**5.7 Biosparging**

This technique is similar to bioventing in this air is injected into soil subsurface to improve microbial activities which stimulate pollutant removal from polluted sites. However, in bioventing, air is injected in saturated zone, which can help in upward movement of volatile organic compounds to the unsaturated zone to stimulate biodegradation process. The efficiency of biosparging depends on two major factors specifically soil permeability and pollutant biodegradability. In bioventing and soil vapor extraction (SVE), biosparing operation is closely correlated technique known as in-situ air sparging (IAS), which depend on high air-flow rates for volatilization of pollutant, whereas biosparging stimulates biodegradation. Biosparging has been generally used in treating aquifers contaminated with diesel and kerosene.

## **5.8 Phytoremediation**

Phytoremediation is depolluting the contaminated soils. This technique based on plant interactions like physical, chemical, biological, microbiological and biochemical in contaminated sites to diminish the toxic properties of pollutants. Which is depending on pollutant amount and nature, there are several mechanisms such as extraction, degradation, filtration, accumulation, stabilization and volatilization involved in phytoremediation. Pollutants like heavy metals and radionuclides are commonly removed by extraction, transformation and sequestration. Organic pollutants hydrocarbons and chlorinated compounds are mostly removed by degradation, rhizoremediation, stabilization and volatilization, with mineralization being possible when some plants such as willow and alfalfa are used [27, 28].

Some important factors of plant as a phytoremediator include: root system, which may be fibrous or tap depending on the depth of pollutant, above ground biomass, toxicity of pollutant to plant, plant existence and its adaptability to predominant environmental conditions, plant growth rate, site monitoring and above all, time mandatory to achieve the preferred level of cleanliness. In addition, the plant must be resistant to diseases and pests [29]. In phytoremediation removal of pollutant includes uptake, translocation from roots to shoots. Further, translocation and accumulation depends on transpiration and partitioning [30]. However, the process

**229**

*Bioremediation Techniques for Polluted Environment: Concept, Advantages, Limitations…*

is possible to change, depending on other factors such as nature of contaminant and plant. The mostly plants growing in any polluted site are good phytoremediators. Therefore, the success of any phytoremediation method mainly depends on improving the remediation potentials of native plants growing in polluted sites either by bioaugmentation with endogenous or exogenous plant. One of the major advantages of using plants to remediate polluted site is that some precious metals can bioaccumulate in some plants and recovered after remediation, a process known as phytomining.

This technique is commonly observed as a physical method for remediating contaminated groundwater. However, biological mechanisms are precipitation degradation and sorption of pollutant removal used in PRB method. The substitute terms such as biological PRB, bio-enhanced PRB, passive bioreactive barrier, have been suggested to accommodate the biotechnology and bioremediation aspect of the technique. In general, PRB is an in-situ technique used for remediating heavy

• In-situ bioremediation methods do not required excavation of the contami-

• This method provides volumetric treatment, treating both dissolved and solid

• It may be possible to completely transform organic contaminants to innocuous

• The time required to treat sub-surface pollution using accelerated in-situ bioremediation can often be faster than pump and treat processes.

• It is a cost effective method because there is minimal site disruption.

Depending on specific site, some contaminants may not be absolutely trans-

When incorrectly applied, injection wells may become blocked by profuse microbial growth due to addition of nutrients, electron donor and electron acceptor. Heavy metals and organic compounds concentration inhibit activity of indig-

Bioremediation techniques are varied and have demonstrated effective in restoring polluted sites. Microorganisms play fundamental role in bioremediation;

If transformation stops at an intermediate compound, the intermediate may be more toxic and/or mobile than parent compound some are recalcitrant contami-

In-situ bioremediation usually required microorganism's acclimatization, which

substances like carbon dioxide, water and ethane.

may not develop for spills and recalcitrant compounds.

metals and chlorinated compounds in groundwater pollution [31, 32].

*DOI: http://dx.doi.org/10.5772/intechopen.90453*

**5.9 Permeable reactive barrier (PRB)**

**5.10 Advantages of in-situ bioremediation**

**5.11 Limitation of in-situ bioremediation**

formed to harmless products.

nants cannot be biodegradable.

**6. Bioremediation prospects**

enous microorganisms.

nated soil.

contaminants.

*Bioremediation Techniques for Polluted Environment: Concept, Advantages, Limitations… DOI: http://dx.doi.org/10.5772/intechopen.90453*

is possible to change, depending on other factors such as nature of contaminant and plant. The mostly plants growing in any polluted site are good phytoremediators. Therefore, the success of any phytoremediation method mainly depends on improving the remediation potentials of native plants growing in polluted sites either by bioaugmentation with endogenous or exogenous plant. One of the major advantages of using plants to remediate polluted site is that some precious metals can bioaccumulate in some plants and recovered after remediation, a process known as phytomining.
