while the pH of the soil system decreased. The resulting Zn removal percentage was
less than 1%, 20%, and 41%, approximately, for conventional EK, catholyte conditioning by HNO 3 , and pretreatment with catholyte conditioning solution, respectively. Kim et al. (2009) observed that the metals (Zn and Ni) were not extracted by
HNO 3 acid if the concentration was less than 0.1 M. They concluded that both
catholyte- and pretreated soil methods are effective and enhance heavy metal
removal in soil. Ryu et al. (2011) conducted an EK experiment for removal of soil
contaminated by As, Cu, and Pb. These observations mainly depended on the
pretreatment of contaminated soils and electrolyte conditions. The electrolyte conditioning and pretreatment soil maintained acidic and basic conditions using HNO 3
and NaOH. The soil was pretreated with 0.05 M HNO 3, and the electrolyte was
maintained in acidic condition; the removal percentage of Cu, As, and Pb was about
48%, 1.3%, and 75.7%, respectively, during 30 days of the EK process. The same set
of experiments was conducted for 15 days in acidic and 15 days in basic conditions;
the removal percentage was about 60%, 0.5%, and 6.2% for Cu, As, and Pb,
respectively, whereas in the experiment conducted in basic conditions arsenic
(As) exists as H 2 AsO 4
À , HAsO 4
2À , or AsO 4
3À . These types of anionic metals
move towards the anode by electromigration. The removal percentage of As was
about 43% for 30 days of the EK process. Kim et al. (2012a, b, c) achieved a
significant amount of As removal from contaminated soil in 8 weeks of the EK
process. In this study, they examined the two types of soil (silty loam soil, dried clay
soil) and used EDTA and NaOH as catholyte and anolyte, respectively. Many
investigators have claimed that the alkaline condition may enhance As removal in
soil (Jeon et al. 2015; Ryu et al. 2011). They concluded that a significant amount of
As was removed in both soils and that energy consumption was about 279 and
179 kWh/m
3 in silty loam and dry clay soils, respectively.
Kim et al. (2013a, b) could not reduce Na
+
, K
+
, and Mg
2+ levels in the contaminated soil using a pulse current, whereas in the conventional DC EK process, the
removal percentage of Na
+ was about 63.6%, 89.3%, and 66.1% at the top, middle,
and bottom sections of the soil, respectively. They concluded that crop growth was
evaluated by the effects of change in pH during the treatment process. The pH
changes in the pulse current were slightly less compared to the conventional DC
system. The soil crop growth highly depended on soil pH in strong acidic conditions
whereas crop growth highly depended on soil electrical conductivity (EC) in normal
pH conditions and on soil pH in optimum EC conditions, thus indicating the
optimum range of soil pH and for crop growth during EK treatment.
2.2.2 A Pilot- and Field-Scale Process
Gent et al. (2004) proposed that the EK treatment of metal-contaminated soil in a
field application was more effective than in the lab experiment. South Korean
research groups (Cho et al. 2011; Kim et al. 2001, 2009, 2010, 2012a, b, c, 2014a,
b, c) are doing significant research in the field of in situ EK remediation for
contaminated heavy metals such as As-, Cu-, and Pb-contaminated soil from
paddy fields. In the EK process, parallel electrode configuration is used in the
8 Electro-bioremediation: An Advanced Remediation Technology for the. . .
189
less than 1%, 20%, and 41%, approximately, for conventional EK, catholyte conditioning by HNO 3 , and pretreatment with catholyte conditioning solution, respectively. Kim et al. (2009) observed that the metals (Zn and Ni) were not extracted by
HNO 3 acid if the concentration was less than 0.1 M. They concluded that both
catholyte- and pretreated soil methods are effective and enhance heavy metal
removal in soil. Ryu et al. (2011) conducted an EK experiment for removal of soil
contaminated by As, Cu, and Pb. These observations mainly depended on the
pretreatment of contaminated soils and electrolyte conditions. The electrolyte conditioning and pretreatment soil maintained acidic and basic conditions using HNO 3
and NaOH. The soil was pretreated with 0.05 M HNO 3, and the electrolyte was
maintained in acidic condition; the removal percentage of Cu, As, and Pb was about
48%, 1.3%, and 75.7%, respectively, during 30 days of the EK process. The same set
of experiments was conducted for 15 days in acidic and 15 days in basic conditions;
the removal percentage was about 60%, 0.5%, and 6.2% for Cu, As, and Pb,
respectively, whereas in the experiment conducted in basic conditions arsenic
(As) exists as H 2 AsO 4
À , HAsO 4
2À , or AsO 4
3À . These types of anionic metals
move towards the anode by electromigration. The removal percentage of As was
about 43% for 30 days of the EK process. Kim et al. (2012a, b, c) achieved a
significant amount of As removal from contaminated soil in 8 weeks of the EK
process. In this study, they examined the two types of soil (silty loam soil, dried clay
soil) and used EDTA and NaOH as catholyte and anolyte, respectively. Many
investigators have claimed that the alkaline condition may enhance As removal in
soil (Jeon et al. 2015; Ryu et al. 2011). They concluded that a significant amount of
As was removed in both soils and that energy consumption was about 279 and
179 kWh/m
3 in silty loam and dry clay soils, respectively.
Kim et al. (2013a, b) could not reduce Na
+
, K
+
, and Mg
2+ levels in the contaminated soil using a pulse current, whereas in the conventional DC EK process, the
removal percentage of Na
+ was about 63.6%, 89.3%, and 66.1% at the top, middle,
and bottom sections of the soil, respectively. They concluded that crop growth was
evaluated by the effects of change in pH during the treatment process. The pH
changes in the pulse current were slightly less compared to the conventional DC
system. The soil crop growth highly depended on soil pH in strong acidic conditions
whereas crop growth highly depended on soil electrical conductivity (EC) in normal
pH conditions and on soil pH in optimum EC conditions, thus indicating the
optimum range of soil pH and for crop growth during EK treatment.
2.2.2 A Pilot- and Field-Scale Process
Gent et al. (2004) proposed that the EK treatment of metal-contaminated soil in a
field application was more effective than in the lab experiment. South Korean
research groups (Cho et al. 2011; Kim et al. 2001, 2009, 2010, 2012a, b, c, 2014a,
b, c) are doing significant research in the field of in situ EK remediation for
contaminated heavy metals such as As-, Cu-, and Pb-contaminated soil from
paddy fields. In the EK process, parallel electrode configuration is used in the
8 Electro-bioremediation: An Advanced Remediation Technology for the. . .
189