Most portable water filters remove contaminants down to 0.1 – 0.3 microns. This level of filtration is fine for most applications but some bacteria and viruses can pass through these filters. Extremely contaminated water can be treated with chemicals, a UV purifier, or by boiling. A few water filters that can remove contaminants down to 0.02 microns. This level of filtration should remove the ultra-tiny bacteria and viruses including:
- Bacteria including Cholera, Botulism, Typhoid, Amoebic Dysentery, E. Coli, Coliform Bateria, Streptococcus, Salmonella
- Protozoan (Cysts) including Giardia, Cryptosporidum, Cyclospora
- Viruses including those that cause Hepatitis A & E, Poliovirus, Norwalk, Rotavirus, Adenovirus Coxackievirus, Echovirus, Reovirus, Astrovirus, Corona Virus (SARS)
Sawyer Zero PointTWOThe Sawyer Zero PointTWO filter uses either gravity or a faucet adapter. The kit contains the filter, faucet adapter, and bucket fittings including a spade bit to drill the hole. Normally you fill a bucket with water and gravity feed the water through the filter and into a clean water container. This filter retails for about $140 and you must purchase a bucket and install the fittings yourself (easy to do). It will filter 3.5 gallons in about 30 minutes. Use the included syringe to backflush and clean the filter. The Sawyer should filter up to 1,000,000 gallons.
MSR GuardianThe MSR Guardian is an amazing filter that is portable, lightweight (only 17.3 oz), can filter 2.5 liters of pure water per minute, has a self-cleaning filter, and the filter lasts for 10,000+ liters. This filter can be used by backpackers or anyone that needs a larger volume of pure water quickly.
The LifeStraw Mission is a gravity purifier that uses an advanced ultrafiltration membrane with a 0.02 micron (20nm) pore size to remove virtually all virus, bacteria, and protozoa. It will filter up to 4,750 gallons (18,000 liters) of water with a flow-rate of 9-12 liters/hour.
I use the Sawyer filter at home. It is a more bulky solution because it requires a bucket for the pre-treated water. The Sawyer is slower because it is gravity fed. The Sawyer also has a much longer lifespan and lower cost. However, if you need a portable filter that will filter a larger quantity of water quickly then the MSR is the best choice. Both of these are excellent filters but each has its own application.