Environmental Engineering Reference
In-Depth Information
O
3
+ H
2
O
2
UV
+ H
2
O
2
O
3
+ UV
O
3
100
90
80
70
60
50
40
30
20
10
0
1
2
3
Sample
FIGURE 7.9
Reduction in 1,4-dioxane in three samples of drinking water (start value: 230 μg/L) through
the use of four different remediation treatments. (H. Davis, personal communication, 2007; Courtesy of
ITT—WEDECO.)
various
ex situ
chemical oxidation treatment technologies for 1,4-dioxane removal, provided by ITT-
WEDECO (H. Davis, personal communication, 2007). Tap water samples from Herford, Germany,
were spiked with 1,4-dioxane at a concentration of 230
g/L and treated with ozone (O
3
), ozone plus
hydrogen peroxide (H
2
O
2
), hydrogen peroxide plus ultraviolet light, and ozone plus ultraviolet light.
These specii c technologies are discussed in further detail in this section, but with 1,4-dioxane
removal rates of up to 90%, these are clearly demonstrated methods to be considered for 1,4-dioxane
treatment. Site heterogeneity and undiscovered source areas often hinder successful applications of
pump-and-treat technologies. When applying oxidation technologies, the effect of oxidizing condi-
tions on inorganic elements present in extracted groundwater or
in situ
materials must be evaluated
and addressed. Most notably, bromate formation from naturally occurring bromide may occur in
chemical oxidation applications involving hydroxyl radicals. Additionally, hexavalent chromium,
which is often a cocontaminant at solvent sites, is not addressed by chemical oxidation, and its con-
centration may be increased by creating strong oxidizing conditions in the subsurface. Arsenic, sele-
nium, and other metals may also exhibit increased solubility, causing elevated groundwater
concentrations under oxidizing conditions.
μ
7. 7.1 H
YDROGEN
P
EROXIDE
AND
O
ZONE
—
E
X
S
ITU
The combination of ozone (O
3
) and hydrogen peroxide (H
2
O
2
) is known in chemistry as peroxone
and has been used for specii c contaminant remediation applications, such as TCE and explosives
(Fleming et al., 1997). At equilibrium in water, hydrogen peroxide is present as HO
-
H
+
. The
hydroperoxide ion (HO
-
) reacts with ozone to form hydroxyl radicals (OH•).
Ex situ
peroxone appli-
cations have been demonstrated in the treatment of drinking water and in the remediation of con-
taminated groundwater.
+
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