Basic water filter for a 4th grade science project?

Answer 1

How much filtration is required? You could use anything from a paper coffee filter to a fancy reverse osmosis filter depending on your needs.

Answer 2

Get a waterproof or water resistant container with an open top and open bottom.

Attach some sort of coarse screen or mesh to the bottom of the container. Window screening will do. This will have to hold substantial weight, so make the attachment strong.

Fill the container with a layer of pea gravel. The layer does not have to be very thick. An inch would be more than enough.

Cover the pea gravel with a fine mesh. A fine nylon mesh is best, but even part of an old tee shirt would do. All this is for is to keep the next layer from falling through the holes in the gravel.

Put in a layer of coarse sand. Again it does not have to be thick. Half an inch to an inch is plenty. Cover the coarse sand with another fine mesh layer.

Put in a layer of very fine sand. The finer the better. This is the layer that does the filtering. The other layers are there only for support. This layer should be thicker, maybe 2 or 3 inches. Another fine mesh layer over the fine sand will help to prevent the sand from being dislodged if you pour water in quickly.

Now you should be able to pour muddy water in the top and have clear water come out the bottom.

This is called, surprisingly enough, a sand-and-gravel filter. It does a very good job of removing particulates from water. It does not remove organisms, nor will it remove dissolved minerals or salts.

The advantage of a sand-and-gravel filter is that it is very low tech and can be built by just about anyone anywhere to greatly improve the quality of the local water - very important properties for lesser developed areas in the world.

Answer 3

In the 4th grade we filtered salt water and made it into fresh water using a tarp, stick, some buckets and a fire.

What kind of water filter are you attempting to build ?

Answer 4

Coffee filter basket w/filter.

If it needs to be pressurized as in hooked to plumbing, you can purchase something like a filter cartridge kit for a refridgerator's ice maker from any hardware store, about $15.