Remediation Technologies - Environmental Investigation and Remediation - page 337

1,4-Dioxane is a relatively stable molecule with strong internal chemical bonding. Therefore, it has
been commonly considered to be nonbiodegradable. However, a substantial amount of research has
been performed to identify specii c organisms that can degrade 1,4-dioxane, the mechanisms of
degradation, and the geochemical conditions necessary for these organisms to thrive.
Information presented in this chapter will focus on studies related to furthering the possibility of
i eld application of bioremediation as a technology to carry sites toward closure. Additional infor-
mation has been presented in Chapter 3 that addresses the identii cation of organisms capable of
degrading 1,4-dioxane and the dei nition of degradation pathways. Although there is some overlap
between these two chapters, the theoretical approaches are primarily addressed in Chapter 3;
Chapter 7 deals with potential applied approaches.

7.6.1 M IXED B ACTERIAL C ULTURES
7.6.1.1 Actinomycete Culture
Adamus et al. (1995) patented a culture comprising an actinomycete, genus Amycolata , identii ed as
ATCC 55486, which they claimed was capable of utilizing dioxane as a sole carbon growth source
under growth or resting aerobic conditions. The actinomycete strain was tested between 15°C and
35°C on 1,4-dioxane concentrations as high as 10,000,000 g/L. Adamus et al. (1995) noted in their

patent application that, among the cyclic ethers, 1,4-dioxane was considered to be remarkably
refractory to biological degradation and generally considered to be not readily biodegradable.
The Amycolata strain can be stored for at least 1 month at 4°C with little loss of activity. Its
activity is maintained indei nitely at

μ

70°C without cryoprotectants such as skim milk or glycerol,
provided that cultures are stored in BSM.
Adamus et al. incubated bacteria in the presence of 100,000-300,000

−

g/L of THF in a BSM
containing 0.1% weight per volume yeast extract. Once THF degradation is coni rmed, the culture
is supplied with both THF and 100,000-500,000

μ

μ g/L of 1,4-dioxane. Transfer cultures degraded

the THF and dioxane to less than 1000 g/L within 78 h.

The culture—designated as “CB1184”—represents a mixed population including irregularly
branched, i lamentous organisms with clumps or mats of organisms formed within these i laments.
The specii c rate of 1,4-dioxane degradation, normalized to 1 mg of the protein of these organisms,
was ~0.2-1.2

μ

μ g/min when the 1,4-dioxane concentration was maintained at 300,000 μ g/L (i.e.,

2-3 nmol/min per 1 mg of the organisms' protein).
Because the mixed population includes both eukaryotic microorganisms (protozoa, fungi, and
yeast) and prokaryotic organisms (bacteria), tests were conducted to determine which degraded 1,4-
dioxane. Antibiotics, which terminate activity in specii c bacteria, were added to the culture; treat-
ment with 50

g/mL tetracycline, streptomycin, and penicillin inhibited the degradation of
1,4-dioxane, whereas treatment with cycloheximide (inhibitor of eukaryotic protein synthesis) did
not inhibit the degradation of 1,4-dioxane. Therefore, the degradation of dioxane was traceable to
the prokaryotic organisms.
Adamus et al. built a large-scale (40 L capacity) packed-bed reactor to treat groundwater contami-
nated with 1,4-dioxane, biphenyl, biphenyl ether, ethylene glycol, chlorobenzene, acetone, chloroform,
1,1-dichloroethane, 1,1-dichloroethylene, 1,2-dichloroethene, methylene chloride, methyl chloroform,
and toluene. At an efl uent temperature of ~15°C, inl uent and efl uent 1,4-dioxane concentrations were
255,000 and 40,000

μ

g/L, respectively, and the hourly volumetric degradation rate was calculated to be
0.016 g/L. When the bioreactor temperature was 27.4°C, inl uent and efl uent concentrations were
250,000 and less than 1000

μ

μ g/L, respectively, and the rate was calculated to be 0.019 g/L.

7.6.1.2 Indigenous Soil Microbes
Taylor et al. (1997) investigated the ability of indigenous soil microbes to degrade a series
of contaminants related to the production of plastic i lms in Rochester, New York. Aerobic and
anaerobic tests were conducted on representative groundwater samples. Quantii cation and isolation