increase uniformity of pollutant distribution, aeration, nutrients, and microorganism
activity, increasing the bioremediation rate, which is done through biotransformation, mineralization, and assimilation (Azubuike et al. 2016).
Bioreactors
Bioreactor is a vessel that converts raw materials to particular product(s) via different
biological reactions. The various bioreactors include batch, sequencing batch,
fed-batch, continuous, and multistage. Market economy and capital expenditure
are the two factors in choosing the operating mode. In a bioreactor, the situation
provides cell natural process via mimicking and retaining its natural environment. It
provides the optimum conditions to grow. Contaminated samples such as dry matter
or slurry can be fed into a bioreactor. One of the important advantages of bioreactorbased bioremediation is outstanding control of bioprocess parameters including pH,
temperature, agitation rates, substrate and inoculum concentrations, and aeration
rates. Control and manipulating the process parameters in a bioreactor provides the
possibility to enhance the biological reactions and thus effectively reduce the
bioremediation time. Other factors that can limit the bioremediation process like
controlled bioaugmentation, increased contaminant bioavailability, addition of nutrient, and mass transfer (collision between contaminant and microbes) can efficiently
be performed in a bioreactor; thus, the bioreactor-based biotreatment can be more
effective. The method can be applied to treat water or soil contaminated by volatile
organic compounds, including benzene, toluene, ethylbenzene, and xylenes
(Azubuike et al. 2016).
Biopiles
This method is used to treat surface contaminated with hydrocarbons and is a
combination of land farming and composting. Biopiles provide an appropriate
medium for indigenous aerobic and anaerobic microorganisms. Biopile-mediated
remediation treats aboveground piling of excavated contaminated soil with aeration
and nutrient amendment to improve biotreatment via enhancing microorganism
activity. This method has some components including irrigation, aeration, leachate
collection systems, nutrient, and a remediation bed. The ex situ method is widely
used because of constructive features such as cost-effectiveness that enables efficient
biodegradation when temperature, nutrient, and aeration are well controlled. This
special ex situ method is being used increasingly (Whelan et al. 2015) because of its
constructive features like cost-effectiveness that provides successful biodegradation
on the condition that temperature, aeration, and nutrient are well controlled. Using
biopiles helps to limit volatilization of contaminants with low molecular weight. The
method is effectively used to treat environments in extreme situations like very cold
regions (Gomez and Sartaj 2014; Dias et al. 2015). It has been observed that the
concentration of hydrocarbons decreases up to 71% and the structure of bacteria
476
M. Fatehi et al.
activity, increasing the bioremediation rate, which is done through biotransformation, mineralization, and assimilation (Azubuike et al. 2016).
Bioreactors
Bioreactor is a vessel that converts raw materials to particular product(s) via different
biological reactions. The various bioreactors include batch, sequencing batch,
fed-batch, continuous, and multistage. Market economy and capital expenditure
are the two factors in choosing the operating mode. In a bioreactor, the situation
provides cell natural process via mimicking and retaining its natural environment. It
provides the optimum conditions to grow. Contaminated samples such as dry matter
or slurry can be fed into a bioreactor. One of the important advantages of bioreactorbased bioremediation is outstanding control of bioprocess parameters including pH,
temperature, agitation rates, substrate and inoculum concentrations, and aeration
rates. Control and manipulating the process parameters in a bioreactor provides the
possibility to enhance the biological reactions and thus effectively reduce the
bioremediation time. Other factors that can limit the bioremediation process like
controlled bioaugmentation, increased contaminant bioavailability, addition of nutrient, and mass transfer (collision between contaminant and microbes) can efficiently
be performed in a bioreactor; thus, the bioreactor-based biotreatment can be more
effective. The method can be applied to treat water or soil contaminated by volatile
organic compounds, including benzene, toluene, ethylbenzene, and xylenes
(Azubuike et al. 2016).
Biopiles
This method is used to treat surface contaminated with hydrocarbons and is a
combination of land farming and composting. Biopiles provide an appropriate
medium for indigenous aerobic and anaerobic microorganisms. Biopile-mediated
remediation treats aboveground piling of excavated contaminated soil with aeration
and nutrient amendment to improve biotreatment via enhancing microorganism
activity. This method has some components including irrigation, aeration, leachate
collection systems, nutrient, and a remediation bed. The ex situ method is widely
used because of constructive features such as cost-effectiveness that enables efficient
biodegradation when temperature, nutrient, and aeration are well controlled. This
special ex situ method is being used increasingly (Whelan et al. 2015) because of its
constructive features like cost-effectiveness that provides successful biodegradation
on the condition that temperature, aeration, and nutrient are well controlled. Using
biopiles helps to limit volatilization of contaminants with low molecular weight. The
method is effectively used to treat environments in extreme situations like very cold
regions (Gomez and Sartaj 2014; Dias et al. 2015). It has been observed that the
concentration of hydrocarbons decreases up to 71% and the structure of bacteria
476
M. Fatehi et al.