Further Information: Transport Processes
The Transport of Contaminated Plumes through the Soil, The Fate of Light and Dense NAPLs and the Formation of Contaminant Residuals.
The additional content on this page is to enhance your understanding about factors that are analysed when pre-evaluating/modelling whether bioremediation technologies would be an appropriate solution to cleaning up subsurface contamination. The additional content includes:
I appreciate there is a lot of information covered within this page and have therefore bullet pointed the key points of information covered within each slideshow to ensure you view only those of interest to you.
- How contamination is transported through the soil (advection, diffusion & dispersion)
- Under which circumstances it becomes sorbed to the soil particles.
- The rates of flow through the soil (e.g. permeability - affecting in situ bioremediation rates).
- Contaminant plumes (particularly analysed when monitoring natural attenuation - lecture 8)
- Volatility and Solubility (lecture 3 & 4)
- NAPLs (lecture 7) affecting where residual contamination would be located (i.e. above or below W.T.)
- Downloadable pdf. files, worked examples and problem sheets.
I appreciate there is a lot of information covered within this page and have therefore bullet pointed the key points of information covered within each slideshow to ensure you view only those of interest to you.
Derivation of Advection, Diffusion & Dispersion Equations, then Typical Contaminant Plumes
The slideshow explains:
1) The difference in contaminant plume location for a continuous source vs. instantaneous release:
- Contaminant transport through soils.
- Contaminant plumes (instantaneous & continuous point sources)
- Advection, Dispersion & Diffusion – definitions & derivation of equations.
- Breakthrough Curve
- The concentration profile for different transports (with & without dispersion).
- The difference in flow between a homogeneous and homogenous aquifer.
1) The difference in contaminant plume location for a continuous source vs. instantaneous release:
- A continuous source remains just as concentrated at the source (where has maximum concentration), however over time spreads in the direction of groundwater flow to exist in a much larger plume. (Think of a continuously leaking fuel tank).
- When not being sorbed to the soil particles, an instantaneous release moves in the direction of the groundwater flow (would be less and less concentrated but over an increasing area - due to advection and diffusion). Here the plume will be most concentrated at its centre.
The downloadable files for advection, dispersion and diffusion, with worked example problems are at the bottom of this page. Each set of notes has a complimentary problem sheet for you to work through if you wish to further develop your learning in this area. Please note, these are not compulsory for the course but I will mark and quickly return any solutions that I receive.
Slide Show: Contaminant Transport Processes & Partitioning
The slideshow below is to provide you additional information into how contamination can be transported through the soil. Note many processes may occur here (all presented in the slideshow, however I have pointed out the key areas of importance to our topic of bioremediation)
Note:
Note:
- In retardation, the contaminant gets sorbed to soil particles and would result in both a contaminated plume of groundwater, and contaminated soil - both requiring treatment. Here the contaminant is either being absorbed or adsorbed to the soil recipient. ---Bio-fixing (seen in phytoremediation) is an example of a retardation process, where instead of being sorbed to the soil as contaminated water flows, some is extracted by the plant roots.
- If the concentration of contaminant remains the same in the plume, it is not being sorbed to the soil.
- The transformation process shows the chemical reaction that occurs transforming a less mobile/persistent chlorinated compound to a more mobile hydrocarbon (alkene). e.g. see that the chlorinated compound is a liquid and the final compound is a toxic gas (a VOC) that would require remediation.
Slide Show: Permeability Tests & Soil Compatibility
The following slideshow contains information regarding the permeability of the soil medium, and how we analyse the rate of flow through the ground. If you have covered the majority of the lectures, you will recall
how important the permeability of the soil is to the success of in situ bioremediation.
Recall: Low permeability soil - low air/water flow rates through, therefore often results in difficulty providing the nutrients, electron acceptors and moisture required for effective rates of bio-degradation.
how important the permeability of the soil is to the success of in situ bioremediation.
Recall: Low permeability soil - low air/water flow rates through, therefore often results in difficulty providing the nutrients, electron acceptors and moisture required for effective rates of bio-degradation.
Slideshow Presenting NAPL Fate and Transport based Calculations
In the following slideshow, you will gain an insight into the calculations required when analysing the solubility and volatility of the contamination present. These are important when first evaluating a contaminated solid or liquid to what will happen to the contaminant with certain types of treatment. Ie.g. if you were to calculate that in certain phases, the hydrocarbon was more volatile - If an organic, you would expect the release of VOCs. This allows the engineer to design the treatment such that the toxic gases could be contained, not simply released to pollute our atmosphere.
The next few slides explain the flow of more viscous (DNAPLs) aqueous liquids and less viscous(LNAPLs) aqueous liquids. These are hoped to enhance your understanding of the formation of residuals in the subsurface - a large factor to consider in bioremediation (see lecture 7).
The next few slides explain the flow of more viscous (DNAPLs) aqueous liquids and less viscous(LNAPLs) aqueous liquids. These are hoped to enhance your understanding of the formation of residuals in the subsurface - a large factor to consider in bioremediation (see lecture 7).
Downloadable Files, Worked Examples and Problem Sheets for Contaminant/Plume Transport through the Ground.
The remainder of this page contains downloadable pdf files regarding the transport of contamination through the soil medium. It contains the information and mathematical problems with worked examples for analysing sources and plumes of contaminant. Each set of notes has a problem sheet related to its content for you to work through. I will mark any solutions that I receive, however these are to enhance your learning and are not compulsory as part of the course.
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