chain of 10–26 carbons and aromatic hydrocarbons with low molecular weight.
High-molecular-weight aromatic hydrocarbons and branched alkanes are two classes
of hydrocarbons difficult to biodegrade (Atlas and Cerniglia 1995). The main genera
of fungi and bacteria for oil degradation are listed in Table 12.22.
In aquatic systems, the dominant hydrocarbon degraders are bacteria. In marine
environment, the concentration of oil and bioavailability of nutrients, the extent to
which the natural biotreatment has already taken place and time affect the biodegradation of an oil spill (Zahed et al. 2010). To grow the hydrocarbon-degraders,
nutrients like phosphorus and nitrogen, which are always found in marine environment with low concentrations, are necessary. However, the natural attenuation does
not proceed with a noticeable rate because of the scarcity of nutrients (Atlas and
Bartha 1973). Moreover, high concentration of oil causes a remarkable lag phase in
around 2–4 weeks into its bioremediation process. Microorganisms normally need at
least 1 week to acclimatize to the environment and the completion of bioremediation
process takes months and years (Zahed et al. 2010). To improve the rate of the
natural biodegradation, addition of dispersants and fertilizers (biostimulation), and
insemination of contaminated seawater with hydrocarbon-degrading microorganisms are essential. Although there is a competition between the indigenous and the
inoculated microorganism because of the vast distribution of fungi and bacteria,
screening the microorganism from the polluted sites and inoculating them to the
polluted seawater is a way for seawater bioremediation. Bioaugmentation cannot be
an effective way for oil spill bioremediation (Venosa et al. 1991). The application of
fertilizers such as nitrogen and phosphorous nutrient supplements for
oil-contaminated seawater is effective but with low efficacy for the bioremediation
of severely degraded oil (Bragg et al. 1994; Zahed et al. 2010). Surfactants or
dispersants improve the oil bioavailability to hydrocarbon degraders and the success
of their application was reported in the study of Zahed et al. (2010). Some studies
have been performed on the eutrophication caused by adding phosphorus and
nitrogen to the water. According to the work of Bragg et al. (1994) and Atlas and
Cerniglia (1995), applying fertilizer has not caused the eutrophication and no critical
toxicity has been found for the sensitive species. Always the resisting
nonbiodegradable components of oil remain as asphaltic residues and can coat
and suffocate marine life. During bioremediation technology, hydrocarbons biota
toxicity is removed from the contaminated site.
Table 12.21 (continued)
Sorbent or tool
Type of oil
Maximum sorption capacity
(g/g) or removal efficiency
(%)
References
Magnetic expanded
graphite
Crude oil
35.72 g/g
Ding et al. (2014)
Modified calcium carbonate
powder
Diesel oil
Crude oil
99.6%
99.5%
Arbatan et al.
(2011)
12 Remediation of Pollution by Oil Spills
465
High-molecular-weight aromatic hydrocarbons and branched alkanes are two classes
of hydrocarbons difficult to biodegrade (Atlas and Cerniglia 1995). The main genera
of fungi and bacteria for oil degradation are listed in Table 12.22.
In aquatic systems, the dominant hydrocarbon degraders are bacteria. In marine
environment, the concentration of oil and bioavailability of nutrients, the extent to
which the natural biotreatment has already taken place and time affect the biodegradation of an oil spill (Zahed et al. 2010). To grow the hydrocarbon-degraders,
nutrients like phosphorus and nitrogen, which are always found in marine environment with low concentrations, are necessary. However, the natural attenuation does
not proceed with a noticeable rate because of the scarcity of nutrients (Atlas and
Bartha 1973). Moreover, high concentration of oil causes a remarkable lag phase in
around 2–4 weeks into its bioremediation process. Microorganisms normally need at
least 1 week to acclimatize to the environment and the completion of bioremediation
process takes months and years (Zahed et al. 2010). To improve the rate of the
natural biodegradation, addition of dispersants and fertilizers (biostimulation), and
insemination of contaminated seawater with hydrocarbon-degrading microorganisms are essential. Although there is a competition between the indigenous and the
inoculated microorganism because of the vast distribution of fungi and bacteria,
screening the microorganism from the polluted sites and inoculating them to the
polluted seawater is a way for seawater bioremediation. Bioaugmentation cannot be
an effective way for oil spill bioremediation (Venosa et al. 1991). The application of
fertilizers such as nitrogen and phosphorous nutrient supplements for
oil-contaminated seawater is effective but with low efficacy for the bioremediation
of severely degraded oil (Bragg et al. 1994; Zahed et al. 2010). Surfactants or
dispersants improve the oil bioavailability to hydrocarbon degraders and the success
of their application was reported in the study of Zahed et al. (2010). Some studies
have been performed on the eutrophication caused by adding phosphorus and
nitrogen to the water. According to the work of Bragg et al. (1994) and Atlas and
Cerniglia (1995), applying fertilizer has not caused the eutrophication and no critical
toxicity has been found for the sensitive species. Always the resisting
nonbiodegradable components of oil remain as asphaltic residues and can coat
and suffocate marine life. During bioremediation technology, hydrocarbons biota
toxicity is removed from the contaminated site.
Table 12.21 (continued)
Sorbent or tool
Type of oil
Maximum sorption capacity
(g/g) or removal efficiency
(%)
References
Magnetic expanded
graphite
Crude oil
35.72 g/g
Ding et al. (2014)
Modified calcium carbonate
powder
Diesel oil
Crude oil
99.6%
99.5%
Arbatan et al.
(2011)
12 Remediation of Pollution by Oil Spills
465