Effects of Salinity on DispersantOil Particle Size - PowerPoint PPT Presentation
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Title: Effects of Salinity on DispersantOil Particle Size
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Effects of Salinity on Dispersant/Oil Particle
Size
- By Clair Hollingsworth
- Research Experience for Undergraduates Program
- Texas AM University
- Summer 2005
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Oil Spill Response
- Mechanical means may be not be practical
- Extreme Ocean Conditions High Winds, Choppy
Waves, etc. - Environmentally sensitive areas
- Dispersant use may be an option
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What Do Dispersants Do
- Stabilize oil droplets in the water column
- Reduce oil-water interfacial tension
- Less mixing energy required
- Droplets incorporated into water column
- Lowered economic and ecological impact on the
shoreline
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What are Dispersants
- Contain Surfactants
- Hydrophilic head
- Hydrophobic Tail
- Solvent
- Reduce viscosity
- Facilitate dispersal
Surfactant molecule
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Salinity Conditions
- Ocean seawater (30-33)
- Costal Environments have a range of salinities
- Bays and Estuaries may be much lower (range 10
- 25)
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Problem Statement
- How effective is dispersant use in coastal
environments? - Lower salinity
- Low mixing energy
- Application effectiveness
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Research Objective
- Investigate dispersant effectiveness in differing
salinities - Lab scale study
- Salinity 10, 20, 30
- Mixing held constant (low level energy)
- Premixed and Non-premixed treatments
- Multiple replications
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Methods
- Continuation of M. Sterling doctoral research
- Experimental Design
- Reactor Set-up
- Saltwater Preparation
- Dispersant/Oil
- Premixed/Non-Premixed
- Sterling did premixed only
- REU non-premixed as well
- LISST 100-X instrument
- Measure oil droplet size
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Methods
- Reactor Set-up
- Rectangular Plexiglas Reactor
- Filled with 32L artificial saltwater
- Mixer w/ impeller
- LISST instrument
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Saltwater Preparation
- Carboy System
- Instant Ocean and DI water
- Hydrometer to check salinity
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Dispersant/Oil
- Corexit 9500 dispersant
- Low toxicity
- (manufactured Exxon/Nalco)
- Arabian Medium Crude Oil
- Artificially weathered
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Premixed/Non-Premixed
- Dispersant oil ratio
- 110
- Premixed scenario
- Injected mixture w/ syringe into water
- Non-Premixed scenario
- oil added to water surface
- Use ring to contain slick
- Sprayed dispersant onto slick
- Remove ring
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The LISST-100X Instrument
- Laser In-Situ Scattering Transmissometry
- Laser diffraction to obtain particle size
distribution - Angle Scattering Distribution
- 32 logarithmically scaled ring detectors
- Particle Size ranges 1.2 to 250 microns
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RESULTS
- 14 four-hour experimental runs
- Lots of data
- Due to presentation time contraints
- Present data for 2 runs
- premixed scenario
- non-premixed scenario
- Then discussion points
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Discussion PointsFor All Salinities
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Salinity 10 Comparisons
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Salinity 10 Discussion
- Premixed (3 runs)
- 2 runs similar
- Visually Chocolate milk like
- 3rd run
- lower initial oil volume
- Visually Oil floating on surface
- Non-premixed (3 runs)
- Fairly consistent
- Premixed more effective than Non-premixed
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Salinity 20 Comparison
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Salinity 20 Discussion
- Premixed (2 runs)
- Runs comparable
- Non-Premixed (2 runs)
- Runs comparable
- Premixed runs more effective than Non-Premixed
runs
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Salinity 30 Comparison
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Salinity 30 Discussion
- Premixed (2 runs)
- Different initial oil volumes
- Non-Premixed (2 runs)
- Different initial oil volumes
- Premixed more effective than Non-Premixed
- Non-Premixed more effective at 30 than other
salinities(10, 20 )
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C/Co Comparisons
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C/Co Discussion
- Resurfacing rates larger at higher salinities
- Particle Surface Charges
- Compression of charge layers surrounding particle
- Van der Waals force (prominent)
- Droplet Coalescence
- Resurfacing of newly formed larger droplets
Negatively Charged Particle
Negatively Charged Particle
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Conclusions
- At all salinities Premixed treatment outperformed
Non-Premixed treatment - For Premixed treatment
- at higher salinities the resurfacing rate was
greater - Non-Premixed treatment
- was more effective at higher salinities
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Application in Real World
- WHAT IF?
- 1-Day-Old oil spill in Galveston Bay
- Low salinity (17)
- Relatively calm water
- Arabian Crude Oil
- Should dispersant use be recommended?
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Recommendations
- Continue investigations of salinity effects
- More replication needed
- Some results appear not very reproducible
- Dispersant application method
- Investigate new data analysis for Non-Premixed
runs - C/Co graphs were not as meaningful
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Recommendations
- Do weights so lifting the LISST is easier
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Acknowledgements
- Mentors
- Cheryl Page
- Shahidul Islam
- Tope Ojo
- Dr. Bonner
- Dr. Honeycutt
- The National Science Foundation for funding the
internship
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