Technical Approach for In Situ Biological Treatment Research: Bench- Scale Experiments

The Fate of Hydrogen Peroxide as an Oxygen Source for Bioremediation Activities within Saturated Aquifer Systems

“…Examples include incineration, solidification/stabilization, composting, and bioslurry treatment. 4,5,6 Invasive technologies utilize highly engineered reactor units that offer elevated levels of process control and relatively rapid soil throughputs. The use of engineered reactors with such high levels of process control results in a treatment process that is kinetically more rapid and complete in terms of contaminant destruction than is typically afforded with noninvasive techniques.…”

“…Pump-and-treatment systems are sometimes costly and time-intensive because of prohibitively slow removal of the contaminants due to sorptive limitations associated with many organic contaminants, resulting in potentially extended remediation times. 5,8 In situ systems essentially convert portions of the aquifers into subsurface reactors. The most common form of in situ treatment is biotreatment; 6 however, soil flushing and vapor extraction have also been successfully used.…”

“…13,15,16 The most developed and commonly practiced form of in situ biotreatment involves the use of indigenous aerobic microbes. 5,6,17 Typically, aerobic biotreatment is used to degrade organic contaminants within polluted aquifers because of rapid removal rates and the achievable extent of contaminant degradation. 6,13 During aerobic degradation, free molecular oxygen accepts electrons released by an electron donor (typically the contaminant), which is reduced to a lower oxidation state.…”

“…Potential oxygen application options include down-hole air sparging, aboveground aeration/reinjection, or injection of H 2 O 2 directly into the aquifer. 5,6,12 Dissolved oxygen, when introduced via aeration, has a limited solubility in aqueous solutions (~9 mg/L at 25 °C and 11 mg/L at 5°C). This solubility limitation can severely hinder establishment of areas of high biological activity due to the suppressed oxygen levels associated with the inherent mass transfer problems found with aeration-based equilibrium concentrations.…”

“…Other attributes of H 2 O 2 as an oxygen source for in situ biotreatment are that H 2 O 2 is (1) reasonably inexpensive; (2) nonpersistent; (3) a stable liquid, which eliminates problems with storage and introduction into the aquifer; and (4) generally environmentally benign. 21 Zappi et al 5 reported that some in situ systems initially using groundwater injected back into the aquifer and charged with oxygen via above-ground aeration were forced to convert to H 2 O 2 injection due to the inability to keep up with the high oxygen demands of the subsurface biomass. Several reports on the use of H 2 O 2 injection to supply oxygen into subsurface biologically active zones indicated various degrees of success.…”