Tuesday, June 14, 2011

Foul Water Lab Report

The purpose of the foul water lab experiment is to clean up a sample of foul water and hopefully purify it enough to be suitable for hand-washing. The procedure of cleaning the water includes three parts; first, oil-water separation. Oil-water separation is the process of using a Beral pipet to remove the top layer of the foul water sample; the thick layer of oil. By the end of this process, my group, Team Metal, had removed almost all oil. The second part of the process is Sand Filtration. Sand filtration is executed by poking small holes into the bottom of a (styrofoam) cup. Then, one must fill the cup with sand and gravel and pour the oil-free soiled water sample into the cup, allowing it to pass through the sand and gravel filter. The filtrate is released from the small holes into a beaker. After this step, my group's filtrate was very dark yellow in color, and did not have enough sand particles to make re-filtering necessary. The third part of the process is charcoal adsorption and filtration. In this step, one must place folded filter paper into a funnel with a beaker underneath. A clay triangle and a ring stand holds these materials in place. After mixing the filtrate with a semi-fine and then ultra-fine charcoal, it is poured into the funnel, and gradually drips filtrate into the beaker. This was the last step, and by the end of this step, our filtrate was completely clear and free from all visible matter such as sand and oil.

First, we were given 100mL of foul water, that stunk of garbage, waste, and coffee, from Dr. Forman. After the sample sat in the graduated cylinder for about a minute, we noticed that the a thick layer of what looked like oil had settled atop the very murky water. By this time, we were able to begin the oil-water separation. We used a Beral pipet to remove as much of the top layer as possible, and placed it into a dry test tube.
In order to be sure the substance we removed was oil, and not just impure water, we added several drops of distilled water to the liquid inside the test tube. Because the liquid we removed from the dirty sample remained on top of the water, we were sure that the substance we removed was oil-- oil is less dance than water, and therefore, floats on top of it. After we separated the oil from the water, and then discarded it, the foul water sample measured 80mL-- it lost 20mL of oil.
We were then able to begin the sand filtration process. First, we used a paperclip to poke small holes in the bottom of a styrofoam cup. Then, we added a layer of gravel, a layer of sand, and then another layer of gravel to the cup, in order to keep the sand from churning when it came time to add the water sample to the cup. Once we moistened the cup with distilled water, we were ready to our our sample through the cup and into a beaker we placed beneath it.
Once the sample was filtered through the sand and gravel, it was no longer murky and brown, or had the large chunks of dirt present at the bottom of the graduated cylinder. The dirt was trapped in the gravel and sand.
Although he filtrate still stunk, it was very dark yellow in color, like dehydrated urine, and actually looked like a liquid substance. This filtrate measured 72mL; the foul water sample lost 8mL.
Finally, we were ready for the final step; charcoal adsorption and filtration. For this last procedure, first, we mixed our filtrate with semi-fine charcoal in a 200mL Erlenmeyer flask.
Then, we added ultra-fine charcoal to the flask and mixed it in as well.
In order to proceed with this process, we placed a glass funnel in the clay triangle and put a beaker on the ring stand beneath it. We folded filter paper, placed it in a glass funnel, and slightly moistened it so it stuck to the sides of the funnel. Finally, we poured our water sample (that was now mixed with charcoal) into the filter paper lined funnel.
Very clear filtrate gradually dripped from the funnel into the beaker, as the charcoal remind stuck to the walls of the filter paper.
Our final product was 69mL, and although it looked like clean water, it still possessed the odor of garbage and coffee, but it was not nearly as strong as our beginning sample.

Final Results:

Data Analysis:
My lab group recovered 69% of our original foul water sample as purified water; this was our percent recovery. We lost 31mL of liquid, or 31% of our original foul-water sample.

Histogram: This shows the percent recovery obtained by all the laboratory groups in the class.
The largest percent recovery obtained was 70%. The smallest percent recovery obtained was 54%. This means the range of the percent recovery data is 16%.

The average percent recovery for my class is 64.5%

The median value of the percent recovery data is 65.5%

Post Lab:
Electrical conductivity is the way to test whether or not water contains salt. Since salt is a conductor, if an electrical current is present when the water is placed under a light bulb, it will light up. If this occurs, in order to purify the water to make it suitable for hand washing, it is necessary to distill the water.

Distillation was our final step in purifying water in order to make it clean enough for hand-washing. Distillation is the process of separating salt from water. Dr. Forman demonstrated the process of distillation for the class. First, he placed water into the larger round flask of the distillation train. Then, he heated water at 99.1°. Because water has a lower boiling point than salt, the water evaporated into the upper tube of the train. It then condensed in the upper, bar-like compartment and fell into the smaller round flask on the other side. Since the salt did not evaporate due to the insufficient measurement of heat it needed to boil, the salt remained in the larger round flask, separated from the newly distilled water in the smaller round flask.

The presence or absence of the Tyndall Effect: In order to test if there were particles inside water, Dr. Forman shone a light (lazer pointer) horizontally, through both murky, and distilled water. Since the beam of light shone all the way through the murky water, we could confirm that the water was not totally pure and needed to be distilled. On the other hand, when the lazer pointer was shone horizontally through distilled water, light was only visible at the edges of the glass beaker. From this, we could confirm that the water lacked salt and dirt particles and was completely pure.
Murky Water:


  1. what conclusion can you get from this ?

  2. Thank you so much for this. I am going to use the images on a PowerPoint presentation to show my ELL students a preview of this lab so they will have an idea of what they will be doing, even if they can't read English.