I can contribute to the water filter research. I have been a student of the subject for about 45 years depending on where I start counting. I could tell a lot of great tales about things I have seen out in the world of water but most the people would question my truthfulness making these tales go better around the firepit.
Many people misunderstand Charcoal filters and their usefulness. In practical terms, they are useful for water that is contaminated with pesticides, complex nasty chemicals, or maybe a tiny bit of Hydrocarbon (Oil, Gasoline) pollution. If you can taste anything like that, start looking for a better water supply. Other nonchemical bad things can be removed by some well cared for sand filters and if you have possible human or animal waste contamination you need clorox, iodine, of even permanganate to finish your filtered water. If you can taste chlorine let it set a minute in open air and try it again. IF you can still taste chlorine strongly, you are using too much or heaven forbid you need that carbon filter before the chlorine and maybe an hour after it sits in the open. Better start looking for new supplies. I have been reading all the good reference sites from Survival Blog for making charcoal just in case I ever need to use it when making a filter.
My view is that for short events like the well pump or city water being down a few days or weeks for localized disasters most of the commercial filters will work fine. They should be cleaned and maintained regularly and instructions that come with each filter usually give a good practice regimen. The most important thing to remember when using a filter is not to contaminate your clean water or parts of your filter mechanism. At home don't let the children the water filter care job. And if you just got back from the pig pen or chicken house you don't do it either. Water treatment should be handled cleanly and carefully.
Ceramic filters allow faster filtration but do not replace charcoal or finishing with chlorine. If you have a really clean surface water supply you can simply use sand filters and forget the chlorine and the charcoal. Yes people will disagree but if you have a long term or grid down supply problem you will be learning to build the old rain barrel filter used commonly a hundred years ago and described here recently. Then advance your learning to build a better sand filter treatment system in some plastic drums with two or three filters in a row.
For your backpack filters in the wilderness do not use glaciated water for your supply, it will jam your filter in a few draws of water. Watch for nasty precipitates on the rocks before you choose your supply. White or red is not good. Look for better and yes rainwater puddles. If running water tastes alkali, move on. If in doubt, flip some rocks and see if anything can live in the stream or water puddle. If it is dead, pick another supply. I have been forced from the main stream to the puddles before and the 2 micron filter did fine.
For long term events and a number of people to supply we need to build larger gravity filters that are simple to maintain and operate. The water first needs pass a small sized gravel filter to screen debris and rough solids, then clean sand filters six to ten inches thick. Build sand filters on a plate with many tiny holes to allow the water to pass and collect under the plate to be piped to the next stage. Next is another barrel with sand and if your supply merits a third filter then build one. These sand filters need to be cleaned if possible back washed with clean filtered water when they noticeably slow down the finished water yield. If you use plastic barrels, it is convenient to use removable tops for easy access. Remove the top one inch of sand from the filter and look to see if the remaining sand is clean, inspect carefully for weak spots or piping in the sand filter and if you see any remove them and replace with prepared sand that you will have on hand for maintenance. If your filters are eight inches thick you might remove two or three inches before replacing sand. Stagger the regimen for several filters so that some are thicker at any particular time. Without pumping pressure to backwash the sand you may have to completely remove all the sand and re-wash it all with a store of clean water then rebuild your filters. The process takes some planning and thinking but the payoff is worth the effort.
All sand is different and you must wash out the fine sediment to make it useable. Building a superior water system requires a little tinkering and experimentation. It you need or want a charcoal filter, for long term water treatment, start reading and watching youtube videos on making your own charcoal. It is a neat skill to learn and will be in demand for trade during a long term event. Many of the people bringing back and improving the technology of charcoal making and hyper efficient "rocket" stoves are thinking of making charcoal for water treatment. The charcoal chunks are pulverized and layered in your last water barrel filter setup. Layer a couple of inches in the middle of a couple of thick sand layers. One issue I seldom see discussed is that these carbon filters have a life time constantly shortened by the amount of nasty stuff (as described above) they must filter. Not much chemical pollution in the water, the charcoal filter layer lasts longer. More to filter, shorter life. Charcoal cannot be cleaned like sand. When it is spent it is finished and you cannot tell by looking but you may taste the difference in the water and that means new charcoal, immediately. If you have an extra barrel build a replacement finish stage with the charcoal layer that you may just change out the barrel and keep producing water. Same for the early stage filters. You can continue to make water while you do your maintenance. Accumulate plenty of new sand as you improve your system.
Recently I wandered down a click bar trail from SurvivalBlog to the University Research document linked below. They have a good example of a home built water filter system near the end of the study. Most of the study was about making the charcoal for the filter.
Sustainable Decentralized Water Treatment for Rural and Developing Communities Using Gasifier Biochar
Version 1.0, March 2012
Director of Science, Aqueous Solutions
PhD Candidate, Environmental Engineering
Engineering for Developing Communties
University of Colorado-Boulder
There are backyard researchers and Professional Companies now designing for wood fuel shortages and learning how to make charcoal in small amounts with out wasting all that wood heat and the wood gases (major BTUs) but cooking meals or heating water while making charcoal as they go. Many are building better low fuel consumption, low pollution stoves and water filters for Third World countries but the same usefulness applies to a grid down event right here at home. - R.W.