Outdoor Classroom: Some Filtering Methods for Outdoor Drinking Water

As the saying goes: "A person can go without food for a day, but cannot go without water for a day." It can be seen that people are very aware of how important water is to human survival. However, unclean water often contains some pathogenic substances, such as toxic products of amoeba, dysentery, typhoid, schistosomiasis, liver leech, cholera, as well as rotten plant stems and leaves, insects, birds, animal carcasses and feces, and some may also contain heavy metal salts or toxic minerals. So when you find a water source when you are extremely thirsty, it is best not to rush to drink it. Instead, you should purify and disinfect the water source as necessary according to the environmental conditions at the time to avoid poisoning or infection from drinking water.

How to filter outdoor water sources into drinking water

There are several simple and practical methods to purify and disinfect the water sources you find.

1. Infiltration method

When the water source you find has floating foreign objects or the water is turbid, you can dig a pit about 50 to 80 centimeters deep and about 1 meter in diameter 3 to 5 meters away from the water source to allow the water to seep out naturally from the gaps in the sand, stones and soil. Then, gently take out the seeped water and put it into a water storage container such as a box or pot. Note: do not stir up the mud and sand at the bottom of the pit to keep the water clean.

2. Filtration method

When the water source you find is turbid with mud and sand, has foreign objects floating on it, and contains microorganisms, worms, leech larvae, etc., and the environment around the water source is not suitable for digging a pit, you can find a plastic bag (good quality, not easy to break) and poke some small holes in the bottom, or use cotton gloves, handkerchiefs, socks, sleeves, trouser legs, etc., or you can use a Coke bottle, remove the bottom of the bottle and turn it upside down, then use a knife to poke a few holes in the bottle cap, and then fill in 5 to 7 layers of 2 to 4 cm thick soil-free clean fine sand, charcoal powder, fine sand, charcoal powder, and fine sand from bottom to top, press tightly, and slowly pour the unclean water into a homemade simple filter. When water overflows from the bottom of the filter, you can collect the filtered clean water in a basin or kettle. If you are not satisfied with the quality of the filtered water, you should make a simple filter to filter the filtered water again until you are satisfied.

3. Precipitation method

Collect the water you find into water storage containers such as basins or pots, add a small amount of alum or kapok branches and leaves (mashed), cactus (mashed), elm bark (mashed), stir it in the water and let it settle for 30 minutes. Gently scoop up the clear water on the top, do not stir up the turbid matter that has settled, so you can get cleaner water.

Generally speaking, except for spring water and well water (deep underground wells) which can be drunk directly, river water, lake water, stream water, snow water, rain water, dew water, etc., or water obtained through infiltration, filtration, and sedimentation, should best be disinfected before drinking. So, how to disinfect? ​​The method is as follows:

1. Put the water purification tablets into the water storage container, stir and shake, let it stand for a few minutes, and then you can drink it. You can also pour it into a pot and store it for later use. Generally speaking, one lotion tablet can disinfect 1 liter of water. If the water is turbid, 2 tablets can be used. At present, this method is used to disinfect water in the field army.

2. If you don’t have water purification tablets, you can use the medical iodine you carry with you instead of water purification tablets to disinfect the water. In every liter of purified water, add 3-4 drops of iodine. If the water is turbid, double the amount of iodine. After stirring and shaking, it should be left to stand for a longer time, about 20 to 30 minutes before it can be drunk or used for later use.

3. Using chlorite, also known as bleach, can also be used for disinfection. Add three or four drops of bleach per liter of purified water. If the water is turbid, double the amount. Shake well and let it sit for 30 minutes before drinking or setting aside. The water just smells like bleach, so be careful not to drink the turbid sediment.

4. If you don’t have any of the above disinfectants, and you happen to carry some vinegar (white vinegar is also fine) for picnics, you can also use it to disinfect the water. Pour some vinegar juice into purified water, stir well, and let it sit for 30 minutes before drinking. There's just a sour taste of vinegar in the water.

5. When the altitude is not too high (below 2500 meters above sea level) and there is fire, boiling the water for 5 minutes is also a good way to disinfect the water, which is simple and practical. When going on outings or picnics in the plains, this method is often used to disinfect river water, lake water, stream water, rain water, dew water, and snow water to ensure drinking water and cooking needs.

6. If you find salty water, boil it with ground peppercorns. Although this cannot remove the original bitterness and saltiness, it can prevent abdominal pain, bloating and diarrhea. If there are heavy metal salts or toxic minerals in the water, you should boil the water with strong tea and do not drink the sediment that appears at the end.

At present, there is a drinking water purification straw, which is very practical in the wild. It is shaped like a thick pen. The water purified by it is sterile, non-toxic, tasteless, and free of any impurities. It can be drunk without boiling and is very light. There are also some water purifiers imported from abroad, which are small in size but effective, and can filter out drinkable pure water from relatively turbid liquids.

Another thing to remind friends is that when drinking water is scarce, you must arrange drinking water reasonably and don’t drink too much just because you are thirsty. When working or exploring in the wild, drinking water should also be scientific. If you drink enough at one time, your body will excrete the excess water after absorption, which will waste a lot of water. If you drink only one or two sips of water at a time, then swallow it slowly with your mouth wide open, and then take another sip when you feel thirsty after a while, and swallow it slowly, repeating this way of drinking water can not only allow the body to fully absorb the water you drink, but also solve the dryness of the mouth, tongue and throat. A standard kettle (0-9) of water, with the correct drinking method, can enable a soldier to sustain himself for 6 to 8 hours, or even longer, during exercise.