I brag about Memphis water a lot, and while some around the globe may not have a lot of interest in Memphis, this article has value for everyone who is interested in drinking water quality.
Many in Memphis will quickly tell you that the reason water here is so good, is because of the Memphis sand (MS). But other than saying, “Oh, it filters the water and makes it pure”, very few can actually explain what the sands do, and why. So, I thought I would do that today.
First off, some will be surprised to learn that the MS has very little to do with the water’s chemical purity. In later articles we can discuss this aspect. Where the MS provides a great benefit is in clarity, color and the silt/particulate matter of the water. For years industry has used combinations of sand, anthracite, gravel and Granular Activated Carbon to filter out debris and color causing contaminants.
In general, using the highest quality industrial sands and media available, man-made media filtration can approach the 7 – 10 micron filtration range. The MS however, is so fine that it can approach 0.5 – 1.0 micron filtration range. This provides water that is virtually free of silt and plugging particles. This has many benefits to homeowners, business and industry. Again, with limited space, we will address those benefits at another time. For now, let’s get to the proof of the pudding!
There is a test to measure the tendency of water to plug things up. It is called the Silt Density Index Test and the scoring range is 0 – plugging. 0 of course is the desirable number. For industry, a lower SDI can translate into tens, even hundreds-of-thousands of dollars in yearly savings.
On surface waters such as the great lakes, the SDI test often plugs the test filter before enough time has passed to take a reading. In this case, a fudge formula is used to get a number.
Reverse Osmosis systems are designed to operate on an SDI of 5 or less. In places like Cleveland, San Francisco, Indianapolis, Nashville and Atlanta, expensive filtration equipment has to be used to barely squeeze into the 3- 5 range.
In Memphis however, the SDI of raw tap water can range anywhere from 0.5 – 1.3. Typically, if a 5 micron household water filter is used in Memphis, it may never plug up because Memphis water may not have any particles big enough to be trapped.
Now you know a little something about the great Memphis Sand.