Remediation Technologies - Environmental Investigation and Remediation - page 346

Control Test 2A

Test 2B

90.0

80.0

70.0

60.0

50.0

40.0

30.0

20.0

10.0

0.0

0 25 50 75 100 125

Time (h)

FIGURE 7.8 Reduction in 1,4-dioxane in duplicate Rhodococcus sp . bioreactor tests (2A and 2B), as well as
a sterile control. (From F. Shirazi, personal communication, 2007.)

degradation rates: 0.7 mg/L versus the initial rate of 0.2 mg/L. Shen et al. attributed this higher
rate to the presence of an established and robust bacterial population. They concluded that the
iron-reducing bacteria were using the 1,4-dioxane as the sole source of carbon; however, depend-
ing on the source of humic material added, other organic compounds may fovored cometabo-
lization of 1,4-dioxane.

7.6.7 F UNGI

A patented remediation process to reduce concentrations of 1,4-dioxane in groundwater has been
developed by Patt and Abebe (1995). The remediation requires the addition of a pure culture of
a fungal microorganism that degrades cyclic ethers, a cometabolite (ideally THF), and oxygen.
The process involves fermentation of the chemical pollutant as the substrate—in this case 1,4-
dioxane—in the presence of THF and oxygen by a nonbacterial fungus ( Aureobasidium pullu-
lans ), identii ed by the Northern Regional Research Laboratories as NRRL 21064. Compared to
bacterial cultures, the fungus has a broader range of pH tolerance and therefore would be suited
to a wider range of site conditions. Additionally, sufi cient dissolved oxygen, as is normally found
in natural groundwater, is a prerequisite for fungal survival. The fungus is also not as sensitive to
temperature, being functional between 5°C and 37°C, although lower temperatures result in
slower metabolism and higher temperatures kill the fungus. The process is proposed as being
applicable in batch mode (lakes, ponds, and reactors) or in continuous mode (reactors, ponds with
inl ow and outl ow, and in situ groundwater). The information provided in the patent does not
elaborate on the relationship between the THF and the 1,4-dioxane except to clearly dei ne the
THF as an obligate cometabolite.