Water Purification in the Wilderness 淨化食水

Hong Kong Hiking Web: 戶外大夫專欄 Outdoor Doctor Forum: Water Purification in the Wilderness 淨化食水
   By 叔夜衣 on Wednesday, August 15, 2001 - 11:50 am:  Edit

咦!為什麼無人提供意見的?我有次到西灣露營,在沙灘n近的水源取水,發現有極多蚊蟲滋生,而且水的顏色非常濁騿A實在難以取用。後來我們入村問人取水,可惜那堛漱蔡酗臛麊漱穭摒O不太清潔。幸好士多老闆給我們清潔的水。但大家無可能次次勞煩別人,那究竟有沒有一些簡單有效的方法去淨化食水呢?各方山友,如有良策,請不吝賜教呀!

   By kchan on Wednesday, August 15, 2001 - 6:13 pm:  Edit

water puification tablets

   By kchan on Wednesday, August 15, 2001 - 6:15 pm:  Edit

Chemical treatment

If water cannot be boiled, treat it chemically. Two chemicals usually found in the home will purify water:


Chlorine Bleach such as Clorox or Purex. Household bleach is a good disinfectant for water. However, check the label to be sure that the active ingredient is sodium hypochlorite at 5.25%. Do not use bleach which contains detergents!

Percent Chlorine Add, per Gallon of Water
1% 40 drops
4 to 6% 8 drops
7 to 10% 4 drops
Unknown 10 drops

Mix thoroughly into the water. Let it stand for 30 minutes. The water should have a slight chlorine odor. If it doesn't, repeat the dose and let the water stand for an additional 15 minutes.


Iodine: Household iodine from the medicine chest of first aid kit will purify water. The iodine should be 2% United States Pharmacopoeia (U. S. P.) strength. Add 20 drops per gallon of clear water, and 40 drops per gallon of cloudy water. Seal the container and let stand for 30 minutes. The water supply will be safe for an indefinite period.

   By drpanda on Wednesday, August 15, 2001 - 6:19 pm:  Edit

But water purification tablets normally contain high concentration of iodine, which is harmful to your health too. Instructions on the bottles tell you to avoid iodine overdose.

I think in the case of 西灣, water from 公眾水喉 should be drinkable after boiling.

   By kchan on Wednesday, August 15, 2001 - 6:21 pm:  Edit

加五滴碘酊劑於一公升的清水內,須待三十分鐘後才飲用。

用於冰凍的或混濁的水則要加十滴碘酊劑於一公升的水內,待幾小時後才可飲用。

如想除去碘酊劑留於水中的氣味,可於加入碘酊劑後三十分鐘再加入五十 毫克維他命C。

請注意以上的方法不能有效地殺除隱胞子蟲,除非對食水進行消毒並放置不少於十五小時。雖然孕婦亦可飲用經碘消毒的水,但只宜短期使用。如須長期飲用,便應使用其他方法。患有甲狀腺疾病或對碘敏感的人都不宜使用碘消毒食水。

除碘之外,不同形態的氯亦可用於化學消毒,但氯的殺菌能力易受水的酸鹼度、溫度及有機物所影響,不及碘之可靠。

市面上有不同類型可隨身攜帶的濾水器供選擇。這些濾水器有不同程度的效能。如你想採用濾水器,可細心研究,選擇最切合你的要求的型號。經過濾的食水仍需用上述的化學方法處理,因過濾方法不能除去水中病毒。

   By Outdoor Doctor (Doctor) on Wednesday, August 15, 2001 - 11:27 pm:  Edit

In the extreme wilderness where you could not find any clean water, I think iodine tablet should be one of the most convenient ways to treat the problem water.

The taste of iodine is bad for some persons. It could kill bacteria (the major concern of unclean water in Hong Kong wilderness), virus and a number of parasite cysts. However, it may not kill a parasite called cryptosporidium which is highly resistant. As mentioned above, the addition of vitamin C can remove the bad taste of iodine. It should be noted that some people may have allergy to iodine.

If you were strong enough to carry every equipment, you might consider to use a water filter too. A filter can remove the cloudiness/ precipitates of the dirty water whereas the chemical treatment cannot.

A good water filter can remove bacteria and parasites including cryptosporidium. However, it could not totally remove all the viruses (because some of the viruses are smaller than the pores of the filter). Therefore, chemical treatment (e.g. iodine) should still be performed after the filtering in order to have maximum safety.

   By jordex on Monday, August 20, 2001 - 8:56 am:  Edit

Is necessary to boil the purificated water from chemical treatment before drinking?

   By kchan on Monday, August 20, 2001 - 4:51 pm:  Edit

For your safety, it is better to boil tbe water to 100C even after chemical treatment.

   By Outdoor Doctor (Doctor) on Tuesday, August 21, 2001 - 12:51 am:  Edit

Boiling has been a traditional and effective method of water treatment. It kills most of the harmful germs (especially when it boils at 100C). However, one needs to bring the fuel and the boiling equipment. He/ she needs to sit down and take some time to boil the water. Afterwards, it also takes time for the water to cool down before one can drink it.

Chemical treatment by using iodine can kill a lot of harmful germs already. Water boiling will not add too much benefit. It is not practical to perform both methods. You have to wait for too long before you can drink the water, if you performed both methods.

In the Hong Kong wilderness: a) If the problem water you collect is very dirty with a lot of precipitate, you should consider using a water filter as a first step to remove the precipitate. Afterwards, you can choose either chemical treatment method (iodine) or boiling method. b) if the problem water you collect appears transparent, you can proceed directly to chemical treatment or boiling.

   By H2O on Friday, March 15, 2002 - 5:22 pm:  Edit

我想問一下經碘消毒的水,可否用活性碳除去碘酊劑留於水中的氣味?
另一方面,我我聽聞可以用高錳酸鉀淨水,不知是否具有淨化水質之功效?

   By Ron on Friday, March 15, 2002 - 6:32 pm:  Edit

Follow the instructions of the iodine tablets, you need to wait for 10-20 min for the iodine to work. After iodine treatment the iodine taste in the water can be removed by Vitamin C tablets (or any drink powder with enough Vitamin C).
One brand of iodine tablet (Potable Aqua Plus) also include the vitamin C in a second bottle for neutralising the iodine taste.

   By H2O on Friday, March 15, 2002 - 10:46 pm:  Edit

首先多謝Ron兄,但是我手上有些活性碳所以想如果可以,便不用維他命C,我記憶中維他命C好像是氧化劑,不知可否用H2O2,高錳酸鉀一類代替?另一方面,我想問一下活性碳其實可以吸取水中的怎麼物質?可以吸取水中的可溶物質嗎?

   By Outdoor Doctor (Doctor) on Saturday, March 16, 2002 - 8:49 am:  Edit

The taste of activated charcoal (活性碳) is bad, isn't it?

I don't think activated charcoal can reduce iodine (the form which causes the bad taste) to iodide. If anybody is familiar with biochemistry, please comment. Please notice that activated charcoal can make some people vomit. Vitamin C should be the most natural way of removing the bad taste of iodine.

Vitamin C is a reducing agent.

H2O2 (hydrogen peroxide) is an oxidizing agent (氧化劑) and a very powerful disinfectant (消毒劑). It kills almost all microorganisms at a certain high concentration. It is used in disinfection (消毒) of some medical instruments and maybe used in the disinfection of fruits in the agriculture industry. It is also used to clean contact lenses. However, it is NOT used for drinking water purification. It could harm you seriously if you drank H2O2 at a certain high concentration.

KMNO4 (potassium permanganate) is used in the medical setting to disinfect some dirty wounds. Without diluting it properly with water, it could irritate the human skin. It is NOT used for the purpose of drinking water purification.

Activated charcoal is also used in the medical setting. It has the ability to adsorb (bind and hold) some poisonous drugs/ chemicals and intestinal gas. During the treatment of poisoning of some patients, activated charcoal aims to hold the poison/toxic substance inside the gut and decrease the absorption of it into the blood.

   By roy on Wednesday, May 07, 2003 - 10:53 pm:  Edit

Where do we buy the chlorine tablets in HK?

   By somenothing on Monday, August 04, 2003 - 6:16 pm:  Edit

so, which kinds of filters are considered 'good'? ones i've heard of are ceramic filters with a hand pump, activated carbon filters that filts onto the hole where you pour out of a water bag, and coffee paper filters... so, could doc please explain more on their the type of filter we should use to drink safely on camp?
thx

   By Outdoor Doctor (Doctor) on Thursday, August 07, 2003 - 12:01 am:  Edit

Each kind of filter has its own advantage and disadvantage. You may want to consider its weight, convenience of use in addition to its filtering ability.

Backpacker has a gearfinder to help you to choose a suitable item. You can look it up at

http://www.gearfinder.com/ss.asp?FAM=filters

Check all the boxes in the "Eliminates", you can find the most powerful filters (including those that can filter organic chemical).

   By somenothing on Thursday, August 07, 2003 - 3:19 pm:  Edit

thx a lot for the site!

hmmm so, how about iodine (or chlorine?) tablets? i guess i should try that on gearfinder.com too...

   By Outdoor Doctor (Doctor) on Friday, August 08, 2003 - 10:42 pm:  Edit

Iodine tablet is convenient and effective, providing that you are not allergic to iodine and you can tolerate its taste (Hint: Adding Vitamin C after disinfection can eliminate the taste)

   By somenothing on Saturday, August 09, 2003 - 8:43 pm:  Edit

where should iodine tablets be purchased? i'm afraid that hiking shops might sell them for quite a high price than the norm...

   By Outdoor Doctor (Doctor) on Sunday, August 10, 2003 - 1:48 am:  Edit

It is not very expensive. Most hiking shops sell iodine tablets at a reasonable price.

   By somenothing on Sunday, August 10, 2003 - 11:14 pm:  Edit

alright, thx!

btw, where could i get water filters that screws into the opening of a water bag? i heard of sth like that on these forums, but didn't get any info afterwards...

   By Chris on Saturday, September 09, 2006 - 5:35 pm:  Edit

Interesting site http://oooauthors.org/Members/derik/poker.html

   By Chr on Saturday, September 09, 2006 - 9:01 pm:  Edit

Interesting site http://www.tchezope.org/Members/de/poker-1.htm http://www.tchezope.org/Members/de/poker-2.htm

   By Brianna on Saturday, September 09, 2006 - 11:35 pm:  Edit

It very interesting http://www.tchezope.org/Members/de/poker-6.htm

   By 過濾器 on Saturday, September 09, 2006 - 11:39 pm:  Edit

Doctor:
我想問Camelbak 有出一種簡單而體積小的過濾器,只需連接Camelbak 出的水袋,但說明書上說"Filters to 0.2 microns and filters out 99.9999% of bacteria ,protozoa and custs",但事實上我們能不能只將山溪或河水過濾後立即飲???

(我強調Camelbak 係現役美國軍方採用)但我又不能只信名氣,所以想問問?????


Topics Profile Close Page Delete Page Move Page Log Out   Administration