Remediation Technologies - Environmental Investigation and Remediation - page 351

Pre-treatment Post-air stripper Post-air stripper with

pH adjustment

700

600

500

400

300

200

100

0

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0

Applied O 3 (mg/L)

FIGURE 7.11 Plot of 1,4-dioxane concentration as a function of applied ozone at the City of Industry AOP
Pilot Study. (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].)

corresponding chlorinated ethene (Bowman et al., 2007). Increasing hydrogen peroxide and ozone
injections to eliminate the methyl chloroform would have increased costs dramatically for the air
stripper system that was already fully capable of removing chlorinated ethanes. Pilot-testing of the
HiPOx advanced oxidation process (AOP) system as a post-treatment option revealed that the ele-
vated pH of the stripper efl uent, caused by the addition of an antifouling agent, reduced the efi ciency
of the AOP. Several different injection rates for ozone were tested to maximize 1,4-dioxane removal
and assess the optimal order of treatment for the system (i.e., pre- or post-air stripper) (Figure 7.11).
On the basis of the results, the system was designed for use before the existing air stripper and was
optimized to achieve the removal of 1,4-dioxane to levels below the detection limit of 2 μ g/L.

Chlorinated VOCs leaving the AOP system were effectively treated in the air stripper.
The third test site, in Mountain View, California, was treating chlorinated VOCs (as high as
8800 g/L were untreated by the existing system

(Boarer and Milne, 2004). Testing coni rmed that treatment goals for all the contaminants of con-
cern, including 1,4-dioxane, could be achieved with the HiPOx as a replacement for the air stripper
while retaining the GAC system as a polishing unit to address compounds resistant to complete
removal by oxidation (e.g., 1,1-dichloroethane) (Bowman et al., 2007). Overall, the HiPOx technol-
ogy has been demonstrated in a variety of applications and conditions and is capable of complete
destruction of 1,4-dioxane and associated chlorinated ethenes. The HiPOx system can also be used
to destroy 1,4-dioxane and decrease the chlorinated VOCs to sufi ciently low levels for enhancing
or prolonging the effectiveness of existing treatment systems.

μ g/L for TCE). 1,4-Dioxane levels as high as 16 μ

7. 7. 2 H YDROGEN P EROXIDE AND O ZONE — I N S ITU
As of the writing of this topic, there are no completed and documented full-scale remediation proj-
ects involving ISCO in the literature. Several pilot studies have been performed coni rming the
efi cacy of the technology.