Remediation-Apr_12-21

Remediation-Apr_12-21 - Environmental & Pollution...

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Environmental & Pollution Microbiology Spring 2010 Remediation Approaches & Technologies See Brock 11: 19.4, 19.5, 19.17, 19.18 See Brock 12: 23.6, 23.7, 24.8, 24.9
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(1.) Monitored Natural Attenuation A. EPA definition of Monitored Natural Attenuation : The reliance upon natural attenuation processes (within the context of a carefully controlled and monitored site cleanup approach) to achieve site specific remediation objectives within a time frame that is reasonable compared to that offered by other more active methods. The “natural attenuation processes” that are at work in such a remediation approach include a variety of physical, chemical, or biological processes that, under favorable conditions, act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in soil or groundwater. These in situ processes include biodegradation, dispersion, dilution, sorption, volatilization, radioactive decay, chemical or biological stabilization, transformation, or destruction of contaminants.
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B. 3 steps to document natural attenuation: Develop a conceptual model of the site. The model should show where and how fast the groundwater flows, where the contaminants are located and at what concentrations, and which types of natural processes could theoretically affect the contaminants. Analyze site measurements. Samples of groundwater should be analyzed chemically to look for footprints of the natural attenuation processes and to determine whether these processes are sufficient to control the contamination. Monitor the site. The site should be monitored until regulatory requirements are achieved to ensure that documented attenuation processes continue to occur. Currently there are 14 guidance documents available for MNA. Documents have been issued by Federal and State agencies, private companies, and industry associations. The guidance documents focus on 2 classes of contaminants: fuel hydrocarbons and chlorinated solvents. [Fig. 3.2a; 3.2b]
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C. Processes affecting natural attenuation: Movement of the contaminant i. Dilution (recharge due to rainfall or snow melt; infiltration from surface water bodies) ii. Advection (transport of a contaminant that occurs with the groundwater movement; also called bulk flow.) iii. Dispersion (spreading of contaminants from the main direction of groundwater flow) Phase transfers i. Sorption (organic matter and clay minerals have the greatest effect) ii. Stabilization (refers to bulk dissolved phase vs. NAPL phase
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This note was uploaded on 10/25/2011 for the course ENVSCI 411 taught by Professor Young during the Spring '11 term at Rutgers.

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Remediation-Apr_12-21 - Environmental & Pollution...

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