Science Buddies: "Ask an Expert"

I'm planning to do this project:
http://mrwilliams.hubpages.com/hub/How- ... lectricity
and I want to know if I can use soil as a filter to recycle the water I would be using in this project?
If I use soil as a filter, would the water still be salt water or just pure water?
Would I be able to use this water (recycled water) to irrigate plants, and what PH should it have in order for me to use it to irrigate plants?
How can I change the PH in this recycled water?
If I use soil as a filter, would I need to change the soil from time to time or is it not necessary?

Hello nando1988,

The answer to whether soil will remove salt from water depends on many factors. As the water flows through the soil, some of the salt may combine with the chemicals in the soil, but it may release other salts such as potassium. Eventually the soil will contain all the salt it can hold, and then it would have to be discarded. Of course, how would you dispose of it? At that point, you come right back to the issue of how to responsibly get rid of the salt. Also, if you place other metal electrodes in the salt water, some of that metal will dissolve into the water and also has to be disposed of.

Good luck, WW

Dear Nando1988,
The first part of the experiment involves using salt water to generate electricity. The vinegar (acid) and bleach (base) are added to keep the pH at a constant value. The idea of purifying the water is a separate topic by itself (aquifers). You can read up on properties of sand water filter by searching on the topic. Here is one link: http://www.allwaterpurification.com/san ... ilter.html

Good Luck.
Raji Pingali