Biorremediation in soils

“In situ” and “ex situ” bioremediation

In situ bioremediation process consists of treating the contaminated material where it is. Ex situ bioremediation requires removing the contaminated material from its original place.

In situ bioremediation for treating the soils is advantageous since we don’t have to remove and transport the contaminated material, which allows us to treat big areas with low costs. However, it requires more time for the treatment, presents less flexibility to treat big amount of pollutants and different types of soil, and it is more effective in permeable soils, such as the sandy soils. Besides, it is a more difficult process to control and evaluate.

Ex situ bioremediation is indicated in cases of some risk of the contamination and when we can’t perform a spot treatment of the pollutants, for instance, due to the difficult accesses to the contaminated spots.

Biostimulation and bioadding are strategies of bioremediation, whose combined or isolated application could lead to a fast and complete degradation of the pollutants. As to the biostimulation, there is an increasing of the number of the degrading microorganisms or a stimulation of their activity in a contaminated area. This is achieved by adding nutrients, oxygen (aerobic process), nitrates, sulfates, carbon dioxide, and so on and is associated to the control of pH, temperature and humidity.

Bioadding is about adding microorganisms which are able to degrade the pollutant in the contaminated area. This technique requires many cares due to the environmental risks that the insertion of a non-native microorganism for the soil can cause.

Not all the contaminants are easily eliminated by bioremediation. The absorption of some metals such as mercury (Hg) can worsen the contamination. Phytoremediation, a strategy of bioremediation that uses plants, is useful in these circumstances, since plants are able to accumulate the toxins in its aerial parts that are collected later.

As any other technique, bioremediation has advantages and disadvantages. Therefore, there must be a detailed study of the conditions this technique will be applied in, so that it won’t cause future losses.

In the last 20 years, bioremediation has grown a lot, having passed from unknown technology to a technology which can be applied in a huge variety of contaminations. We are sure this is a good solution in order to treat polluted places and, this way, protect people and the environment.