The method is ideal for the treatment of VOCs and semivolatile organic compounds (SVOCs) in groundwaters, wastewaters, drinking water, and leachates. The
compounds that have been widely studied are the halogenated species such as PCBs,
easily oxidizable and attacked by HO
• (Chaychian et al. 1999).These compounds can
be mineralized or degraded to products of lower molecular weight. The method does
not generate sludge or other wastes that would need ulterior treatment, or toxic
compounds such as dioxins. In contrast, if the radiation doses are low, aldehydes,
organic acids, and resistant SVOCs can be formed. The process requires high
electrical consumption; it is not economically effective for high concentrations of
pollutants. Industrial scale installations are currently being developed. The first fullscale application in the treatment of emulsifiers was reported at the Voronezh rubber
plant in Russia (Pikaev 2001) and, since then, some other plants have been installed
(Wojnárovits et al. 2018). The combination with ozone increases the efficiency
because of the fast formation of additional reactive species.
Radiation technology has been proved useful for the discoloration and degradation
of dyes (Chen et al. 2008; Ma et al. 2007), sewage sludge processing (Park et al. 2009),
oxidization of organic pollutants (Al-Sheikhly et al. 2006; Hu and Wang 2007),
removal of pesticides (Basfar et al. 2007), and for the decomposition of pharmaceutical compounds (Sanchez-Polo et al. 2009). The application of radiation technology to
sewage sludge processing and degradation of dyes has been reviewed in detail (Rauf
and Ashraf 2009; Wang and Wang 2007; Wojnárovits and Takács 2008).
7.2.7 Non-thermal Plasma
Plasma is considered the fourth state of the matter and it contains ions and free
electrons (electrical gas). Plasma can be generated in non-thermal form from an
electrical discharge or bombardment of gas with an electron beam of high energy;
the energy of the electrons in the plasma is around 10 eV, which is equivalent to high
temperatures. Such plasma is a good source of highly reductive and oxidative
reactive species such as O(
3 P), HO
• , N, H, NH, CH, O 3 , O 2 (
1
Δ), the own plasma
electrons, etc. The presence of these species allows using the method in multiple
applications: SO x and NO x removal from gas exhausts, decomposition of aliphatic
and halogenated aliphatic hydrocarbons, gases of industrial exhausts and incinerators, treatment of VOCs in soils and groundwaters (with previous transfer to the
vapor phase by pumping), treatment of polluted soils with VOCs (with previous
application of heat and fluidization in an inert gas), etc. (Domènech et al. 2004;
Rosocha and Korzekwa 1999).
Two types of treatment processes can be employed to apply plasma methods to
degradation of pollutants: (a) indirect plasma, represented by ozone generators
whereby the plasma is used to generate the oxidant, which is then delivered to a
separate reactor for water treatment; (b) direct plasma, which contacts directly the
liquid phase containing the contaminants (Rosocha and Korzekwa 1999; Mededovic
Thagard and Locke 2018).
7 Introduction to Oxidative Technologies for Water Treatment
133
compounds that have been widely studied are the halogenated species such as PCBs,
easily oxidizable and attacked by HO
• (Chaychian et al. 1999).These compounds can
be mineralized or degraded to products of lower molecular weight. The method does
not generate sludge or other wastes that would need ulterior treatment, or toxic
compounds such as dioxins. In contrast, if the radiation doses are low, aldehydes,
organic acids, and resistant SVOCs can be formed. The process requires high
electrical consumption; it is not economically effective for high concentrations of
pollutants. Industrial scale installations are currently being developed. The first fullscale application in the treatment of emulsifiers was reported at the Voronezh rubber
plant in Russia (Pikaev 2001) and, since then, some other plants have been installed
(Wojnárovits et al. 2018). The combination with ozone increases the efficiency
because of the fast formation of additional reactive species.
Radiation technology has been proved useful for the discoloration and degradation
of dyes (Chen et al. 2008; Ma et al. 2007), sewage sludge processing (Park et al. 2009),
oxidization of organic pollutants (Al-Sheikhly et al. 2006; Hu and Wang 2007),
removal of pesticides (Basfar et al. 2007), and for the decomposition of pharmaceutical compounds (Sanchez-Polo et al. 2009). The application of radiation technology to
sewage sludge processing and degradation of dyes has been reviewed in detail (Rauf
and Ashraf 2009; Wang and Wang 2007; Wojnárovits and Takács 2008).
7.2.7 Non-thermal Plasma
Plasma is considered the fourth state of the matter and it contains ions and free
electrons (electrical gas). Plasma can be generated in non-thermal form from an
electrical discharge or bombardment of gas with an electron beam of high energy;
the energy of the electrons in the plasma is around 10 eV, which is equivalent to high
temperatures. Such plasma is a good source of highly reductive and oxidative
reactive species such as O(
3 P), HO
• , N, H, NH, CH, O 3 , O 2 (
1
Δ), the own plasma
electrons, etc. The presence of these species allows using the method in multiple
applications: SO x and NO x removal from gas exhausts, decomposition of aliphatic
and halogenated aliphatic hydrocarbons, gases of industrial exhausts and incinerators, treatment of VOCs in soils and groundwaters (with previous transfer to the
vapor phase by pumping), treatment of polluted soils with VOCs (with previous
application of heat and fluidization in an inert gas), etc. (Domènech et al. 2004;
Rosocha and Korzekwa 1999).
Two types of treatment processes can be employed to apply plasma methods to
degradation of pollutants: (a) indirect plasma, represented by ozone generators
whereby the plasma is used to generate the oxidant, which is then delivered to a
separate reactor for water treatment; (b) direct plasma, which contacts directly the
liquid phase containing the contaminants (Rosocha and Korzekwa 1999; Mededovic
Thagard and Locke 2018).
7 Introduction to Oxidative Technologies for Water Treatment
133