Soil Remediation Methods Part II

Some of the common methods of soil remediation: 

1. Water-treatment/filter method: not favorable for places with water shortages and water sources which are used directly without treatment.

2. Soil screening: 

•       Soils are sorted by machines (sieves), and smaller clay, slit and organic matter are removed for further treatment because most organic and inorganic contaminants tend to bind, chemically or physically to these particulates.
•       Soils can also be sorted by electrokinetics: A current is passed between the two electrodes to attract and separate heavy metal contaminated soils.

3. Soil removal and landfill disposal: This method is usually used when other remediation methods are not able to remove contaminants to acceptable levels according to land-use requirements (i.e. for residential or school uses, contaminant levels are required to be at very low levels). However, the landfill disposal infrastructure must be able to prevent pollutants from seeping into the surrounding environment, and huge disruptions are made to the original landscapes. 

4. Soil washing: after soil has undergone physical screening, chemical extraction (acid, chelating agents EDTA, surfactants) will be added to remove contaminants. Usually acids are used:

• desorption of metal cations via ion exchange or de-complexation,
• dissolution of metal compounds
• dissolution of soil mineral compounds (Fe/Mn oxides)

However, strong acids also destroy the soil structure, creates problematic waste water and there needs to be proper disposal of solid/liquid waste.

5. Phyto-remediation: uses plants certain plant species—known as metal hyperaccumulators which have the ability to extract elements (heavy metals) from the soil and concentrate them in the easily harvested plant stems, shoots, and leaves (ARS, 2014). This method is preferred as it does not disrupt the landscape as compared to other methods, but the time taken for remediation is much longer. 

There are no perfect solutions to soil remediation, and every method has its advantages and disadvantages. Therefore, it is paramount that we control and minimize soil pollution before it needs remediation. 

References: 
ARS (2014) Phytoremediation: Using Plants To Clean Up Soils. Online, Available at: http://www.ars.usda.gov/is/ar/archive/jun00/soil0600.htm

All these methods are elaborated in detail on many online videos, such as: 

Video of soil washing in London before the summer Olympics 2008.
Available at: https://www.youtube.com/watch?v=wJ8Vp_KZ4lE

Video of Phytoremediation rehabilitation hydrocarbon contaminated soils in Belgium. Available at: https://www.youtube.com/watch?v=wt0hkcHYTe0