26 i.e. atrazine ATR, sulfamethoxazole SMX, and N-nitrodimethylamine NDMA
were quite similar, even though the NDMA transformation was more effective using direct photolysis. Park et al. [55] used the combination of microwaveUV and ozone
to degrade bromothymol blue in water solution, and reported a complete degradation of bromothymol blue within 10 minutes of reaction time. During ozone based process,
phosphate and carbonate were found to be the scavenger of the degradation reaction for sulfamethoxazole using UVTiO
2
O
3
[56]. The available literature on the ozone based oxidation process for different pollutants are summarized in Table 2.5.
2.3.4 High Voltage Electrical Discharge Processes
High voltage electrical discharge frequency of 60Hz process is a process when a strong electrical field induced chemical and physical processes and commonly known
as corona discharge. Application of electrical discharge short high voltage pulse 200
– 100 ns in liquid phase and at non-thermal condition results in the formation of various active species such as HO
•, H •, •
O, HO
2 -
, O
2 -
•, H
2
O
2
, etc Equation 2.16 – 2.18.
H
2
O + e
-
→ HO •+ H
•
+ e
-
2.16 H
2
O + e
-
→ H
2
O
+
+ 2 e
-
2.17 H
2
O + H
2
O
+
→ H
2
O
+
+ HO •
2.18
This process is very effective for treatment of biological microorganism and dissolved chemicals in liquid phase [30, 33]. The radical species present in the system
usually react with each other and produce H
2
O
2
, H
2
or H
2
O Equations 2.19 – 2.21.
HO • + HO
• → H
2
O
2
2.19 H
• + H • → H
2
2.20 HO
• + H • → H
2
O 2.21
27
Table 2. 5 Ozone-based oxidation processes for various contaminants.
Contaminat References
Experimental Results
Reactor Lamp
Conc. pH
Temp. Mineral oil-
contaminated wastewater
Andreozzi et al., 2000 [48]
Semi-connector reactor
Cap = 0.2 – 1 L
17 W LP UV
= 254 nm _
4.9 buffer KH
2
PO
4
25 ⁰C
O
3
UV was proved to be more effective to reduce the COD value compared to the
O
3
H
2
O
2
. Approximately 80 – 90 COD
was removed within 30 minutes of reaction time.
Atrazine Ma and Graham, 2000
[51] Reactor gas
bubble-connecting column
Cap = 3.651 L _
Mn
2+
sol. = 24.8 mlmin
7.0 _
The presence of small amount of Mn
2+
0.3 – 1.2 mgL greatly enhanced the
degradation of atrazine.
Methyl-ter-butyl ether MTBE
Safarzadeh-Amiri, 2001 [52]
Bubble column as reactor with
circulation of mixture 2 Lmin Cap = 6 L
_ [MTBE]
= 80 mgL [O
3
] = 150 mgL [H
2
O
2
] = 50 mgL _
_ The O
3
H
2
O
2
provides an economical and efficient process for the reduction of
MTBE-contaminated water. Nearly complete reduction of MTBE 80 to 0.05
mgL was achieved by using 150 mgL ozone and 50 mgL H
2
O
2
.
Acetone Hernandez et al., 2002
[49] Glass borosilicate
reactor Cap = 1 L
LPUV MPUV
Ozone inlet = 35 weight
[aceton] = 5 ppm 7.0
borate buffer
20 ⁰C
LPUVO
3
was reported as more effective for acetone degradation among UVO
3
, H
2
O
2
O
3
, and UVH
2
O
2
. Acetone removal was 99 within 30min of reaction time.
Increasing O
3
concentration increased the degradation rate.
27
28
Pretreated drinking water from Paris area
France Meunier el al, 2006 [50]
Brown glass screwed with dispenser fitted
for ozone injection Cap = 500 ml
UV at = 254 nm.
_ 8.0
6±1ºC 25±1ºC
Introducing UV in the system reduced the ozone dosege and the combination of
UVO
3
improved the water quality with regard to disinfection, oxidation of micro-
pollutant and minimization of bromate concentration.
Carbaryl Carbamat pestiside
Rajeswari and Kanmani, 2009 [53]
Cilinder photoreactor Cap = 500 ml
125 W MP UV lamp
[carbaryl]o = 40 gL O
3
input = 0.28 gh [TiO
2
] = 5 g _
19±1 ⁰C By this process, 92 COD and 76.5 TOC
were removed and the ratio of BOD
5
COD increased to 0.38.
Sulfamethoxazole SMT
Beltrán et al., 2009 [56]
Tubular borosilicate glass Cap = 1 L
HP Hg lamp [O
3
] = 10-30 mgL _
_ The degradation of sulfamethoxazole was
caused by direct ozonenolysis, direct photolysis, and HO
•. Phosphate and
carbonate was found to be the scavengers.
Bromothymol Blue BTB
Park et al., 2010 [55] Quartz reactor with
Microwave = 2.45 Hz max power 1 kW
circulation = 300 ccmin.
Cap = 1L UV-C
O
3
= 0.75 – 3.26 gh
[BTB] = 3.0 x 10
-5
M _
_ Decomposition rate of BTB increased
significantly with increasing of catalyst dosage, microwave intensity when applied
together with ozone. Complete degradation was achieved when 3.26 gh of O
3
was injected in the UVMWTiO
2
system.
Micropollutants i.e.: Atrazine,ATR,
sulfametoxazole SMX and N-
nitrosodimethylamine NDMA
Katsoyiannis et al., 2011 [54]
Batch reactor Cap = 500 ml
15 W LP Hg lamp
[pollutant] = 0.5
– 1 µM [O
3
] = 1.5 mM
[H
2
O
2
] [O
3
] = 1:2
8.0 20
⁰C Transformation rate of micropollutants
increased with the use of O
3
H
2
O
2
. Energy requirement for O
3
H
2
O
2
and UVH
2
O
2
is quite similar for the NDMA transformation.
28
29 Based on the reactions according to Equations 2.16
– 2.21, the degradation of organic contaminant in the system follow three mechanisms i.e. direct reaction with
hydroxyl radical, indirect reaction of radicals formed from stable molecules H
2
O
2
, and direct reaction with stable molecule [57].
2.3.5 Others AOP ’s
