Science Buddies: "Ask an Expert"

Hi, my name is Symone and I'm in the 10th grade currently conducting a project about how tropical communities around the world can utilize natural and sustainable resources to create fresh water, free of harmful microbes. Right now, I am working on building three different water filter designs that all include sand and gravel as the base, with different sustainable and accessible materials that will vary from filter to filter. I will then test each water in trials with water quality testing kits to see how effectively they each filter the dirty water. After some further research, I have found that using solar stills are an incredibly effective way to get rid of salt and microbes that a water filter may not catch, and can be helpful to smaller tropical communities who may not be able to boil filtered water. I would love to implement the solar stills into my testing design, but I can't figure out the best way to do that. At first, I was thinking of taking the cleanest water trial from my original filter designs and putting those through a solar still and recording my result, but I am not sure. Any help or suggestions would be greatly appreciated, on the solar still idea or refining the experiment overall.

Thank you so much!

Hi Symone!
I love this idea for a solar still!
From what I gathered, you are trying to compare the effectiveness of different water filters based on the sustainable materials they are made of, right?
If so, then I think you should have a completely different set of trials for the solar still to compare the results of the other water filters to the solar still.
Once you get some results from these trials, it seems interesting to try your original idea of using a water filter first, and then the solar still (just make sure you have a completely different set of trials for this to not confuse any of the results).
Does that make sense?

Other than that the experiment setup seems good! Just make sure that you keep the amount of salt, the type of water, and the amount of water constant, as well as the amount of time you keep the water filters/solar still in each design. 3-5 trials should do for each design with each water filter/solar still.

Let me know if you need any more help

Hello Symone,

This is an interesting project addressing important issues! I do have a couple of suggestions to add to the helpful comments by the previous expert:

First, I suggest that you be sure to measure and record in your lab notebook/data sheets information at the beginning of each trial (both the first stage of water filters and the second stage using the solar still):
water quality tests and water purity tests, initial volume of water, water temperature and air temperature.

And for the solar still trials, it would be really good to take these measurements every hour during the trials:
time of measurements, air temperature, wind (unless you are using a heat lamp indoors).

Also, when you set up the first stage water filters, try to use enough water for each trial so you have sufficient output (filtered) water to use for the second stage solar still trials. This Science Buddies project is evaluating solar stills for the purpose of desalinating salt water but you might find the approach useful for removing residual salt and microbes from the output from your first stage water filters: https://www.sciencebuddies.org/science- ... salination

The procedures recommend 250 ml water in the solar still. I realize that you might not have enough output from each individual trial in your first stage to get enough water for 3 trials (3 x 250 ml) from a single first stage trial. So you might need to use the water output from each of the 3 trials from your "best" first stage water filter to test 3 solar still trials - e.g., first stage trial 1 output used for trial 1 of the solar still, first stage trial 2 for trial 2 of the solar still, etc. This is why I suggest carefully measuring and recording the initial info for each solar still trial that I suggest above so you can use that data in your statistical analyses of the results for each of the 3 solar still trials. For example, you could plot the initial water quality/purity for each of the 3 solar still trials on the horizontal axis and plot the output solar still water quality/purity for each of the 3 solar still trials on the vertical axis. And use a similar plot to show the initial volume or temperature on the horizontal axis versus the yield of the 3 solar trials on the vertical axis.

Please let me know if you have any questions about my suggestions. Best of luck with this project!

Madeline