Water Well Journal

August 2015

Water Well Journal

Issue link: http://read.dmtmag.com/i/543740

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Page 22 of 71

W ater well disinfection is one of the most common forms of maintenance performed. It is also one of the most misunderstood pro- cedures in our industry. Water well disinfection is typically employed for one of two main reasons: mandated or reactionary. As a mandated procedure, it is con- ducted following development of a new well prior to placing the well into active use—or in the case of existing wells, if any maintenance has been conducted such as pump work, rehabilitation, or modification. As a reactionary proce- dure, disinfection is conducted in response to a "coliform hit" or as a rehabilitation effort in response to a loss of capacity or produced water quality. Facing Limitations The first issue to understand is the limitations of well disinfection. Disin- fection will not solve a significant loss of capacity, target heavy mineral scale, sterilize the well, or solve a breach of the well structure. Disinfection is used as a means of reducing the bacterial community and limiting the potential for pathogenic organisms to exist within the well—not clean the well. Disinfection failures often stem from one of several reasons—including im- proper use or application of the chemi- cals, insufficient agitation or contact time, and commonly, suspected fouling being greater than anticipated. The second issue to examine is the use and employment of the disinfection solution. Chlorine has been used to treat water since the late 1800s and remains today as the most common chemical used to treat well systems. Chlorine is available in gas, liquid, and solid forms. As a gas, chlorine is dangerous, and its use as a disinfectant should be lim- ited to a controlled environment such as a water treatment plant. In the liquid form, commonly as sodium hypochlorite, chlorine is avail- able in a variety of strengths. At a gro- cery or local discount store, you can purchase a 3% to 6% solution as bleach. However, be sure to never get and use a scented or "enhanced" formula as it may DISINFECTING NEW AND EXISTING WELLS SCHNIEDERS continues on page 22 Sampling the well and evaluating the well site are important steps to identify what type of treatment is needed. Common but often misunderstood, it's important to know how to do this form of maintenance. By Michael Schnieders, PG, PH-GW (COVER STORY) WWJ August 2015 21 Twitter @WaterWellJournl

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