Wednesday, 28 August 2013

The Effect Of An Oil Water Separator's Shape On It's Effectiveness


The purpose of this experiment was to determine if the shape of an oil-water separator affected how effectively it separated oil from water

I became interested in this idea when Mr. Norm Hepner, a department of ecology professional engineer, informed me that some oil-water separators could be more effective than others.

The information gained from this experiment will affect us all because if oil mixes with wastewater it is a danger to everyone. It is people who own or manage parking lots or carwashes who have the legal responsibility to make their wastewater cleaner, but all of us are affected.


My hypothesis was that the circular shaped oil water separator would work better because it has less dead space (places where the water sits in one spot) so the oil would have less setting time in the primary chamber

I based my hypothesis on my understanding of fluid dynamic principles and oil water chemistry (stoke’s law).  Fluid dynamics are the characteristics of how a fluid will act, this is also known as Fluid mechanics.  Oil water chemistry depends on something’s density and its viscosity.  The density is a measure of a quantity such as mass per unit volume, and the viscosity is how thick or sticky something is.  Stokes law is the formula showing the velocity at which a less dense liquid will rise through a more dense liquid.


The constants in this study were:

  • Size of buckets
  • Temperature of water
  • Amount of water
  • Amount of oil
  • Type of oil
  • Rate at which mixture was poured in
  • Size of polypropylene pads
  • Polypropylene Pad absorbency

The manipulated variable was the shape of the oil-water separators.

The responding variable was how much oil was in the polypropylene at the end of the experiment.

To measure the responding variable I used a scale to measure the change in mass of the polypropylene pad after it had absorbed the oil.

rectangular 7.5 liter bucket
rounded 7.5 liter bucket
gallons of water
gallon of oil
pads of polypropylene
separate buckets to mix oil and water in
paint stirring rod
caulking gun
tubes of Epoxy


1. Build two separators
a) Find measurements of separators
b) Cut separator to required lengths
c) Put divider in bucket
d) Use epoxy to keep in bucket
e) Wait for epoxy to dry
f) Drill hole in side of bucket
g) Place plastic nozzle in separator
h) Put epoxy on nozzle to secure
i) Wait for epoxy to dry
j) Repeat steps A-I using other separator 
2. Fill Separator with clean water
3. Cut 6 polypropylene pads
4. Weigh all polypropylene pads
5. Weigh all Ziploc bags
6. Place 1 pad in each of the six bags
7. Weigh all bags containing pads
8. Pour .5 liters of oil into solution bucket
9. Pour 7 liters of water into solution bucket
10. Pour 7.5 liters of water into separator
11. Use paint stirring rod to mix solution
12.  Open solution bucket valve
13. Open separator nozzle
14. Wait for solution bucket to empty
15. Close separator nozzle
16. Let it sit for 5 minutes
17. Place polypropylene pad in collection bucket
18. Stir around for 5 minutes
19. Take pad out of bucket
20. Hang up to dry
21. Wait 45 minutes
22. Place in Ziploc bag
23. Put rubber band around bag
24. Place on scale
25. Measure weight
26. Clean out all buckets and separators
27. Repeat steps 2-26 for trials 2 and 3
28. Repeat steps 2-27 using other separator


The original purpose of this experiment was to find if an oil water separator’s shape affected the separator’s ability to do its job.

The results of the experiment were that the square separator worked better than the circular separator, I know this because the square had an average weight gain of 42.13 grams, where as the circular separator had an average weight gain of 50.37.  I think this was because the circular did not have as much surface area causing the oil to go down deeper and letting it pass through the separator.


My hypothesis was that the circular separator would work better because there would be less dead spaces.

The results indicate that this hypothesis should be rejected because the square separator was more effective than the circular.

Because of the results of this experiment, I wonder if varying the depth of the separator would have any effect on how the oil water separator performs.

If I were to conduct this project again I would make the separators have the same surface area to eliminate the possibility of that having an effect on the experiment.  I would also have more trials, and test lighter and heavier types of oil.

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