4

Bioremediation for Sustainable Environmental Cleanup

1.4.1.1 Bioaugmentation

Bioaugmentation is an effective method to increase the biodegradation of chemical compounds which

are added to the contaminated soil or water. When bioattenuation or biostimulation is ineffective

against resistant compounds, this strategy is thought to be effective. This approach is primarily used

to remediate aromatic and chlorinated hydrocarbon-contaminated municipal wastewater and soil.

Microorganisms from different cultures are brought together to enhance bioaugmentation efficiency.

The proper utilization of microbes which are naturally occurring can help to degrade and entirely

mineralize organic pollutants (Bender and Phillips 2004). Bioaugmentation-aided phytoextraction

with Plant Growth-Promoting Rhizobacteria (PGPR) or Arbuscular Mycorrhizal Fungi (AMF) is

also a potential option for metal-contaminated soil cleanup (Lebeau et al. 2008).

1.4.1.2 Biostimulation

The process of stimulating microbial enzymes for the bioremediation of diverse xenobiotic

chemicals is known as biostimulation, which involves adding soil nutrients, trace minerals, electron

acceptors or donors to a contaminated site until the optimum pH is reached (Li et al. 2010). If

natural degradation does not occur or occurs at a slow rate, the environment must be manipulated

in order to stimulate biodegradation and increase reaction rates. This method is primarily intended

to remediate fuel, hydrocarbon, metal contaminated sites, non-halogenated Volatile Organic

Compounds and Semi-Volatile Organic Compounds (VOCs, SVOCs) pesticides and herbicide

pollution of soil and groundwater. The availability of carbon, nutrients such as N and P, temperature,

available oxygen, soil pH and the kind and quantity of organic pollutant itself all influence the rate

of microbial turnover of chemical pollutants (Carberry and Wik 2001). There are several examples

of contaminants being biostimulated by indigenous microbes. Microorganisms have been observed

to convert trichloroethene and perchloroethylene to ethane in a short period when lactate is added

during biostimulation (Shan et al. 2010). In-situ biostimulation is predicted to become a dependable

and safe cleaning solution as scientific data accumulates via these types of field tests.

1.4.1.3 Bioventing

Bioventing is an in-situ approach in which different microorganisms are used to degrade organic

components adsorbed on soils in the unsaturated zone. This approach involves adding very little

oxygen to contaminated soil at low airflow rates, which is sufficient for successful microbial

biodegradation while minimizing pollutant volatilization and emission into the atmosphere (Atlas

and Philp 2005). In this technique, organic materials that are added to soil in the unsaturated zone

are biodegraded by the native microorganisms. TCE (trichloroethane), ethylene dibromide and

dichloroethylene are the most common volatile pollutants found at locations containing mid-weight

petroleum products (such as diesel and jet fuel) (Lee et al. 2006, Latha and Reddy 2013).

1.4.1.4 Bioslurping

Bioslurping is a technology that combines a number of procedures, including vacuum-enhanced

pumping, bioventing and soil vapor extraction, to remove contaminants from soil and groundwater

while also accelerating microbial biodegradation. One disadvantage of this strategy is the soil’s low

permeability, which reduces the pace at which oxygen is transferred and further suppresses microbial

activity. These methods are often used to remove volatile and semivolatile organic pollutants from

soil and liquids (Vidali 2001).

1.4.1.5 Biosparging

Biosparging also known as air sparging is an in-situ treatment method that involves injecting air

under pressure below the water table to clean polluted groundwater and raising subsurface oxygen

concentrations to enhance biodegradation in saturated and unsaturated soils. VOCs that have

polluted groundwater or soils in the saturated zone are treated using this method. Vapors that have