Quick Guide on Water Purification – Germs in Water

Do you get confused by the various different technicaI terms that water purifier manufacturers use?

Terms like :

  • Turbidity
  • Crysptosporidum
  • Giardia
  • E.Coliform

It is absolutely essential that you understand terms like these before you buy a water purifier, in order to be able to cut through the marketing language the brands use and truly understand what a product can and cannot do.


Unless, that is, you want to be at the mercy of other opinion/product review articles on the internet- some of which aren’t always accurate, some of which are downright misleading. Like I always say, knowledge is power. Let’s start from the biggest to smallest contaminants in size.

#1  Turbidity

Turbidity or cloudiness in water is caused due to visible contaminants such as mud, sand, silt, etc and can be removed by a simple mesh filter or by letting them settle down. Turbid water hinders the purification process and encourages growth of germs.

 #2  Bacteria

Bacterial contamination in water usually occurs from human or animal waste. They vary in width from 0.2-1 micron(micrometer). Common bacteria that most labs will test for are E.Coliform and  Legionella. E. Coli indicates fecal matter contamination in water and is 0.5 microns wide. A Legionella cell, on average will be about 0.5-1 micron wide and can cause Legionnaires disease.

#3  Protozoa and Cysts

Protozoa(such as Cryptosporidum, Giardia) are unicellular germs that usually enter water supplies through sewage or animal waste and can cause gastrointestinal diseases, diarrhea, etc.

Cysts are a stage in the life cycle of some protozoa, which form a protective wall around themselves. It can be hard to remove cysts from water using conventional methods such as chlorination.

The good news is that, Cysts and Protozoa are both are bigger than 1 micron in size, so you can rest assured that any mechanical filter media (such as Lifestraw, Sawyer) that filters out bacteria can filter out protozoa as well.

#4  Virus

Viruses are the smallest contaminants in water, ranging in size from 0.005-1 micron. They are tough to kill and can stay dormant in frozen water for a long time. A lot of water filters do not filter out viruses. Talking about membrane based systems, only Ultrafilters and Nanofilters can claim a considerable reduction in virus in the water source. Reverse Osmosis, of course will completely remove viruses.

If you take away one thing from this article, it should be the knowledge of the sizes of different kinds of germs in water. This will help you make a decision on whether the water purifier you are going to buy can actually filter out these contaminants or not

For Part-2 of the Guide on Water Purification, go here.

Any questions? Jump into the comments section below and I will answer them soon enough!

Live Better,


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