Discover Black Blum Charcoal Water Filter Sticks here. The Black Blum range of activated charcoal water filters purify water by absorbing impurities such as chlorine. Carbon water filters like this have been used by the Japanese for over 500 years and will make your tap water taste great. Black and Blum’s artisan makers follow a traditional Japanese technique to make their charcoal. They only prune and coppice branches of fast-growing native trees. Buy their natural water filters from Planet Organic here.