Water Well Journal
Issue link: https://read.dmtmag.com/i/767379
I n the normal operational life span of a water well there are repair and maintenance procedures not only to keep the well operating and producing water but also to assure the water is safe for potable use. The process of well disinfection falls into both these areas as the buildup of bacteria can foul the well and impede capac- ity. However, in this case disinfection is only part of the reso- lution and not a standalone process. Secondly—and perhaps more commonly—disinfection is the resolution to unsafe bacterial conditions in the well and a common practice that should be administered with full knowledge of the source problem. Disinfection is mandated after initial construction and de- velopment of the well, following service and repairs to the well, and of course, if unsafe conditions are found through testing of the well. However, well inspection procedures for identifying the source are important in the case of unsafe bac- terial conditions. These include noting surface contamination or a septic system influence in the subsurface. Once these sources have been corrected, the well can be disinfected as the final step in resolving the problem. Use of disinfection chemicals in the water industry was ini- tiated in the late 1800s after the development of the "Germ Theory" in the 1850s identified specific waterborne bacteria as the cause of epidemics such as cholera and typhoid. The initial chemistry of choice was, and still remains today, chlorine. The Chlorine Chlorine is available in gas, liquid, and solid forms. Gas chlorine is a dangerous chemistry to transport, store, and apply. Consequently, it is limited to a controlled environment such as a water treatment plant and not to field application procedures. The solid form, calcium hypochlorite, is the common tablet or granular products seen throughout the water industry. It is actually a mixture of calcium carbonate and calcium chloride marketed as chlorine powder or bleach powder. Calcium hypochlorite comes in a variety of product forms and concentrations representing the available chlorine by weight. It is used in the disinfection of water wells, but the chemical is not active until dissolved in water. As such, dis- solving it at the surface, then applying it to the well is recom- mended to assure the chemical is active and biocidal. In wells and aquifers exhibiting high hardness content, the use of calcium hypochlorite should be avoided as the further addition of calcium can help enhance the formation of scale deposits downhole. DISINFECTION continues on page 26 The dynamics of the well and downhole conditions must be fully understood before using potentially dangerous oxidizers like hydrogen peroxide or household bleach for disinfection. No Bleach! A guide to smart disinfection. By Roger Miller (COVER STORY) Twitter @WaterWellJournl WWJ January 2017 25