When All Hell Breaks Loose (40 page)

Distillation

While the above-mentioned water disinfection techniques work well at killing organic waterborne pathogens,
they will do nothing to remove other potential containments from water such as heavy metals, salts, and chemicals
. Distillation requires boiling water for many minutes and catching the resulting steam. The Seri Indians in northern Mexico desalinate seawater by boiling it in fifty-five-gallon drums. They wrap a wet, cool rag around a copper pipe exiting the container, which cools down the escaping steam that is then caught in a waiting container. This method is extremely fuel intensive, yet dying of dehydration trumps deforestation. Although tedious and a fuel hog, distillation gives survivors a much better chance of removing suspected dangerous contaminants from gathered water.

For small-scale water distillation, fill the largest cook pot you have halfway with nondisinfected water. As the water will need to be boiled for several minutes, there is no need to disinfect it beforehand. This cook pot should have a lid or one that's improvised that will conform to the following directions. The lid will be put on the pot
upside down
to allow for its resulting convexity to direct trapped steam, as it cools and turns to water droplets, toward the center of the lid. Before putting on the upside down lid, attach a smaller, heat-resistant container such as a cup or bowl to the lid's handle using wire or string so that it hangs right side up inside the pot without touching the water. This cup or bowl catches the directed water droplets from the lid. Boil the water for as many minutes as required to fill the attached cup or bowl. The resulting water that drips from the lid into the cup or bowl is distilled and should be free from waterborne pathogens and other contaminants. Although making a water distiller may be a pain in the butt, once it's made, it can be used many times. Water can also be distilled after being disinfected by other methods for those who are dealing with extremely nasty water or who simply want added protection.

The SODIS Water Treatment Method:
Using Free Ultraviolet Radiation from the Sun

In 1991, research for the future SODIS water treatment method was undertaken by SANDEC (the Department of Water and Sanitation) at the EAWAG (Swiss Federal Institute for Aquatic Science and Research). They conducted wide-ranging laboratory and field tests to develop and refine for general use the Solar Water Disinfection Process (SODIS). Their extensive testing revealed what some of us desert rats have suspected for years, that the ultraviolet radiation from intense sunlight shining through a nonopaque container filled with nonpotable water will irradiate and kill undesirable waterborne pathogens, rendering the water safe to drink. In truth, the inspiration for using radiation from the sun to kill pathogens in nonpotable water started to develop in India as long ago as 2000 BC.

For the past decade, SANDEC has been providing information, technical data, and advice to local institutions and more than twenty developing countries worldwide. Currently, the SODIS method is used to treat the daily drinking water of more than two million people around the world. Studies into the effectiveness of the SODIS program have shown a reduction in dysentery by 20 to 50 percent. For developing nations, further benefits were achieved by combining SODIS with hand-washing programs.

You as a reader are aware by now that many hundreds of thousands of people die each year in developing counties from dysentery and disease caused directly or indirectly from contaminated water. My hat goes off to the people at SANDEC and EAWAG and many other organizations for their work in solar water disinfection; they are spending time and money to truly make a difference in our world, a difference that can be owned and operated by the people themselves, not corporations.

SODIS does not completely sterilize water of all critters, as it's primarily used to inactivate the pathogenic microorganisms that predominantly cause diarrhea. When the SODIS bottle is exposed to the sun, other harmless bacteria present in the water may keep growing. The SODIS method does not produce sterile water, as drinking water does not have to be sterile. Laboratory research has shown that many bacteria, viruses, and protozoa are eliminated including, but not limited to, the bacteria
Escherichia coli (E.coli), Vibrio cholerae, Streptococcus faecalis, Pseudomonas aerugenosa, Shigella flexneri, Salmonella typhii, Salmonella enteriditis
, and
Salmonella paratyphi;
the viruses
bacteriophage f2, rotavirus
, and
encephalomyocarditis virus;
the protozoas
Giardia spp
., and
Cryptosporidium spp
.; and the yeasts and molds
Aspergillus niger, Aspergillus flavus, Candida
, and
Geotrichum
.

In a nutshell, the SODIS method involves filling up a clear, plastic, one- to two-quart container with nonpotable water. This bottle is then put into direct sunlight, on the roof of a house or elsewhere, for several hours until the ultraviolet radiation from the sunlight disinfects the water for drinking. While there are several specifics to the methodology to ensure success, and I write about them below, this data can also be found on the SODIS Web site at www.sodis.ch/.

Finding and Using Containers Compatible with the SODIS Method

Concentrated sunlight (ultraviolet radiation) is the name of the game so stay away from containers with more than a one- or two-quart (or liter) capacity. Don't use large containers!

Ultraviolet radiation is reduced by increasing water depth. The more surface area-to-volume ratio you can achieve, in other words, the more of the sun's rays that can shine through the smallest "thickness" of water, the better the method will work. Although clear soda bottles are not optimal for the SODIS method as they have a small area for exposure to sunlight, they are common and readily available in most towns and cities. (See comments on using plastic bags below.)

Use only newer, clean, clear plastic containers with lids. These containers should be in good shape, not old, dinged, and scratched up ones that will block UV radiation. In like manner, opaque, tinted or colored plastics will block the necessary radiation from the sun and should
not
be used for SODIS. Older clear containers and colored plastics can be utilized, if clean, to store water that has already been treated in the newer clear bottles. All plastics break down and age when exposed to the sun, thereby reducing their transparency for maximum UV radiation. This breakdown transforms plastic materials into
photoproducts
. SODIS laboratory and field tests showed that the resulting photoproducts were generated only at the outer surface of the bottles. No photoproducts or additives (UV-stabilisators) were observed leaching into the water itself. For the length of most urban disasters, sun-weakened bottles won't be a problem, as the SODIS people recommend that you retire all containers used for SODIS after one year of continuous daily use.

Research carried out in Canada at Montreal's Brace Research Institute (BRI), in collaboration with international colleagues, found that plastic bags are the best material for solar water disinfection. Heavy-duty freezer bags, as mentioned, will hold either a quart or a gallon of water sealed and will lie flat in comparison to soda bottles when full, thus exposing more water to greater concentrations of UV radiation. While this departs from the SODIS method of plastic bottles, plastic bags, although far less durable, may be a viable option for you. Any labeling printed on the bag should be turned down so as not to impede solar radiation. Be careful of hot, conductive surfaces as they may deform and melt the bags.

A note about glass: While clear glass bottles can be used, glass is thicker than plastic and will block some of the UV radiation and add time for the water to heat up. Glass containers are also heavier when empty and can be easily broken. Tests done with improvised large containers made with window glass did not work, as the glass did not transmit enough UV radiation. Many windows on the market have UV inhibitors to keep your couch and chairs from fading in the sun.

If possible, use plastic bottles made from PET (Poly Ethylene Terephtalate) instead of those made from PVC (Poly Vinyl Chloride). PET bottles provide a greater transmittance of UV radiation as they contain less UV stabilizers, are readily available, and are cheap, durable, and contain fewer additives than bottles made from PVC. PET containers can be distinguished from PVC containers by burning a sample. PET will burn easily, the smell of the smoke is sweet, and the flame goes out slowly. PVC is difficult to burn and the smell of the smoke is strong and nasty. Bottles made with PVC will also have a blueish glimmer.

If you use bottles that are longer than they are wide (soda bottles, for example), be sure to lay the bottles down on their sides, thereby exposing maximal surface area to the sun while creating a minimal amount of water depth. If the bottles are laid onto a reflective/conductive surface such as metal corrugated roofing or some other like surface, the water temperature will be increased. Don't forget about the physics of convection, radiation, and conduction as learned from the shelter chapter. The key to SODIS being effective is maximum ultraviolet radiation, and to a lesser extent, heat. Try whatever types and combinations of reflectors, conductive surfaces, and protection against cooling breezes it takes to maximize radiation and heat into the water, especially in marginal solar gain locales or during the winter. People living in really hot climates should watch out that the bottles don't start to deform from too much heat. Desert ground temperatures exposed to summer sun, let alone metal, can reach more than 140 degrees F (60 degrees C). Each year, Phoenix, Arizona, has several contests where gung-ho participants see who can cook an egg on the pavement the quickest. Experiment in your locality to see what works.

When the bottle(s) are filled with water, place them on a surface that will get
full sun
during the hours needed for treatment. Avoid areas that will become partially shaded at some point during the day. Southern exposure niches for the top half of the planet work well at having the most available sunshine during the winter months. Protect the bottles from cooler convective breezes and enhance reflective radiation if necessary. Do NOT place the bottles on flammable materials such as grass, cloth, straw, or hay, thinking you'll insulate the bottle from heat loss. The water in clear bottles can condense the sun's rays like a magnifying glass and quickly set fire to combustible surfaces.