9

Soil Microorganisms and Nematodes for Bioremediation and Amelioration

TABLE 1.2 Optimum Conditions for Bioremediation of Environmental Pollutants

Environmental Factor Conditions Required for Microbial Activity

References

Available soil moisture 25–85% water holding capacity

Harekrushna &

Kumar (2012);

Oxygen

Aerobic, minimum air-filled pore space of 10%

Haghollahi,

Soil type

Low clay or silt content

Fazaelipoor, &

pH

5.5–8.5

Schaffie (2016)

Temperature

15–45°C

The detoxification or remediation of the site requires oxygen and nutrient

by circulating the polluted soil to facilitate the degradation of the organic

pollutant by the naturally occurring bacteria. The process of bioremediation

was reported to be the cheapest and most effective method for detoxification

of heavy metals in soil (Kumar et al., 2011). In situ bioremediation is of

mainly two types: (i) intrinsic in situ bioremediation; and (ii) engineered in

situ bioremediation.

1.3.1.1 INTRINSIC/NATURAL ATTENUATION IN SITU BIOREMEDIATION

It uses the biodegradation of toxic pollutants to harmless substances by the

innate capacity of the microorganisms already present in the environment

(Vidali, 2001). In this process, there is no interference of humans, and it is

considered the cheapest method of bioremediation which is widely known.

Scientists turn to engineered bioremediation when the intrinsic bioremedia­

tion is not feasible under certain circumstances.

1.3.1.2 ENGINEERED/ENHANCED IN SITU BIOREMEDIATION

The aforementioned process requires the introduction of the microbes into the

site of the contamination. Moreover, in this method, there may be the addi­

tion of engineered microbes for the bioremediation process. This enhances

and accelerates the process of degradation of heavy metals by improving the

physiochemical condition and growth of microbes. Mainly, electron accep­

tors, nutrients, and oxygen are added along with nitrogen and phosphorus

to enhance the development of the microbes (Rodríguez et al., 2009). Some

important in situ bioremediation processes are discussed hereunder.