Yolanda, water purification tablets use a number of ways to 'Purify' the water from biological pathogens. (living Organisms)What do purification tablets do? Do you to do anything else to the water if you have purification tablets?
Remember, we are talking about 'Clear' water here, not stagnated, or full of debris that can hide pathogens...
You will need to let solids settle and pour off the 'Clear' water,
Or you will need to filter the solids out of the water before you attempt to 'Purify' it.
Solids can, and will, hide pathogens from the treatments, chemical, thermal and UV...
The 'Purification Tablets' come with three basic active ingredients,
Iodine is non removable from the water, will kill off beneficial bacteria in the gut, and iodine is hard on organs, including liver, kidneys, but especially the thyroid gland.
For very short term use, the iodine tablets, or tincture of iodine can be used to purify water well enough to keep you alive, but for the very young, very old, sick or pregnant, it's not a good idea.
A chlorine derivative in solid form that will kill about everything in water that isn't hiding.
(there are several besides Sodium Hypochlorite)
Chlorine will attempt to return to a gas state, and will evaporate off quite readily at room temprature when water is poured between containers and allowed to aerate.
This is beneficial to people that are sick, pregnant, have weakened immune systems, the very young or very old.
Ozone is an unstable gas, normally generated by an electrical current, but can also be made by chemical processes.
Regular O2 is what you breather (2 Oxygen Molecules),
Ozone is O3 (3 Oxygen molecules) and it's deadly to all pathogens...
Ozone will also oxidize most metals, minerals, chemicals it comes into contact with and make the precipitate out of the water.
(meaning if there is anything left of them after they come into contact with the 03, what's left will escape an open container as a gas, or heavier than water will settle to the bottom of the container)
Ozone leaves nothing behind but oxygen when it reacts with outside air, there is no pollution, no chemical residue (like chlorine, salts or iodine) when it's finished working.
Being quite expensive to produce, the best source right now is surplus from the South African army.
There were so many water sources polluted by everything up to and including chemical weapons in South Africa, this was the only way to keep their people alive...
Safe for ALL people, young, old, sick, pregnant. There are NO chemical leftovers from the ozone tablets you need to worry about, and most of the time the water even tastes good!
(Ozone removes most things that make water taste strange while it's removing the other chemicals and pathogens!)
Personally, I've given up on ALL chemical treatments.
Too much aggravation!
I've gone to Filtering and UV purification of spring/well water and it works GREAT!
Small scale UV purification is as easy at turning on a 'Light Stick' type UV light and dropping it in a container of water.
Large scale UV purification is as easy as a set of sediment filters (0.05 micron) to get the 'Chunks' out,
Then a quick run through a UV light tray (Solar powered here!) then off to the potable water holing tank!