Page 196 - Soil Degradation, Conservation and Remediation

6.2 Sources of Soil Pollutants 185

be highly reactive due to their high surface-to-volume ratio and greater number
of reactive sites and higher intrinsic reactivity on reactive sites. In addition, NIP can
be injected directly into the contaminated zones, making the in situ remediation
faster and effective. Reddy ( 2010 ) has developed inexpensive and environmentally

benign lactate-modified NIP that are stable and capable of transporting in soils
and groundwater and dehalogenating organic pollutants such as pentachlorophenol
and dinitrotoluene.
Electrokinetic (EK) remediation (Lu et al. 2005 ) is a green remediation technology
developed recently for treatment of soils contaminated by heavy metals and
organic pollutants. It has become an important development in soil remediation
and has showed promising application prospects (Lageman 1993 ). The main advan-
tages of EK remediation are as follows: (1) capable of using for remediation of soils
with low permeability, (2) in situ remediation and decreasing on-spot pollution
to the least, (3) shorting remediation time, and (4) lowering the cost. Saichek and
Reddy ( 2005 ) summarized the applications of electrokinetically enhanced remedia-
tion of soils contaminated by hydrophobic organic compounds. Yap et al. ( 2011 )
reviewed Fenton-based treatments specifically for polycyclic aromatic hydrocarbon-

contaminated soils. Huang et al. ( 2012 ) summarized the performances of six enhanced
EK remediation methods for soils contaminated with organic pollutants: direct EK
technique, EK combined with Fenton technique, EK combined with surfactants/
cosolvents technique, EK combined with bioremediation method, the method of
Lasagna, and EK combined with ultrasonic remediation method.

Bioremediation of Organic Pollutants

Bioremediation is defined as the elimination, attenuation, or transformation of
polluting substances by the use of biological processes (Shukla et al. 2010 ). It uses
relatively low-cost, low-technology techniques, which generally has a high public
acceptance and can often be carried out on-site (Vidali 2001 ). It employs biological
agents, mainly microorganisms, for example, yeast, fungi, or bacteria, to clean up
contaminated soil. This technology includes biostimulation (stimulating viable native
microbial population), bioaugmentation (artificial introduction of viable population),

bioaccumulation (live cells), biosorption (dead microbial biomass), phytoremediation
(using plants), and rhizoremediation (plant and microbe interaction). So, bioremedia-
tion may broadly be grouped into (1) microbial remediation, (2) phytoremedia-
tion, and (3) rhizoremediation. Here, microbial remediation will be considered as
bioremediation proper. Phytoremediation and rhizoremediation will be discussed
separately.

Microbial Remediation

The first patent for a biological remediation agent was registered in 1974, which

was a strain of Pseudomonas putida (Prescott et al. 2002 ) able to degrade petroleum.
Now, more than 100 genera of microbes are used for organic pollution control of