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| Version | User | Scope of changes |
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| Apr 16 2008, 5:22 PM EDT (current) | lamontequinn | 1 word added |
| Apr 16 2008, 5:22 PM EDT | lamontequinn |
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Typically, groundwater is relatively clean and safe to drink, having been filtered by the soil, sand, gravel, and rock that it percolated through on its way down to the water table. This is part of a process known as natural attenuation, which may also involve microorganism break-down of substances. Unfortunately, it is still rather easy to contaminate groundwater and difficult to clean. Sources of contaminants may come from agricultural runoff, industrial/chemical waste, environmental sources, domestic sources, and so on. Aquifers that are confined by an aquiclude generally do not become contaminated easily, but many aquifers lie uncovered without any impermeable layer on top. Contaminants may linger for years in some areas. The process of decontaminating groundwater is known as remediation.
Common methods of remediation consist of pumping water out of the water table,
treating it, and injecting it back into the ground or another natural water source. Contaminant plumes can also be contained and removed by manipulating the flow of groundwater through pumps. By injecting clean water into the ground, pressure is created which directs the plume to a certain area for containment or pump for removal. This procedure, however, can be costly and time-consuming. Other approaches to remediation involve air sparging, whereby air is pumped into the water table, generating bubbles that flush out contaminants and enhance the growth of organisms that can break down the contaminants naturally.
In-situ oxidation involves pumping an oxidizing agent, such as hydrogen peroxide, which will oxidize a contaminant plume, producing, for the most part, carbon dioxide and water.
Another method involves digging a trench and filling it with reactive materials, such as iron filings, activated carbon, or peat, that filter the groundwater as it flows through. This method, known as a permeable reactive barrier, is effective only for shallow aquifers.
Phytoremediation involves the use of plants and trees that are good at absorbing metals (e.g. Pb, U, Cd), metal-like elements (e.g. As, Se), hydrocarbons, and other toxins. The plants are positioned so that their roots grow directly into the water table. Once they have absorbed large amounts of contaminants, they are removed and disposed of. As with the trench barrier described above, this method is limited only to shallow aquifers.
Biodegradation involves using microorganisms to synthesize and
break down organic contaminants. The process usually results in carbon dioxide and methane products. Bioremediation is effective for removing hydrocarbons, and it often occurs naturally when bacterial levels are high and contaminant levels are low. Some bacteria do not require oxygen for contaminant break-down. Bacterial growth can be enhanced by injecting nutrients, carbon compounds, and oxygen (if necessary).
Sources:
oceanworld.tamu.edu
www.aquatechnologies.com
Common methods of remediation consist of pumping water out of the water table,
treating it, and injecting it back into the ground or another natural water source. Contaminant plumes can also be contained and removed by manipulating the flow of groundwater through pumps. By injecting clean water into the ground, pressure is created which directs the plume to a certain area for containment or pump for removal. This procedure, however, can be costly and time-consuming. Other approaches to remediation involve air sparging, whereby air is pumped into the water table, generating bubbles that flush out contaminants and enhance the growth of organisms that can break down the contaminants naturally. In-situ oxidation involves pumping an oxidizing agent, such as hydrogen peroxide, which will oxidize a contaminant plume, producing, for the most part, carbon dioxide and water.
Another method involves digging a trench and filling it with reactive materials, such as iron filings, activated carbon, or peat, that filter the groundwater as it flows through. This method, known as a permeable reactive barrier, is effective only for shallow aquifers.Phytoremediation involves the use of plants and trees that are good at absorbing metals (e.g. Pb, U, Cd), metal-like elements (e.g. As, Se), hydrocarbons, and other toxins. The plants are positioned so that their roots grow directly into the water table. Once they have absorbed large amounts of contaminants, they are removed and disposed of. As with the trench barrier described above, this method is limited only to shallow aquifers.
Biodegradation involves using microorganisms to synthesize and
break down organic contaminants. The process usually results in carbon dioxide and methane products. Bioremediation is effective for removing hydrocarbons, and it often occurs naturally when bacterial levels are high and contaminant levels are low. Some bacteria do not require oxygen for contaminant break-down. Bacterial growth can be enhanced by injecting nutrients, carbon compounds, and oxygen (if necessary). Sources:
oceanworld.tamu.edu
www.aquatechnologies.com
