Column: Our Water Quality

Messages from water-quality overview

By: Stephen Wiman
Published online: Sunday, February 05, 2012
Appeared in: Home, Santa Fe Real Estate Guide
Edition: February 2012 Vol. 14 No. 11

“Purchase and use a drinking water system no matter where you buy it locally.” This response just automatically came to mind when asked, after a water-quality overview, what single message I would like the listener to take away. For residents on a chlorinated municipal or community water system, adding a drinking water system should rival acquiring carbon filtration for whole-house chlorine removal. Chlorination of public-water supplies has greatly improved public health, but microbiological control is intended for water-conveyance systems and certainly not for water taste or for our bathing pleasure.

When asked if our municipal water is safe, I have a standard reply: “Yes, it is EPA- compliant on an annualized basis, by law.” But is it contaminant-free water? No, but any contaminants present are below the EPA’s primary drinking-water standards. What about water from the Rio Grande, via the new Buckman Direct Diversion (BDD) project? Yes, it is EPA-compliant. You will have to be the judge of how much, if any, additional filtration you desire. BDD water is filtered to 0.1 microns and reverse-osmosis (RO) water is filtered to 0.0001microns. (A micron is one millionth of a meter.)

At the very mention of reverse osmosis, here’s what frequently comes to mind for many: wasting water, stripping the water of its nutrients, and producing corrosive water. Additional water is required to produce good water. I have always found it curious that RO systems are said to “waste” water, yet the term is never applied to our dishwashers and washing machines. Water used in all these processes is not consumed in the same sense as a fossil fuel, but rather is returned to the hydrologic cycle. A high-quality system, one that is certified to remove contaminants, uses about two gallons of water for every gallon of product water it produces, or 33 percent recovery. A low-quality RO (which is probably not certified and does not have a water-conserving permeate pump) may use 15 gallons per gallon of product (6 1/4 percent recovery). But why would you want a wasteful system that’s not certified to remove contaminants?

Reverse osmosis gets a bad rap from people who do not understand the process and the benefits of removing contaminants. In a previous column, I have addressed the bogus criticism that RO strips the water of essential minerals. Now, really, do you depend on water as your source of vitamins and minerals? One valid criticism is that the membrane-filtration process does lower pH, because it removes virtually all constituents from the water. But the real issue of low pH water is potential corrosiveness. We always use NSF-certified, food-grade tubing (not copper) and add a remineralization filter, which raises the pH above neutral (7.0) and produces both non- corrosive and delicious water.

One of the big breakthroughs for us has been using a coarser nanofiltration membrane (with a pore size of 0.001 microns), which offers the advantage of on- demand filtration, better recovery factors (90 to 95 percent on municipal water), and high removal factors for the naturally- occurring constituents common in our local water supply (albeit at legal levels below EPA requirements).

Stephen Wiman has a background in earth science (Ph.D. in geology) and is the owner of Good Water Company and a member of the Santa Fe’s Water Conservation Committee. He may be reached at 505-471-9036 and skwiman@ goodwatercompany.com.