posted April 07, 2004 09:14 PM         

I'm wondering if anyone else knows how to make fresh water in their own home? How do you turn dirty nasty rain into pure drinking water? Would you care to explain?

posted April 07, 2004 09:50 PM         

In many many instances, harvesting rainwater makes a great deal more sense than pumping our precious aquifers dry. I think it's great that you are interested.

Here's some of the filters we learned about at E.A.T.-
*Charcoal- removes some bacteria, some particles
*Mesh- particulates(dirt, clay)
*Ozone- finer particulates
*Utraviolet light (75-100 watts)- bacteria
*Reverse osmosis- bacteria, minerals, majority of chlorine

Add limestone to bottom of collection tank for acid rain

As for collection- Here's a good picture I found-

I wish I could find a picture from Bill Mollison's "Permaculture- A Designer's Manual" He illustrates an simple but innovative pully system for discarding the first wash of the roof before diverting it to the tank. I can't recommend his book enough if you are interested in permaculture.

posted April 07, 2004 10:54 PM         

juniperb

posted August 24, 2008 05:06 PM         

At the moment I can't afford a reverse-osmosis system for my home, but I started buying reverse-osmosis filtered water at Whole Foods a few months ago. I was astounded at what this process can do to nasty city tap water -- it tastes WONDERFUL!! We drink/cook about a gallon and a half per day at our house, at a cost of about 49 cents per gallon. I have noticed a subtle change in the way I feel when I drink this water consistently -- and I think it's the heavy metals and fluoride etc being filtered out that has improved my vitality, and even my skin

Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. More formally, it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure. This is the reverse of the normal osmosis process, which is the natural movement of solvent from an area of low solute concentration, through a membrane, to an area of high solute concentration when no external pressure is applied. The membrane here is semipermeable, meaning it allows the passage of solvent but not of solute. This phenomenon is commonly noticed in case of the water falling from the leaves of a tree.

The membranes used for reverse osmosis have a dense barrier layer in the polymer matrix where most separation occurs. In most cases the membrane is designed to allow only water to pass through this dense layer while preventing the passage of solutes (such as salt ions). This process requires that a high pressure be exerted on the high concentration side of the membrane, usually 2–17 bar (30–250 psi) for fresh and brackish water, and 40–70 bar (600–1000 psi) for seawater, which has around 24 bar (350 psi) natural osmotic pressure which must be overcome.

This process is best known for its use in desalination (removing the salt from sea water to get fresh water), but it has also been used to purify fresh water for medical, industrial and domestic applications since the early 1970s.

When two solutions with different concentrations of a solute are mixed, the total amount of solutes in the two solutions will be equally distributed in the total amount of solvent from the two solutions.

Instead of mixing the two solutions together, they can be put in two compartments where they are separated from each other by a semipermeable membrane. The semipermeable membrane does not allow the solutes to move from one compartment to the other, but allows the solvent to move. Since equilibrium cannot be achieved by the movement of solutes from the compartment with high solute concentration to the one with low solute concentration, it is instead achieved by the movement of the solvent from areas of low solute concentration to areas of high solute concentration. When the solvent moves away from low concentration areas, it causes these areas to become more concentrated. On the other side, when the solvent moves into areas of high concentration, solute concentration will decrease. This process is termed osmosis. The tendency for solvent to flow through the membrane can be expressed as "osmotic pressure", since it is analogous to flow caused by a pressure differential.