Reverse Osmosis Water

By Adam Calder

Ames residents are lucky to have some of the cleanest water in the country. Unfortunately, sustainable agriculture practices are not as wide spread as over-fertilization and pesticide use. Even though the water in the Ames area is safe and drinkable, there may still be certain things contained in the water that you may or may not wish to consume.

Fortunately, your local cooperative has just the thing if you are worried about water quality: a reverse-osmosis water vending machine.

Reverse osmosis works in the opposite way of regular osmosis (hence the name). In normal circumstances, if you had a large tank with salt water on one end, sand in the middle and fresh water on the other, the freshwater would slowly diffuse into the salt water.

This movement is caused by Brownian Motion, which is the name given to the movement of molecules caused by constant collisions with other molecules. If a body of water with a lower pressure is near (like fresh water) the osmosis would favor the movement of fresh to salt water because the salt would clog up its side of the semi-permeable membrane (the sand). The constant molecule collisions would push the fresh water out of its side of the tank, through the sand and into the salt water since there is nothing to clog up the fresh water side of the semi-permeable membrane.

In reverse osmosis, pressure is applied to the salt water. The water is forced through the sand, but the salt remains behind. Instead of a tank with a mix of the salt water and fresh water, you end up with all fresh water on one side and a pile of salt on the other. With the reverse-osmosis system at Wheatsfield, the “salt” left behind is a variety of contaminants that you do not have to consume.

‘Just what sort of contaminants do I have to worry about’ you ask? The reverse-osmosis system at Wheatsfield has six stages to filter out a variety of things.

The first stage, an activated carbon filter, removes chlorine and other particles that have an ionic charge and are therefore attracted to the activated carbon.

The second stage, a micron filter, gets rid of dirt, rust and other silt particles suspended in the water which are stirred up by fish, other aquatic life and the tributaries and watersheds that feed water reserves.

The third stage in the water purification system involves UV light being used to kill any microscopic organisms like plankton which may be living in the water.

The fourth stage is the actual reverse-osmosis stage to rid the water of salt, lead, sugar, proteins, dyes, fecal matter and any other solids that may be suspended in the water.

The fifth stage is another carbon filter to get anything the first one may have missed.

The final stage is another UV light bath that kills pathogens like amoebas and viruses. If you are interested in purchasing water at Wheatsfield, we have a variety of options for you. We sell refillable plastic containers in one-, three- and five-gallon sizes. These cost $.99, $21.99 and $26.99 respectively. Once you have purchased the containers, the refill price is $.39 a gallon. You may also bring in your own clean containers to refill if you already have some.