Boiling is a very effective method to kill protozoa, bacteria, and viruses. The CDC recommends bringing water to a rolling boil for one minute (additional time at higher elevations). However, the vast majority of backpackers do not boil their water because it is fuel and time intensive.

Filtration can be an effective method for the removal of protozoa and bacteria; however, filtration is NOT effective in removing viruses. Some factors that influence the effectiveness of filtration include pore size of the filter, particle size of contaminant, and the amount of the contaminant. Some issues that may arise with filters include clogging (which leads to a reduced flow rate) and ruptures (which can lead to contaminants greater than the pore size getting through).

Disinfection with chemicals (such as iodine, chlorine, and chlorine dioxide) can be an effective method for killing bacteria and viruses; however, disinfection can have low to moderate results against protozoa. Some factors that influence effectiveness of chemical disinfection include contact time, disinfectant concentration, water temperature, water turbidity, and pH.

• Ultraviolet (UV) light can also be used as a disinfection method for reducing pathogens, however, cloudy water impairs effectiveness which results in the need for prefiltering. An obvious drawback is the need for a battery.

The CDC states that when boiling is not possible, “a combination of filtration and chemical disinfection is the most effective pathogen reduction method in drinking water” for backcountry use.

Katadyn Hiker

Miles Used: 0 to 109 (Franklin, NC)

Description: Hand pump filter with inlet hose (including pre-filter) and outlet hose that adapts to fit many bottles.

Filter: 0.2 micron glassfiber/carbon core

Removes: Protozoa and Bacteria

Link: https://www.katadyn.com/us/us/350-8018270-katadyn-hiker-microfilter

Notes: This is a great product. However, it is not ideal for a thru-hike. It involves more setup, cleanup, and time than other options. When using this product, raw water is typically filtered while you are at the source. Additionally, it is heavier than other products popular among thru-hikers. I began my hike using this filter knowing that I would likely be swapping it out for a more compact system. I recommend this product for groups backpacking together and for any camping trip.

Sawyer Squeeze

Miles Used: 109 to 625 (Pearisburg, VA)

Description: Filter that screws onto specific bottles (e.g. Smartwater) and reservoirs (e.g CNOC). The bottle or reservoir is squeezed to force raw water through the filter.

Filter: 0.1 micron hollow-fiber membrane

Removes: Protozoa and Bacteria

Link: https://sawyer.com/products/sawyer-micro-squeeze-water-filtration-system/

Notes: I switched to this system in Franklin, NC. It presented two advantages over the hand pump filter: (1) it’s lighter and (2) it was easier to grab water and keep moving. Raw water can be carried in a bottle or reservoir and filtered while on the move, or at camp later. This system involves the use of at least one “non-potable” bottle or reservoir.

Picture credit: Rich “Flip” Bartlebaugh, NOBO ‘19

*Katadyn BeFree*

Miles Used: 625 to 2,192 (Katahdin, ME)

Description: Filter that screws onto a collapsible soft flask (0.6, 1, or 3 liter). The flask is squeezed or hung upside down to push water through the membrane filter.

Filter: 0.1 micron hollow-fiber membrane

Removes: Protozoa and Bacteria

Link: https://www.katadyn.com/us/us/37914-8019640-katadyn-befree-3.0L_usa

Notes: This was my favorite treatment product during my thru-hike. I carried a 3-liter flask to fill with non-potable raw water, and Nalgenes for the filtered water. When the filter is new the flow rate is excellent (approx. 2 liters/minute). The flow rate slows over time, but the shake backwash is quick and easy.