Environmental Engineering Reference
In-Depth Information
Table 3.2
Classification of Advanced Oxidation Processes.
Non-photochemical
Photochemical
Ozonation
Photocatalytic oxidation, UV/Catalyst
Ozonation with hydrogen peroxide
(O
3
/H
2
O
2
)
UV/H
2
O
2
Fenton (Fe
2+
or Fe
3+
/H
2
O
2
)
UV/O
3
Wet air oxidation (WAO)
UV/O
3
/H
2
O
2
Electrochemical oxidation
Photo-Fenton (Fe
3+
/H
2
O
2
/UV)
will mainly focus on these processes and only brief information will be
given on electrochemical oxidation, ultraviolet irradiation and hydrogen
peroxide (UV/H
2
O
2
) and photocatalytic ozonation (UV/O
3
) processes.
3.2.1
Nonphotochemical Advanced Oxidation Processes
There are several well known methods for generating hydroxyl radicals
without using light energy. These are ozonation, Fenton's reagent oxida-
tion, wet air oxidation and electrochemical oxidation. In the following
sections, information on these processes will be given.
3.2.1.1 Ozonation
Ozone and ozone-based advanced oxidation processes are powerful, envi-
ronmentally friendly technologies capable of degrading a variety of organic
pollutants [24].
Ozonation is the method which is widely preferred for removal of col-
ored substances since the chromophore groups with conjugated double
bonds, which are responsible for color, can be easily broken down by
ozone, either directly or indirectly forming smaller molecules [25].
It is a promising treatment process due to its unique features such as
decolorization and degradation that occurs in one step; increases dissolved
oxygen; reduces oxygen demanding matter, no remaining sludge; little
space is required and it is easily installed on a site [26,27]. In contrast, there
are some disadvantages of ozonation such as high capital cost, high electric
consumption and its being highly corrosive.
The ozonation process is realized in three steps:
1. Generation of ozone
2. Dissolution of ozone in the wastewater
3. Oxidation of organic matter
Search WWH ::
Custom Search