lecture 1: introduction to soil remediation engineeringbaiyu/engi 9621_files/lecture 1.pdf ·...

ENGI 9621 – Soil Remediation Engineering

Spring 2015 Faculty of Engineering & Applied Science

Lecture 1: Introduction to Soil

Remediation Engineering

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a sub-discipline of environmental engineering the development and implementation of strategies to clean up (remediate) the environment by removing the disposed hazardous soil contaminants

1.1 Definition of soil remediation engineering

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Muti-disciplinary involvement Various sources and complex cocktail of contaminants 3

1.2 Sources of soil contamination

Infiltration of contaminated surface water Land disposal of solid and liquid wastes Accidental spill Fertilizers and pesticides …

(1) Originating on the ground surface

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Waste disposal in excavations Landfills Leakage from underground storage tanks Leakage from underground pipelines …

(2) Originating above the water table (Vadose Zone)

Waste disposal in wet excavations Deep well injection Mines …

(3) Originating below the water table (Saturated Zone)

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1.3 Common soil contaminants

Heavy metals (Pb, Cd, Cr, Ni…) Arsenic (inorganic and organic forms) Chlorinated solvents (PCE, TCE, TCA, MC…) Polycyclic aromatic hydrocarbons (PAH) Polychlorinated biphenyl (PCBs) Pesticides (organochlorines, organophosphates and carbamates)

More information Visit Web of Federal Contaminated Sites at http://www.federalcontaminatedsites.gc.ca/index-eng.aspx

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1.4 Selecting and/or designing a right remediation technology

complex contaminants as well as unique site features (geology, hydrology, etc) tailored technologies are required on a site- by-site basis

(1) Site characterization：

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end goal for clean-up how clean the site is required to be risk stakeholder concerns technological feasibility and convenience effectiveness/practicality ease of integration into remediation systems cost and acceptance

(2) Comprehensive consideration for a particular site

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Steps involved in remedial action Source: USEPA, 1991

Site discovery

Preliminary assessment

Site inspection

Hazard ranking analysis

National priorities list

Remediation investigation

Remedy selection/ Record of decision

Remedial design

Remedial action

Project closeout

No federal remedial action required

Feasibility study

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1.5 Overview of Remediation technologies

(1) Technologies to remediate contaminated soil fall into two principal clean-up approaches

In-situ (which is always done on-site) deals with contamination without removing material from the ground Ex-situ (which can be done on- or off-site) requires the removal of contaminated soil for treatment or land-filling

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(2) Technologies to remediate contaminated soil fall into two classes

Source control technologies to contain or treat sources of contamination Management of migration technologies to control the movement of contaminants away from sources

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(3) Popular remediation technologies

Soil remediation

Soil Vapor Extraction In Situ Bioremediation and Natural Attenuation Soil Flushing Soil Fracturing Phytoremediation Surface capping

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Groundwater remediation

In situ Air Sparging with Vacuum Extraction In Situ Bioremediation and Natural Attenuation Pump and Treat In situ reactive walls

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Soil Vapor Extraction

Source: Suthersan, 1997

Schematic of SVE implementation in the field 16

Presenter

Presentation Notes

Soil Vapor Extraction (SVE) is the primary technology for removing VOCs and other contaminants from the vadose zone of the soil matrix of a contaminated site. Vacuum is applied to a recovery well where the screened portion of the well is exposed to the vadose zone. Vacuum levels typically range from 30"WC on a very sandy soiled (high permeability) site to very deep vacuum levels of 28"HG on very tight clay soiled (low permeability) site. Blowers for remediation of these sites are dominated by regenerative and rotary lobe blowers. Liquid Ring and Vane blowers are used on projects that require the much deeper vacuum.

SVE treatment Source: WRScompass, 2008

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In Situ Bioremediation

Source: Hardisty, 2005 In-situ bioremediation implementation 18

Injection of enhanced bioremediation product Source: G&R Remediation , www.envirocoregr.com

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http://www.envirocoregr.com/

Natural Attenuation

Source: Hardisty, 2005

Schematic of natural attenuation 20

Presenter

Presentation Notes

How is natural attenuation different from the "do nothing" approach? Natural attenuation is sometimes mislabeled as the "do nothing" or "walk away " approach to site cleanup. The truth is that natural attenuation is a proactive approach that focuses on the verification and monitoring of natural remediation processes rather than relying totally on "engineered" processes. Before natural attenuation can be proposed for any site, significant soil and groundwater data must be collected and evaluated to document that natural attenuation is occurring and to estimate the effectiveness of natural processes in reducing contaminant concentrations over time. If natural attenuation is selected as the preferred site remedy, the party responsible for site cleanup must commit to long-term monitoring to verify that the contaminants pose no risk to human health or the environment and that natural processes are reducing contaminant levels and risk as predicted. Land use and groundwater use are generally controlled on these sites to prevent human exposure to contaminants.

Source: NAVFAC POC, 2009 Contaminant plume formed during natural attenuation

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Soil Flushing

Source: Sharma and Reddy, 2004 Typical in-situ soil flushing in vadose zone 22

Presenter

Presentation Notes

Soil washing has been used for many years to remove inorganic contaminants such as salts and heavy metals from soils. The process is relatively simple. A solvent, in many cases fresh water, is passed over and percolated through the impacted soil dissolving and removing the contaminants from the soil. The solvent containing the dissolved contaminants are then collected and either treated and reused, land applied, or transported for disposal. In some cases additives are used to enhance contaminant solubility. The treatment can be used on-site or, if the correct conditions exist, it can be used beneath the ground surface (in-situ). Etech has designed, constructed, and operated soil washing systems that have successfully removed contaminants from thousands of yards of impacted soil, reducing costs over conventional disposal methods by as much as 40%.

Soil washing plant Source: LITAI, www.dllitai.com 23

http://www.dllitai.com/

Soil Fracturing

Source: Sharma and Reddy, 2004

Two types of soil fracturing 24

Hydraulic Fractures Source: Slack , 1998

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Presenter

Presentation Notes

Hydraulic fracturing can be used to create features that promote recovery of fluids from low permeability media. This slide shows three fractures exposed as irregular white traces on the wall of this trench. The straight white line is a horizontal string that has been hung for reference. A hammer is stuck in the wall perhaps fifteen feet from the camera. The round dot is a dime. Thus the fracturing process creates roughly horizontal lenses of sand about a centimeter thick that extended several feet away from the parent well. The sand-filled lenses act as preferential flow channels from portions of the formation that would otherwise be considered isolated from the well.

Phytoremediation

Source: Suthersan, 1997

Phytoextraction of heavy metals 26

Hybrid poplar tree for phytoextraction Source: Chappell, 1997

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Source: Federal Remediation and Technologies Roundtable, 2003

Surface Capping

Landfill Cap

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Presenter

Presentation Notes

Where regulations allow and when feasible, capping and/or containing can be a successful means to addressing site contaminants. Etech has designed and installed caps and containments to address a variety of issues. Etech maintains the equipment and other resources needed to construct containments or caps for all types of remedial strategies.

Source: Fernald Environmental Management Project, 2002 Geomembrane 29

In situ Air Sparging with VES

Source: Hardisty, 2005

Schematic of AS-VES

(VES)

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Source: G&R Remediation , www.envirocoregr.com AR-VES equipments

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Pump and Treat

Source: Hardisty, 2005 Schematic of pump and treat

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Source: G&R Remediation , www.envirocoregr.com A well for PAT 33


In Situ Reactive Walls

Source: Grubb, D. G. and N. Sitar, 1994

Reactive walls

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Source: U.S. Department of the Interior, 2003 Building reactive walls 35

lecture 1: introduction to soil remediation engineeringbaiyu/engi 9621_files/lecture 1.pdf ·...

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