Teabag Filter

Water is a common substance on earth, covering over 75% of its surface. Potable water, that is, water free enough of salt or pollution to drink, not so much. People in many of the poorer parts of the world have only rivers and ponds to drink from. RIvers and ponds that often contain some kind of pollution and give them a bad case of the runs.
Well, that's all about to change, says PhysOrg, a science reporting site. South African environmental scientists have invented a new type of filter, one that resembles a common tea-bag. Only instead of tea, it contains a fiber-like material that absorbs mud, pollution, bacteria, and heavy metals. The water is then as clean as bottled water and can be drunk. The filter is inexpensive and can then be thrown away, where it will break down. (Please discard it away from the water source.) The filters cost three South African cents each, and even the poorest South African can afford to buy several per day. The filter can purify up to a liter of water.
The filter doesn't scale up very well, so it wouldn't be useful for, say, purifying a municipal source of water. There, heavier technology would have to be employed.