Activated charcoal is full of nanoholes. It traps everything that's not water.

Right way to filter unpolluted water, as I learned in primary school is stack of filter material like pebbles, then smaller rocks, then sand, then activated charcoal top to bottom, with a hole at the bottom of the container to let clean water drip through.

The water can still have microorganisms in it. An easy way to kill those is to put it in any transparent plastic bottle and then leave it in the sun for a day. The UV from the sun will disinfect it.

If you your water is seawater or contains industrial or sewage runoff, such as drugs, chemicals, heavy metals, then this isn't enough. Those molecules are 100,000 times smaller than virii or bacteria.

In that case, I would recommend collecting the water in a plastic bottle, and leaning the mouth at 45 to 60 degrees into another bottle. Put some rocks or plinths to keep them in place like this and leave in the sun or start a fire under container 1 (then it must be made from heat resistant material). The water evaporating from 1 will collect in 2. Provided 2 was clean, you will have pure H20 even from a polluted source.