Water treatment methods

Outbreaks of waterborne illnesses are one of the biggest risks after a calamity. It's vital that survivors have access to clean water for drinking and washing. As a general guideline, America's ready.gov website recommends households store at least 4 liters (1 gallon) of water per person, per day and and have a minimum of three days supply per person. These figures are likely to be too low for a country like the Philippines with its tropical climate and scattered islands. No matter how much you store, supplies may eventually run low before infrastructure is restored or relief arrives so it's important to know how to treat water before drinking. Here's a summary of a few simple methods that use equipment or ingredients accessible to most Philippine households.


Many of us, especially those who have spent time the provinces, may remember our parents and grandparents boiling water for drinking. It's still the safest method of treating water but it does consume fuel. To boil water for drinking:
  1. Put some water in a pot or kettle. Make sure the water has been filtered of debris, sediment and has not been contaminated by chemicals.
  2. Boil the water until it's bubbling vigorously for one full minute.
  3. After boiling, let it cool before drinking.

Chlorination with household bleach

  1. Add approx. 2-4 drops of bleach per liter of water (approx. 16 drops per gallon).
  2. Stir and leave it for 30 minutes.
  3. The water should have a slight bleach smell after 30 minutes.
  4. If you don't smell any bleach, treat the water again and wait an additional 15 minutes.
  5. Do not use the water if it still doesn't smell of bleach after the second treatment.
Make sure you use a new bottle of plain household chlorine bleach (5.25 to 6.0 percent sodium hypochlorite) with no additives. Opened and older bleach bottles may have lost its potency over time. More information: FEMA and American Red Cross guide: Food and Water in an Emergency (PDF download).

Solar water disinfection (SODIS)

Solar water disinfection, or SODIS is a new method that's starting to gain acceptance in tropical countries. It's simple, free and uses low-tech, easy-to-find materials. The World Health Organisation, UNICEF, and the Red Cross recommend the SODIS method for treating drinking water in developing countries.
Pictogram showing the SODIS method
Pictogram showing the SODIS method by Samuel Luzi, Fundacion SODIS
See related article: A cheap and effective way to disinfect water in tropical countries.

Other water treatment methods

There are many other methods you can use to create potable water for your family. However, they need more research, practice or require equipment or supplies that aren't so readily available.

Chemical contamination

Most of these methods work by killing disease-causing micro-organisms in the water. Unless you distill the water or use an appropriate filter, any chemical contaminants will remain in the water. It's therefore important to stay way from water that may have been fouled by dangerous chemicals. Continue Reading

A cheap and effective way to disinfect water in tropical countries

There are many ways to make water safe for drinking. One method that's starting to gain acceptance in tropical countries is solar water disinfection, or SODIS, because it is simple, practically free and uses low-tech, easy-to-find materials. The World Health Organisation, UNICEF, and the Red Cross recommend the SODIS method for treating drinking water in developing countries.
Pictogram showing the SODIS method
Pictogram showing the SODIS method by Samuel Luzi, Fundacion SODIS

How to apply the SODIS method to make safe drinking water

The process uses sunlight to disinfect water stored in common PET bottles which are used for soft-drinks. It works because sunlight contains radiation that kills pathogens including bacteria, viruses and parasites that cause diarrhea.
  1. Collect some colorless, transparent PET soft-drink bottles that will contain no more than 2 liters of liquid. Choose bottles that have few surface scratches and blemishes. Remove any labels and wash well with clean water. Sunlight may not penetrate the water adequately if the bottles are too large or heavily scratched.
  2. Fill the bottle three-quarters full with the water to be disinfected, screw on the cap and shake well for 20 seconds. After shaking, fill the bottle with more water but leave a space at the top for air, then screw on the lid once again. This step oxygenates the water which helps speed up the disinfection process.
  3. Expose the bottle to sunlight. A good place is on a sloped surface facing the sun, like a corrugated iron sheet roof. The length of exposure depends on your weather conditions.
  4. Once treated, the water should be stored in and consumed directly from the bottles to avoid re-contaminating the water.
Suggested exposure times
Weather conditions Minimum exposure duration
Sunny (less than 50% cloud cover) 6 hours
Cloudy (50-100% cloudy, with little or no rain) 2 days
Continuous rainfall The SODIS method cannot be reliably used to disinfect water

Important considerations

  • The SODIS method kills pathogens in the water but does not remove toxic chemicals.
  • Turbid (cloudy) water must first be filtered to remove the particles before being used to fill bottles.
  • Old bottles that are scratched or discolored should be replaced.
  • PET or PETE (polyethylene terephthalate) bottles should be used. The easiest way to find out if a bottle is made out of PET is to look for the recycling mark shown below. 1 is the resin identification code for PETE or PET.
    PET resin identification code: 1
    PET resin identification code stamp


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After a disaster, beware of diarrhea

The aftermath of a disaster can often kill more people than the disaster itself and one of the main risks is disease. Poor sanitation caused by the disruption often leads to outbreaks of acute diarrhea. We saw this during Typhoon Ondoy where diarrhea was one of the top killers in evacuation centers. It was also a huge problem in post-earthquake Haiti when a cholera epidemic infected 1,500 people in just a few days. Even during normal times, diarrhea is the 3rd leading cause of child illness and the 4th leading cause of deaths among children less than 5 years in the Philippines. Diarrhea kills through rapid dehydration and children are especially susceptible as they can succumb in a matter of hours. Nevertheless, deaths can be prevented by simply making sure that the patient drinks a lot of clean water with oral rehydration salts. Unfortunately, these are difficult to find after a disaster. Aid workers in Haiti were distressed to find that many were dying for want of something that costs so little.

Simple ways to safeguard your family

There's no reason why your family should suffer from an outbreak of diarrhea.
  • Stock up on Oral Rehydration Salts. These are available from Watsons and Mercury Drug for around Php10 to Php15 per sachet.
  • Stock up on antidiarrheal medications like Diatabs (Loperamide) which are less than Php30 for four capsules.
  • Make sure you have access to clean water for drinking and washing.
  • Eat cooked food or food washed well in clean water.
  • As much as possible, continue with your usual sanitation habits.
Oral Rehydration Salts and Diatabs
Oral Rehydration Salts and Diatabs

Household alternatives

If you don't have any commercially produced ORS at home, rehydrate.org suggests the following alternatives:
  • Breastmilk
  • Gruels (diluted mixtures of cooked cereals and water)
  • Carrot Soup
  • Rice water (congee)
  • Fresh fruit juice
  • Weak tea
  • Green coconut water (buko juice)
  • A home-made solution of salt, sugar and if possible, orange juice or mashed banana (see link for recipe and instructions)
Remember: make sure you first check with your pediatrician if these alternatives are suitable for your child.

Additional resources

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