Generally speaking, contamination occurs when years of improper industrial activities have taken place on-site. This could be from unsuitable waste disposal methods or even pollution from agricultural activities. Soil contamination can also occur with the presence of underground storage tanks that leak. If the subject site had a landfill in the past, it also concerns because their waste can produce leachates that are harmful to the environment. Any form of contamination is a significant cause for concern as it poses threats to human health, animals, and the environment. Some types of contaminants release vapours or can be ingested directly if leaked into the water supply pipes.
The first step is to conduct a Phase I ESA to determine if contamination exists, which involves completing a records review and visual site inspection. If past activities indicate that contamination may exist, the assessor will move on to a Phase II ESA. This phase requires collecting samples of the contaminated media which are analyzed at a lab. The results dictate what the media’s composition is, and when contamination is confirmed, a Phase III ESA with a remediation plan is initiated.
Remediation is required when environmental contamination has been confirmed through a Phase I and Phase II ESA. Environmental remediation is usually considered to be Phase III of Environmental Site Assessments. This process involves removing chemicals from the soil, groundwater, surface water, or any form of environmental media. The types of chemicals that indicate contamination exists are any form of hydrocarbons, volatiles, semi volatiles, Sulphur, lead, heavy metals or cyanides. There are three main types of environmental remediation. This includes:
- Sediment remediation
- Groundwater remediation
- Soil remediation
Sediment remediation is required when clay, sand, or other sediments are contaminated in a water body. Groundwater or surface water remediation is necessary when the quality of water is below safe levels due to contaminants. This can occur when there are abandoned wells, septic tanks, landfills, etc. Surface water is more susceptible to contamination since it is water found in lakes, rivers, or other significant bodies. The contamination can also come from industrial wastes, agricultural wastes, etc.
The focus of this article is on soil remediation. Soil remediation, simply put, is when contaminants or pollutants that exist in the soil are removed. Depending on the type of chemical that exists, the remedial process can be thermal, physical, biological, or chemical.
Thermal remediation is usually used when there are hydrocarbon contaminants. It includes heating the contaminated media to evaporate water and other hydrocarbon impurities. A Primary Treatment Unit (PTU) is used to carry out the evaporation step in thermal remediation and is operated at high temperatures ranging from 340°C to 500°C. Then, the material is transferred to a cooling unit which is cooled by adding water. Once the material is discharged from the cooling unit, it is tested and recycled.
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