Read the (micron) rating of the filter. The smaller the number the smaller the holes, and hence the less stuff can go throu.
To remove bacteria it should be at (0.2 micron), but most likely what you have is 5 micron or so. That is good enough for dirt particles, rust ..etc.
However, if it is a carbon filter, then it is not made to remove stuff, rather it is to remove taste and odor.
As said above, best thing for bacteria is to boil the water. You can bleach water , but boiling may also remove other stuff (like volatile organics).