I think people were assuming limited resources were available and we could not just go buy a Berkey. I think a 12 litre Berkey would do the trick and can clean some pretty bad water. I think some pathogens would still get through. If you dug down low enough, I'd say at least 7 meters pathogens would not be so much of an issue. Also sealing the well is very important to keep pests out.
I would not advise putting charcoal around your well pipe as it would likely break down into dirt. If you are going to do that, do it at the surface.
Also you can do a shallow well with a driven well screen. I live in an area where the ground water is pretty shallow and people are able to get clean enough water, at less than 4 meters.
The issue with bugs and frogs is probably because the well isn't sealed. I dug an 8 meter well and forgot to seal because I had to go work on something else and it got filled with frogs and rodents when the weather changed... Cleaning that out was wonderful...
If you are looking for quick, drive what is called a point well head. You need to have a high water table for this. Digging a drilled well by hand with a hand auger is doable, it only took me a week of evenings, so about 24-30 hours for an 8 meter well. Get a clam shelled auger that will accept extra pipe for extension.