The old army method of filtering water is by using a 'millbank bag', see one at http://www.strikeforcesupplies.co.uk/stock.php?page=cooking. Its a pretty tried and tested method, and well a bargain at £16
Presumably, if you were confident enough about the state of any dissolved stuff, you could just filter it and ignore the iodine. Or is the iodine necessary to counter something that the bag does.
£16 for a longterm solution does seem good value for money.
G