The black Binchotan coal you see above is actually white charcoal made from Japanese oak heated in an oxygen-starved kiln until it turned to carbon. (These charcoal purifiers have been around for a few years.) Place one of these sticks in a jug of water and it will reportedly absorb chlorine and unpleasant tastes and odors while infusing your water with natural minerals.
The black sticks are very delicate, like porcelain. One stick will last about 3 months, and at the end of its life you can crush it and mix it with soil so plants can benefit from it.
(Images: Merchant No. 4 and DWR)