Make Water Safe During An Emergency

When visiting places with unknown water quality—whether you head to a remote location to camp or hike or travel to a new place—it may be necessary to disinfect the water to kill waterborne germs before using it.

Drinking contaminated water or using it for cooking, washing food, preparing drinks, making ice, and brushing teeth can make you sick with diarrhea, vomiting, and stomach pain. Treating these symptoms can be difficult while you are away from home or abroad and without access to medical care.

Exposure to contaminated water is more likely in places where there is no sanitation or water treatment infrastructure, such as at campgrounds, remote areas, or in some foreign countries.

Water contaminated with bacteria, viruses, and parasites can sometimes look clean, which is why it is important to know the source of the water, if and how it has been treated, and whether it is safe before drinking it. Bottled water can be an easy option, but it is also important to know where your bottled water comes from and how it has been treated, especially when traveling in remote locations.

Boiling

If you don’t have safe bottled water, you should boil your water to make it safe to drink. Boiling is the surest method to kill disease-causing organisms, including viruses, bacteria, and parasites.

You can improve the flat taste of boiled water by pouring it from one container to another and then allowing it to stand for a few hours; OR by adding a pinch of salt for each quart or liter of boiled water.

If the water is cloudy:

    Filter it through a clean cloth, paper towel, or coffee filter OR allow it to settle.
    Draw off the clear water.
    Bring the clear water to a rolling boil for 1 minute (at elevations above 6,500 feet, boil for three minutes).
    Let the boiled water cool.
    Store the boiled water in clean sanitized containers with tight covers.

If the water is clear:

    Bring the clear water to a rolling boil for 1 minute (at elevations above 6,500 feet, boil for three minutes).
    Let the boiled water cool.
    Store the boiled water in clean sanitized containers with tight covers.


Disinfectants

If you don’t have safe bottled water and if boiling is not possible, you often can make small quantities of filtered and settled water safer to drink by using a chemical disinfectant such as unscented household chlorine bleach.

Disinfectants can kill most harmful or disease-causing viruses and bacteria, but are not as effective in controlling more resistant organisms, such as the parasites Cryptosporidium and Giardia. Chlorine dioxide tablets can be effective against Cryptosporidium if the manufacturer’s instructions are followed correctly.

Disinfect water using household bleach, if you can’t boil water. Only use regular, unscented chlorine bleach products that are suitable for disinfection and sanitization as indicated on the label. The label may say that the active ingredient contains 6 or 8.25% of sodium hypochlorite. Do not use scented, color safe, or bleaches with added cleaners.If water is cloudy, let it settle and filter it through a clean cloth, paper towel, or coffee filter.

Locate a clean dropper from your medicine cabinet or emergency supply kit.

Locate a fresh liquid chlorine bleach or liquid chlorine bleach that is stored at room temperatures for less than one year.

Use the table below as a guide to decide the amount of bleach you should add to the water, for example, 8 drops of 6% bleach, or 6 drops of 8.25% bleach, to each gallon of water. Double the amount of bleach if the water is cloudy, colored, or very cold.    

Stir and let stand for 30 minutes. The water should have a slight chlorine odor. If it doesn’t, repeat the dosage and let stand for another 15 minutes before use.
    
If the chlorine taste is too strong, pour the water from one clean container to another and let it stand for a few hours before use.

 

Solar Disinfection

In emergencies, sunlight in the UVA range can improve the quality of water. This is done by filling 0.3-2.0 liter plastic soda bottles with clear water, shaking them to oxygenate, and placing the bottles on a roof or rack for 6 hours (if sunny) or 2 days (if cloudy).

Solar disinfection does not work on cloudy, opaque water. If the headlines in a newspaper cannot be read through the bottle of water, the water will need to be filtered before solar disinfection can we used.

 

Three Pot Method

 

Slow Sand Filtration 

A slow sand filter is a sand filter adapted for household use. The version most widely implemented consists of layers of sand and gravel in a concrete or plastic container approximately 0.9 meters tall and 0.3 meters square. The water level is maintained to 5-6 cm above the sand layer by setting the height of the outlet pipe. This shallow water layer allows a bioactive layer to grow on top of the sand, which contributes to the reduction of disease-causing organisms. A diffuser plate is used to prevent disruption of the biolayer when water is added. To use the filter, users simply pour water into the top, and collect finished water out of the outlet pipe into a bucket. Over time, especially if source water is turbid, the flow rate can decrease. Users can maintain flow rate by cleaning the filter through agitating the top level of sand, or by pre-treating turbid water before filtration.

Slow sand filter lab effectiveness studies with a mature biolayer have shown 99.98% protozoan, 90-99% bacterial, and variable viral reduction. Field effectiveness studies have documented E. coli removal rates of 80-98%.

The benefits of slow sand filtration are:

• Proven reduction of protozoa and most bacteria
• High flow rate of up to 0.6 liters per minute
• Simplicity of use and acceptability
• Visual improvement of the water
• Production of sufficient quantities of water for all household uses
• Local production (if clean, appropriate sand is available)
• One-time installation with low maintenance requirements
• Long life (estimated >10 years) with no recurrent expenses

The drawbacks of slow sand filtration are:

1. Not as effective against viruses
2. No chlorine residual protection – can lead to recontamination
3. Routine cleaning can harm the biolayer and decrease effectiveness
4. Difficult to transport due to weight – high initial cost