>>675414Not OP, but yes, if the mesh isn't fine enough the charcoal will get in the water.
Some thoughts on charcoal. Activated charcoal (activated carbon) is GOAT for this, as activation means that are lots of pores in the really tiny particles, which gives a huge surface area to bind and catch bacteria and contaminates. It is absolutely safe to injest, in fact we use it in the hospital to bind poisons in the gut. It's cheap ($5/lb on ebay), will last forever if tightly sealed, and totally worth keeping on hand for DIY water filters. Even if it turned my water black I would not hesitate to drink it.
On making your own activated charcoal - just don't do it! People don't have access to the industrial equipment to make pressure-activated charcoal. There are YouTube videos on how to make chemical-activated charcoal; they use dangerous chemicals, and home ovens don't give enough heat to make the activated charcoal much better than plain charcoal.
Plain charcoal made at home from wood can be effective for water filtration, but not of much medical use. You just have to be careful, it depends on the species of wood whether it's safe. Never make plain charcoal with wood you haven't harvested yourself. Oleander, mountain laurel, cocobolo, and many others can cause massive allergic reactions or excruciating death. Any wood used for smoking meat should be relative safe for making plain charcoal. Plain charcoal is okay, but meh tier compared to activated charcoal.
Charcoal briquettes should never be used, as most are made using coal dust, which contains heavy metals and high levels of sulfur, which will give the water a rotten egg smell and taste. There are coal-free briquettes, but all briquettes use a chemical (sodium nitrite) as a release agent that turns into a cancer causing chemicals (nitrosamines) by stomach acid.
Long-winded, but I hope some anon finds this info useful.