Our Water Quality
For public water systems, disinfectants are widely and successfully used to protect public health and to ensure that water is safely conveyed to the most distant connections. But for private well users, additional protection such as ultraviolet (UV), chlorination, or ozonation may be required. We estimate that about 10 percent of our well-water customers opt for the more convenient UV disinfection systems. That percentage is probably equally divided between customers who simply want the additional peace of mind and customers who have experienced unpleasant health issues from waterborne organisms. Medical professionals, when diagnosing the cause of intestinal complaints, do not always immediately correlate microbiologically contaminated well water with its possible symptoms.
But installing UV sterilization systems is not simply a plug-and-play operation, because gthey have limitations with regard to water quality, including hardness, iron, and turbidity (clarity). We have seen amateur installations where UV systems are installed on rather complex water without proper pretreatment and are placed first in an array of treatment components. UV should be placed at the end of the treatment array. We have seen cases when the homeowner leaves the UV in place and simply unplugs it when sufficiently annoyed by the countdown clock and its alarm that signals when it is time for the annual bulb replacement.
UV systems should not be installed on well water in the absence of water testing. When harmful bacteria are confirmed by lab testing, after UV is installed and whenever plumbing lines are disrupted, it is highly recommended that the well and plumbing infrastructure be “shocked” using chlorine or 7 percent hydrogen peroxide.
Chemical approaches to disinfection work by killing the microorganisms, but UV sterilization is a physical process that provides rapid and effective inactivation of bacteria, viruses and protozoa, rendering them incapable of reproducing and infecting. UV light is invisible and occupies the portion of the electromagnetic spectrum between X-rays and visible light. The range of the germicidal UV wavelength is between 200 and 300 nanometers (billions of a meter), with the optimal effective wavelength for DNA absorption being 254 nanometers.
Although chlorination can also be used for well sterilization, UV offers the distinct advantage of neutralizing protozoan parasites such as Cryptosprodium and Giardia, which are chlorine-resistant. The pathogen Cryptosporidium garnered national attention in 1993 when more than 400,000 Milwaukee residents became ill with Cryptosporidiosis from a chlorinated surface water supply.
Another effective technology for neutralizing bacteria, viruses and spores is ozonation. Ozone (O3) is simply oxygen with an extra molecule, which reverts to pure oxygen, the only by-product of this chemical-free technology, within minutes. Ozone systems typically consist of ozone generators located inside atmospheric water cisterns installed for low-volume producing wells or wells that have severe sediment issues.
Without question, there are more opportunities for using UV systems to ensure sterilization of well water and when properly installed and maintained, and with appro- priate pre-treatment (as dictated by water chemistry parameters), UV sterilization is an effective and affordable means of achieving bacteriostasis. Other advantages for UV are that it is environmentally friendly and chemical-free and that no disinfection by-products are created.
Stephen Wiman has a background in earth science (M.S. and Ph.D. in geology) and is the owner of Good Water Company and a member of the City of Santa Fe’s Water Conservation Committee. He may be reached at 505-471-9036 and [email protected]watercompany.com