Disinfection with Potassium Permanganate

Potassium Permanganate is a very versatile chemical. It can be used for disinfection, removing hardness, removing iron and manganese. It has another health related use, it can be mixed into a paste and used as a topical salve for athlete’s foot (or similar problems). As a result potassium permanganate is a great addition to any emergency preparedness supplies.

Potassium Permaganate has the chemical formula of KMnO4, and it comes as a deep purple dry powder. This chemical is a very powerful oxidizer and it should not be stored anywhere near acids or fuel sources or it could result in fires, explosions and/or toxic gases being formed. Explosives is another use of this chemical (one which I will not be explaining here). This chemical can be stored for over a year if it is kept clean and dry and in a sealed container.


Before touching the dry powder, make sure you wear a particle mask (ideally a N95 or better). This chemical will irritate the airways if inhaled directly. Also the powder once mixed with water becomes a powerful dye. It will stain clothes permanently, stain skin temporarily and cause corrosion on any metal or masonry it touches. Anything that becomes exposed to a potassium permanganate solution becomes brown, a similar shade of brown to a henna tattoo.

To make a topical treatment with KMnO4 mix the dry powder with water until it has the consistency of playdoh. Apply the mixture on the affected area and repeat as necessary. Remember that I am not a doctor and I am not giving medical advice. I am only outlining that this chemical CAN be used for medical purposes. Whether or not you SHOULD use KMnO4 for medical applications is not something I can tell you.


Potassium permanganate is very similar to sodium hypochlorite in the sense that they both disinfect water through oxidation. Disinfection of drinking water can be achieved by adding it to the water until the water turns pink. The pink in the water is the residual potassium permanganate. Meaning that there is nothing left to use up the chemical and any bacteria has been used. Think of the pink water as being similar to the point where you can smell bleach when using sodium hypochlorite for disinfection. Just like with the smell point of bleach has surpassed the disinfection point, you do not need to keep adding KMnO4 until you see pink. Disinfection has occurred well before you can see a lasting pink tint to the water. Using the color change is a simple and easy to remember method for disinfection of drinking water. And if the pink tint disappears at any time then you know you need to add more of the chemical to redisinfect the water.
If you want to avoid pink water and spend less money on chemicals you can buy a testing kit for manganese. Most kits can measure the residual levels of KMnO4 at levels well below the pink water threshold and well above the disinfection requirements.


For better results with disinfection it is best to filter the water through a greensand filter. Now this is not an indication of the color of the sand (it is actually black in color). Greensand is an activated filter media designed for removing iron and manganese through a process called ion exchange. The good news with a greensand KMnO4 combination is that the potassium permanganate will reactivate the filter media.

One thing to note is that potassium permanganate once added to water will make the water more corrosive. If the water is very pink it can also stain any container it is stored in. The pink water is perfectly safe to drink. I mean the water is not dangerous because of the pink coloring. It may however be dangerous for another reason or contaminant.

Another thing to note about KMnO4, is that if you add it to chlorinated water it will form a percipitate (solid). This is manganese dioxide, it is harmless except it will consume all the available chlorine in your water leaving you open to contamination from microorganisms.

With a few simple precautions KMnO4 is an excellent chemical to have on hand. It can be stored longer than sodium hypochlorite (bleach) and it can be added directly to the water unlike calcium hypochlorite. It also is very easy to see when enough of the chemical has been added. If there is a lasting pink tint that doesn’t disappear with time then the water has been disinfected.

When it comes to disinfecting your own drinking water, always be careful with the quality of chemical you use. They are not all created equal. The north american standard for chemicals used in drinking water is NSF/ANSI 60. Choose chemicals that meet this standard above ones that don’t. The will be significantly safer for your health and well being.

As with all my disinfection articles, I will remind you to always drink the safest water you can and combining treatment techniques is the best way to achieve safe drinking water

Can I use a storm-water pond as a back-up source of water?

Storm-water ponds are the closest alternative source of water for many people living in urban areas. In an emergency this source of water may be all that is available to you.  Eventually any water you have stored will be consumed and the water in a storm-water pond may be the difference between life and death.  With the proper treatment your local storm-water pond can be a great backup source of drinking water.

Industrial storm-water pond (source: info.evergreen.ca)

Storm-water presents a unique set of challenges during treatment. Because storm-water ponds collect surface water, the water is exposed to all the contaminants on the ground in the catchment area. This includes but is not limited to pesticides and fertilizers applied to lawns, motor oil and gasoline leaking from vehicles and litter like cigarette buts. It all ends up is the storm-water pond. Those chemicals are already in storm-water ponds on a normal day. During an emergency there may be additional contamination from sewage runoff from an overloaded or broken sewage system. The water in the pond will also contain all the microorganisms like ecoli, giardia and cryptosporidium normally in surface water. Any one of these will make you very sick if you get infected with them.
Finally, there will be high levels of nitrates in storm-water ponds. Too much nitrates consumed by young children can cause blue baby syndrome.

The first step in treating water from a storm-water pond is straining. Straining the water through a cloth or loose sand filter will remove large particles (ones you could pick up with your fingers). Remove as much of the suspended particles from the water as you can. Straining the water first will extend the life of your proper water filter.

If you have a clarifying agent like aluminum sulfate, this is the best time to add it to the water.  It will make contaminants too small to be filtered become attracted to each other and become significantly larger.  Larger particles are easier to remove from the water. Let the water sit still for at least 30 minutes without disturbing it.  All the newly formed large particles (called floc) will sink to the bottom.  When you take the water from this container, make sure you leave the majority of the settled material at the bottom of the container.

Urban Storm-water pond (source: greenbmp.blogspot.com)

The next step is to filter the water. Filter the water even if it looks clear, the human eye is five times too weak to detect dangerous levels of particles. Filter the water at least once through an activated carbon filter. Activated carbon is known to remove many different chemicals from water including pesticides, chlorine and fluoride. Activated carbon is not the same as charcoal. Charcoal is similar, it can remove toxins from water but it is nowhere near the efficiency of activated carbon.

The third step is oxidation. Oxidation will help with disinfection as most disinfectant chemicals are also oxidizers. Chemicals like sodium hypochlorite and potassium permanganate are both oxidizers and disinfectants. Oxidation will break down many of the remaining contaminants and inactivate many of the remaining bacteria. Keep adding the oxidizer/disinfectant till you can detect a residual after 20 minutes. The 20 minutes is the minimum you should wait for a gallon of water. Wait longer for larger volumes. This is because oxidation is a chemical reaction that isn’t instant. It needs time to complete the reaction.

The fourth step is to filter the water again. Filtering again is necessary because the disinfection/oxidation step will create some potentially carcinogenic byproducts. We filter before oxidation to minimize the amount of chlorine (or other chemical) and to limit the possibility of forming dangerous byproducts. We filter the second time to remove any byproducts that have been formed.

The final step is to boil the water.  This will help with disinfection, but the main goal of boiling at this point is to remove any volatile chemicals.  Any chemical with a boiling point lower than water will be removed after boiling.

A note about disinfection.  If all of these steps are followed there is no need for a step dedicated for disinfection.  Between the oxidation and the boiling of the water any microorganisms will be inactivated.  If you are storing the water for a long time then add some sodium hypochlorite for a residual disinfectant.  The residual disinfectant will prevent the water from becoming recontaminated before you drink it.

One additional possible step is to aerate the water.  Ponds are frequently stagnant.  Stagnant water is green with algae, it smells bad and tastes worse. After the water is made potable, transfer the water back and forth between two glasses. This adds oxygen to the water and will make the water taste better.

This may seem like a lot of work for something as small as a storm-water pond.  What I have described are the basic steps to turn the potentially toxic water in the pond into clean and safe drinking water.

Disinfection Of Water Using Ultraviolet Radiation

Ultraviolet light is a very popular method of disinfecting water.  UV radiation is part of the electromagnetic spectrum that has incredible properties for the killing of microscopic organisms.  While there are varying degrees UV resistance within microscopic organisms, not one has yet been able to develop a total resistance.  Because UV disinfection systems are not chemical or biological they have an extremely long shelf life.

The Electromagnetic Spectrum with a UV Focus (From: agtuv.com)

There is a wide variety of ultraviolet disinfection systems that range from the size of a pen to large banks of meter long light bulbs and many options in between. UV systems tend to be very simple to install and operate and UV leaves nothing behind and there are no disinfection by-products from its application.  In fact ultraviolet radiation can break down some potentially harmful chemicals like chlorine and chloramine compounds.

Ultraviolet Lamp (from: halmapr.com)

The limitations of UV disinfection are; distance, time, turbidity and electricity.

Proximity is critical for UV disinfection, the water needs to be very close to the UV light source. The farther away the water is the more radiation is absorbed by the water. Meaning that with increasing distance you get weakening disinfection.  Proximity becomes even more critical in hard water.  Hard water sources leave a white chalky residue of calcium carbonate which covers the UV light bulb, making the radiation emitted significantly weaker.

Time is another significant limitation of UV disinfection. The amount of time pathogens spend in the UV greatly affects whether or not the pathogen is neutralised. This is similar to how people get worse sunburns the longer they are exposed to the sun.  Time is directly related to the flow of the water, if the flow is too much, the water will not spend enough time exposed to the radiation and will not be disinfected.  Slow moving water or even static water is best.

The efficiency of UV disinfection is greatly reduced by turbidity. Turbidity physically shields the organisms from the UV light. Exactly the way a beach umbrella shades people from the sun. This is called line of sight disinfection.  There is no disinfection in the shadows when using UV radiation.

Electricity is another limitation of UV disinfection systems.  They are limited in two ways by electricity.  First by the fact that  they are quite literally light bulbs placed underwater and secondly by fluctuations in the electrical source cause fluctuations in the UV radiation field emitted from the bulbs.  Both these problems are easily overcome.  By sealing the system in clear waterproof chambers can effectively keep the system safe from the water.  Fluctuations in the electrical source can be minimized through proper system design and using fresh/charged batteries in battery powered systems.

SteriPen Portable Ultraviolet Disinfection (from wikipedia.org)

Portability is a mixed blessing with UV disinfection systems. Smaller, pen-like devices are easy to transport, but are significantly less powerful. That means they need to be used on slower moving/still water and used for longer than larger UV systems.  Another mixed blessing of ultraviolet disifection is the fact that there is no disinfection residual left in the water.  Not having a disinfection residual is great if you are drinking the water immediately, otherwise recontamination can occur very quickly after the UV lamps are shut off.  UV is not enough if you plan on storing the water for a long period of time.

Recirculating the water to be disinfected a second or third time will greatly increase the chances of proper disinfection.  Remember that disinfection whether by UV or chlorine or any other method is one of the final stages of water treatment.  Forgetting to filter the water first will make disinfection significantly more difficult.  Regardless of the size of the of the system used, ultraviolet radiation can be used to supplement any water treatment process.

How Does A Water Filter Work?

Whether you are building, operating or just buying a water filter, filtration is an essential part of most water treatment processes. Filtration is used in the counter top/faucet filter all the way up to municipal water treatment facilities serving tens of millions of people. Even in emergency and survival situations filtering with a shirt or other cloth is often the first thing recommended for water treatment. A shirt isn’t adequate on its own by a long shot, but it is better than un-filtered/untreated water. Used in conjunction with other water treatment steps, filtration makes the rest of the disinfection process significantly easier and cheaper.

We filter water primarily as part of the disinfection of water. Disinfection is the inactivation and removal of pathogenic organisms. Filtration is part of the removal portion of disinfection. (The other part being settling or clarification).
Filters work to physically remove contaminants from the water. They do this by passing the water through a filter media. The media presents a barrier to solids in the water. They literally collide into each other and become trapped. The media can be made of almost anything. As long as it has the ability to let water through and preventing solids from passing through. The pore size (size of space between the media) dictates the performance of a filter. The smaller the pore size the more that gets removed from the water. That sounds like smaller is better, but small pore sizes reduce the rate you can filter water and the total volume of water you can filter. It is always a trade off between ability to remove contaminants from the water and the ability to filter larger volumes of water.

Below is a diagram of pore sizes and which contaminants can be removed at a given pore size. Filters with smaller pore sizes tend to be more expensive. They require precise manufacturing techniques and maintenance.

Particle Size Diagram And How Fine A Filter Needs To Be To Remove Them

This trade off lead to the development of chemically assisted filtration. The filter media and the water itself is treated with chemicals. The water is treated with chemicals to make the particles in the water larger called floc (large groups of particles stuck together). At the same time the filter media is treated with a chemical to make the media attract and trap the particles in the water. Most chemically assisted media, has a electro-static charge opposite the one in the floc. Typically the media has a positive charge and the floc has a negative charge. Now instead of waiting for the particles to collide with the filter media, the floc is attracted onto the surface of the media (adsorbtion) and into the filter media itself (absorbtion). These types of filter media are said to be activated. Below is a diagram outlining the difference between straight filtration and chemically assisted filtration.

Direct Filtration Versus Chemically Assisted Filtration

Continue reading

PurifiCup Natural Water Purifier Product Review

When camping or hiking or even during an emergency drinking water becomes very important (water is important everyday really). You can store water easily if you don’t have to travel or evacuate, but carrying enough water if you are on foot is very difficult and very heavy. There is a need for a portable, simple, effective way to make safe drinking water.

PurifiCup is a commercially available portable water solution. I had the opportunity to test one and I put it up against some laboratory tests and my own personal judgments. It is very simple to use and is compact enough to fit into any bag and most cup holders.
This filter fits perfectly over wide mouth Nalgene bottles and screws directly onto standard water bottles. This product is very versatile and that makes it useful in a wide variety of situations.

PurifiCup Natural Water Purifier over a Nalgene Water Bottle

Some useful statistics on the PurifiCup. The cup is 10 fl oz, and it can filter 100 to 150 cups before it needs a new cartridge. It is 7.3 cm in diameter and 16 cm in height. The filter media includes ion exchange resins, activated carbon and nanoscale silver coating membrane.  The PurifiCup retails for $59.99 for the cup and filter, and replacement filters costing $13.99

Normal filters treat water by physically removing suspended materials in the water. A good physical filter removes particles as small as 0.2 microns. This will make the filter capable of removing all sizes of bacteria (but not all viruses).

The PurifiCup however isn’t a normal filter. It for one doesn’t filter below the 1.0 micron level. That is not rearly fine enough to remove all types of bacteria. This may seem like a bad thing, but the Purificup does something that no other portable water filter does (that I am aware of). The PurifiCup disinfects as it filters the water with a nano-silver membrane. Nano-silver has been shown to kill over 600 different types of bacteria.

What I wanted to know was, in a real world setting does it work? Does the product come close to meeting the claims? I tested the PurifiCup’s ability to remove turbidity, chlorine, color and its ability to kill bacteria.

PurifiCup Packed Up For Storage Or Travel

I took a sample of treated water to measure chlorine removal. The water sample I chose here is typical municipal drinking water. I also took a sample from a nearby river. This river represents a typical backup water source that could be used while hiking or in a survival situation.

There was a chlorine residual of 2.03 mg/L to start with. After filtering with the PurifiCup chlorine was reduced to 0.16 mg/L. To put it simpler, there was a 97% reduction of chlorine in the tap water. That level or chlorine reduction is amazing.

In the river sample I tested trubidity and color. Turbidity is the measure of suspended particles in the water, or the measure of the cloudiness of the water. Color is the measure of clarity of water, how close to perfectly clear is the water separate from suspended particles.
(Science Note: turbidity measures the scatter of light through the water sample and color measures the absorption of light by the sample). If you think of loose leaf tea, turbidity is the leaves in the water and color is the brown tint the water takes on. In general the lower the turbidity an the lower the color the safer the water is to drink (this is NOT always true).

The river sample started with 18.4 NTU (Nepheletic Turbidity Units) and after filtration it was 4.72 NTU. To put a little perspective to these numbers anything under 5NTU is invisible to the naked eye and at my water system I am not allowed to go over 1NTU. There was a 75% reduction in turbidity. The remaining turbidity is not terribly impressive but expected from a filter of 1.0 micron. Remember, the PurifiCup doesn’t claim to physically remove everything from the water.

Color is the final parameter I tested. Color isn’t in itself a health related property of water. A lot of color doesn’t necessarily mean the water is unsafe to drink. Removal of color however is a good indicator of the removal of many dissolved chemicals. The Color of my river sample was 128 (there are no units for color). The PurifiCup reduced that number to 81. Therefore 63% of the color was removed. This may not seem like a lot, but color is one of the most difficult things to remove from water.

Now for the parameter I was most curious about on a professional and personal level. Bacteria; does the PurifiCup actually disinfect water? I had to send this to an external environmental laboratory as I don’t have access to a biological lab. This limited the number and types of bacteria I tested. I chose to test for heterotrophic bacteria (heterotrophic plate count or HPC). These bacteria are not pathogenic, but they are resistant to many treatment processes and that makes them an excellent indicator of treatment success. I tested the HPC of the river and PurifiCup effluent.
First, bacteria tests are measured in colony forming units (cfu). A cfu is a group of bacteria that group into a visible blob (colony) of bacteria. The raw water from the river had a cfu count of 800 and the treated water had a cfu count of 500. 500 may seem like a lot, but it is a misleading number. Remember the disinfection doesn’t mean the killing of all bacteria, that’s sterilization. Disinfection is the removal or inactivation of pathogenic bacteria. Inactivation stops the ability of bacteria to reproduce and cause disease. Like I said before 500 cfu may seem like a lot. But these 500 cfu were inactivated. Remember the 1micron filter? A lot of bacteria go through the filter, but unlike the raw sample the 500 cfu didn’t grow. So while 500 cfu is a big number, they are not able to cause disease. The PurifiCup made the sample significantly safer to drink.

I highly recommend this product as part of a water purification system.  The portability and low cost of the PurifiCup makes this product a simple addition to your emergency preparations or for an avid outdoors-man’s kit.

What To Do When Your Backup Water Is Contaminated

Storing water in case of an emergency is a good idea. Having a reserve enables people to weather emergencies and minor service disruptions. A backup source of water is essential for emergency preparedness, three days without water will lead to death from dehydration, but serious and lifelong complications can occur well before you die from dehydration. Did you know that water sometimes needs to be retreated because clean water becomes contaminated? Water typically gets re-contaminated as people use water and they aren’t careful enough to prevent re-contamination, think about when you are washing up, hands are dirty and that leads to contamination of your stored water. Also a lot of stored water is stored for a long time “in case of emergency”. The problem with long term storage is the disinfectant residual deteriorates with time, reducing the water’s ability to prevent bacterial growth.

Preventing contamination is easier than removing contamination. Leave your stored water is a sealed and preferably airtight container. This physical barrier will stop bacteria in the environment from coming into contact with your drinking water. Next is to only open your reservoir with clean hands. Preferably washed with soap and water. It is better to pour the water you need for clean up before you make a mess. This is actually very important when you go to the bathroom, microscopic pieces of fecal matter on your hands will transfer to everything you touch, including the spigot/lid of your reservoir. Bacteria in that fecal matter will travel up the spigot into the water, it will only be a matter of time. Clean hands and routinely cleaning the exterior of your water storage tank/bottle/container/reservoir are essential to prevent contamination.

Another way to help prevent contamination is Continue reading

How to Make a Solar Water Distiller

Distillation is sometimes the only possible for of treatment to purify water. After disasters and during emergencies there are times when there isn’t enough fuel for boiling, or there isn’t a suitable container available to place over an open flame.  In a true end of organized society situation or even just disruptions to the supply chains, replacement water filters will not be available and new supplies of disinfection chemicals will disappear.  Even backup sources of water need to be disinfected.  This is something everyone with have to deal with and a small solar distiller can be built by anyone.  Solar water distillers can be created using household items. What you need is a clear glass pot or bowl. As long as it is oven safe. A cup, also glass and tin foil. The tin foil could be better served with something clear, like the lid to your glass pot. Plastic wrap can work if it is thick enough to withstand the heat generated in the device.

The construction is simple:
1) Place the cup in the bowl.
2) Fill bowl with water. Do not go over the height of the cup. Less water will distill faster.
3) Cover the bowl. With the lid/tin foil/plastic wrap.
4) Place the still out in an area that receives a lot of sun.

Solar Water Distiller (Image Source: http://www.teachscienceandmath.com)

This is a solar still at it’s simplest, All you have to do is set it up in a sunny area and come back an hour later.  The main drawback is the volume of water treated, in this example you only get a cup of water every few hours.  There are additional things you can do to increase the effectiveness and the efficiency.  The first thing you can do is add another cup, or two to collect more of the distillate.  If your bowl has a lid with a handle in the centre, place the lid on the distiller upside down with the handle pointing into the cup.  This should look like a funnel (of sorts) and it will direct more distillate into the cup.

Keeping the water shallow will heat it up faster, using a wider bowl or tray will help with this. There is a balance however to be kept to ensure the water condenses into the cup, which is favored by a narrow bowl.

Placing the still on a black piece of metal will also greatly assist in the heating of the water. You could also place something black and metal in the water or paint the bottom of the bowl. The point is, black surfaces heat up faster.

There are specifically designed lab glassware for distillation. If you can buy these, I suggest you do as they will be your most efficient, and can be placed over a flame if you buy the right ones. The piece that is most useful is the condenser tube. The collection of the distilled water is much more efficient with a condenser tube.  Collecting the distilled water in another container allows for faster distillation due to a rapid drop in temperature from the heated vessel to the cooling vessel.

Laboratory Distillation Setup (Image Source: http://kids.britannica.com)

There is only one type of contaminant not removed by distillation, those are volatile chemicals with a boiling point less than water.  Volatile chemicals are usually dissolved gasses in the water, they aren’t removed by distillation because these chemicals follow the water through the phase change to a gas and back again into a liquid.

Distillation has another big problem in my opinion.  Distilled water tastes bad.  You may have different tastes than I do, if you do then go ahead and drink distilled water.  Now taste is a luxury in a survival situation and drinking bad tasting clean water is better than contaminated water.  As I say at the end of all my emergency water treatment articles, always drink the safest water possible.  This is another water disinfection tool you can use when you really need it.