Is two step water purification needed? This could be in the event of a collapse of society, or on a hiking / camping trip.
There is a common misconception about filtration and purification. Filtration removes bacteria, protozoa and cyst, but does nothing to viruses. Purification affects bacteria, protozoa, cyst and viruses. Purification can be by any means – UV light, filters that remove a virus, chemical treatment.. etc.
Most water filters on the market have a pore size of 0.1 microns. The CDC recommends a maximum pore size of 0.01 microns for viruses. If a purifier says it has a pore size of .1 or .2 microns, it is only a filter. A virus will slip through a .1 or .2 micron filter.
What is two step purification?
It is when two separate steps are used to purify water. For example, my first step is to run the water through a filter. Such as the Katadyn Vario. Then a SteriPen is used to kill any pathogens that slipped though the filter.
When do I use two step purification?
For the most part, I only use two step purification when I am down stream from where people live. While camping on the Angelina River, I use two step. People living in rural areas usually have a septic system. Sometimes the systems over-flow and waste water will be on top of the ground. When a rain comes along, human waste is washed into streams, ponds, lakes rivers… etc.
While hiking in the woods there is no source of human waste, so rarely do I use two step. the biggest threat in nature will usually be from some kind of bacteria or cyst, such as cryptosporidium.
When in doubt, purify
I have a saying, “When in doubt, purify.” It only takes a few seconds to get the SteriPen out and purify a canteen of water. Aren’t those few seconds worth your health or even your peace of mind?