In the normal osmosis process, the solvent naturally moves from an area of low solute concentration (high water potential), through a membrane, to an area of high solute concentration (low water potential). The driving force for the movement of the solvent is the reduction in the free energy of the system when the difference in solvent concentration on either side of a membrane is reduced, generating osmotic pressure due to the solvent moving into the more concentrated solution. Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis. The process is similar to other membrane technology applications.
While reverse osmosis systems are widely used for industrial and commercial purposes, smaller home units can be purchased and installed under the kitchen sink and dispensed through the faucet. Home RO units typically run on a 3-stage system which includes a carbon filter, RO membrane, and re-mineralizing filter for taste. Some systems can include 5, 7, or even 10 stages. While the additional stages offer extra benefits such as pH level balance and UV filtration, a simple 3-stage system has everything required to produce pure, drinkable water. RO systems require frequent maintenance and replacement of filters in order to keep it functioning properly. Read our article on reverse osmosis systems for home use for a detailed guide on how they work and which brands to use.
• Snow: The energy it requires for your body to absorb the water from snow is high. Instead of eating the snow, melt it first. This can easily be done over a fire or with a camp stove. If those aren’t options, use the sun. Accelerate the process by chopping up ice and hanging it in a water bag in direct sunlight. If there’s no sun, use your body’s heat.
The first part of the purification tag team must eliminate microorganisms, like harmful bacteria and parasites. There are a handful of tried and true methods for doing this. The most familiar is boiling. Simply bringing water up to its boiling point of 212 degrees Fahrenheit will kill almost all microorganisms, so just a few minutes of boiling will do the job.