Ex-situ bioremediation

Ex situ bioremediation may use various biological wastewater treatment processes, soil piles, or land appHcation. With in situ bioremediation, the basic process is the same microbes, soil, and water working together as a bioreactor. Where the in situ techniques differ are in how contaminants and microbes are brought in contact and how oxygen, nutrients, and other chemical supplements ate distributed in the soil—water—air matrix. Typical in situ bioremediation techniques include natural or intrinsic attenuation, air sparging, and bioventing. 

Fava F, D Di Gioia (1998) Effects of Triton X-100 and quillaya saponin on the ex situ bioremediation of a chronically polychlorobiphenyl-contaminated soil. Appl Microbiol Biotechnol 50 623-630. 

Expression cloning, 10 263, 10 264 Expression profiling, 13 354-355 Expression vectors, 12 474 in Escherichia coli, 12 476 Ex situ bioremediation defined, 3 759t... 

Soil treatment, 25 834-843, 843-845 bioremediation, 25 835-836 electrokinetics, 25 843-844 ex situ bioremediation, 25 836, 842-843 in situ air stripping, 25 844 in situ bioremediation, 25 836-842 plume containment, 25 835 soil flushing, 25 844 soil vapor extraction, 25 844 sulfur use in, 23 591 vitrification, 25 844-845 Soil-vapor extraction defined, 3 759t... 

Engineered ex situ bioremediation (the treatment of contaminated soil or water that is removed from a contaminated site). 

Bio-Spin is an ex situ, bioremediation technology that treats soils contaminated with petroleum hydrocarbons. According to the vendor, the Bio-Spin system first screens and separates oversized debris. Then the system adds enzymes, uses rotation to mix the enzymes and contaminated soil, and then discharges the treated soil into a stockpile. The treated soil is kept separate from surrounding soils until bioremediation is complete. 

Biosolids-enhanced remediation (BER) is an ex situ bioremediation technology used to treat soils contaminated with petroleum hydrocarbons and polycychc aromatic hydrocarbons. The BER technology was developed by isolating particular microorganisms with the ability to degrade the specific components of petroleum products. The technology has been applied full scale and is commercially available. 

Dames and Moore has developed bioinfiltration technology that combines in situ bioremediation of soils with ex situ bioremediation of groundwater. The vendor states that the technology... 

TCE-degrading bacteria is a patented technology for the treatment of soil, groundwater and wastewater contaminated with trichloroethylene (TCE). The particular strain of bacteria used in this technology does not require the addition of a toxic co-substrate to activate the bacterial destruction of TCE. The technology can be used to remediate virtually any media type contaminated with one or more volatile organic compounds (VOCs), including TCE, and can be used for in situ or ex situ bioremediation. 

The engineered bioremediation system (EBS) is a proprietary process for the ex situ bioremediation of organic contaminated soils. The system is designed to enhance the natural bioremediation rate of organic constituents by controlling factors affecting microbial growth and metabolism. 

The Bioscrubber is an ex situ bioremediation technology for removing organic contaminants from gaseous streams. 

BioSparge is a closed-loop, in situ and ex situ bioremediation technology that uses vapor extraction, gas injection and biodegradation to remediate contaminant plumes below the ground-water level. This process works by extracting soil vapor from wells placed at the perimeter of... 

Figure 1. Aerated static pile for ex situ bioremediation of chemically contaminated soil. Adapted from Rynk (1992). Reprinted with permission from Northeast Regional Agricultural Engineering Service (NRAES), Cooperative Extension, Ithaca, New York.

U.S. EPA (1994). Fact Sheet, March 1994, Superfund Innovative Technology Evaluation (SITE). Demonstration of the J. R Simplot ex Situ Bioremediation Technology for Treatment of... 

With ex situ treatment of contaminated soils, a controlled environment for soil treatment can be maintained- With mixing, nutrient addition, aeration, and other environmental controls, mass transfer rates that typically limit in situ bioremediation can be greatly increased. Of course, the disadvantages of ex situ bioremediation are the costs of soil excavation and reactor operation. Thus, ex situ bioremediation is favored by localized, shallow soil contamination. 

Sims, R. G, Sims, J.L., Sorensen, D. L., Stevens, D. K., Huling, S. G., Bledsoe, B. E., Matthews, J. E. Pope, D. (1994). Performance evaluation of full-scale in situ and ex situ bioremediation of creosote wastes in ground water and soils. In Proceedings, Symposium on Bioremediation of Hazardous Wastes Research, Development and Field Evaluations, pp. 35-9- EPA/600/R-94/075. Cincinnati, OH US EPA. 

Seech, A. G., Marvan, I.J. Trevors, J.T. (1994). On-site/ex situ bioremediation of industrial soils containing chlorinated phenols and polycyclic aromatic hydrocarbons. In Bioremediation of Chlorinated and Polycyclic Aromatic Hydrocarbon Compounds, ed. R. E. Hinchee, A. Leeson, L. Semprini S. K. Ong, pp. 451-5. Boca Raton, FL Lewis Publishers. 

For facilities treating groundwater, the predominant technology chosen has been pump and treat. The innovative technologies selected include in situ bioremediation, ex situ bioremediation, thermal desorption, and chemical treatment. The facilities requiring soil treatment are selected based on established technologies, such as off-site disposal and incineration. The innovative technology most often selected has been SVE. 

Ex situ bioremediation relies on management of groundwater flow, with optimization of retention times in the bioreactor, biomass retention in bioreactors, temperature and pH control and most importantly, maintaining aerobic conditions. In addition, co-contaminants as BTEX compoimds or iron, Fe(lll), can jeopardize aerobic degradation of MTBE, both in and ex situ. 

Fava F, Di Gioia D, Marchetti L. (1998). Cyclodextrin effects on the ex-situ bioremediation of a chronically polychorobiphenyl-contaminated soil. Biotechnology and Bioengineering 58 345-355. 

At present, bioremediation is receiving a lot of interest as it appears sustainable, low cost, and low energy and therefore meets the needs of a remediation solution that will both benefit the environment directly and also have a relatively low carbon footprint. In practice, it often needs to be combined with other approaches to achieve an effective solution. This requirement is frequently driven by the need to remediate over a short timescale, in the case of ex situ bioremediation, or the need to promote long-term effectiveness under a regime such as monitored natural attenuation or permeable reactive barriers. The engineering of bioremediation to enhance its effectiveness has been studied for the last few decades with considerable success. It has become a mainstream part of the toolbox for contaminated sites. 

The use of foams to remove heavy immiscible fluids such as DNAPL from soil was developed by the petroleum industry for crude oil production. Subsequently, The Gas Research Institute developed the use of foams to release and mobilized DNAPL contaminants in the subsurface. Coupled with in situ or ex situ bioremediation, foam-enhanced product recovery can, potentially, transport CHC contaminants upward in the groundwater, flius reducing the potential for driving the contamination to previously non-impacted areas. 

Several field demonstration studies were conducted in the United States, mainly in the 1990s. These demonstrations have shown that surfactant-enhanced subsurface remediation (SER) is relatively rapid and economical, and can be competitive with conventional pump and treat remediation, if—in ex situ bioremediation—surfactant losses can be minimized, contaminated elution maximized, and surfactant-contaminant separation and the former s reuse implemented [46]. 

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