Groundwater pollution (also called groundwater contamination ) occurs when the pollutants are released to the soil and into the ground water. This type of water pollution can also occur naturally due to the presence of small and undesirable constituents, contaminants or impurities in ground water, in this case more likely to be referred to as pollution than pollution.
Pollutants often create lumps of contaminants in the aquifer. The movement of water and dispersion in aquifers spread pollutants to a wider area. The advanced boundaries, often called the boast edges, can tangle with groundwater wells or sunlight into surface water such as seepage and springs, making water supplies insecure for humans and wildlife. The movement of bursts, called the plume front, can be analyzed through a hydrological transport model or groundwater model. Analysis of groundwater pollution can focus on soil characteristics and site geology, hydrogeology, hydrology, and contaminant properties.
Pollution may occur from on-site sanitation systems, final waste disposal sites, sewage from sewage treatment plants, leaking drains, gas stations or excessive use of fertilizers in agriculture. Pollution (or contamination) may also occur from naturally occurring contaminants, such as arsenic or fluoride. Using tainted ground water causes harm to public health through poisoning or the spread of disease.
Different mechanisms have an effect on the transport of pollutants, such as diffusion, adsorption, precipitation, decay, in ground water. The interaction of groundwater contamination with surface water was analyzed using a hydrological transport model.
Video Groundwater pollution
Type of pollutant
Contaminants found in groundwater include various chemical, organic, chemical, and radioactive, inorganic chemical parameters. In principle, many of the same pollutants that contribute to surface water pollution can also be found in contaminated ground water, although their respective interests may be different.
Arsenic and fluoride
Arsenic and fluoride have been recognized by the World Health Organization (WHO) as the most serious inorganic contaminant in drinking water worldwide.
Metalloid arsenic can occur naturally in groundwater, as is most commonly seen in Asia, including in China, India and Bangladesh. In the Ganges Plains of northern India and Bangladesh, severe groundwater contamination by naturally occurring arsenic affects 25% of well water in shallow two regional aquifers.
Arsenic in groundwater can also be present where there is mining operations or disposal of mine waste that will rob arsenic.
Natural fluoride in ground water is a concern as more groundwater is being used, "with more than 200 million people at risk of high concentrations of drinking water." Fluoride can mainly be released from volcanic rocks of volcanic acid and ash dispersed when the water hardness is low. High levels of fluoride in groundwater are a serious problem in Pampas Argentina, Chile, Mexico, India, Pakistan, East African Rift, and some volcanic islands (Tenerife)
In areas that naturally have high levels of fluoride in ground water used for drinking water, dental and bone fluorosis can occur in general and severe.
Pathogen
A deep and limited aquifer is usually considered the most safe source of drinking water from pathogens, however, pathogens from treated or unprocessed wastewater are known to contaminate certain aquifers, especially shallow ones.
The pathogens contained in the dirt can cause groundwater contamination when they are given the opportunity to reach groundwater, making it unsafe to drink. Of the four types of pathogens present in feces (bacteria, viruses, protozoa and worms or worm eggs), the first three types can be found in contaminated groundwater, whereas relatively large eggs are typically filtered by soil matrix.
Groundwater contaminated with pathogens can lead to the transmission of fatal fecal-oral diseases (eg cholera, diarrhea).
Nitrate
Nitrates are the most common chemical contaminants in ground water and aquifers in the world. In some low-income countries, nitrate levels in groundwater are very high, causing significant health problems. It is also stable (not degraded) under high oxygen conditions.
Nitrate levels above 10 mg/L (10 ppm) in ground water can cause "blue baby syndrome" (acquired methemoglobinemia). The drinking water quality standards in the EU set less than 50 mg/L for nitrate in drinking water.
However, the relationship between nitrate in drinking water and blue baby syndrome has been debated in other studies. Outbreaks of the syndrome may be caused by factors other than high concentrations of nitrate in drinking water.
Increased levels of nitrate in ground water can be caused by on-site sanitation, sewage sludge disposal and agricultural activities. It can therefore have a town or agricultural origin.
Organic compound
Volatile organic compounds (VOCs) are harmful contaminants from ground water. They are generally introduced into the environment through careless industrial practice. Many of these compounds were not known to be dangerous until the late 1960s and it was some time before groundwater testing regularly identified these substances in drinking water sources.
Primary VOC pollutants found in ground water include aromatic hydrocarbons such as BTEX (benzene, toluene, ethylbenzene and xylene), and chlorinated solvents including tetrachlorethylene (PCE), trichlorethylene (TCE), and vinyl chloride (VC). BTEX is an important component of gasoline. PCE and TCE are industrial solvents that have historically been used in dry cleaning processes and as metal degreasers, respectively.
Other organic pollutants present in ground water and derived from industrial operations are polycyclic aromatic hydrocarbons (PAHs). Due to its molecular weight, Naphthalene is the most soluble and mobile PAH found in ground water, while benzo (a) pyrene is the most toxic. PAH is generally produced as a by-product by the incomplete combustion of organic matter.
Organic pollutants can also be found in groundwater as insecticides and herbicides. Like many other synthetic organic compounds, most pesticides have very complex molecular structures. This complexity determines water solubility, adsorption capacity, and pesticide mobility in ground water systems. Thus, some types of pesticides move more easily than others so they can more easily reach drinking water sources.
Metal
Some metal traces occur naturally in certain rock formations and can enter the environment from natural processes such as weathering. However, industrial activities such as mining, metallurgy, solid waste disposal, paint and enamel work, etc. can lead to increased concentrations of toxic metals including lead, cadmium and chromium. These contaminants have the potential to make their way into groundwater.
Metal (and metalloid) migration in groundwater will be affected by several factors, especially by chemical reactions that determine the contaminant partition between different phases and species. Thus, the mobility of the metal depends mainly on the pH and the redox state of the groundwater.
Pharmacy
Tracking the number of medicines from processed waste water infiltrated into the aquifer is among the emerging groundwater contaminants being studied throughout the United States. Popular drugs such as antibiotics, anti-inflammatories, antidepressants, decongestants, sedatives, etc. Usually found in treated wastewater. This waste water is discharged from the treatment facility, and often into the aquifer or surface water source used for drinking water.
Tracking the number of medicines in both ground water and surface water is far below what is considered dangerous or alarming in most areas, but can become an increasing problem as populations grow and more reclaimed waste water is used for municipal water supplies.
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Other organic pollutants include various organohalides and other chemical compounds, petroleum hydrocarbons, various chemical compounds found in personal hygiene and cosmetic products, drug pollution involving pharmaceutical drugs and their metabolites. Inorganic pollutants may include other nutrients such as ammonia and phosphate, and radionuclides such as uranium (U) or radon (Rn) naturally exist in several geological formations. Salt water intrusion is also an example of natural contamination, but it is very intensified by human activity.
Groundwater pollution is a world problem. A study of groundwater quality from major US aquifers conducted between 1991 and 2004 showed that 23% of domestic wells had contaminants to a greater extent than human health benchmarks. Other studies show that major groundwater pollution problems in Africa, given the importance sequence are: (1) nitrate pollution, (2) pathogenic agents, (3) organic pollution, (4) salinization, and (5) acid mine drainage.
Maps Groundwater pollution
Cause
Causes of groundwater contamination include:
- Occurs naturally (geogenically)
- On-site sanitation system
- Waste (treated and not treated)
- Fertilizers and pesticides
- Commercial and industrial leaks
- Hydraulic breaking
- Landfill leachate
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Occurs naturally (geogenically)
"Geogenic" refers naturally as a result of geological processes.
Natural arsenic pollution occurs because aquifer sediments contain organic matter that results in an anaerobic conditions in the aquifer. This condition results in the dissolution of the iron oxide microbes in the sediment and, thus, the release of arsenic, usually highly bonded with iron oxide, into the water. As a result, arsenic-rich ground water is often iron-rich, although secondary processes often obscure the association of soluble arsenic and dissolved iron. Arsenic is found in the most common groundwater as the arsenite of the reduced species and the oxidized species of arsenate, becoming acute. arsenite toxicity is somewhat greater than that of arsenate. Investigations by WHO indicate that 20% of the 25,000 boreholes tested in Bangladesh have an arsenic concentration exceeding 50 μg/l.
The occurrence of fluoride is closely related to the abundance and solubility of fluoride-containing minerals such as fluorite (CaF2). The very high concentrations of fluoride in ground water are usually caused by a lack of calcium in the aquifer. Health problems associated with dental fluorosis can occur when the concentration of fluoride in ground water exceeds 1.5 mg/l, which is the WHO guideline value since 1984.
The Swiss Institute of Water Science and Technology (EAWAG) has recently developed an interactive Groundwater Assessment Platform (GAP), where the geogenic risk of contamination in certain areas can be estimated using geological, topographic and other environmental data without the need to test the sample. from every groundwater source. The tool also allows users to generate probability risk mapping for both arsenic and fluoride.
High concentrations of parameters such as salinity, iron, manganese, uranium, radon and chromium, in ground water, may also be derived from geogenic. These contaminants can be important locally but they are not as widespread as arsenic and fluoride.
On-site sanitation system
Groundwater pollution with pathogens and nitrates can also occur from liquids entering the soil from sanitation systems in places such as latrines and septic tanks, depending on population density and hydrogeological conditions.
The factors that control fate and transport pathogens are complex and the interactions between them are not well understood. If local hydrogeological conditions (which may vary within a few square kilometers) are ignored, a simple on-site sanitation infrastructure such as a latrine can cause significant public health risks through contaminated ground water.
The liquid flows from the hole and passes through an unsaturated soil zone (which is not completely filled with water). Furthermore, this fluid from the pit enters groundwater where they can cause groundwater contamination. This is a problem if the nearest water well is used to supply ground water for drinking water. During travel on the ground, the pathogen may die or be adsorbed significantly, depending largely on the travel time between the pit and the well. Most, but not all pathogens die within 50 days of travel through the subsurface.
The degree of pathogen removal varies greatly with soil type, aquifer species, distances and other environmental factors. For example, the unsaturated zone becomes "washed" during long periods of heavy rain, providing a hydraulic pathway to pass pathogens rapidly. It is difficult to estimate the safe distance between latrines or septic tanks and water sources. However, such recommendations about safe distance are largely ignored by those who built pit latrines. In addition, household plots are of limited size and hence pit latrines are often built closer to groundwater wells than can be considered safe. This causes groundwater pollution and household members to fall ill when using this ground water as a source of drinking water.
Sewage (treated and not handled)
Ground water pollution can be caused by unprocessed waste discharges that cause diseases such as skin lesions, bloody diarrhea and dermatitis. This is more common in locations with limited wastewater treatment infrastructure, or where there is a systematic failure of the on-site waste disposal system. Along with pathogens and nutrients, untreated waste can also have an important charge of heavy metals that can seep into groundwater systems.
Wastes treated from a sewage treatment plant may also reach the aquifer if the waste is infiltrated or disposed of into local surface water bodies. Therefore, substances that are not disposed in a conventional waste treatment plant can reach ground water as well. For example, the concentrations of pharmaceutical residues detected in groundwater are in the order of 50 ng/L in some locations in Germany. This is because in conventional waste processing plants, micro pollutants such as hormones, pharmaceutical residues, and other micro pollutants contained in urine and feces are only partially removed and the remainder discharged into surface water, from where it can also reach groundwater.
Groundwater contamination can also occur from leaky culverts that have been observed eg in Germany. This can also lead to cross-contamination of drinking water supplies.
Spreading wastewater or mud wastes on farms can also be included as a source of fecal contamination in groundwater.
Fertilizers and pesticides
Nitrates can also enter the ground water through excessive use of fertilizers, including the spread of feces. This is because only a small part of the nitrogen-based fertilizer is converted into production and other plant matter. The rest accumulates on the ground or disappears as run-off. High application levels of nitrogen-containing fertilizers combined with the high solubility of water from nitrate cause increased runoff to surface water and washing into ground water, thus causing groundwater contamination. Excessive use of nitrogen fertilizers (both synthetic and natural) is extremely destructive, as many of the nitrogen not picked up by plants is converted to nitrate that is easily washed.
Nutrition, especially nitrates, in fertilizers can cause problems for natural habitats and for human health if they clean the soil into the water stream or wash through the soil into the ground water. The use of many nitrogen fertilizers in planting systems is the largest contributor of anthropogenic nitrogen in groundwater around the world.
Feedlots/animal roots can also lead to washing of nitrogen and metal potentials into ground water. More than the application of animal waste can also result in groundwater contamination with pharmaceutical residues derived from veterinary medicines.
The US Environmental Protection Agency (EPA) and the European Commission are seriously addressing nitrate issues related to agricultural development, as a major water supply problem requiring sound management and governance.
Pesticide runoff can seep into ground water causing human health problems from contaminated wells. The concentrations of pesticides found in ground water are usually low, and often the lower human health-based limits are also very low. Monocrotophos insecticide organophosphorus (MCP) appears to be one of several harmful, persistent, dissolves and mobile (not binding with minerals in the soil) pesticides are able to reach drinking water sources. In general, more pesticide compounds are detected because the groundwater quality monitoring program is becoming more widespread; however, fewer monitoring has been undertaken in developing countries due to the high cost of analysis.
Commercial and industrial leakage
Various kinds of inorganic and organic pollutants have been found in the aquifers underlying commercial and industrial activities.
The ore mining and metal processing facilities are primarily responsible for the presence of metals in groundwater of anthropogenic origin, including arsenic. The low pH associated with drainage mine acid (AMD) contributes to the potential toxic metal solubility that can eventually enter the ground water system.
There is increasing concern over groundwater contamination by leaking gasoline from underground petroleum storage tanks (USTs) from gas stations. The BTEX compound is the most common additive of gasoline. The BTEX compound, including benzene, has a lower density of water (1 g/ml). Similar to an oil spill in the sea, an un-mixable phase, called a Light-Fluid Fluid (LNAPL), will "float" above the water surface in the aquifer.
Chlorinated solvents are used in almost all industrial practices where degreasing remover is required. PCE is a highly used solvent in the dry cleaning industry because of its relatively low cleaning and cost effectiveness. It has also been used for metal scouring operations. Because it is highly volatile, it is more commonly found in ground water than in surface water. TCE has historically been used as a metal cleaner. The Anniston Army Dept. (ANAD) military facility in the United States is deployed on the US EPA Superfund National Priorities List (NPL) due to groundwater contamination with as much as 27 million pounds of TCE. Both PCE and TCE can reduce vinyl chloride (VC), the most toxic chlorinated hydrocarbon.
Many types of solvents may have been disposed of illegally, leaking from time to time into the groundwater system.
Chlorinated solvents such as PCE and TCE have a higher density of water and an incompatible phase is referred to as the Non-Aqueous Liquid Phase (DNAPL). Once they reach the aquifer, they will "drown" and eventually accumulate above the low permeability layer.
Historically, wood processing facilities have also released insecticides such as pentachlorophenol (PCP) and creosote into the environment, affecting groundwater resources. PCP is a highly soluble and toxic worn pesticide recently registered in the Stockholm Convention on Persistent Organic Pollutants. PAHs and other semi-VOCs are common contaminants associated with creosote.
Although it can not be mixed, LNAPL and DNAPL still have the potential to slowly dissolve into an aqueous (mixed) phase to create clots and thus be a source of long-term contamination. DNAPL (chlorinated solvents, heavy PAHs, creosots, PCBs) tend to be difficult to manage because they can be deeply groundwater systems.
Hydraulic breakage
The recent growth of Hydraulic Fractures ("Fracking") of wells in the United States has raised concerns about the potential risks of pollution of groundwater resources. The Environmental Protection Agency (EPA), along with many other researchers, has been delegated to study the relationship between hydraulic fracturing and drinking water sources. While it is possible to conduct hydraulic fractures without having any relevant impact on groundwater resources if strict controls and quality management measures exist, there are a number of cases where groundwater pollution due to improper handling or technical failure is observed.
While the EPA has not found significant evidence of the widespread systematic impact on drinking water with hydraulic fracturing, this may be due to lack of systematic prior and after systematic hydraulic data on drinking water quality, and the presence of other contamination agents that hinder the relationship between oil/shale gas and its effects.
Despite the widespread lack of evidence from the EPA, other researchers have made significant observations of increased groundwater contamination near major oil shale/drilling sites located in Marcellus (British Columbia, Canada). Within one kilometer of these specific places, a small fraction of shallow water consistently exhibits higher concentrations of methane, ethane, and propane concentrations than normal. Evaluation of the higher concentrations of Helium and higher gases along with the increase in hydrocarbon levels supports the difference between hydraulic fracture gases and naturally occurring "background" hydrocarbon content. This contamination speculates as a result of a leaking gas well casing, failing, or incorrectly installed.
Further, it is suggested that contamination may also occur due to capillary migration from the remnants of deep hyper-saline water and hydraulic fracturing fluid, slowly flowing through cesarean and fractures until finally in contact with groundwater resources; However, many researchers argue that the permeability of rocks above the shale formation is too low to allow this to occur sufficiently. To finally prove this theory, there must be traces of toxic trihalomethanes (THM) because they are often associated with the contamination of wild gases, and usually occur along with high halogen concentrations in hyper-saline waters. In addition, very salty water is a natural feature common in deep ground water systems.
While the conclusions about groundwater pollution as a result of hydraulic fracture fluid flow are limited in time and space, the researchers have hypothesized that the potential for systematic wild gas contamination is highly dependent on the integrity of shale oil/gas shale structures, together with their relative. geological location to a local fracture system that potentially provides a flow path for gas migration of the fugitives.
Although extensive and systematic contamination by hydraulic fractures has been highly debated, one major source of contamination that has the greatest consensus among researchers as the most problematic is the accidental spillage in certain places from the hydraulic fracturing liquid and the resulting water. So far, most groundwater contamination events have come from the surface level of the anthropogenic route rather than the subsurface flow of the underlying shale formation. Examples of such events include: a turbulent liquid spill at Acorn Fork Creek, Kentucky that caused widespread death among aquatic species in 2007; a 420,000-gallon spill of water produced by hyper-saline that transforms fertile farmland in New Mexico into a dead zone in 2010; and a 42,000-gallon liquid spill in Arlington, Texas that requires the evacuation of more than 100 homes by 2015. While the damage can be seen clearly, and much effort is being made to prevent these accidents from occurring so often, the lack of data from oil spill fracking continues to leave the researchers in the dark. In many of these instances, data obtained from leaks or spills is often very unclear, and thus will cause the researcher to have no conclusions.
Researchers from the Federal Institute for Geosciences and Natural Resources (BGR) undertook modeling studies for the formation of deep-shale gas in the North German Basin. They conclude that the small likelihood that the emergence of fracking fluids through geologically subsurface to surface will impact shallow groundwater.
Landfill leachate
Leachate from sanitary landfills can cause groundwater pollution.
Love Canal is one of the most well known examples of groundwater pollution. In 1978, residents in the Love Canal neighborhood of New York said the high rates of cancer and birthrate were alarming. This is ultimately traced to organic solvents and dioxins from an industrial TPA whose environment has been built over and over, which is then infiltrated into the water supply and evaporates in the basement to further contaminate the air. Eight hundred families were replaced for their homes and relocated, following legal battles and extensive media coverage.
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Further causes of groundwater contamination are chemical spills from commercial or industrial operations, chemical spills occurring during transport (eg diesel fuel spills), illegal waste disposal, infiltration of urban runoff or mining operations, road salt, frozen chemicals from airports and even atmospheric contaminants since groundwater is part of the hydrologic cycle.
Their subsequent burial and subsequent degradation may also pose a risk of contamination of groundwater.
Mechanism
Waterways through subsurface can provide a reliable natural barrier for contamination but only work under favorable conditions.
Regional Stratigraphy plays an important role in the transport of pollutants. An area may have sandy soil layers, cracked rocks, clay, or hardpan. The topographical area of ​​karst in limestone rocks is sometimes susceptible to surface pollution from ground water. Earthquake disturbance can also be the entry route to enter contaminants down. Water surface conditions are essential for drinking water supply, agricultural irrigation, waste disposal (including nuclear waste), wildlife habitats, and other ecological issues.
Many chemicals undergo reactive decay or chemical changes, especially over long periods in the groundwater reservoir. Noteworthy classes of such chemicals are chlorinated hydrocarbons such as trichlorethylene (used in the degreasing metal industry and electronics manufacturing) and tetrachlorethylene used in the dry cleaning industry. Both of these chemicals, which are self-carcinogens, undergo partial decomposition reactions, leading to new harmful chemicals (including dichloroethylene and vinyl chloride).
Interaction with surface water
Although interconnected, surface water and ground water are often studied and managed as separate resources. Surface water seeps through the soil and becomes ground water. Conversely, ground water can also feed the surface water source. The sources of surface water pollution are generally grouped into two categories based on their origin.
The interaction between groundwater and surface water is very complex. As a result, groundwater contamination, sometimes referred to as groundwater contamination, is not easily classified as surface water pollution. By their very nature, groundwater aquifers are susceptible to contamination from sources that may not directly affect surface water bodies, and point differences versus non-point sources may be irrelevant.
An ongoing spill or ongoing chemical or radionuclide contaminant (located away from surface water bodies) can not create source or non-point pollution but can contaminate the aquifer below, creating a toxic lump. The movement of lumps, can be analyzed through a hydrological transport model or groundwater model.
Prevention
Prudential principles
The precautionary principle, which evolved from Principle 15 of the Rio Declaration on Environment and Development, is essential in protecting groundwater resources from pollution. The precautionary principle stipulates that "where there is a threat of permanent damage, lack of full scientific certainty will not be used as an excuse to delay cost-effective measures to prevent environmental degradation."
One of the six basic principles of water policy of the European Union (EU) is the application of prudential principles.
Groundwater quality monitoring
Groundwater quality monitoring programs have been implemented regularly in many countries around the world. They are an important component for understanding hydrogeological systems, and for the development of conceptual models and aquifer vulnerability maps.
Groundwater quality should be monitored regularly throughout the aquifer to determine trends. Effective groundwater monitoring should be driven by specific objectives, for example, special contaminants of concern. The level of contaminants can be compared with the World Health Organization (WHO) guidelines for drinking water quality. Not infrequently the contaminant limit is reduced because more medical experience is gained.
Adequate investment should be provided to continue monitoring over the long term. When a problem is found, action must be taken to correct it. Water-borne outbreaks in the United States declined with the introduction of tighter monitoring (and treatment) requirements in the early 90s.
Communities can also help monitor groundwater quality.
Land zoning for groundwater protection
The development of land use zoning maps has been implemented by several water authorities at different scales around the world. There are two types of zoning maps: aquifer vulnerability maps and source protection maps.
Map of aquifer vulnerability
This refers to the intrinsic (or natural) susceptibility of groundwater systems to pollution. Intrinsically, some aquifers are more susceptible to pollution than other aquifers. A shallow aquifer is more at risk of contamination because there are fewer layers to filter out contaminants.
Unsaturated zones may play an important role in slowing down (and in some cases eliminating) pathogens and should be considered when assessing the susceptibility of aquifers. The largest biological activity in the upper soil layer where attenuation of pathogens is generally most effective.
The preparation of vulnerability maps usually involves overlaying some of the thematic physical factor maps that have been selected to illustrate the susceptibility of the aquifer. The GOD index-based parametric mapping method developed by Foster and Hirata (1988) uses three generally available or predictable parameters, the level G hydraulic round water barrier, the geological properties of O verify strata and D seventh to ground water. A further approach developed by the US EPA called DRASTIC employs seven hydrogeological factors to develop susceptibility index: D ep to water table, net R echarge, A media quifer, S oil media, T opography (slope), I mpact in vadose zone, and hydraulic C onduktivitas.
There is a special debate among hydrogeologists, whether aquifer susceptibility should be generalized (intrinsic) for all contaminants, or specifically for each pollutant.
Source protection map
This refers to areas of catching around individual groundwater sources, such as water wells or springs, to protect them from contamination. Thus, potential sources of degradable pollutants, such as pathogens, can be placed at distances traveling along long flow paths for pollutants to be removed by filtration or adsorption.
The analytical method uses the equation to determine the flow of ground water and the most widely used contaminant transport. WHPA is a semi-analytical groundwater flow simulation program developed by the US EPA to describe the catchment zone in the wellhead area of ​​protection.
The simplest form of zoning uses a fixed distance method where activities are excluded within a certain range that are applied uniformly around the point of abstraction.
Finding an on-site sanitation system
Because the health effects of most toxic chemicals arise after prolonged exposure, the health risks of chemicals are generally lower than those from pathogens. Thus, the quality of source protection measures is an important component in controlling whether pathogens can be present in the final drinking water.
On-site sanitation systems can be designed in such a way that groundwater contamination of these sanitation systems is prevented. Detailed guides have been developed to estimate the safe distance to protect groundwater sources from pollution from on-site sanitation. The following criteria have been proposed for the determination of a safe location (ie location determination) of on-site sanitation systems:
- Horizontal distance between drinking water source and sanitation system
- The guide value for the horizontal separation distance between on-site sanitation systems and water sources varies considerably (eg horizontal distance between 15 to 100 m between the pit and groundwater wells)
- The vertical distance between drinking water and sanitation systems
- Type aquifer
- Ground water flow direction
- Layers that are easy to unravel
- Tilt and surface drainage
- Volume of leaking wastes
- Superposition, which is the need to consider larger planning areas
As a very general guideline it is recommended that the bottom of the pit should be at least 2 m above the groundwater level, and a minimum horizontal distance of 30 m between the hole and the water source is usually recommended to limit exposure to microbial contamination. soup> [1] However, no general statement is made regarding the minimum lateral separation spacings required to prevent well contamination from the pit pit. For example, even a 50 m lateral separation distance may be insufficient in a strong karstification system with a supply of downgradient or spring wells, while a 10 m lateral separation distance is sufficient if there is a well-developed clay cover layer and the annular chamber of groundwater is well sealed well.
Legislation
Institutional and legal issues are critical in determining the success or failure of groundwater protection policies and strategies.
United States
In November 2006, the Environmental Protection Agency issued the Ground Water Regulations in the Federal Register of the United States. The EPA is worried that the ground water system will be vulnerable to contamination from impurities. The point of the rule is to keep pathogenic microbes out of public water sources. The 2006 Ground Water Regulation was an amendment to the Safe Drinking Water Act of 1996.
Ways to deal with groundwater contamination that have occurred can be grouped into the following categories: they contain pollutants to prevent them from migrating further; removing pollutants from aquifers; reheating aquifers by paralyzing or detoxifying contaminants while they are still in the aquifer; treating ground water at its point of use; or abandon the use of this aquifer ground water and seek alternative sources of water.
Management
Care point-of-use
Portable water purification or point-of-use (POU) water treatment and field water disinfection techniques can be used to remove some form of groundwater contamination before drinking, ie fecal pollution. Many commercial portable water purification systems or chemical additives are available that can remove pathogens, chlorine, bad taste, odors, and heavy metals such as lead and mercury.
Techniques include boiling, filtering, active charcoal absorption, chemical disinfection, ultraviolet purification, ozone water disinfection, solar water disinfection, solar refining, homemade water filters.
Arsenic removal filters (ARF) are special technologies that are usually installed to remove arsenic. Many of these technologies require long-term capital investment and maintenance. Filters in Bangladesh are usually abandoned by users due to their high cost and complicated maintenance, which is also quite expensive.
Groundwater improvement
Ground water pollution is much more difficult to subside than surface pollution because groundwater can move far past an invisible aquifer. A non-porous aquifer such as clay partially purifies bacterial water by simple filtration (adsorption and absorption), dilution, and, in some cases, chemical reactions and biological activity; However, in some cases, the pollutants simply turn into soil contaminants. Groundwater moving through open fractures and caves is not filtered and can be transported as easily as surface water. In fact, this can be exacerbated by the human tendency to use natural exhaust pits as a disposal site in karst topographic areas.
Pollutants and contaminants can be removed from ground water by applying various techniques so it is safe to use. The groundwater treatment (or remediation) technique extends to biological, chemical, and physical treatment technologies. Most groundwater treatment techniques use a combination of technologies. Some biological treatment techniques include bioaugmentation, bioventing, biosparging, bioslurping, and phytoremediation. Some chemical treatment techniques include ozone and oxygen gas injection, chemical deposition, membrane separation, ion exchange, carbon sequestration, aqueous chemical oxidation, and increased surfactant recovery. Some chemical techniques can be implemented using nanomaterials. Physical maintenance techniques include, but are not limited to, pumps and treatments, air suction, and multiple phase extraction.
Abandonment
If care or remediation of contaminated groundwater is considered too difficult or expensive then ignoring the use of this aquifer groundwater and finding an alternative source of water is the only other option.
Society and culture
Example
Hinkley, U.S.
The town of Hinkley, California (USA), has contaminated ground water with hexavalent chromium which began in 1952, produced a legal case against Pacific Gas & Electricity (PG & E) and the settlement of millions of dollars in 1996. The legal case was dramatized in the film Erin Brockovich, released in 2000.
Walkerton, Canada
Walkerton,In 2000, ground water contamination occurred in the small town of Walkerton, Canada which caused seven deaths in what is known as Walkerton E. coli outbreak. Water supply extracted from ground water is contaminated with the highly dangerous O157: H7 strain of bacteria E. coli. This contamination is due to agricultural runoff to adjacent water wells susceptible to groundwater contamination. Lusaka, Zambia
The suburbs of Lusaka, the capital of Zambia, have very hardened soil conditions and for this reason - along with the increasing population density in the suburbs - the well water pollution of latrines is a great public health. threats there.
References
External links
- The USGS Ground Office
- UK Groundwater Forum
- IGRAC, International Land Resource Assessment Center
- IAH, International Hydrogeological Association
- The Argoss Project from the British Geological Survey
- Groundwater and sanitation pollution (document at the library of Sustainable Sanitation Alliance)
- UPGro - Unlocking Groundwater Potential for the Poor
Source of the article : Wikipedia
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