5

Soil Microorganisms and Nematodes for Bioremediation and Amelioration

that can have possible human health hazards or threats to the environment

from an infected area. Remediation is a cleanup and disinfecting process.

Conventional methods of remediation followed ‘cap and contain’ strategy,

i.e., digging up and removing it to a landfill and then maintaining it on the

same land. In this case, the products barely lose their hazardous nature as

they stay in their original form but in isolation. However, in recent times

with the development of advanced techniques these pollutants could be

destroyed, if possible, be transformed into harmless substances. However,

they have major drawbacks viz. lack effectiveness, high cost of application

(expensive), technological complexity, lack of public acceptance, and more

secondary toxic compounds being released during the incineration process.

Bioremediation (bio = living, remediate = to bring the sites and affairs

into the original states) makes an effective better sustainable approach

possible to achieve amelioration of polluted soils (Arora, 2018). The term

bioremediation is defined as any process which uses the biological system to

reduce the toxic effect of the pollutants. The biological system might include

microorganisms, green plants, fungi, or enzymes derived from the biological

system that reduces the contaminant concentration in soil (Schaechter,

2009). As microorganisms are easy to manage and plants are easy to grow,

bioremediation is superior to the use of conventional methods for remedia­

tion purposes. The other terms which are generally used for the process of

bioremediation are bio-reclamation, biotreatment, and bio-restoration. It can

be carried out in situ or in advanced reactors (ex-situ). Bioremediation by

microorganisms and nematodes requires a good atmosphere for the polluted

sites to be cleaned up. The process of microbial activity in the polluting

sites might require the addition of extra components so that the microbes

can thrive well. These extra components include the addition of nutrients,

favorable temperature, moisture, and terminal electron acceptor (O2/NO2)

that help to enhance the growth of a specific organism (Lal et al., 2022; Altaf

et al., 2022).

Soil microorganisms and nematodes can degrade pollutants consisting

predominantly of heavy metals, hydrocarbons, oils, polychlorinated

biphenyls (PCBs) and polyaromatic hydrocarbons (PAHs) as they have the

capacity to mitigate heavy metals and also decompose well after its effect

on microbes (Jariyal et al., 2020; Meena et al., 2022; Tiwari et al., 2021).

However, bioremediation is not readily used for the treatment of all pollut­

ants; certain heavy metals, such as Pb and Cd are not readily absorbed or

captured by microorganisms and nematodes (Kumar et al., 2011). It is a

natural alternative mechanism, rather than a panacea to strategies such as