There are many types of micron filters. The ones you want have the PVDF membrane in them at .2 microns. Bacteria range from .2 to 5 microns in size, so the .2 micron filter will purify damn near all bacteria out of the solution. They range in price from $5 each to $150+ for a pack of 50. This is where I usually purchase mine:
http://www.gpzservices.com/items/products/filtration/-br-syringe-filters/list.htm
Heres the gist of how I do it:
Taxe oxycontin piils (I start with 15 at a time) and toss them into an almost empty water bottle (I open a clean bottle and empty most of it into a glass and drink it) then I seal the bottle and shake vigorously until the coating is off of the pills. Pour into glass funnel with hole small enough to not allow the pills to pass through, rinse pills with clean bottled water and dry in paper towel. Take a pestel (crushing device) and get a pyrex quality glass dish and crush the pills into a fine powder. Then I use about .15 Ml of sterile water per pill (You need to get the sterile bacteria resistant water - I have a source if you need it) so for 15 pills, thats 2.25 Ml (or CCs) of sterile water into the powder ... then I take a large syringe plunger and using the top flat plastic part, I crush the power in with the liquid until I have a really nice goupy soup. Then I calculate how much in one dose and in my case I use .75cc per dose, so .75 times 15 is 11.25 units (cc) of sterile water. I toss that in and stir for a good 5 minutes or more making sure every last ounce of powder is dissolved.
Next, I grab a couple of cotton balls, a 20 guage 1.5" needle and a 25cc syringe and I make fairly large, tight cotton balls (about 1/4th of a cotton ball) then I insert the needle perpindicular to the rolled ball so that the hole of the needle is looking down on the cotton ball from the top. Then I dip the cotton ball about half way into the solution and wait for it to soak up the liquid. I then SLOWLY draw back on the syringe. I say slow because the pill binders will accumulate around the cotton ball very quickly so you want to avoid this so that you dont have to use so many cotton balls. Repeat until youve got nothing left but white mudd with little water in it.
Remove the needle from the syringe, lock on the micron filter and A NEW NEEDLE/ Next, get a sealed sterile media bottle, insert another small needle for air bleeding, then insert the needle from the filter and push slowly through the filter. The filters can only stand 75 ft lbs of force so be careful not to puncture the seal on the membrane filter. Before I get to the bottom of the syringe, I pull back on the plunger making sure the needle isnt submerged to get an air buffer between the plunger and the end of the syringe. I also unscrew the filter to draw up about 10cc of air. I then continue and use that air buffer to force as much liquid out of the micron filter as I possibly can.
The resultant solution in your media bottle will look crystal clear - damn near medical grade. And we used bacteria resistant, sterile water designed for injection use, in addition to a micron filter that filters out damn near all bacteria (it wont filter most viruses so be aware of that), and you can then draw what you need from the media bottle and enjoy.
