In Situ Bioremediation When Does it Work? (1993) / Chapter Skim
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3 The Current Practice of Bioremediation
3 The Current Practice of Bioremediation
Pages 47-62
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From page 47... ...
Since 1972, bioremediation has become well developed as a means of cleaning up spills of gasoline, diesel, and other easily degraded petroleum products. In general, in situ bioremediation has not developed to the point where it can be used on a commercial scale to treat compounds other than easily degraded petroleum products.
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From page 48... ...
Factors contributing to cost reductions in bioremediation compared to pump-and-treat systems include reduced time required for site monitoring, reporting, and management, as well as reduced need for maintenance, labor, and supplies. Furthermore, the surface treatment methods that are part of pumpand-treat systems typically use air stripping and/or carbon treatment to remove contaminants from the water processes that transfer the contaminant to another medium (the air or the land)
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From page 49... ...
The source area and tne ground water plume may be treated by engineered bioremediation, intrinsic bioremediation, a combination of the two, or a mixture of bioremediation with nonbiological treatment strategies. Contaminant concentrations in ground water plumes are typically much lower than in the source area.
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From page 50... ...
Engineered Bioremediation Engineered bioremediation may be chosen over intrinsic bioremediation because of time and liability. Because engineered bioremediation accelerates biodegradation reaction rates, this technology is appropriate for situations where time constraints for contaminant elimination are short or where transport processes are causing the contaminant plume to advance rapidly.
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From page 51... ...
Thus, engineered bioremediation is effected primarily through the use of an aeration system, oxygen being the electron acceptor of choice for the systems used so far to treat petroleum contamination. If the contamination is shallow, simple tilling of the soil may accelerate oxygen delivery sufficiently to promote bioremediation.
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From page 52... ...
The infiltration gallery in the center of the diagram supplies water to replace lost moisture and nutrients to stimulate microbial growth. engineered bioremediation system for unsaturated soils.
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From page 53... ...
Figure 32 shows a diagram of a water circulation system, with oxygen supplied by hydrogen peroxide (H2O2) and the recovered water treated with an air stripper to remove any remaining volatile contaminants.
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From page 54... ...
As the amended water moves through the contaminated portions of the site, it increases microbial activity by providing the elements that limit intrinsic biodegradation. At the Wexford County, Michigan, gas-processing plant pictured on the right, a water circulation bioremediation system is being used to clean up ground water contaminated with gasoline spilled from a tanker truck.
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From page 57... ...
The injected air displaces water in the subsurface, creating pores tem At the Hanahan, South Carolina, petroleum tank farm pictured on the left, a water circulation bioremediation system is being used to clean up extensive ground water contamination from leaks in storage tanks and disposal of tank bottoms. The site contains a mixture of a wide variety of petroleum hydrocarbons, including aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs)
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From page 58... ...
As the injected air sweeps upward through the contaminated zone, it can carry volatile contaminants to the soil above the water table for capture by a vapor recovery system. Essential to the proper use of air sparking is delineation of the extent of contamination and the subsurface geological profile.
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From page 59... ...
In addition, the effectiveness of intrinsic bioremediation must be proven with a site-monitoring regime that includes chemical analysis of contaminants, final electron acceptors, and/or other reactants or products indicative of biodegradation processes (as explained in Chapter 4~. Intrinsic bioremediation may be used alone or in conjunction with other remediation techniques.
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From page 60... ...
For example, techniques designed to vent volatile contaminants may increase the oxygen supply, encouraging microbial growth. Such synergistic effects can maximize rates of contaminant loss.
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From page 61... ...
The in situ vapor recovery system uses a series of recovery wells or trenches to extract air and volatile contaminants from above the water table. In addition to withdrawing volatile contaminants, the wells and trenches provide oxygen for biodegradation.
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From page 62... ...
62 IN SITU BIOREMEDIATION track record of reliable performance that cart be determined by reviewing the firm's references. Box 3-1 lists standards of practice that all contractors should follow.
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