the finer the filter, the more it will take out. Start with a single layer of your t-shirt. That'll filter out the chunks, sticks, etc. Then do something finer, like your pants.

Even if you are using an actual water filter, this is still good practice to prefilter tohelp keep the filter cleaner longer.

but no clothing is going to get out the really nasty stuff, so so far all you've done is eliminated how much chewing you need to do before you swallow your water.

Here is how iodine works:
Iodine kills the bacteria in water by disrupting the ionic balance within the pathogenic cells. It replaces the chemicals necessary for the bacteria or virus to thrive with iodide ions.


Note:
If you remember correctly, iodine smelled funny and it dyed your skin orange. It does the same thing to your water and can be toxic if you use too much, just like bleach can. It can be especially harmful to kids and pregnant women and we don’t recommend that you use iodine as your primary water purification method in a survival situation.

However, it will do in a pinch and is most assuredly effective.

Another note:
Iodine only kills living pathogens. If water is contaminated with poisons such as fertilizers or pesticides, heavy metals, certain parasites, radiation, or other forms of toxins, iodine isn’t going to help.


more info here:

http://www.survivopedia.com/how-to-p...r-with-iodine/