I have been looking into a lot of different water purification methods recently. Generally we are lucky in N.Ireland to have good good water quality in most places. Obviously you can't drink the water from the river Lagan in the centre of Belfast but the water in the hills, mountains and upland areas is usually ok to drink from source.
All the same it is best to treat all water as bad if you are out for any length of time because getting sick ruins a trip.
There are lots of different pro's and cons of different methods which I am not going to go into.
This is obviously chemical!
You can buy Chlorine Dioxide from Life Systems in droplet form or as tablets.
The tablet version which is what I bought came in a hard plastic box which is easy to open and close and is quite tough.
The instruction are clearly printed on the back of the box and on each individually foil wrapped tablet too.
I took 1 litre of clear water from a local river and added 1 tablet. The water was visibly clear to begin with which is good for chemical means which can be unreliable in turbid water. I added 1 tablet and waited 30 minutes. I also turned the bottle unside down and loosened the cap slightly to allow the chemicals to cleanse the threads too.
The water took on a very slight greenish tinge and had a detectable chlorine scent and slight taste. The taste was much better than the old chlorine tablets by far.
I would definitly use this method again if the available water is clear. In combination with a filter it would be unbeatable really.