Why is my water that color?

As someone who works in water treatment I fequently receive questions about red, black, pink or cloudy appearances in drinking water. Contrary to what might be expected none of these colors are inherently dangerous to human health. They do however make the water look unappetizing. They are called asethetic water quality indicators. Well the colors themselves isn’t the indicator, what causes the water is. I will outline the causes below.

Red water is usually caused by the oxydation of iron and iron bacteria. To be a little more accurate the color is a reddish brown, if you see a red that belongs in a paint can then I highly recommend NOT drinking it. Iron oxydation (rust) is not dangerous at all. Many water sources contain iron naturally. Iron is prevalent in groundwater. The red color comes from iron particles rusting when they come into contact with oxygen in the water. The rusting is accelerated when the iron is introduced to chlorine. As you know chlorine is very commonly used as a disinfectant. When there is a lot of iron and a lot of chlorine then there can be a visible particles of rusted iron in the water. This looks really bad when you turn on the faucet but iron is something they add to mineralized bottled water and iron is a necessary element in proper nutrition.
Iron bacteria can enter the water at the source or if the water is stored in a metal container or watermain. Wells can become contaminated with iron bacteria. When they do, read this to know what to do about it.

Black colored water is not to be confused with black water which is a term used for sewage. Sewage is often a yellowish brown, unless it has gone septic and then it is very black and very smelly. An odorless black tint to water is usually due to manganese. Manganese behaves a lot like iron does except it oxidizes a lot slower. Water stored for a couple days or more will turn black if there are high levels of manganese in the water. Manganese is more often found in groundwater than in surface water. Sometimes it wont be noticeable in the water. It will however be noticable as a black stain on appliances and reservoir walls.

Pink water comes from potassium permanganate (KMnO4). Permanganate is a treatment chemical used to help oxidize iron and manganese. When too much is added the water turns pink. When a lot is added then the water turns purple. The pink isn’t dangerous to human health. It is hower alarming to see pink coming out of a faucet. To read how to use potassium permanganate as a disinfectant read this.

To remove iron, manganese and permanganate is accompolished with greensand filtration. Don’t let the name fool you, greensand is black in color. Greensand is chemically activated to remove oxidized minerals from water.

A yellowish tint (sometimes brown) to the water IS potentially dangerous. Yellow tea colored water is indicative of organic material in the water. Organic material is mostly non living particles but it also includes bacteria, viruses, and other pathogens. Sewage is also this color. So beware of yellowish water.

Not many different things can cause a truely cloudy appearance to water. Turbidity is sometime said to be “cloudy” but it is caused by suspended particles blocking light from passing through. Usually turbidity is also colored at the same time. Unless the particles are white in color, then turbidity isn’t cloudy, it is dirty.
Cloudy water is caused from dissolved gasses (usually oxygen) in the water getting released. This happens when the temperature in the water is significantly different than the temperature of surrounding environment. Since large bodies of water are slower to heat up and slower to cool down, this difference happens every spring and fall. It is called reservoir turnover. The way to test if it is just dissolved gasses in the water is to let a glass sit for five minutes. All bubbles of gasses will disappear and the water will look and taste normal. If the water is still cloudy after five minutes, then the problem is caused by turbidity and it must be removed by filtration.

Not everything that can happen to drinking water is dangerous. Reddish tints from iron and blackish tints from manganese are natural and harmless. This article should help you determine when visual changes to the water are cause for alarm and when they can be ignored safely.

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.