Filtration is worthwhile, as Scafool says, it removes solids and stuff which can make your purification more difficult or less effective. If you can filter, you should, even if it is a little bit. Linen, coffee filters or sand in a plastic bag or water bottle are easy and do not require carrying a lot of supplies.

You really need layers of charcoal and sand to make this work.
Spagum moss if its available.

Precautionary boil afterwards would be advisable.

I am familiar with filtration vs purified.....we didn't expect it to remove everything. Yes we knew it would remove the 'large' chunks....and I am not so naive as to think it was purified......I did however expect there to be some (even slightly) lower numbers of organisms.....I figured that the sand with the coffee filter would do a bit better than it did....and we did start with the gravel > the sand > coffee filter. There was (what I thought was) a decent amount of sand for the water to filter through. We didn't use that much in the way of gravel as we only expected it to get the large stuff....the water did take a decent amount of time to drip through (read that as slowly) so we expected (if nothing else) a "Slightly" better result......were we suprised.......but I agree that it brings up the question....how many people out there have the idea that a similar set up would be good for them? Is there an easier way to accomplish the same goal with less a bulkly set up?

Oh and no the instructor was the first to say..."This is only FILTERED !!!NOT!!! PURIFIED!!! so DON'T drink it." They were surprised though at our results.....

The class was a discussion of things that 'civilizations' need to survive. Water being so precious, the instructor thought that this hands on project would give them an idea of how much you need to do to get 'cleaner' water....the kids realized how hard it is to find clean water........

I think all the bacterial stuff you were looking at were somewhere in the range of .5 to 10 microns, and the coffee filter was in the 15 micron range, so it would be like sifting flour through a wire sieve. All the stuff you were looking at in under the microscope were smaller than the pore size of your filter. All your filter did was hold back the lumps and chunks so you could see the bacteria without other debris in the way.

Sue

Without micro pore pressure filters or semipermeable (osmosis) membranes you will have a lot of bulk.

With slow sand filters you need almost 2 feet of sand and they have to have a biological layer active on the top.

The small slow sand biofilter will clean more than 20 liters of water an hour of water once it is working but it takes about 2 days for the biologically active layer in the top of the sand to get established.

Dr. David Manz at the University of Calgary had managed to get the slow sand filter down to the size of a 5 gallon pail with 99% or better pathogen reduction but that is still a pretty large package.

So I think the answer to the question if there are easier and less bulky expedient filters is no.

For the KISS approach for water filtering, use a Milbank Bag prior to purification. Cheap, small, light weight, and simple to operate. This bag is still used by British military forces.