How to Purify Water in an Emergency or Disaster Situation
Imagine that a disaster has occurred and access to cheap, clean, and uncontaminated water was suddenly interrupted. How would you ensure that you had an ample supply of water to enable the survival of you and your family? Given the fact the an average human being can only survive about 3 days without water, would you know what to do?
This is probably the most common and effective method you can use to prepare water for drinking. Boiling will kill most types of microorganisms and is relatively easy to do. Boil the water for at least 1 minute (5 minutes is better) and allow it to cool in a covered/protected location. (Drinking water that’s too hot can dehydrate you more). Water can be boiled over a fire, a stove (if there is power or gas), a solar oven, or even a car engine. After the water is boiled it may have an unpleasant taste. To correct this, aerate the water by shaking it in a closed container or pouring back and forth from one container to another. Follow aeration by adding a pinch of salt to improve the flavor.
If boiling your water isn’t option, chemical purification may provide the disinfection that you need. There are a variety of off the shelf chemicals that you can use to make water much safer to drink:
Charcoal. Did you know that charcoal can be used to help purify your water? Yes, it's true! In fact, most filtration systems sold at retail stores actually contain a good deal of charcoal inside of them. Charcoal is a great purifying substance because it has the unique ability to absorb sediments and contaminants while also improving taste. Charcoal is also easy to find because it is created whenever you burn wood (like when you have to create a fire to survive).
The process to use charcoal to filter your water is fairly simple. All you will need is charcoal, something heavy to crush it up with, and a container to hold and strain your water. There are plenty of guides online which show how simple it is to create a charcoal filtration system by using some campfire remains and a 2-liter bottle. Also, keep in mind that it's always a good idea to boil your water after you've treated it with charcoal because some bacteria may still remain inside.
Chlorine. To make water safer to drink, you can add about 8 drops (1/8 teaspoon) of unscented chlorine bleach (5.25% chlorine concentration) to each gallon of raw water. If the bleach has a different concentration of chlorine in it, you will need to use a different amount of it to prepare your water. For 1% concentration bleach, use about 40 drops per gallon. For 8% concentration bleach, use about 4 drops per gallon. After adding the bleach, stir the mixture well and let the container rest for at least 30 minutes. Bleach will kill some, but not all of the microorganisms that cause diseases. If there is a strong chlorine odor afterwards, you may need to aerate the water to remove the smell.
Chlorine tablets, which can be found in the camping supply section of your local big-box store, can be used to make water safe to drink. These tablets will have instructions on the packaging that will guide you to properly prepare your water for use.
Calcium Hypochlorite: Granular calcium hypochlorite (bleaching powder) can also be used to disinfect water. You can obtain this chemical from a pool supplier or the pool section of your local big-box store. To prepare the water for drinking, dissolve ½ teaspoon of the high strength powder in 1 gallon of water. Stir the mixture well and allow it to sit for at least 30 minutes before drinking. If there is a strong chlorine odor afterwards, you may need to aerate the water to remove the smell.
Iodine: Tincture of Iodine (2% concentration) can also be used to disinfect water. This chemical is sometimes available in first aid kits. Add about 20 drops of this substance (40 drops for cloudy water) to 1 gallon of raw water. Stir the mixture well and allow it to sit for at least 30 minutes before drinking.
Iodine tablets may be available in the camping supply section of your local big box store as well. These tablets will have instructions on the packaging that will guide you to properly prepare your water for use. If there is no instructions available, use one tablet for every quart of water you need to treat.
Stabilized Oxygen: There is some evidence to suggest that a “stabilized oxygen solution” can provide antibacterial properties when added to water. There isn’t much knowledge or research about this product as of yet, so this should be used as a last resort. In fact, there are many sensational or controversial reports about this product on the internet. Some websites have even made the claim that stabilized oxygen can cure diseases such as skin cancer. Stabilized oxygen can be found at most health food and nutrition supply stores.
Solar Water Disinfection (SODIS)
The SODIS method is one of the easiest methods you can use to purify water. It is so easy in fact that there are many organizations that are attempting to teach this method to people who are in danger of succumbing to water borne illnesses. Essentially all you need to clean your water using this method is the sun, a transparent PET plastic bottle (most plastic beverage bottles are made out of PET, just check the bottom of the container), and about 6 hours of your time.Simply fill the PET bottle with water and let it sit in the sun for about 6 hours. The sun's UV-A radiation will penetrate the bottle and destroy the bacteria and parasites in it. The SODIS method can even be used in cold climates! If you need more information, check out the SODIS website.
A fourth option that you have to create clean, disease-free water is to make use of the sun's energy by building a solar still. This method requires lots of time and sunshine to get any appreciable amount of water. Another downside to this method is that the water will be devoid of any minerals or flavor. Salting and aerating the purified water can help with this.
To build a solar still, you will need a sheet of clear plastic and at least 2 open containers to hold water. Fill one container with the dirty water and place it under the plastic sheet. Place the clean and empty container under the plastic sheet as well. Stretch the plastic taught over both of the containers. Use a rock or another object to create a depression on the plastic sheet just above the clean water container. As the sun shines through the plastic, it will heat the dirty water causing it to evaporate. Water vapor will condense on the underside of the plastic sheet and begin dripping into the clean container. If you have plastic tubing available, you should consider connecting it to the clean water container so you won't disturb the system when you need a drink.
Clarifying Water First
If the only water available to you is cloudy or laden with sediments, you should make an attempt to clarify it prior to disinfection. This can be accomplished by either straining the water through several layers of fabrics, such as clothing, or allowing the solids to settle out.
Surprisingly, one of the easiest ways to purify water is to use the sand and silt that makes up the Earth's surface all around us. It's a known fact that water that is pumped out of the ground is often free of contaminants because it has been naturally strained through the pores of sands and silts. With one of Earth's most basic natural processes in mind, one can easily create a devise that mimics nature and purifies water using only sand and silts.
To build a basic bio-sand filter you will need a couple of items: 1) a tall container,2) a hose or drain tube, and 3) a variety of clean sands, silts, and gravels. First connect the hose to the bottom of the container by boring a hole in the side of it. Next, fill the container first with a few inches of gravel then by a few more inches of sand. Next filled 2/3 of the remaining container volume with very fine sand and silt. Finally, fill the remainder of the container with regular sand and gravel. Some biosand filters also incorporate a layer of charcoal inside. If you have some available I would recommend including it in your filter design.
To use your new bio-sand filter, simply pour your dirty water into the container and let it slowly filter through the container and in then out the hose.
I have include a few links to more detailed guides on how bio-sand filters work and how they can be easily constructed in an emergency situation: