Water filtration is the process of removing particulate matter from water, such as mud, sand, large plant cells such as algae and phytoplankton. Water filtration does not remove pathogens and other very small particles that can make you sick, so it does not make the water potable. Water should be filtered before it is purified.
Not all water needs to be both filtered and purified. Some natural water from fast-flowing streams or springs may have very little particulate matter in it and be very clear already, and will only need purification if you're going to drink or cook with it. As a general rule, filtered water is fine for showering or cleaning with; while purified water is needed for drinking and cooking. Not all water can be made safe for use; it is not practical to purify water that is tainted with certain chemicals, minerals, or radioactivity.
Water filters
Most commercially-available water filters are made of a screen with many tiny holes in it. These filters can remove protozoa and some bacteria, but they cannot filter out viruses because viruses are too small. Filters also remove bigger contaminants like leaves, silt, dirt, and sand. If the water is cloudy or has floating material in it, you should filter it even if you plan to boil or disinfect it.
Be sure to use and care for your filter according to the manufacturer’s instructions. Filters don’t work as well if they aren’t taken care of over time.
Mechanical filtration has become more common and less expensive. Straw-like personal filters are now sold, for example.
The main drawback of filtration are clogging (addressed by adequate pre-filtration) and relatively slow filtration rate. Look for filters that can be gravity fed so the filtration time isn't tiresome.
- 1-micron filters will filter protozoa like giardia spores and Cryptosporidium out of clear water.[1] These may be labeled NSF/ANSI Standard 53.[2]
- 0.1-micron will filter all waterborne enteric bacteria from clear water
- Consumer-grade filtration will not remove viruses because of their tiny size.
The CDC points out the difference between nominal and absolute (or "mean") micron ratings: The absolute 1 micron filter will more consistently remove Cryptosporidium than a nominal filter.[3]
Fabric filtration
Much sediment can clear itself if allowed to rest; let the water sit still for 30-60 minutes, then pour or siphon off the top and leave the sediment behind.
Alternately, you can strain from coarse to fine. For example:
- sieve or strainer to remove large debris
- bandana, cloth, or paper towel to remove smaller debris
- coffee filter to remove larger particles
- actual water filter
Note that filtration through layered fabric is much better than nothing. In India, for example, researchers found: a filter made of four layers of worn cotton material held back more than 99 percent of all cholera bacteria - using more layers or newer cloth slowed water collection too much.[4]
Both saris and coffee filters have about a 20-micron pore size: Typically coffee filters are made up of filaments approximately 20 micrometres wide, which allow particles through that are less than approximately 10 to 15 micrometres[5]
The best we should assume for with such ad hoc filtration is a pathogen reduction. Combination with SODIS (below) might be useful.
Further reading: this page is about reducing airborne pathogens with homemade mask materials, but may be useful.
Resources
| Search Amazon | Search Amazon for related products. | |
| Wikipedia | Wikipedia article on "Water filtration". | |
| Search forums and groups | Search van life discussion groups for "water filtration" | |
| Search related sites | Search van life sites for "water filtration" | |
| Search NomadLife.wiki | Search other pages on this wiki for "water filtration" |
Some or all of the content on this page was originally sourced from this page on RVWiki
- ↑ https://www.who.int/water_sanitation_health/hygiene/envsan/sdwtravel.pdf
- ↑ https://www.cdc.gov/parasites/crypto/gen_info/filters.html
- ↑ https://www.cdc.gov/parasites/crypto/gen_info/filters.html
- ↑ https://www.fic.nih.gov/News/GlobalHealthMatters/january-february-2015/Pages/nursing-cholera-sari-water-filter.aspx
- ↑ https://en.wikipedia.org/wiki/Coffee_filter