel, gasoline, or chemicals in on-site tanks.
Meanwhile, industries use storage tanks to store chemicals for various industrial processes.
There are approximately 4 million underground storage tanks in America. Over the years, many of these tanks have spilled into the ground.
The content can go into the soil and groundwater whenever a leak occurs. Indeed, tanks that meet the state standards are less likely to leak. However, they are not 100% foolproof. Moreover, abandoned underground tanks are another problem that can threaten groundwater.
Sloppy materials, improper chemical storage, and poor containers can threaten groundwater. Train cars and tanker trucks can also pose a hazard to the environment.
Around 16,000 chemical spills occur annually from trains, storage tanks, and whenever materials are transferred. In the spill area, the chemicals can be diluted with water. They can also be washed away into the soil, increasing the contamination.
Landfills
In industrial landfills around America, solid waste is being disposed of. The chemicals which were supposed to be disposed of in the hazardous landfills end up in municipal landfills. Also, the disposal of household waste is not regulated.
As soon as the chemicals reach the landfill, they can leach into the groundwater through runoff and precipitation. To protect the groundwater from possible contamination, the authorities require new landfills to have synthetic or clay liners.
However, the old landfills do not have these safeguards. These are often located close to the surface waters or over the aquifers. It is in permeable soils with shallow water tables. This can increase the potential for the liquid from the landfill, known as leachate, to reach the groundwater.
Though landfills are closed, they can continue to threaten, especially if they are not capped with materials like clay.
Surface Impoundments
Surface impoundments are shallow lagoons or ponds that municipalities use to store, dispose of, and treat liquid wastes. Like landfills, the new surface impoundment facilities require liners to prevent leakage.
Pipelines and Sewers
Sewer pipes that carry human waste can sometimes leak fluids into the groundwater and soil. Sewage contains inorganic salts, organic matter, viruses, bacteria, and heavy metals. Other pipelines that carry industrial chemicals tend to leak. This is true whenever the materials being transported are corrosive.
Fertilizer and Pesticide Use
Millions of tons of pesticides and fertilizers are used in crop production in the United States, and farmers, businesses, homeowners, and municipalities also use these chemicals.
Following registered use, these fertilizers and pesticides have contaminated groundwater. Some pesticides can remain in the soil or water for months or even years.
One source of contamination can be animal wastes that get into the ground from the farms.
Floor Drains and Injection Wells
The injection wells, which are shallow and include sumps, can collect stormwater runoff, contain spilled liquids, and dispose of industrial wastewater and commercial waste. The dry wells are used to collect stormwater.
Meanwhile, businesses use the floor drains to handle spills. If a business can operate or handle the waste fluids in the septic system, it must submit information regarding its operation to the authorities.
Disposal wells that can pose threats to drinking water must be closed.
Improperly Constructed and Maintained Wells
If the water wells are improperly constructed, groundwater contamination can result. Problems such as a lack of concrete pads, inadequate covers, or faulty casings can allow outside water to enter the well.
Meanwhile, if the wells are abandoned or improperly maintained, they can act as a conduit for the contaminants to reach the aquifer.
Moreover, some people use abandoned wells to dispose of their wastes, such as motor oil. These wastes may reach the aquifer, which supplies drinking water. Abandoned wells are usually uncovered, a potential habitat for viruses and bacteria.
Mining Activities
Active and even abandoned mines can contaminate groundwater. Soluble minerals from the mines can be leaked into the groundwater through precipitation. The waste contains minerals, sulfides, metals, and acids. Abandoned mines are used as waste pits.
Moreover, mines are pumped to keep them dry. Pumping can cause the contaminants to shift above groundwater.
Effects of Groundwater Contamination
Contaminated groundwater can result in poor water quality, high cleanup costs, loss of water supply, and degraded surface water systems.
The consequences of contaminated groundwater are serious. Estuaries impacted by high nitrogen levels have already lost their shellfish habitats.
When we talk about the water supply, groundwater contamination is severe. This is the reason why groundwater is not a recommended drinking water source. Occasionally, groundwater can be cleaned and used again only if the contamination is not too severe. This is true if the municipality is willing to spend money on it. Through the years, follow-up monitoring is required.
Since groundwater moves slowly, contamination can remain undetected even for a long time. This makes cleaning very difficult and impossible. If the government results in the cleanup, it can cost millions.
Cleaning the Groundwater
Groundwater can be treated when the contaminant source has been detected, controlled, or removed. First, the contaminant can be contained to prevent it from migrating to other water sources. Second, the water can be pumped, treated, and returned to the aquifer.
Third, you can leave the groundwater in its place and treat either the contaminant or the water. Finally, using appropriate source control, you can allow the contaminant to reduce naturally.
The selection of appropriate technology depends on various factors, including the cleanup goals and potential risks. Different technologies are used for different types of contaminants, and sometimes, several technologies are combined to achieve an effective treatment.
Because cleaning is expensive and difficult, some abandon the wells and find other water sources. Although this technique is more expensive, it is safer than obtaining water from contaminated wells.
A temporary solution is to buy bottled water. However, this is not realistic for long-term consumption. You can also try installing water filters inside your home.
The community might decide to install new wells in a different aquifer area.
In this case, it is best to monitor the new wells to ensure that contaminants do not move into the new water supply.
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