I cary these three bags specifically for filtering dirty water. Two of them are used together; one inside the other for very murky water.
Even my kettle bag could be used to filter water.
Food bags can be used to filter water.
A kettle can be used to collect rainwater or carry water from its source. It is also needed to boil water to purify it. Scoop the water up in the bag/s and run the water through the bag into the kettle. Don't forget to top up your water bottle once the boiled water has cooled down.
Always carry a water bottle with you. You can't always be sure to find water when you need it. When you find water, you need something to carry it in. Always top up your water bottle at every opportunity.