Contamination of soil can occur due to human activities where unsafe substances may not be disposed of or used in a safe manner. High soil contamination occurs in industrial sites and urban areas, where land development, manufacturing, waste disposal, industrial dumping, and excessive fertilizer or pesticide use could likely arise.
Agricultural chemical contaminants are set to the surface of the soil. The rest are contaminated beneath the surface, due to leaking from landfills, tanks, or sewage pipes that are buried. Atmospheric contaminants that contain substances that are hazardous are also a problem. Contamination isn’t limited to 1 site or area; it can move to close by waterways and land in dust or rainwater or seep through the soil into groundwork. Listed below are some of the most effective environmental oil contamination treatment methods.
The harmful effects of Soil Contamination
Animals and people can become exposed to contaminated soil in many ways by breathing dust and violates, ingesting soil, if you eat food that was growing in degraded and infected contaminated soil, or by the absorption of contaminants through the skin. Depending on the level of exposure and the contamination type, contaminated soil can cause many significant health issues. This can hinder building work and potentially hinder land use. Until soil remediation has occurred, you will continue to be at risk from the environment.
Contaminated soil treatment methods
Once you have performed a test to resolve the level and type of contaminants that are present, remediation methods can take place in the soil for the purpose of site decontamination. Treatment options include:
- Bioremediation/ biological treatment
- Soil stabilisation
- Methods that are physical like soil washing
- Chemical oxidation
Bioremediation treatment involves using a biological process to transform, remove, and essentially degrade contaminants from water and soil. This method relies on microorganisms including fungi or bacteria which they use as a food source. For this reason, bioremediation is an effective means of mitigating and is widely used for remediating organic contaminants.
- Nitrogen compounds
- Halogenated organic solvents
- Metals (chromium, lead, mercury)
- Non-chlorinated herbicides and pesticides
- Halogenated organic compounds
Bioremediation can take from 1 to many months to fullfill and often presents as a more economical choice for disposing. Since the very beginning, bioremediation has been natures favoured method for reestablishing harmony to soils and groundwater. In today’s environment, bioremediation has become more fundamental than any other time due to the huge increment in man-made contaminants.
Benefits of bio remediation
- No toxic end products
- Low cost
- Treat mixed contaminants in situ method (no transportation costs)
- Creates a green ecosystem when used with a phytoremediation approach
- Environmentally friendly (no chemical treatments and incineration)
- Can be used to treat very large volumes of soil
- Stabilise heavy metal pollutants in soil matrix (prevents dispersal by wind)
Bio augmentation is a method where contaminated degraded bacteria are introduced to the contaminated media to enhance/promote degradation. The method isn’t that simple as the bacteria are in suitable to certain types of PHs, and soil and therefore introducing them to a new environment involves determining the right type of bacteria for that environment and to manage the contaminated materials once the bio augmentation has taken place. Bioremediation can be undertaken ex-situ or in-situ.
Ex-situ bio remediation
Ex-situ bio remediation process involves excavated soil being placed in a lined above ground treatment area and aerated following processing to enhance the degradation of organic contaminants by the indigenous microbial population. Ex-situ bioremediation can remediate a wide range of hydrocarbon contaminants which include:
- Polycyclic aromatic hydrocarbons
- General hydrocarbons
- Straight chain aliphatic
- Semi-volatile organic compounds
- Diesel range hydrocarbons lubricating oils
Also, cooking oils from restaurants are another part of the environmental problem, companies such as Frylite offer free waste cooking oil collection and recycling through the UCO initiative.
In-situ bioremediation is a biological treatment of contaminated groundwater and soil without treating and pumping groundwater above the soil and without excavating the soil. It relies on the use of plants or microbes to immobilise or degrade contaminants in situ and the technology brings together a combination of geological, microbiological, engineering, and chemical sciences.
Bio stimulation is a method of increasing the rate of the natural degradation processes. This technique involves determining the limit factors in the natural process, I.e. oxygen availability for the bacteria which is often limited in soils at depth, and balancing that factor to increase the rate of degradation.
Soil stabilisation involves locking soil contaminants effectively in the soil reducing the risk of contamination. You can achieve this process in 2 ways, these include:
- By solidification, by reducing the contaminant mobility and binding it in position so it cannot reach any receptors.
- By modifying the contaminant in the ground to a less dangerous form.
Stablising the soil relies on the addition of immobilizing agents which reduces a contaminants bioavailability and leachability. This method can also help with the improvement of the geotechnical competency of the ground, which would make it more suited for the construction industry due to lower permeability and higher resistance.
Physical methods (soil washing)
Soil washing is a soil washing technique using liquid soap solution to eliminate the hazardous contaminants. During the method, soils that are finely grained such as clays and silts along with the contaminants which can be prone to bind to fine soils are washed away. Both the cleaned coarse soils such as gravel and sand are separated from the contaminated fine grains. The coarse soils can be reused and are safe. Soil washing doesn’t remove or destroy the contaminants so the soil that is contaminated must be destroyed in a facility that is fully licensed.
The chemical oxidation method involves reactive chemical oxidants are injected into the groundwater and the soil for the purpose of complete and rapid contaminant destruction. ISCO In Situ chemical oxidation is a versatile solution, typically when remediating contaminants located in difficult to access areas such as soils beneath buildings and deep soils. Chemical oxidation has a wide range of applications and can be used to treat various organic contaminants such as PCBs, TPH, and BTEX.
Soil contamination can cause many different health risks to plants, animals, and humans, therefore in many cases soil remediation is necessary.