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26 Novel Biotechnological Approaches for Removal of Emerging Contaminants

for the treatment of contaminated soil. Bioremediation in the reactors involves the

processing of contaminated solid material (soil, sediment, and sludge) or water

through an engineered containment system. A slurry bioreactor will have contain-

ment vessel to create three-phase mixing condition to increase the bioremediation

rate of soil-bound and water-soluble pollutants. In general, the rate and extent of

biodegradation of EC is greater in a bioreactor system than other system because

the contaminated environment is more manageable and hence more controllable

and predictable. The contaminated soil requires pretreatment using excavation;

alternatively, the contaminant can be stripped from the soil via soil washing or

physical extraction like vacuum extraction before being placed in a bioreactor.

Bioreactors have been used to treat soil and other materials contaminated with

petroleum residues.

26.6.4.3

Biostimulation

Biostimulation involves the modification of the environment to stimulate the exist-

ing microorganisms for the remediation of the EC. This can be done by adding vari-

ous forms of rate-limiting nutrients. This can also be done using electron acceptors,

such as phosphorus, nitrogen, oxygen, or carbon.

26.6.4.4

Bioventing

The process of passing oxygen through the contaminated medium stimulates the

microbial growth and activity. Bioventing is the most common in situ treatment and

involves supplying air and nutrients through wells to contaminated soil to stimu-

late the indigenous bacteria. Bioventing uses low airflow rates and provides only the

required amount of oxygen that is necessary for the biodegradation while minimiz-

ing the volatilization and release of contaminants into the atmosphere. It works for

simple hydrocarbons and can be used where the contamination is deep under the

surface. In many soils, effective oxygen diffusion for desirable rates of bioremedia-

tion extends to a range of only a few centimeters (30 cm), although depths of 60 cm

and greater have been effectively treated in some cases.

26.6.4.5

Composting

Compositing is an aerobic and thermophilic process, and EC will be mixed with a

bulking agent here. Composting may be performed using static piles, aerated piles,

or continuously fed bioreactors. Here, EC will be combined with nonhazardous

organic amendments, such as manure or agricultural wastes. The presence of these

organic materials supports the development of microbial population and elevates

temperature which is characteristic of composting. Typical compost temperature

ranges from 55 to 65 ^∘C. The increased temperatures result from the heat produced

by microorganisms during the degradation of the organic material present in the

waste. Composting of EC is done by following the basic steps. The ECs are exca-

vated, screened, and transported to a composting pad (with a temporary structure

to provide containment and protection from weather extremes). Amendments

(straw, alfalfa, manure, agricultural wastes, and wood chips) are used as a supple-

mental carbon sources. Soil and amendments are layered into long piles, known as