These tend to be less polluted than streams and ponds. Then carefully decant off the clear water, leaving any sediment behind. Even if the water is clear, discard the bottom third. Add a small amount of alum. This helps remove organic and solid matter that can interfere with the purification process.
Many organisms adhere to matter.
The most commonly used chemical disinfectants are halogens - iodine and chlorine. These kill organisms by oxidizing essential cellular structures. Halogens are inexpensive, relatively safe, not bulky, and can disinfect any quantity of water. Moreover, disinfection can be accomplished overnight or while you carry the water. Most experts prefer iodine over chlorine.