1.1.      Terms in Remediation

Pollution is the discharge of a toxic or contaminating substance that is likely to have an adverse effect on the natural environment or life. Contaminant makes a place or a substance (such as water, air, or food) no longer suitable for use. Remediation restores contaminanted site to return them to their natural state. Environmental remediation is the removal of pollution or contaminants from soil, water (both ground water and surface water) and air. These waste products are removed for the protection of human health, as well as to restore the environment. These cleaned up sites can also be used for urban development. Environmental remediation is highly regulated and subject to an array of legal requirements, which are generally based on assessments of human health and environmental risks. Remediation projects can range from large, expensive projects, on which a great deal of effort is spent to clean up contaminated sites, to smaller, less costly projects, such as cleaning up a highway accident in which oil is spilled. Remediation projects usually begin with a site assessment to determine the costs of the project, as well as the technology that would be the most appropriate for the particular site.

Environmental remediation is carried out on various environmental media, including soil (topsoil, subsoil and sediment), water (groundwater and surface water) and air. Soil contamination can result from chemical spills, industrial activity, and the use of certain fertilizers and pesticides. Soil contamination is caused by many of the same factors that cause groundwater contamination. Water contamination may be the result of industrial practices (mining or drilling for natural gas and oil) and release of pollutants directly into the water or by runoff from the ground. Air contamination is caused by any substance that people introduce (greenhouse gases such as carbon dioxide (CO2), methane, sulfur dioxide (SO2) and chlorofluorocarbons) or natural causes (forest fires, volcanic eruptions, wind erosion, pollen dispersal, evaporation of organic compounds, and natural radioactivity) into the atmosphere.

Soil remediation refers to strategies that are used to purify and revitalize the soil. Water remediation is the process of removing contaminants from water. Often, the soil and groundwater are contaminated from the same source (chemical spills, industrial activity, and the use of certain fertilizers and pesticides) and both must be remediated at the same time. Air remediation is the process of removing the presence of pollutants from the air.

The available remediation technologies for contaminated enviroment are mainly divided into two groups such as in situ and ex situ. In situ technology involves treating the contaminanted material at the site. Ex situ technology is a remediation option where the contaminant is removed from it’s original location and cleaned on-site or off-site. Various remediation technologies can be used to remove contaminants from the environment. The methods used at a particular site depend on the type and extent of the pollution, as well as the characteristics of the site itself. There are many different remediation methods, and new technologies are regularly being developed.

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