There are many different ways in which soil can become contaminated. Perhaps the most obvious is when chemicals are split or pollution is discharged from a factory. Any contamination in the soil will affect the environment surrounding it.
Soil can also be contaminated by industrial processes, such as mining. In these cases, water and chemicals are blasted into surfaces and some of these substances will end up in the soil.
If left untreated, the contaminated soil is likely to disrupt the ecosystem, effectively killing small living organisms and damaging the very bottom of the food chain.
It’s essential that the latest soil washing techniques are understood and implemented.
How Soil Washing Happens
The majority of contaminants in the soil will bind with clay. That’s not surprising considering how sticky it is when it’s wet. To prevent these contaminants from damaging the surrounding environment it is necessary to extract the contaminants.
There are several distinct stages to the process:
The first stage requires the excavation of contaminated soil. It’s possible but rare to treat it in-situ. The pre-treatment stage is designed to remove larger particles. This is achieved through the use of heavy metal mesh and a jiggling table. Scalping is also an option.
Materials removed are not generally contaminated but they will get in the way of the treatment process.
The soil is now filtered again to separate the coarse grains from the finer ones. The definition of whether a particle is large or not can be set by the operator. It’s normal to set this at between 63 and 74 microns.
This process is completed using trommels or even mechanical screening.
The soil washing process starts with introducing a water and cleaning solution to the contaminated soil. A cleaning solution is chosen according to what contaminants are in the soil.
The solution and soil are left in a tank, allowing heavier particles to settle. The liquid is filtered off the top and checked for contaminants. It can be treated separately to eliminate any.
It’s common to use a variety of different chemical solutions in a wash-and-rinse type cycle to help remove all the contaminants in the soil.
The heavier particles that sink to the bottom of the tank can be removed separately. These should be free from contaminants and the soil can be put back where it came from.
Post-treatment means testing the soil for contaminants, re-introducing it to where it was extracted, and monitoring the area to ensure it remains uncontaminated.
Heavy machinery makes the soil washing process much easier and more manageable. The main reason to use a soil washing technique is to protect the environment. Contamination in the soil can be absorbed by small creatures in the soil.
These are food for larger creatures and the toxins they carry are likely to move up the food chain, ultimately posing a threat to humanity.
In short, everyone who has a risk of soil contamination needs to have an established and efficient soil washing procedure.
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