Environmental Engineering Reference
In-Depth Information
Bowman et al. (2007) demonstrated the effectiveness of injecting hydrogen peroxide and ozone
under high pressure in a continuous in-line process to treat feed water containing an aqueous mix-
ture with 1,4-dioxane and chlorinated compounds. In the HiPOx™ (Applied Process Technology,
Inc., Pleasant Hill, CA) system, hydrogen peroxide is injected into the water stream i rst, followed
by high-pressure ozone. Ozone is produced at 40-50 psig on site from a solid-state ozone generator
supplied with liquid oxygen or from oxygen from the atmosphere, generated with a pressure swing
absorption system. The ozone is injected at specii c locations along the in-line reactor l ow path to
avoid the creation of undesirable by-products, such as bromate (Figure 7.10).
The HiPOx system was tested with water from three groundwater extraction and treatment
systems operating in California with elevated chlorinated VOC and 1,4-dioxane levels. A system
at South El Monte, California, was pilot-tested at 10 gpm for perchloroethylene levels of 150
μ
g/L
and 1,4-dioxane of 20.2
μ
g/L. Efl uent levels in initial testing achieved perchloroethylene reduc-
tions to 2.1
g/L. Because the existing
water treatment for the contaminated drinking-water production well included liquid-phase GAC
for effective treatment of chlorinated VOCs, the scaled-up design for the permanent production
well solution was optimized for the removal of 1,4-dioxane. The i nal 490-gpm system was installed
pre-GAC and effectively lowered the 1,4-dioxane concentration from 4.6
μ
g/L and 1,4-dioxane reductions to the detection limit at 2
μ
μ
g/L to below the detec-
tion limit at 2
g/L (Bowman et al., 2007), but allowed low levels of chlorinated VOCs to exit the
system. This approach addressed the 1,4-dioxane issue, while keeping the inexpensive GAC sys-
tem operational and extending the life of the existing GAC media by lowering inl uent chlorinated
VOC levels.
A second system in the City of Industry, California, was tested as pre- and post-treatments to an
existing air stripper that was effectively treating chlorinated ethenes and ethanes as high as 730
μ
g/L
(for methyl chloroform) to below California's regulatory threshold. 1,4-Dioxane levels as high as
610
μ
g/L, although the exact mechanism for its
removal was not determined or documented. Pilot-testing was optimized for 1,4-dioxane removal
and not for the removal of chlorinated ethanes (e.g., methyl chloroform, 1,1-dichloroethane) because
these compounds are approximately one-tenth as susceptible to hydroxyl radical oxidation as the
μ
g/L decreased slightly in the air stripper to 430
μ
Line pressure
reaction
40-50 psig
Multiple
injection
points
Continuous reactor
Influent
Effluent
[O 3 ] = 6%-10%
by weight
in O 2
O 2
H 2 O 2
injection
system
Solid-state
ozone
generator
H 2 O 2
FIGURE 7.10 Schematic of HiPOx TM advanced oxidation system. [From Bowman, R.H., Miller, P., Purchase,
M., and Schoellerman, R., 2007, Ozone-peroxide advanced oxidation water treatment system for treatment
of chlorinated solvents and 1,4-dioxane. http://www.aptwater.com/assets/tech_papers/Paper-1.4Dioxane.pdf
(accessed August 1, 2007).]
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