I have just been reading that research has shown that the Prickly Pear cactus can be used to purify water up to a degree of 98%. I've written a post about it in my other blog Be The Change.
I previously wrote about Prickly Pears in Corfu here - we have several cacti around the house and they are extremely prevalent on the island as a whole. So, I'm going to investigate and see exactly how it is done and give it a try - apparently, it's quite simple and was common practice amongst 19th century Mexican communities.
It is the actual cactus that is used, not the fruit, and you need to cut it up and boil it, but I'm going to try and find the exact method. Hopefully, I'll be able to publish the results here soon!