Water Purification Basics: a few questions before I begin

I have been asked to do a compare-and-contrast covering the various methods of water treatment available for preppers. Having spent 18 years operating a waste water treatment plant (the same technology as drinking water treatment, just with looser standards), I'm the closest we have to an expert on the subject so I'll give it a shot. This will be just an introduction to water treatment, with more details in future articles. This is a very important subject and I don't want to leave out information, but I also don't want to write a ten page article that nobody is going to finish reading. 

Before getting into specific methods or brands of treatment I need to ask a few questions. All of these will come into play when you start looking at filters and other treatment methods.

1. How clean do you want/need your water? I have worked in labs that required water so pure it would dissolve copper tubing, and I spent many years discharging treated water into a major river that was dirtier than what I was putting into it. Some uses may not require water as clean as others, I'm pretty sure your dog (who drinks out of the toilet and stray mud puddles) doesn't need water treated to the same standards as you'd use for mixing baby formula. The EPA and WHO have established drinking water quality standards, technical data that I'll try to put into layman's language.
   
   Also, not all raw water needs to be treated. Rain water and melted snow would be safe to drink in all cases, unless you're dealing with chemical or nuclear fallout. I grew up drinking water straight from a (fairly deep) well and have never had any issues with it. You can also develop a resistance or immunity to any local microbes that don't immediately kill you, but changing location will change the definition of “local” and you may run into problems until your body adjusts (Montezuma's Revenge).

2. What's in the water that you need to remove? Unless you have some idea of what you're trying to remove, you'll be lucky to pick the right method of getting it out of your water. A filter that will remove giardia cysts may not be good enough if you're dealing with chemical contaminates. Even without access to a microbiology/chemistry lab, you can do some research before a crisis to get an idea of what to expect. This is where things get personal, because there are too many possibilities for me to list them all. You'll need to think about where you may be when you need a water treatment system and do the research now.

3. How much water per day are you treating? The standard is one gallon per person per day for drinking and cooking purposes, but what about cleaning your body and clothes? Does your water system need to be cleaned periodically? For how many people are you prepping? Larger demands are going to require larger systems to clean your water or multiple smaller ones.

4. How long are you going to be treating your water? It's just common sense that a pocket filter might get you through a weekend in Mexico, but it isn't likely to last for several years' worth of daily use. Be wary of the claims made by manufacturers, unless you've thoroughly checked their system out. The filter that you pick for your BOB may be different than what you'll want to use once you get to your safe location, or you may only need to treat your water until the city gets their plants back online and the pipes flushed. Different needs for different plans.

5. Are you prepared for when your water purification system fails? Nothing lasts forever, so having a back-up plan is essential. It may be as simple as just drinking untreated water for a short period and dealing with the consequences (that weekend in Mexico), or it may be as complex as making another treatment system, but you need to be thinking of redundancy. A good idea for a fixed location would be to store your treated water and rotate through your stocks. That way, when the filter fails, you'll have a buffer supply to give you time to repair it or get another system online.

6. Are you aware of the indications for when your purification system fails? Do you have a way to test your system and the materials and skills to run those tests? One of the first filters I bought for hiking and camping came with a bottle of blue dye. The instructions were to add a few drops of the dye to some water and run it through the filter. If the dye passed through the filter it was a sign that it had failed. I'll get into specifics for each type of system as I cover them, but you need to be aware that there are simple ways to test water systems and you need to be able to run those tests.

7. Are you aware of how important maintenance and hygiene are going to be? Some filters require an occasional backwash to flush them clean while others require boiling or chemical cleaning and others just need to be replaced. Be prepared and learn your system before you need it. Make sure everyone who may need to use it is also trained.
   
   Hygiene is an absolute must-have in any crisis situation. Sharing a water bottle with another person is also sharing their diseases. Unless you're comfortable sharing bodily fluids with someone, get them their own bottle. Keeping your water treatment equipment clean will avoid cross contamination. Think about it: if your hands are filthy, do you really want to touch anything that is going into your mouth? It would be wise to pad the numbers in your answer to number 3, above, to allow for some surplus water for hygiene purposes.

Those questions should give you something to think about, and maybe form a few questions of your own. I'll discuss the different methods of water treatment and some of the various types of equipment in the next few articles. If you have questions you would like to see answered here, feel free to leave comments and I will do what I can to find an answer.

Water Purification, Part 4 - Water Sources

A few weeks ago I was asked to explore urban water sources and its treatment To answer that question, first I need to explore some of the possible water sources and what type of treatment would be best for each. A very technical description of the various types of water found in the ground can be found on the USGS website, but I'll try to make it a bit more understandable. I'll start with the worst and work my way through to the cleanest sources.


Surface Water
Surface water is literally water found exposed on the surface. No digging of a well is required to get to it, which means that surface water is likely to be your first choice as a source of drinking water during an emergency. Surface water is also more likely to be contaminated than other sources because of the fact that it is exposed to animals, air, runoff, and sewage discharge.

Here's an aerial photo-map of the county I live in with the lakes, rivers, streams, and drainage ditches shown in blue. The legend didn't save with the picture, but for about 90% of the county you can't travel more than about a mile without finding water of some sort. For a rough estimate, the left (West) border has squared off bumps that are scaled in one mile increments. I am blessed with an abundance of surface water where I live, but I know that others aren't as lucky.

This photo-map came from an online service (beacon.schneidercorp.com) that provides GIS (Graphical Information Service) data to local county and State agencies. It is free to use and they cover a lot of the central US. There are other sites with similar data for other states. The maps are very detailed and you can select the information presented (roads, waterways, political subdivisions, etc.) 

Here's a resource for finding a similar photo map of an area in your area. Road maps and atlases can often give you a good idea of the waterways in your area, and a topographical map will give you details on lakes, ponds, swamps, rivers, and streams.

Photo my own work and copyrighted

Surface water can be contaminated with just about anything and everything you can imagine. Unless you can see the source of the water (spring, glacier, etc.), you should expect that it is contaminated. Somewhere upstream of you could be a dead beaver or raccoon laying in that crystal-clear mountain stream, or the field next to that lake might have been sprayed with 13 different chemicals in the last year. Your choice of filters must have excellent biological removal, and a charcoal filtration step would be prudent in areas where agriculture and industry are found. A good prefilter followed by chlorine or iodine treatment will take care of most surface water if you don't have a filter for removing the biological contaminants. A solar still (like this one) will take care of most of the contaminants and produce potable water in a stationary situation.

 

Photo my own work and copyrighted

How long you expect to rely on surface water will be a determining factor in the size of the filter you will need. My needs would be a filter that would allow me to travel to a place with safe water, which in my normal daily routine would be no more than 30 miles. Even on foot I can travel that far in 72 hours or less, so a small filter with high efficiency is in my GHB. Once at my bug-out location my water needs are taken care of, so my choice of filters is a lot simpler than some of you may have.

Where you are, and to where you are trying to get, are also important;

• If you're in a metropolitan area, traveling through one, or sheltering in place in one, the water you find in drainage ditches, mud puddles, and storm sewers is going to be the surface water you'll find. 
• Runoff from roads will have oil from vehicles, rubber from the tires, trash, salt and sand from de-icing, and roadkill remnants, so the treatment option you choose should be capable of removing all of them. 
• If you see an oil sheen on the water, it's best to look elsewhere for water if you don't have a reverse osmosis system or an excellent filter system capable of removing petroleum from the water.
• Water stored in a rain barrel or stock tank should be treated as surface water, since it is open to the air and animals. There are few things worse than getting to the bottom of a rain barrel and finding a dead mouse or squirrel. 
• Rainwater that has run off of a roof will probably contain some bird droppings, leaves, and anything else that could land on the roof so it should be treated before drinking. 
• Seawater is a special class of surface water, in that it contains enough dissolved salt to be unfit to drink untreated. Distillation and reverse osmosis (RO) are the only good methods of making seawater drinkable, and there are several units designed for this purpose out there. 
• Brackish water refers to the water found where fresh water streams mix with seawater and should be treated as seawater. By the time the water in a river makes it to the sea it has picked up all of the run-off and discharges upstream and it will need a very good filter to clean it up.

Groundwater

Groundwater is the water trapped or contained in the soil between the surface and the bedrock of an area. Groundwater sources are recharged by water seeping through the soil and porous rock above it, and the water is filtered in the process:  if water can travel through a few inches of ceramic and come out clean, then a few feet of soil and then a few yards of rock will have the same effect. Ground water recharge takes time, though, which varies with the local weather patterns and the make-up of the geology underfoot. Dirt and rocks are capable of desalinating sea water -- if given enough of the right type of rocks and enough pressure.

Photo my own work and copyrighted

If you see a windmill or irrigation system, you will find a well attached. The old windmills may not be working, but if you see a center pivot irrigation system in the field, it is hooked up to a good well. Irrigation systems are fed by pumps run on electricity or an internal combustion engine (usually with a large fuel tank or propane tank next to the motor).

If you have the time and equipment to dig, drill, or drive a well, then you'll need to know if you have a chance of hitting water. The well-drillers around my area have always kept detailed records of their successes and failures at finding water, and pass that information on to each other. If you need to know how far you'd have to dig or drill to find water, try checking this page. Dowsing is another option, but would be best attempted before an emergency.

Photo my own work and copyrighted

If your water table is close to the surface -- within 20 or 30 feet -- a simple well is easily driven with a “sand point”, some pipe and a sledge hammer. Instructions are available online, and the parts can be ordered or purchased at farm supply or plumbing supply store.

Groundwater comes pre-filtered by the soil that it had to percolate through, so it will be free of most of the biological contaminants unless your well is open enough for animals to enter. You can get by with a slightly less efficient biological filter (or no filter at all) depending on the quality of the source. I grew up drinking water from a well and the only reason we ever wanted to treat it at all was to remove the iron and lime content. The chemical filtration step (carbon or RO) becomes more important with shallow wells, especially in areas where agricultural chemicals are used, there are leaking underground storage tanks, or industrial chemicals have been stored/dumped. In general, the deeper the well is, the cleaner the water will likely be. Sand point wells are commonly used for livestock and irrigation purposes in areas where the water table is high, but drinking it untreated may expose you to chemicals and pollutants because the water doesn't have as much soil to travel through.


Deep Water

Water that is below impermeable bedrock or clay is “deep” water. Usually part of an underground aquifer this water has been where it is for thousands of years, cut off from exposure to the air and any other source of contamination. Drilling through several layers of rock to reach this deep water usually takes professional equipment and several thousand dollars, but will provide a source of clean water for many years. The deeper the well, the harder it will be to draw the water up to the surface. Without electricity for a submersible pump, deep wells need good hand pumps to be useful. Bison Pumps have gotten good reviews, but I have no personal experience with them.

Deep wells will provide water that needs no filtration unless the aquifer itself has been contaminated. This is possible through blown-out oil/natural gas wells, severe earthquakes, and other things that may occur in a major catastrophe.


Trapped or Stored Water

Water that is locked up inside plants or left in pipes/containers is what I call “trapped” water.

Plants filter water by drawing groundwater through pores in their roots and carrying up into the body of the plant. The pores and capillaries inside most plants are small enough to filter out bacteria but not chemicals, and a lot of plants will actually concentrate metals in their flesh. Depending on the metals in question this can be good or bad; magnesium, iron, and calcium are good for your body but lead, arsenic, and mercury would be bad. Plants found in the wild would be safer to use than some random weed growing on top of a landfill or next to a factory building. Know the plants in your area and avoid the poisonous ones.

Cactus plants store water, as do the other succulents, and make a handy source of emergency water. Eating or tapping a cactus is pretty straightforward and has been covered in desert survival instructions for many years.


Foliage (leaves) are another plant source of water. Plants lose water through their leaves in a process known as “transpiration”, where water evaporates from the leaves into the surrounding air. Wrapping a clear, clean plastic bag around a tree branch overnight will provide a little bit of water for drinking. Another method is to place cut plants into a solar still and collect the moisture produced as they dehydrate.

Water trapped in pipes or containers is usually water that has been treated by a municipal plant or came from a well that is no longer under pressure. If used within a reasonable amount of time (a few weeks for most sources) no treatment will be needed. However, once it has sat stagnant for a long while, it will start to absorb materials from the container or pipes that it is sitting in, and any bacteria present has a good chance of reproducing and reaching levels of contamination that may be dangerous.  

Bottled water is usually treated with ozone or run through an RO unit (drinking water vs, purified water) and will last months on the shelf, but it can leach chemicals from the plastic bottle into the water. Toilet tanks (not the bowl!) hold 3 to 5 gallons of water; water heaters hold 30 to 50 gallons of water; and standard ½ inch water pipes contain a gallon of water in about 100 feet of pipe (this chart gives values for other pipe sizes). Since the water is trapped, you'll probably need to open the pipe/container at top (vent) and bottom (drain) to get the water out.

Fresh Water 

Fresh water is captured rainwater, snow melt, or other source of condensation or precipitation. Unless your collection system is contaminated, or the air itself is unsafe, this is the best source of water as it needs no treatment. Ice harvested from a frozen lake or river is clean enough to drink once melted, as is freshly fallen snow.




These are the main sources that I think about when I think of water. I haven't given any brands or suggestions for a specific situation because I am not able to test your water sources and then test the resulting water in a proper manner. I am also not getting paid by the makers of water filters, so I am not going to promote any one brand over the other. Check the specifications, reviews, and the maker's claims and compare more than one brand before you buy. You are going to have to do your own research and figure out what treatment method makes the most sense for your situation. If you have question about specific methods, let me know and I will do what I can to help clarify things for you.

The Chlorine Shortage

Clean water is essential for life. Chlorine is one of the easiest and most common ways to disinfect (kill microbes) water, and has been covered several times here and on other blogs. I even showed the basics for making your own chlorine bleach, and there is a post in the archives about a solar-powered bleach producer.

Chlorine is a basic industrial chemical, used in a lot of processes, but a majority of it (~60%) is made in two plants. One of those plants burned last year, and the other was recently flooded. This has put pressure on the market; as supply goes down, prices go up. Add in the quarantine-based surge in home swimming pool construction and you can add increased demand to further raise prices. 

What does this mean for a prepper? 

• Since most municipal water plants use Chlorine gas as a final disinfectant for the water they supply, we can expect higher costs for our drinking water.
• Some places may try to get by using less Chlorine, which raises the potential for bacteria in our water.
• Household bleach prices will rise and availability will drop.
• Swimming pool bleach will follow household bleach.
• Suppliers may switch to imported Chlorine, which raises costs and means more transportation. 

Chlorine is a gas at normal temperature and pressure, and is shipped as a liquid under pressure. Pure Chlorine stores well, but once converted to household bleach it has a shelf-life measured in months. (Pool bleach lasts longer, but is chemically different.) Stockpiling bleach is a waste of money, so if you're counting on using it for water purification you need to either make your own or investigate other methods. Erin has written about Potassium Permanganate as an alternative method of water purification (it has other uses, too) so give that some thought.

Some other things to consider:

• Conserve water if you're on a municipal system. Reducing the demand will ensure they can treat what they are pumping.
• Have a backup water purification system on hand. If your city declares their water unsafe, they will usually enact a "Boil Order", so keep an eye on the local news. Use the search box and look for Reverse Osmosis for my recommendation.
• If you have a swimming pool (a great way to store lots of water), check with local suppliers for a season's supply of chemicals. Look into alternative methods, which is outside my realm of experience.
• Keep a supply of drinking water on hand. Having been through a few floods and other disasters, you won't get much warning before they shut down the water supply.

We live in a connected world where a failure at one location will have ripple effects that can affect you and yours. Do what you can to avoid the worst of the problems.

eBook Review: “Water Storage for Survival”

I've been interested in what other prepper sources are publishing, so I decided to check a few of them out. I'm working long hours at the moment, but I do have time to read a bit here and there. The Kindle app on my phone tends to deplete the battery faster than any other app I have, but it's convenient to have a couple dozen books on hand.

I did a simple search for “prepper” and browsed through the results. Since we've written several articles about water, I picked one titled Water Storage for Survival by Ronald Williams. What I found was a mixed bag of common-sense information that is readily available on the internet on a dozen different sites. The chapters were broken down like this (with my commentary):

1) Why You Need to Store Water
He covers the basics of how your body uses water and the importance of avoiding dehydration. I did find it odd that he states, “...traveling back and forth between your home and a natural source of water is simply not practical.” Without a specific scenario, I fail to see how he can make such a blanket statement since people have been traveling to central wells for centuries and it seems to still be working. 

2) How Much Water Do You Need?

The basic “one gallon per person per day” formula. His example of a family of four, for a month, equaling 120 gallons (which he states is “simply not practical” to store) is a normal starting point. Erin covered a simple, cheap way to store 100 gallons of water here, so it's not that difficult to store water. One gallon jugs of drinking water come six to a case, so 20 cases would last a family of four a month and would fit along a wall quite easily. Stack them four wide and five high or fit them under a set of stairs, they don't take up that much room.

He also covers how to store water in this section instead of giving it a section of its own. Good, common-sense storage information.

3) Making a Rain Catchment System
This is how to modify your gutter system to catch rain water. Some of the steps aren't very clear, and he specifies food grade materials for some things but not all. We had a guest post that covered the process in detail with pictures back in 2014.

4) How to Purify Water

Boiling: He gets some things right and some wrong. Boiling water for 15 minutes is not needed, and simply boiling it will not necessarily render it safe to drink since it will concentrate any chemicals that aren't destroyed by the heat.

Bleach: A standard which I have covered in detail in several articles. His instructions are basic but workable.

Distilling: “Guaranteed to eliminate even the most deadly and resistant of chemicals, heavy metals, and microorganisms” according to Mr. Williams. Not always true; just ask anyone who has tried to distill alcohol.

As an afterthought, Williams covers filtration and purification tablets in a somewhat dismissive fashion. There is no mention of reverse osmosis, unless that's what he meant by “pump action water filters”.

5) Collecting Water From the Wilderness
These are simple methods of finding water, like going to the lowest point of the terrain to find the wettest area. Collecting dew on rags tied to your ankles may sound good, but unless you're living in a rain forest you're not going to gather much water.

6) Collecting Water From an Urban Environment
These are mostly sources of trapped water, something I covered in detail in my water purification series.

7) Myths About Storing Water
I'm not a fan of myths, so I'd never heard of most of these. 

Conclusion: Do Not Buy This eBook
Having read through the entire book, I must mention how much work our editrix does behind the scenes. This author needs to find someone to at least proof-read his work before he publishes it, just to point out the spelling and grammar errors. I read a lot and I expect a certain minimum level of competence from someone who want to trade me words for money.

All in all, this is pretty high on my list of the worst waste of $2.99 that I can think of. Since it was a digital book, I guess the best I can do is coin a new term for an e-book that's not worth buying: digital toilet paper.

Bleach for Water Purification

Editor's Note: Evelyn had to take a personal day, so Tim is filling in for her with an article that is both topical and relevant to preppers. She will return next week. 

Background

I spent 18 years running a multi-million dollar industrial wastewater treatment plant. The methods of cleaning water for drinking and for discharge to public waters are the same, but they vary in their application and allowable levels of contaminants. Most of the time the water that we discharged to the local river was cleaner than what was already there, and there are hundreds of cities and towns downstream that draw their drinking water from that same river.

To be blunt about it, every drop of water that you drink has been passed through the body of countless millions of animals and people before it got to you. What comes out of your faucet or bottle of water was dinosaur urine at one time. We live on a planet where new materials are not being imported, so what we have has to be reused.

Microcystin

Adding household bleach to suspicious water or water of unknown quality is a staple of disaster preparations, but the recent finding of microcystin toxin in the water supply of Toledo, OH has brought up a few questions. Microcystin is a toxin produced in the cells of certain blue-green algae and is released into the water when the algae die or are destroyed. It is a liver toxin that can cause permanent damage to the liver as well as nausea, diarrhea, and vomiting. Boiling water will only concentrate the toxin by killing the algae and reducing the amount of water that it is in. The problem is not the algae, it is the chemical that they produce. Filtering out the algae (disinfection) is only the first step in cleaning up the water; any decent water filter will do that. However, getting rid of the toxin (purification) is another matter.

Purification using Bleach

https://amzn.to/2VB9TZd

You'll need a way to test for chlorine. Any swimming pool or hot tub shop will have these nifty little test strips. Quick and easy tests are the best, and they don't require much more than normal color vision. You simply follow the directions on the side of the bottle (dip the test strip into the water for 30 seconds, if I recall correctly) and then compare the colored spots on the strip to the color bars on the bottle. Where the colors match is where your chlorine level is. If you don't have any test strips, use your nose. The human nose can detect chlorine at about 0.3 mg/L in water so if you can smell it easily, it is over the 0.5 mg/L lower limit, which means it is safe to drink. 

The active ingredient in household bleach is Sodium Hypochlorite (NaClO), which is derived from common table salt (NaCl). Bleach works as a disinfectant (kills nasty microbes) because of the chlorine content. Chlorine tends to disrupt the cell walls of microorganisms, causing them to rupture and die.

In Toledo

Using bleach to treat water for microorganisms is well established, but in Toledo they're not dealing with the algae itself; they're dealing with the toxin it produces.  Fortunately, bleach will also work on the microcystin by oxidizing it into a more benign chemical. The World Health Organization has set out standards for treating water for microcystin, found here, that are fairly easy to follow if you know what you have on hand and how to use it.

From the WHO paper:

“Chlorination and ozonation are effective for the removal of microcystins. A residual of at least 0.3 mg/L of ozone for 5 minutes will be sufficient for all of the most common microcystins. For chlorine a dose of 3 mg/L applied to obtain a residual of 0.5 mg/L for at least 30 minutes will be effective.”

Ignore the part about ozone, that's beyond most people's capabilities. The important part is about the Chlorine- the 3mg/L and the 0.5mg/L for at least 30 minutes part. Those of you who never took Chemistry, or who just hate math, are probably looking at that as if it were written in a foreign language. I will try to explain it in a way that makes sense outside of a lab.

Translating Chemistry Terms Into English

mg/L is one of the standard ways of expressing the concentration of a substance in water. If you're familiar with the metric system, you'll read it out loud as “milligrams per liter”. Since water is the original base of the metric system, a lot of the units of measure are interconnected. One milligram of water is equal to one milliliter (or cubic centimeter, “cc”, in medical jargon) of water. That means that there are 1,000 milliliters in one liter, and since one liter of water weighs one kilogram (1,000 grams) there are 1,000,000 mg/L total. Did I lose anybody on that one?

Let me try again.

• 1 liter (L) of water weighs 1 kilogram (1 kg).
• There are 1,000 grams (g) in a kilogram (kg).
• 1 gram (g) contains 1,000 milligrams (mg).
• 1,000 mg (1 g) times 1,000 equals 1 kg.
• There are a total of 1 million mg in 1 kg (which is what a liter [L] of water weighs).

So when you see something expressed as “mg/L” what they're trying to say is “parts per million” (ppm), another form you may see used. Remember, this only works for water and mixtures that are mostly water, but that's all we're interested in for now. Both ppm and mg/L are used interchangeably when measuring small quantities of substances.

This becomes important when you pick up your jug of handy-dandy bleach and look at the label and it says that it has 5% Sodium Hypochlorite (NaClO). Oh, wait. The store was out of your normal brand, so you grabbed the generic store brand. That bottle says it contains 8.25% NaClO instead!

The advent of high efficiency washing machines required that they start increasing the concentration of NaClO in household bleach. Now what? Percent means “parts per hundred”, so 1% means that there is 1 part (whatever unit you are using) per 100 parts (as long as you keep using the same units). Percent concentration is used when measuring large concentrations of a substance. Converting 1% to parts-per-million (ppm) is simple. 1 million divided by 1 hundred equals ten thousand. One percent equals ten thousand ppm, that's why it is used to measure larger concentrations. So 5% is the same as 50,000 ppm (or mg/L).

More Math

You need to dose a bottle of water in order to have something safe to drink and the WHO says that you need to add at least 3 ppm (mg/L) and after 30 minutes there needs to be at least 0.5 ppm of chlorine left. A one gallon milk jug holds about 3.78 L, so let's round it up to 4 L. How much bleach do you need to add to get 3 ppm (mg/L)? 3mg/L * 4 L = 12 mg of chlorine.

Since your bottle of bleach is only 5% (or 6% or 8.25%) NaClO, you need to know how much bleach to add to your gallon of water get it over 3.0 mg/L chlorine. You also have to figure in the fact that there is more than just chlorine in your bleach. That sodium and oxygen is taking up enough space to knock the chlorine down to only 60% of the NaClO. Let's go with the low number (5%), just in case that's all you have or your bleach has been sitting on the shelf for a year or two. Slightly overdosing with bleach is acceptable, just let the water sit in an open container in the sunlight for a few hours and the excess bleach will burn off by turning back into salt and water*.

We're starting with 5% NaClO, which is only 60% Cl, so we actually only have 3% chlorine available. That works out to 30,000 mg/L Cl in the bottle of bleach. We need to get 12 mg of Cl into the water, so we need to divide 12 mg by 30000 mg/L to get 0.0004 L of bleach. That's 0.4 mL or 0.4 cc of bleach. Again, let's round it up to 0.5 mL.

Want to try it for the concentrated bleach? If your bottle of bleach says it is 8.25% NaClO, that means that it is (60% of 8.25 =) 4.95% Cl, or about 50,000 mg/L. Divide the 12 mg Cl we need for the gallon of dirty water by 50,000 and we get 0.00024 L or 0.24 mL. Close enough to 0.25 cc for us to use.

In Practice

Now that I've got the math out of the way, how do you measure out that small of an amount of bleach? The standard in a lab or pharmacy for a “drop” is 15 drops per mL. A “drop” from an eyedropper actually has its own unit symbol or abbreviation: gtt. Since we need 0.25 or 0.50 mL of bleach to remove the microcystin that started this whole article, we need to find an eyedropper (glass will work best - bleach will eat plastic and metal ones) and slowly count out 4 drops for the concentrated bleach or 8 drops for the normal bleach for a gallon of water. Stir or shake and let it sit for 30 minutes and check for chlorine (by sniffing it, or by using test strips). If there is at least 0.5 mg/L still in your water, it is safe to drink. If not, dose it again until you do get the desired residual chlorine.

Why All the Math?

All of this is to show you how to calculate dosage rates for bleach. The charts that are available on the internet are based on the old standard of 5% or 6% NaClO, and use as a disinfectant as far as I can tell. If you're worried about blue-green algae, doubling the dose seems to be the best bet.




* Household bleach has a short lifespan; it will turn back into salt and water by as much as 20% per year, even when stored in unopened containers. Long-term storage won't work, and producing your own bleach is a topic for another time.

Distillation Basics

Water is critical to life.  The recent situation in Ohio and Michigan has demonstrated how fragile our water supplies can be. Yesterday, Chaplain Tim covered bleach for water purification, which is good knowledge any time your water is questionable. Today, I'll cover distillation, as it relates to making pure water. (Sorry, I have zero knowledge of how to make booze.)

Advantages & Disadvantages

Distillation is the process of converting water to steam, then cooling it back to a liquid in another container. This process removes everything from the water at the end of the process, leaving pure H2O.

Distillation is also inefficient, compared to filtration or chemical treatment.  You only get back a fraction of the water you initially put in, where other methods return virtually all input water.  There are several off-the-shelf distilling options available, such as this one, but they aren't exactly cheap.  The big benefit, though, is that you can put pretty much any water into it and have it come out clean.

Assembling Your Still

So, how do we distill water on a shoestring budget?  The parts themselves are actually fairly simple.  You need:

• a container to hold your source water
• a container to catch your distilled water
• a way to move steam between the two

The chief requirement of the source water container is that it be able to tolerate high heat.  A metal soup pan or stock pot fits the bill nicely.  These also have the advantage of often having snug-fitting lids, preferably made of metal, which provides a variety of options for attaching your steam conveyance.

The clean water container mostly needs to be, well, clean.  Don't let it come into contact with any of your source water, or you risk contaminating it and needing to replace it.  In the same sense, your source water pot is for that purpose only, and cannot be used for cooking, etc., after it starts life in a still.

To move steam between the source pot and the final container, my solution is as follows:

1. Drill a roughly 17/32" hole in the lid of your source pot. 9/16" is also acceptable, if you cannot find the muck less common 17/32. 
2. Thoroughly wash one each of this and this, then install them in the lid, with the barb stem facing out from the pot, and the nut on the inside of the lid.  
3. Attach a full length (at least 10 feet) of this tubing to the barb, and run the other end into your clean water container.  
4. Support the tubing to keep it out of the way and clear of your source pot, preferably running it up above both of your containers.  
5. You now have a basic still.

Blue Collar Distillation

To run your still, simply put a quantity of water into your source pan and add heat.  You're trying to generate steam, so a rolling boil is what you're after.  As the water heats up, steam vents up the tube and cools back into water, which then flows down into your clean container as pure, drinkable water.

You can use a wide variety of methods to convey the steam between the containers.  My recommendation is based on the tools and supplies I have handy, but there are endless ways to accomplish the same end result. Longer tubes give the steam more time to cool into water. making the still run far more easily.  The more sealed your initial pot/lid/tube assembly is, the more efficient your still will be, and the more water you'll get back in relation to your input water amount.

Lokidude


(Author's note. The initial version of this article contained references to distilled water stripping minerals from the body. This was based on old science that appears to have been successfully rebutted. The references have been removed. My apologies.)

Potassium Permanganate for Water Purification

Not actually Erin.
Picture by KJ Photography
& is used with permission. 

Water week concludes with a discussion about a chemical no prepper should ever be without: Condy's crystals, aka potassium permanganate. An entire series of articles could be written about the uses of this substance, as it can do so many things:

• disinfect wounds
• treat skin conditions like eczema, canker sores, and fungal infections
• start fires via chemical reaction when glycerin is added (video at link)
• dye snow or clothing as an emergency signal

But what we are interested in today is its ability to disinfect and purify water. 

Words of Caution

Before we begin, however, I need to make the following disclaimer:  Potassium permanganate can be harmful or fatal if used improperly. 

• Crystals, powders and concentrated solutions are caustic and can burn the skin. Wear gloves!
• Too much PotPerm can cause poisoning if ingested. Be aware of concentration in water!

What It Purifies

Not only does PotPerm disinfect water (it is used in the water treatment industry), it also removes microcystin toxins like the ones that compromised Toledo's water supply and inspired this week of articles: 

Potassium permanganate at 1 mg/L was found to achieve 95 percent removal of microcystin-LR at a starting concentration of 200 µg in 30 minutes, and higher permanganate doses achieved complete removal. 

However -- and this is important -- if you add PotPerm to water still contaminated by blue-green algae (such as in Toledo), the chemical reaction could result in the algae releasing more microcystin. 

Therefore, before you treat your water with potassium permanganate, it is recommended that you always, ALWAYS, filter your water (such as with the system David talked about on Wednesday). 

Procedure for Purification

First,  filter your water.  This will remove sediment, blue-green algae, and other nastiness you don't want to drink. 

Second, pour your water into a clear container. It needs to be clear so you that can judge PotPerm concentration from the coloration. If you do not have a clear container, use a one with a sufficiently large opening (like a canteen cup) so that you can see the coloration without having to look through a narrow bottleneck. 

Third, add PotPerm crystals to the water. Ideally, this is done with tweezers or a very small spoon, as it doesn't take much to disinfect water. The rule of thumb is 3-4 crystals per liter (roughly 1.06 quarts) of water.

Fourth, stir the water/shake the bottle to dissolve the PotPerm and disperse it completely into the water. Judge its coloration (below) to ensure you have the proper 1:10,000 (0.01%) solution. 

Finally, wait 2 hours before drinking. Keep the water in a dark place as PotPerm decomposes in sunlight. 

Color

http://chemistry-chemists.com/N6_2011/U7/ChemistryAndChemists_6_2011-U7-3.html

Above is a picture of several different concentrations of potassium permanganate in water. 

From left to right:

1. The leftmost bottle does not have enough PotPerm dissolved in it to make it safe to drink, unless it had already passed through a strong antibacterial filter. 
2. This is the darkest solution I would drink. Ideally you would want something halfway between #1 and #2, like the water in this picture:  

   

   http://www.practicalsurvivor.com/waterfiltration

3. This is too dark to drink, although it would make a good solution for treating wounds. If you needed to drink this, first add more water to dilute it. 
4. Use only for skin treatment. 
5. and 6. are too dark to be used as anything other than dye. 

A handy way of remembering this is "If it's pink, it's safe to drink." Aesthetic arguments over whether or not bottle #3 is pink or magenta are outside the scope of this article. My only recommendation is to choose pale pink over any other shade -- think steak, not Barbie or bubble gum. 

A Little Goes a Long Way

Remember, I said that 3-4 crystals per liter, or 1 part per 10,000 parts of water, is all that is necessary to achieve water purity:

• According to Cyanobacterial (Blue Green Algal) Toxins: A Resource Guide, one milligram per liter is enough to achieve 95% microcystin removal (each crystal is approximately 1 mg). 
• Per the United States EPA, a dose of 2.5 mg/L will completely kill bacteria. 
• Viruses can be killed, but dosages vary to be effective -- in some cases 50 mg/L are necessary for complete virus inactivation. This amount is close to toxic levels of PotPerm, however, and therefore I encourage you to get a filter with a high effectiveness against viruses if that is a concern 

As potassium permanganate is a salt, it can be stored for decades without losing potency, and since a little goes a long way it can be part of your preps for a long time to come.  You can buy it on Amazon in different volumes, depending on your needs. My only suggestion is that if you choose to include PotPerm in your bug-out or get-home bags, make sure it is tightly secured within a watertight container -- you don't want caustic salt spilling all over your emergency preps!

Here is a useful video for constructing a small, watertight container suitable for BOBs or GHBs. 

Water Purification, Part 3 - Technologies

Treating water to make it potable is done through a few basic processes (or a combination) to reach the desired quality of water.


Heat
Pasteurization is the process of heating water or food to a temperature high enough, and for long enough, to kill the pathogenic organisms present. Boiling is not needed; all that is needed is to get the water above 160° F (71° C) for a few seconds. There is a simple pasteurization indicator called a WAPI, but if you don't have one, just boil the water and let it cool. Overkill usually works.

Boiling only affects biological contaminants and may actually concentrate chemical contaminants (for an example, see my post concerning Microcystin and blue-green algae).

Distillation is boiling the water to a vapor state and then condensing it back to a liquid state. Distillation will remove all of the biological and most of the chemical contaminants, but chemicals that have a boiling point below that of water can carry over and actually be concentrated in the distillate; the larger the difference in boiling point there is between water and the chemical in question, the better chance there is that it will be removed. Anyone who has ever tried to distill alcohol will tell you how hard is is to get that last 5-10% of the water out of the alcohol (which is actually an azeotrope, and a subject for another time).

Distilling large quantities of raw water will require a lot of maintenance on the equipment to remove the sediment, known to boiler operators as "mud". Anyone who lives where the water is "hard" knows what a teapot looks like after a month's use, and the build up of lime reduces the efficiency of your boiler (and may cause failure its failure).


Cold
Cold means freezing. Freezing water will kill most of the larger and more complex organisms, but won't affect viruses or some of the more hardy forms of life. Chemical contaminants can be reduced or eliminated through freezing (depending on the specific chemical involved), but any chemical with a freezing point close to that of water has a good chance of being left in the ice.

Water is odd in the chemical world because it expands when it freezes, where most everything else contracts and gets denser. This is why ice floats, which is a good thing because it separates the water from the contaminates. Ice harvested from a lake or river starts off fairly clean and is usually potable untreated. Fresh snow and rain are also safe, unless there are abnormally high amounts of crap in the atmosphere (volcanic ash, nuclear fallout, ash from forest fires, etc).


Chemical Treatment
The three main chemicals used to treat water are Oxygen, Chlorine, and Iodine.

Oxygen works by burning (oxidizing) the organisms, and can also remove some of the metals found in raw water by converting them into forms that are easier to filter out. Potassium Permanganate is a strong oxidizer, and is a good source of oxygen for treating water (see this post for details). Ozone is a more energetic form of Oxygen that works well, but requires special handling and equipment.

Chlorine acts on the organisms by disrupting the cell walls. Pure Chlorine is a corrosive gas and is not to be played with unless you have the training and equipment to do so safely. Bleach contains both Cl and O, so it works both ways. I discussed bleach in an earlier post, specifically about the threat of blue-green algae.

Iodine tablets have a long shelf-life, small size, are solid instead of liquid, and work in the same manner as Chlorine. Iodine tablets are convenient because they are sized for a typical quart or liter canteen. Iodine works well on bacteria and common parasites, but does nothing for viruses. Both Iodine and Chlorine require time (typically 30 minutes) to kill the microbes present. Potable Aqua is one of the common brands of Iodine tablets.


Filtration
Filtration is the process of passing water through a membrane or substance that allows the water molecules to pass through but traps impurities. Filter media is made up of a variety of things, with ceramic and plastic being the most common methods of removing biological impurities, and carbon being used to remove unwanted chemicals. Since the individual filters all have varying claims of efficiency, I'll try to list a few for you to compare. When doing your research, be careful to check the efficiency rating as well as the price and rated flow for each filter. Your mileage will vary, and I am not going to lie and tell you that there is one perfect filter that will fit everyone's needs. Most of the better filters on the market (or ones you can make) use more than one form of filtration. Simple is good, but when you're dealing with one of the most vital things you need to stay alive, it may help to add a level of complexity if it makes enough of an improvement in the quality of water.

Several filters also incorporate a coating or layer of silver as an additional antibacterial step. I'm not totally sure (meaning I haven't had it proven to me) of the effectiveness of silver as an antibacterial. There is plenty of anecdotal evidence of silver's effects on bacteria, but I haven't seen any honest, unbiased lab trials proving the claims.

A word of warning: if you live in an area where the ambient temperature drops below freezing, you must make provisions for keeping your filter warm after use. It is almost impossible to get all of the water out of a filter between uses, and because water expands when it freezes, the formation of ice crystals inside any filter will lead to rapid failure of the filter media. I carry a Sawyer Mini for many reasons, one of them being that I can cap the ends and hang it around my neck (inside my clothes) in between uses to keep it from freezing.

Coarse filtration
Also known as prefilters, anything from a clean piece of cloth to a bed of fine sand will remove large (> 10 micron) particulates and will extend the life of any further filtration method used. Sand filters are commonly used in the operation of swimming pools to remove algae and large debris, and would make a good prefilter for a large group. Just allowing cloudy water time to sit undisturbed will let the larger particles settle to the bottom of your container. If you carefully pour the clearer water off of the top (decanting) it will take some of the load off of your water filter and will help extend its life. Here's a repeat of a chart I posted before to give you an idea of the sizes of common contaminates.

"Cut-offs of different liquid filtration techniques" by Peter in s - Own work.
Licensed under Creative Commons Zero, Public Domain Dedication via Wikimedia Commons

Carbon filters
Carbon filters use activated carbon, a heat-treated form of charcoal, to trap chemical impurities. By heating charcoal in the absence of oxygen, the process opens up millions of micro-pores in the surface of the charcoal, making a filter media with a very high surface area and an affinity for impurities. Carbon filters are rarely seen alone; they are generally a part of a system that uses multiple methods of filtration to clean the raw water. Carbon is very effective at removing chemical contaminants but do almost nothing to remove biological contaminants (and may even serve as a breeding ground for some if left wet).

Ceramic filters
By using proprietary methods of making very small voids (empty spaces) or pores in a piece of ceramic, several companies have developed ceramic media that are capable of blocking anything larger than 0.1 micron. Large ceramic filters tend to use gravity to force the water through, while the smaller ones will have some sort of pump attached to allow the use of a smaller filter element and still get reasonable flow through it.

Just Water is one of the standard ceramic filters. Berkey, Katadyne, and Doulton are some other well-known names of ceramic filters. Ceramic filters generally have the ability to clean more water over their useful lifetime than plastic membrane filters, but are larger and more expensive. They are also more fragile since the filter media is brittle and heavy. Ceramic filters are easy to clean, usually requiring nothing more than wiping the media off with a clean sponge or scouring pad. Sometimes scrubbing with a toothbrush is needed to clean the surface and restore the flow rate. Several brands include a mesh or cloth sock over the filter itself as a prefilter. 

Variations in manufacturing will change the size of the pores, changing how effective they are at removing contaminants. Some of the simpler and cheaper ceramic filters are quite popular for NGO's (like Potters for Peace) to distribute or produce in third-world countries as a reliable and moderately effective method of cleaning water. Sometimes just getting the majority of the pollutants out can make a big difference.

Plastic filters
Plastic filters such as the Life Straw, the Sawyer Mini, and the Platypus use a series of tubes and the force of gravity or suction to force the water through them. The brands I listed are not the only ones on the market, but they are the ones with the best consumer and lab ratings. I tend to avoid buying life-support equipment made in factories in China and Mexico, since they don't seem to have a good grasp of the concept of quality control.

Micro-filtration/ Ultra-filtration
Micro-filtration uses very tightly controlled pores in a plastic membrane to allow very small things like water molecules to pass through, while rejecting anything bigger than the pores. There are two different modes of operation;

• Laminar flow: the raw water is passed over the membrane and the filtered water (filtrate) is collected while the contaminants are carried away by the flow. This wastes some water, but doesn't require as much maintenance.

• Radial flow: the raw water is forced through the membrane and the contaminants are trapped in or on the filter membrane. This method requires back-flushing to clear the membrane.

Reverse Osmosis (RO)
RO is a higher form of micro-filtration, capable of separating water from even dissolved solids like salt. RO requires high pressures to force the water through a semi-permeable membrane, and it is both slow and energy-consuming. Most RO units are laminar flow systems that force the raw water along the surface of the membrane: a portion of the water passes through the membrane and the impurities are carried away in the left-over water as a waste stream. Be aware that the waste stream can concentrate chemicals enough to be a hazardous waste, although that's normally only a problem with very large RO units. Maintaining RO systems consists of replacing the filter modules when they get fouled too badly.


UV light sterilization
Fairly new technology, UV light destroys microorganisms by disrupting the DNA within the individual cells. The main advantage to using UV light is the speed with which it kills microorganisms, usually measured in seconds. Industrial and municipal treatment plants use large UV light sources to disinfect water and there are a few rechargeable personal-use UV devices on the market. UV will not affect chemicals to any noticeable extent.


Ion exchange
The average water softener is a good example of ion exchange technology. Using resin beads of two types (anionic, or negatively charged, and cationic or positively charged) mixed together, they trap dissolved chemical contaminants based on the ionic charge of the chemical. The common pitcher-style home filters like Brita, Pur, and ZeroWater are ion exchange filters with a carbon stage to help remove bad tastes. The small household filters of this type are disposable, since they have no provision for regenerating the resin once it becomes saturated with impurities. Large ion exchange systems keep the anionic and cationic resins separate and are regenerated using strong acids and bases to knock the trapped impurities off of the resin, then rinsing them to remove the acid or base. Ion exchange methods will have little to no effect on biological contaminants by themselves.

Next week I will examine, in detail, some of the possible sources of raw water and what you may expect to find in them. This should help you decide what level of treatment you're going to need and what to look for in a filter.

Purifying Water with Bleach, part 2

Not actually Erin.

Picture by KJ Photography

& is used with permission.

Last month I was asked about how to purify stored water. This woman's concern was that the water was good enough coming out of the tap, but she was worried that long-term storage would result in bacterial growth which would render the water undrinkable.

Purification of water is something that we've covered extensively on this blog, and one of the earliest articles we made on that topic was Chaplain Tim's essay on using bleach to neutralize a toxin produced by an algal infestation of Toledo's water supply.

While filtration and boiling are still the best and easiest methods to purify water, sometimes they just won't work, as in the Toledo case. In that situation, the toxin was left behind by the algae as it died off, and even though filtration would remove the algae itself it would still leave the toxin behind. Worse, boiling the water would concentrate the toxin, actually making the problem worse!

I encourage you all to go read Tim's article, as it explains the chemistry behind why this works and how you should use it. Still, if you're like me and your eyes get a bit watery at all the math, I present to you this handy cheat sheet for storing and purifying water.

I don't recall where or when I found this image; all I know is that it was years ago during a web-wander. If you know where it's from, please let me know so I can give credit where due.

I added my own notes to this to enhance usability. We have teaspoons in my kitchen, but not 1/4 or 1/8 tsp and I don't trust my eyes to be able to accurately eyeball those amounts, so I used Tim's math from his post to convert their measurements into units I could use, which were drops.

Please note: This chart is for standard bleach, not concentrated bleach! Concentrated bleach is 8.25% NaClO (sometimes listed as Sodium hypochlorite) instead of the standard 5 to 6% solution, so you need to use less of it. According to his article, it's 4 drops of bleach to the gallon for clear water instead of the listed 8.

A few things I want to point out before I wrap this up:

• Cloudy water is treated the same way as clear water because, as the text above indicates, you need to filter cloudy water before drinking it. 
• If for whatever reason you can't filter it, I would treat it as surface water. 
• Surface water gets special treatment because there's no telling what's in it. See this article for more explanation. 
• Cold water needs more bleach because the cold inhibits chemical reaction. For a great example of this, do an experiment: take two mugs of water, one from the tap and one hot from the kettle or microwave, and stir in an equal amount of powdered coffee or cocoa. Watch how the hot water absorbs the powder easily, while the cold water causes the powder to clump. The same principle applies here. 
• Allow at least 30 minutes for the bleach to do its job! If the water is cold, make that 60 minutes. 
• The human nose can smell chlorine in water at a ratio of 3 parts per million. A ratio of chlorine to water which makes it safe to drink is 5 ppm. Therefore, if you can easily smell the chlorine without it being supter-strong, it's safe to drink. 
• Chlorine loses its effectiveness years, becoming inert in 5 years. Powdered bleach lasts longer, although I don't know by how much. Here are directions on how to make your own bleach, although be advised that it will be more diluted than commercial versions. 

Water Purification Basics, Part 2

When I started this series on filtration and other methods of treating water to make it fit to drink (the proper term is potable), I asked a series of questions on this blog about what a prepper might need from a water filter. In this post I will address the first two questions in more detail, and will cover the rest as I continue the comparison of treatment methods.

Those first two questions were "How clean do you need your water?" and "What is in the water that you need to remove?" For water to be considered potable, it must be free of any impurities or contaminates that would cause you harm when you drink it. That is the standard I use for how clean I need my water: will drinking it make me ill?

These questions are tightly linked due to the many sources of water available and their variations in toxicity. 

1. Rainwater, snow melt, condensation, and water from deep wells are the least possibly contaminated sources that may be available. 
2. Clear running water, like a mountain stream, is the next cleanest...
3. ... followed by cloudy or dirty running water. 
4. Shallow wells are prone to contamination from anything that hits the soil above the well, so I rank them below cloudy running water. 
5. Stagnant or standing water is the most likely to be contaminated. 

Water that is supplied by a municipal (city or district) water treatment plant should be safe, but they are not infallible. There have been several “boil orders” issued in recent years for water that went through a municipal plant and wasn't fit to drink.

As a general rule of thumb, the closer you are to the origin of a source of water the better chance you have of it being clean. Rivers and streams collect contaminants as they flow toward the ocean. The poor folks that live downstream are going to have to work a lot harder to clean their water than the people upstream.

The EPA breaks contaminates down into six different categories that can be condensed into two --microorganisms and chemicals -- and that's how I deal with them. Most portable filters are rated for microorganism removal, with a few adding a carbon stage to remove some chemicals.


Microorganisms
Microorganisms are treated either by filtering them out of the water or by killing them. Because they are considerably larger than chemical contaminates, they are easier to remove. I'm not going to list all of the possible bacteria, viruses, and parasites that can be transmitted through water since they are going to vary from location to location. There is one exception, however: Escherichia coli. E. coli is fairly easy to detect in a lab and is used as a standard for microbial contamination. Everyone has heard of E. coli, a form of bacteria that causes gastric (gut) illnesses when consumed. Most of the cases that make it into the news are from tainted, under-cooked meats or vegetables, but it is also often found in water. E. coli is a naturally occurring bacteria found in the digestive tract of mammals, and it survives outside the body quite easily. There is a threshold value to the amount of E. coli (and similar bacteria, all lumped into the phrase “coliform” or “fecal coliform”) that your body can handle; get too much, or the wrong type, and it will bring on nausea and diarrhea until/unless your body can kill off enough to get back into balance.


Chemicals
Chemicals are removed from water by breaking them down using heat or other chemicals, separating them out with a reverse osmosis membrane, or adsorbing them in a carbon filter. There are limits to how much of a chemical a body can tolerate, which vary by which chemical you're looking at. Some chemicals are dangerous in small amounts, with immediate consequences; others can be tolerated in larger doses over longer periods before they have an effect. Cyanide is immediately deadly in small doses, but lead can be ingested in for years before effects show. Heavy metals (lead, mercury, cadmium, etc.) are a widespread hazard that can have serious long-term effects on your health. Volatile Organic Compounds (VOC) are common solvents, pesticides, herbicides, and fuels that are sometimes found in water.

I need to make a definitive statement about filtration: 100% purity is not economically possible for preppers. There is no cheap way to get to zero contaminants, despite what some politicians and managers may say. (Chemically pure water is a pain to work with, anyway. It tends to dissolve metal pipes and containers.) 

With advances in technology, detection limits for most chemicals has gone from the parts per million (ppm) to the parts per billion (ppb) or even parts per trillion (ppt) range. To give some perspective, 1 ppb is being able to find one specific tire out of all of the cars registered in the USA, and 1 ppt is being able find one specific ¼ inch crack in a paved road stretching from Boston to LA.

1% = 10,000 ppm= 10,000,000 ppb=10,000,000,000 ppt. 

• Since they can reproduce, removal of microorganisms at 99% is bad. 
• 99.9% is still potentially dangerous.
• 99.99% is bare minimum.
• 99.999% will handle most contaminants.
• 99.9999% is good.
• 99.99999% is about the best you're going to find. No one thing is going to remove 100% of everything potentially present in water. You may see these percentages listed as “four nines” or “log four” (for 99.99%) removal.

Chemical removal will usually be listed as a percentage removed. If you don't see a log or percentage rating, you may see a micron rating for the filter element. Since most bacteria are around 0.2 to 2.0 microns in diameter, you'll want to look for a filter capable of 0.1 micron or better. Large organic molecules will range from 0.1 to 0.01 microns, while minerals and simple chemicals will range from 0.001 to 0.0001 microns. 

Top Names

I've been looking at various filtration systems that are on the market and here are some of the claims of removal efficiency. If I still worked in a lab, and I had the budget, I'd be tempted to test a few of these claims. Here are some of the common ones by brand:

Berkey
Berkey is one of the big names in the water filter market, but they're not cheap. They insist that their units are water purifiers, and not just filters, which is fair since they use more than one type of treatment to purify water. They claim:

• log 5 removal of viruses
• log 9 removal of dangerous (pathogenic) bacteria
• greater than 95% removal of heavy metals
• VOC removal below detection limits

Sawyer
Sawyer makes a variety of things for backpackers and campers that also fit a prepper's needs. Their filters are a single-stage microfilter that traps everything larger than 0.10 micron and is rated only for microorganism removal:

• log 7 removal of bacteria
• log 6 removal of protozoa

Katadyn
One of the older names in water filters, Katadyn makes ceramic filters as well as reverse osmosis (RO) desalination units for a wide variety of uses. They are a bit shy about giving detailed specifications, but their ceramic filters are rated at 0.2 microns and their RO units are rated at 98.5% salt removal.

MSR
MSR makes a variety of camping gear as well and has bought the Sweetwater filter company. The Sweetwater uses a silica/carbon filter and is rated at 0.2 microns with some VOC and chemical removal by the carbon layer.


Please note that I am not endorsing any of these claims just yet. More info will follow, as next week I will delve into the physical methods used by the various types of filters and expand on the pros and cons of each. There's no magic involved in cleaning up your water before you use it, just a lot of technical jargon and marketing BS to dig through. I'll see what I can do to help make sense of some of it.