What is Turbidity in Drinking Water?

Turbidity is a water quality term that refers to the cloudy appearance of water caused by particles, or 'suspended matter'. 

Let's look at this like a good bottle of wine.  Have you ever got to the end of a bottle of wine and found sediment?  That sediment is a by-product of wine making and is a great example of particles that are no longer suspended in the wine; they have fallen out of solution.

With turbidity, the particles of matter never fall out of solution; they are permanently 'suspended' in the water. Even gravity doesn't affect them.

The best way to identify turbid water is when it is contained in something with a white background, like a toilet bowl or bath tub.  You can see that the water has a slight tinge of colour to it or looks a little hazy but you can't actually see what is causing this discolouration.  That's because the particles are too small to be seen without magnification.  

What size is turbidity?

To put this in perspective, the human eye can only see particles down to 40 microns.  A micron is 1/25,000th of an inch in size.  A human hair is 75 microns in size. Turbidity doesn't have a specific size because it is made up of so many different things but suffice to say, it's pretty darn small and can get down as small as 1 micron.  The amount of turbidity in water is measured in terms of NTU or more simply TU - turbidity units. 

Water turbidity is a normal function of nature usually resulting from debris that water picks up as it travels through streams and rivers.  However, turbid water may contain a variety of particles, including:

- Clay
- Asbestos
- Bacteria and viruses
- Debris from plants, animals and biofilms
- Bio-colloids, including proteins and complex carbohydrates from plants
- Corrosion products, such as rust, lead and copper oxides
- Lime scale

Is turbid water dangerous?

It is so important to remove turbidity from water before it is disinfected that waterworks facilities in Canada are mandated to test every day for the presence of turbidity.  The safe drinking water standard in Canada is 1 NTU or less.

While turbid water is not necessarily harmful, it can be a sign of more serious problems.  Particles in turbid water interfere with the disinfection process because they shield harmful water contaminants, such as viruses and bacteria, from destruction by the disinfectant. 

In addition, turbidity particles adsorb other dissolved water contaminants and carry them through the system. Turbidity particles known to be harmful themselves include asbestos, lead, bacteria and viruses, and protozoan cysts such as Giardia and Cryptosporidium.

Although water is tested and treated for turbidity before it leaves the waterworks facility, water can pick up turbidity particles on its way to your faucet.

Removing turbidity

Turbidity problems are easily solved with point-of-use (POU) water filtration systems specially designed to remove small particles. Activated carbon is especially effective because it can remove many things by adsorption onto its enormous surface area.

It is important to look for a model that is certified by NSF International to Std. 53 for turbidity.  NSF is an independent testing agency that sets product standards and certifies the performance of POU systems.

All Everpure Residential Drinking Water Systems are NSF certified to standard 53 for turbidity reduction as well as cysts, such as Giardia and Cryptosporidium.