Different additives, such as nutrients, activated sludge from an oil-refining
wastewater facility, compost, TPH-degrading bacteria, and fern chips were also
used for landfarming system enhancement in the study by Wang et al. (2016). The
most efficient amendments were the activated sludge and the compost with 83% and
80% efficiency of TPH removal and the highest first-order TPH degradation rate
0.016 and 0.015 per day, respectively. The fern chip addition and TPH-degrading
bacteria had also a positive effect on the TPH removal efficiency with the same
decay rate 0.013 per day. The sludge and compost supplement caused an increase in
the bacterial diversity, resulting in higher TPH decay rates. Thus, these supplements
can substitute TPH-degrading bacteria addition.
Bioremediation works in a wide range of temperatures. Martínez Álvarez et al.
(2017) proved the bioremediation process of soil contaminated with hydrocarbons in
Antarctica to be efficient at a mean temperature of 6.7
C. The high density
polyethylene geomembranes were used to protect the treated soil (biostimulation
and also control piles) against wind and ice. A biostimulation pile, involving
nitrogen (as ammonium nitrate) and phosphorus (as monosodium phosphate) addition, was significantly higher than the control pile without nitrogen and phosphorus
additions (75.8% vs. 49.5%). However, most microorganisms with biodegradation
potential are mesophilic with optimal temperatures ranging from 25
C to 37
C
(Admassu and Korus 1996). The microbial activity of most bacteria important to
petroleum hydrocarbon biodegradation also diminishes at temperatures greater than
45
C. For practical use, the temperature range from 10
C to 45
C was set up by
EPA as an effective temperature range for the landfarming system (US EPA 2017).
The ratio of C:N:P should be considered before each bioremediation. The optimal
ratio has been reported as 100:10:1 (Dibble and Bartha 1979). The scarcity of
essential nutrients such as nitrogen and phosphorus has been recognized as a crucial
factor that inhibits the microbial bioremediation performance. The lack of suitable
and available nutrients in the contaminated soil required the implementation of
engineered bioremediation strategies. Each soil has a different microbial diversity
and requirements and the optimal C:N:P ratio should be determined before each
bioremediation process.
If we take into account all the above-mentioned conditions, the process of ex situ
bioremediation technology for TPH removal is summarized in Fig. 21.1.
21.3 Biodegradation of Persistent Organic Pollutants
Persistent organic pollutants (POPs) are chemicals of global concern because of their
potential for long-range transport, persistence in the environment, and ability to
bioaccumulate in ecosystems as well as their significant negative effects on both
human health and the environment. The most commonly emerged POPs are organochlorine pesticides, such as DDT, industrial chemicals, polychlorinated biphenyls
(PCB), or unintentional by-products of many industrial processes, especially
polychlorinated dibenzo-p-dioxins and dibenzofurans (WHO).
440
P. Najmanová and M. Halecký
wastewater facility, compost, TPH-degrading bacteria, and fern chips were also
used for landfarming system enhancement in the study by Wang et al. (2016). The
most efficient amendments were the activated sludge and the compost with 83% and
80% efficiency of TPH removal and the highest first-order TPH degradation rate
0.016 and 0.015 per day, respectively. The fern chip addition and TPH-degrading
bacteria had also a positive effect on the TPH removal efficiency with the same
decay rate 0.013 per day. The sludge and compost supplement caused an increase in
the bacterial diversity, resulting in higher TPH decay rates. Thus, these supplements
can substitute TPH-degrading bacteria addition.
Bioremediation works in a wide range of temperatures. Martínez Álvarez et al.
(2017) proved the bioremediation process of soil contaminated with hydrocarbons in
Antarctica to be efficient at a mean temperature of 6.7
C. The high density
polyethylene geomembranes were used to protect the treated soil (biostimulation
and also control piles) against wind and ice. A biostimulation pile, involving
nitrogen (as ammonium nitrate) and phosphorus (as monosodium phosphate) addition, was significantly higher than the control pile without nitrogen and phosphorus
additions (75.8% vs. 49.5%). However, most microorganisms with biodegradation
potential are mesophilic with optimal temperatures ranging from 25
C to 37
C
(Admassu and Korus 1996). The microbial activity of most bacteria important to
petroleum hydrocarbon biodegradation also diminishes at temperatures greater than
45
C. For practical use, the temperature range from 10
C to 45
C was set up by
EPA as an effective temperature range for the landfarming system (US EPA 2017).
The ratio of C:N:P should be considered before each bioremediation. The optimal
ratio has been reported as 100:10:1 (Dibble and Bartha 1979). The scarcity of
essential nutrients such as nitrogen and phosphorus has been recognized as a crucial
factor that inhibits the microbial bioremediation performance. The lack of suitable
and available nutrients in the contaminated soil required the implementation of
engineered bioremediation strategies. Each soil has a different microbial diversity
and requirements and the optimal C:N:P ratio should be determined before each
bioremediation process.
If we take into account all the above-mentioned conditions, the process of ex situ
bioremediation technology for TPH removal is summarized in Fig. 21.1.
21.3 Biodegradation of Persistent Organic Pollutants
Persistent organic pollutants (POPs) are chemicals of global concern because of their
potential for long-range transport, persistence in the environment, and ability to
bioaccumulate in ecosystems as well as their significant negative effects on both
human health and the environment. The most commonly emerged POPs are organochlorine pesticides, such as DDT, industrial chemicals, polychlorinated biphenyls
(PCB), or unintentional by-products of many industrial processes, especially
polychlorinated dibenzo-p-dioxins and dibenzofurans (WHO).
440
P. Najmanová and M. Halecký