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1. Basic Survival

2. First Aid and Wellness

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5. De-Industrialization

6. Tactical Skills and Discussions

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8. Food Gathering and Production

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Water Treatment

If you are in doubt, treat the water. You can die a lot faster or be sick for a lot longer from drinking a drop of contaminated water than you can from drinking no water at all. See the table below for a comparison of the effectiveness of different methods.

Effectiveness of different treatment methods:

Legend:

Effectiveness:

For a more detailed comparison, see WELL Technical Brief #48.

Simple Treatments

Straining

Straining turbid (cloudy) water through a clean handkerchief or other fine, cotton cloth is a good way of straining out larger particles of suspended contaminants like dirt. It can also remove certain tiny organisms (like copepods) that may carry pathogens, though such organisms are not present in all climates. Straining turbid water will improve the effectiveness of most other treatment methods, and is a good first step.

Aeration

Aeration adds air to water and reduces the concentration of “volatile” substances like hydrogen sulfide, which affect the taste and smell of water. It can also oxidize and immobilize elements like iron and manganese, which can cause taste and smell problems with water if present in excess. (They also stain clothes if the water is used for laundry.)

To aerate water, just shake a partly filled container of water vigorously, or pour it through a perforated tray containing small, clean pebbles.

Storage

Just storing untreated surface water will improve its quality. Particles settle out, and parasites that may be present will die, usually within a few days, without access to a host. Storing water for only 24 hours will kill about half of the bacteria in it. The improvement in quality will be greater at higher temperatures and over longer periods. If you are leaving turbid (cloudy) water to settle out, remember to take your water from the top layer, once the visible particles have settled.

Water containers should always be covered to prevent contamination.

WELL (see water notes) suggests using a three container system. The first container is used to put new water into, and the water may be strained as it is poured into this container. After one day, this water is poured into the second container, being careful to leave sediment or cloudy layers behind to be discarded. Using a tube to siphon water to the next container can help to leave the sediment undisturbed. The next day, water from the second container is poured into the third. The water in the third container has sat for at least two days, and is used for drinking water. WELL suggests occasionally rinsing this container with scalding water to sterilize it.

Glass containers are good for maintaining water quality, but are heavy and can break. You can look for food grade plastic containers for storing water. The preferred types of plastic for food are “Polyethylene Terephthalate” (PETE) or “High Density PolyEthylene” (HDPE). Look for the letters “PETE” or “HDPE” or the recycling numbers “1” or “2” stamped on the bottoms. However, keep in mind that some chemicals stored in the containers originally may leach into the drinking water stored inside. For example, the toxic aspartame in containers used in diet pop may leach into the drinking water, so such containers should be avoided if possible. Never reuse a plastic container that has stored toxic chemicals.

Disinfection

Disinfection kills the pathogens in the water. It is most effective if the water is relatively free of sediment and organic materials, so it should be the final stage in water treatment, after other contaminants have been removed.

Disinfection by Boiling

You can kill the pathogens in water by boiling it. At sea level, water simply brought to a boil is safe, but add one minute to the boiling time for every additional thousand metres (3300 feet) in altitude. (It’s something of a myth that water has to be boiled for five or ten minutes to be safe—this is just a waste of fuel. See Miller below, and other sources.) Be sure to strain out any larger particles by straining through a cloth, first. If it tastes “flat”, pour it back and forth between two containers a few times to aerate it. You can also add a chunk of charcoal from your fire, or some pine needles, during boiling, and remove them before drinking, to improve taste.

Boiling notes:
Miller, DeWolfe, ‘Boiling drinking-water: A critical look’, Waterlines, Vol.5, No.1, IT Publications, London, 1986.

Chemical Disinfection

Disinfection by adding chlorine (usually in the form of bleach) is also an option. However, it isn’t ideal, because the proper amount of chlorine to use can be difficult to determine, as well as because of the unpleasant taste and possible health side effects of ingesting chlorine. However, it is a very effective disinfectant.

The strength of chlorine compounds varies widely, and depends on storage conditions. Household bleach will rapidly lose its strength over time, though powdered chlorine (calcium hypochloride) will last longer, up to ten years under ideal storage. Use only pure bleach. Do not use bleach with fabric softener, or other laundry additives, because they are very likely poisonous.

To disinfect clear water with liquid bleach, first look at the concentration of chlorine you have in your bleach. For 1%, use 10 drops per litre, for 2-6% try 2 drops per litre, for 7-10% use 1 drop per litre, and let sit for at least 30 minutes. For slightly cloudy water, use at least double the number of drops. There should be a slight chlorine odour after. Otherwise, repeat the dose and wait another 15 minutes. Let it sit to reduce chlorine taste and smell.

Aerating chlorinated water after disinfection will also help the taste, as will adding a pinch of powdered vitamin C, which will neutralize the chlorine.

You can use household, medical iodine to purify water as well. For 2% USP strength, add 5 drops to clear water and 10 drops to cloudy water.

Chemical disinfection notes:
“Be Prepared with a 3-Day Emergency Food Supply,” by E. Schafer, C. Hans, E. Jones Beavers and D. Nelson, Iowa State University Cooperative Extension, November, 1997

Solar Disinfection

Solar disinfection works by a combination of exposing the water to the ultraviolet rays of the sun and raising the temperature, which kills microorganisms present. This technique is most effective in areas between approximately 35°N and 35°S, areas which receive large amounts of solar radiation each year. The American Southwest is an area in North America which also receives a lot of solar radiation.

In this method, containers of water are placed in direct sunlight, for a period of at least six hours. The water must be relatively clear, and shallow, to allow penetration of UV rays.

Glass containers can be used (but not window glass, which does not transmit UV radiation very well), but they are heavier, can break, and take longer to heat up. Plastic bottles made of PETE (polyethylene teraphtalate) or PVC (polyvinyl chloride) are both good choices, but PETE is preferable, since it is not likely to leach harmful additives into the water. Bottles made of PVC often have a bluish tinge, and when burned, smells strong and unpleasant. PETE burns more easily, and has a sweetish smell.

Bags of water can also be used, and can be more effective since they can store water more shallowly.

Aerating the water by shaking it before placing it in the sun will significantly increase the effectiveness of this method of disinfection. When bottles become old and scratched, and start to become opaque, they should be replaced. Newer bottles will transmit UV light better.

The Swiss development agencies EAWAG and SANDEC recommend leaving the water out for at least six hours on sunny or partly cloudy days, or two consecutive days in cloudy weather. This primarily applies to very sunny regions, so solar disinfection is not a reliable method in less sunny regions.

Painting bottles black on one side (the side placed down) will help to heat the water up. If the water reaches a temperature of more than 50°C (122°F) for at least one hour in the middle latitudes, it is safe. Placing the bottles on corrugated metal roofing will keep them in place and help to increase the temperature.

Using reflectors to concentrate sunlight on the water vessel will increase the effectiveness of this method by increasing the amount of UV radiation the water is exposed to, and increasing the temperature.

Solar disinfection notes:
Swiss development agencies have a large amount of information about solar disinfection at www.sodis.ch.

Distillation

Distillation works by evaporating water from a suspect source, which then condenses, leaving distilled water. This is an excellent way to get drinking water from seawater, and is the only method described here which will remove salt.

You can make a stove-top still, like the one shown, very easily. You place the still on top of a pot which is cooking (assuming that you aren’t using a fuel-saving haybox as discussed in “Cooking”.)

Solar stills can be made easily and cheaply to provide a quick source of clean water. They provide enough water for personal use, but not enough for gardening, since they would have to be as large as the garden itself to provide enough water. They use solar radiation to evaporate water from a contaminated or questionable water source.

To make a solar still, make a small greenhouse out of the materials you have available. See the Cloche Style still for an example using windows or plastic. Make a container for the source water lined with black, so that the water will heat up as much as possible in the sun. You may want to insulate underneath the source container if you are going to place the still on the ground. Then place a shallow trough along the lower edge to capture the condensed droplets as they slide down the glass.

Plastic sheeting can also be used, but some people report that droplets usually do not cling to plastic as well as glass, so they may drop back into the source container. However, the “clinginess” can be improved by lightly rubbing sandpaper over the interior surface of the plastic. If you do use plastic, make sure that it is pulled tight over the frame, or the wind may flap and tear it.

You can make a solar still with a sloped glass covering like the one shown below. This same device can be used as a solar food dehydrator, or a cold frame for gardening. (This is an example of how you can create equipment appropriate to your bioregion and climate: for example, if you have rainy springs, hot dry summers, and moderate autumns, you can use this device to start your vegetables in the spring, while you are drinking rainwater, and then use it as a still to provide drinking water in the summer, and then to dry the produce in the fall.) You can make this kind of still (dehydrator, coldframe) from 3’ by 6’ patio door windows, which are regularly replaced at many apartment buildings. You may be able to buy them cheaply by the hundred. Admittedly, you might not be able to use them all yourself, but your neighbours will thank you when you share. (If you store glass in such numbers, be sure to store the panes with spacers so that they don’t touch - water trapped between them will etch and mar the glass permanently.) For discussion on the glass’s best angle see page 34.

You can also make a lightweight, portable version, like the one shown below. (Design from the excellent “Survival Scrapbook” volume three). This design would also work well on a rooftop.

A still can produce about 4 litres of water per square metre (1.26 litres per square yard), per day, on a good day.

The upside of the solar still is that you can put your wash water back into the still to get drinking water again. You could even put urine in.

For stills, keep in mind that the distilled water produced also has no trace minerals present, so it is not ideal as the sole drinking water source for young children over extended periods of time.

Exercise: Build a solar still for you and your family or housemates. Can you live off of the product for a week? How much of your water needs can you meet?

Sand Filters

Slow Sand Filters

In slow sand filtration, the source water flows slowly through a bed of fine sand. To work, the water must be relatively clear, and the flow relatively constant. The water flows through at a rate of about 10 to 20 centimetres per hour (4 to 8 inches per hour). The minimum acceptable depth of sand to function effectively is 65 centimetres (25.6 inches).

The slow sand filter works because of a biologically active microbial film that forms on the top layer of the sand, known as the “schmutzdecke”. The schmutzdecke captures and “eats” organisms in the water. The schmutzdecke takes about one to two weeks to form, and so water coming from the filter before that should not be used for drinking.

To get a quantity of fine, uniform sand, you can try sifting it through a mosquito net or other fine screen.

The filter should be filled from the bottom up, to prevent the formation of air bubbles in the sand which would slow the flow of water.

Eventually the sand filter will need to be cleaned, because the schmutzdecke will thicken and slow the flow of water excessively. Fortunately, this thickening will not impair the safety of the filter. To clean, drain the water to slightly below the top of the sand, and scrape off the very top layer. Then fill up from the bottom. It will require another one or two weeks for the schmutzdecke to regrow.

Rapid Sand Filters

Rapid Sand Filters work to remove particles and turbidity in water, but do not form a schmutzdecke, and are not effective against pathogens.

One type of rapid sand filter that you can make is simply a barrel with a thick layer of sand on top of a perforated metal plate, on top of a layer of stones, similar to the slow sand filter. However, the water travels upward instead of downward, and can travel at a faster rate; about 0.5 to 1.5 metres per hour (20 inches to 60 inches per hour). The sand in this filter is at least 30 cm thick. The rapid sand filter needs to be “backwashed” (that is, flushed of sediment by letting the water flow in the opposite direction) regularly, perhaps as often as every day, depending on the turbidity of the water and the amount of spare water available for flushing.

Since slow sand filtration requires clear water, and rapid sand filtration provides clear water, you can put them in a gravity-fed sequence, as shown. Additionally, since the maintenance downtime for the slow sand filter is so long, you may wish to have several slow sand filters running simultaneously, so that you will always have at least one working.

Sand filter notes:
http://www.refugeecamp.org/learnmore/water/slow_sand_filter.htm
http://www.ce.vt.edu/program_areas/environmental/teach/wtprimer/slowsand/slowsand.html
http://www.esemag.com/0500/sand.html
WELL Technical Brief #59: Household Water Treatment 2

General Water Notes

There are a few methods which I skipped over in this section, because they didn’t fit into the requirements. Solar pasteurization is a treatment method which is distantly related to solar disinfection, but slightly more difficult. Essentially it involves elevating the temperature of water to more than 65ºC (149ºF) for more than six minutes, using sunlight (or other sources). The advantage is that it does not require UV radiation for disinfection and is more appropriate for non-equatorial latitudes. For more information, check out:
http://solarcooking.org/docs.htm#Water%20Pasteurization

There are also numerous commercial, small scale means of water treatment which aren’t appropriate for improvised situations, which you can find out more information about for yourself. These include halozone tablets, and other chemical treatment methods, which you can get at pharmacies or camping / outfitting stores.

There are other general sources for learning more about drinking water below, which I used writing this section.
The IRC International Water and Sanitation Centre has an extensive online database of water-related publications: www.irc.nl/ircdoc/
UNHCR Water Manual for Refugee Situations
UNHCR Handbook for Emergencies
These and other UN refugee references are available online at:
www.the-ecentre.net/resources/e_library/index.cfm
WELL Technical briefs, available at: www.lboro.ac.uk/orgs/well/resources/technical-briefs/technical-briefs.htm
Water for the World Technical Notes
www.lifewater.org/wfw/wfwindex.htm has an extensive number of technical briefs on water and sanitation.
The Drinking Water Book, by Colin Ingram

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