How to filter outdoor water sources into potable water
There are several simple and feasible methods to purify and disinfect found water sources.
I. Infiltration Method
When the water source you find has floating debris or is murky, you can dig a pit about 50–80 cm deep and 1 meter in diameter, 3–5 meters away from the water source. Allow the water to naturally seep out through the gaps in the sand, stones, and soil. Then, gently collect the seeped water and place it in a container such as a box or kettle. Note: Do not stir up the mud and sand at the bottom of the pit, and keep the water clean.
II. Filtration Method
When the water source you find is muddy with debris, floating objects, and microorganisms or worm and leech larvae, and digging a pit is not suitable due to the surrounding environment, you can use a high-quality plastic bag (one that doesn’t easily tear) and poke small holes in the bottom. Alternatively, you can use a cotton glove, handkerchief, sock, sleeve, or trouser leg, or even a cola bottle. Remove the bottom of the bottle, turn it upside down, and poke several holes in the cap with a small knife. Then, fill it from the bottom up with 5 to 7 layers of clean fine sand (2–4 cm thick), charcoal powder, fine sand, charcoal powder, and fine sand. Press and compact the layers. Slowly pour the unclean water into this makeshift filter. Once clean water begins to drip from the bottom, collect it using a basin or kettle. If you're not satisfied with the filtered water quality, you can construct another simple filter and run the water through it again until it meets your standards.
III. Sedimentation Method
Collect the water you find into a basin or kettle, then add a small amount of alum or mashed mulberry leaves, mashed cactus, or mashed elm bark. Stir the mixture in the water and let it settle for 30 minutes. Gently scoop up the clear water from the top without disturbing the settled impurities. This way, you’ll get relatively clean water.
Generally speaking, aside from spring water and well water (especially deep underground well water), which can be consumed directly, other types of water—whether river, lake, stream, snow, rain, or dew water—or water obtained through infiltration, filtration, or sedimentation should preferably be disinfected before drinking. So how do you disinfect it? Here are the methods:
1. Place water purification tablets into the water container, stir and shake, then let it sit for a few minutes before drinking. You can also pour it into a kettle for storage. Typically, one water purification tablet can disinfect 1 liter of water. If the water is relatively murky, use two tablets. This method is currently used by field armies for water disinfection.
2. If you don’t have water purification tablets, you can use the medical iodine you carry instead. Add 3–4 drops of iodine per liter of purified water. For murky water, double the amount of iodine. Shake well and let it sit longer—about 20–30 minutes—before drinking or storing for later use.
3. Sodium hypochlorite, i.e., bleach, can also serve as a disinfectant. Add 3–4 drops of bleach per liter of purified water. Double the amount if the water is murky. Shake well and let it sit for 30 minutes before drinking or storing. Just note that there may be a slight bleach taste in the water, and make sure not to consume any settled impurities.
4. If none of the above disinfectants are available, and you happen to have vinegar for outdoor cooking (white vinegar works too), you can use it to disinfect the water. Pour some vinegar into the purified water, stir, and let it sit for 30 minutes before drinking. The water may have a slight vinegary taste.
5. If you’re at a relatively low altitude (below 2,500 meters) and have access to a heat source, boiling the water for 5 minutes is also an excellent and simple method of disinfection. During outings or picnics on the plains, this method is commonly used to disinfect river, lake, stream, rain, dew, and snow water to ensure safe drinking and cooking.
6. If you find saltwater, boil it together with thorny elsholtzia. While this won’t remove the original salty bitterness, it can prevent abdominal pain, bloating, and diarrhea. If the water contains heavy metal salts or toxic minerals, boil it with strong tea, and do not drink the resulting sediment.
Currently, there is a type of drinking water purification straw that is very practical in the field. Shaped like a thick pen, the water purified through it is sterile, non-toxic, tasteless, and free of any impurities. It can be consumed without boiling and is very portable.
There are also some water purifiers imported from abroad. They are compact and highly effective, capable of filtering potable pure water from relatively turbid liquids.
Additionally, it’s important to remind everyone that in situations where drinking water is scarce, you must ration your water intake wisely and avoid drinking excessively out of momentary thirst. When working or exploring outdoors, drinking water should also be approached scientifically. Gulping down a large amount of water at once will only lead your body to expel the excess absorbed water, wasting a lot in the process. If you take just a sip or two at a time, hold it in your mouth and slowly swallow, then wait until you feel thirsty again before taking another sip, repeating this process allows your body to fully absorb the water while also relieving dryness in the mouth, throat, and tongue. Using proper drinking techniques, a standard water bottle (0–9) capacity can help a single person stay hydrated for 6–8 hours or even longer during movement.
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