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Well disinfectant chemicals & their properties: this article describes the properties of three most common disinfectants used to shock or sanitize a water well: chlorine (common household bleach), chloramine, and chlorine dioxide.
Page top sketch illustrating both deep and shallow water well construction and depths is provided courtesy of Carson Dunlop Associates.
Comparison of the 3 Common Well Water Disinfectants: Chloramine, Chlorine and Chlorine Dioxide
Chloramine, Chlorine and Chlorine Dioxide Used for Well Shocking / Disinfection Procedures
Chloramine (as Cl2)
Chloramine is a water additive used to control microbes ... as a residual disinfectant in drinking water distribution system pipes.
Chloramine is formed when ammonia is added to water containing free chlorine. Monochloramine is a form of chloramine commonly used for disinfection by municipal water systems
Drinking water with excessive levels of chloramine above the maximum residual disinfectant level (MRDL) could experience irritating effects to their eyes and nose, stomach discomfort or anemia
MRDL = 4.0 mg/L or 4 ppm as an annual average
Chlorine (as Cl2)
As a gaseous or liquid form of chlorine (CL2) chlorine is a powerful oxidant used by municipal water systems to control microbes.
Chlorine is relatively inexpensive and has the lowest production and operating costs and longest history for large continuous disinfection operations.
Some people who use water containing chlorine well in excess of the maximum residual disinfectant level could experience irritating effects to their eyes and nose.
Some people who drink water containing chlorine well in excess of the maximum residual disinfectant level could experience stomach discomfort.
MRDL = 4.0 mg/L or 4 ppm as an annual average
Chlorine dioxide (as ClO2)
Chlorine dioxide is added to water to control microbes and can be used to control tastes and odors. Highly volatile, chlorine dioxide rapidly disappears from stored water.
Some infants, young children, and fetuses of pregnant women who drink water containing chlorine dioxide in excess of the maximum residual disinfectant level could experience nervous system effects
. Some people who drink water containing chlorine dioxide well in excess of the MRDL for many years may experience anemia.
MRDL = 0.8 mg/L or 800 ppb
Household Bleach e.g. Clorox® contents & purposes of each chemical
Sodium hypochlorite (NaClO)
Sodium chloride (NaCl)
Sodium carbonate (Na2CO3)
Sodium chlorate (NaClO3)
Sodium hydroxide (NaOH)
Sodium polyacrylate (C3H3NaO2)n
In Clorox's EPA-registered disinfecting and sanitizing products, sodium hypochlorite is the active ingredient that helps to kill certain germs. This is the principal ingredient in household bleach.
Sodium chloride (table salt) is used as a thickener in some products.
Sodium carbonate (washing soda) is an alkalinity builder that boosts the cleaning power of laundry detergents
Sodium chlorate is an intermediate product in the break-down of standard bleach (sodium hypochlorite); it further breaks down into sodium chloride (salt) and oxygen.
Sodium hydroxide (lye, caustic soda) is used to adjust the pH of cleaners and to assist in breakdown of fats & oils
Sodium polyacrylate helps keep soils suspended during washing to avoid re depositing them on fabrics being cleaned.
According to the US ATSDR's fact sheet on chlorine:
Watch out: Drinking small amounts of hypochlorite solution (less than a cup) can produce irritation of the esophagus.
Drinking concentrated hypochlorite solution can produce severe damage to the upper digestive tract and even death. These effects are most likely caused by the caustic nature of the hypochlorite solution and not from exposure to molecular chlorine.
Spilling hypochlorite solution on the skin can produce irritation. The severity of the effects depends on the concentration of sodium hypochlorite in the bleach.
For emergency disinfection of drinking water (his is NOT the same thing as disinfecting a well) add 8 drops of Clorox bleach to a gallon of clear water, (or just two drops to a quart) and let the solution stand for at least 15 minutes (a very slight "bleach" odor should remain.
If there is no bleach odor the water may not be adequately disinfected.
The above information is adapted from US EPA, Water: Basic Information about Regulated Drinking Water Contaminants, retrieved 8/27/2013, original source water.epa.gov/drink/contaminants/basicinformation/disinfectants.cfm 
and from information provided by clorox.com
Watch out: The US EPA recommends that you test your water every year for total
coliform bacteria, nitrates, total
dissolved solids, and pH levels.
If a review of local well water contaminants found by local testing labs, your local health department, or other information about your particular property suggests that there is a risk of other chemical contaminants (such as agricultural chemicals, pesticides, or local chemical spills or dumps) then you should include a test for these contaminants as well.
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 ATSDR Agency for Toxic Substances Disease Registry, Toxic Substances Portal: Chlorine Toxicity, [PDF] November 2010, retrieved 8/27/2013, original source: www.atsdr.cdc.gov
[2a]Thanks to reader Jerry Highsmith for discussing well shocking procedures where a water filter or water softener are installed - August 2010
 "Bacteria in Drinking Water" - "Chlorine," Karen Mancl, water quality specialist, Agricultural Engineering, Ohio State University Extension. Mancl explains factors affecting the effectiveness of chlorine in water as a means to destroy bacteria and other microorganisms. OSU reports as follows:
Chlorine kills bacteria, including disease-causing organisms and the nuisance organism, iron bacteria. However, low levels of chlorine, normally used to disinfect water, are not an effective treatment for giardia cysts. A chlorine level of over 10 mg/1 must be maintained for at least 30 minutes to kill giardia cysts. -- http://ohioline.osu.edu/b795/index.html is the front page of this bulletin.
[5a] "Chemical Cleaning, Disinfection and Decontamination of Water Well" John Schnieders. Johnson Screens Inc. St. Paul, MN
[5b] Water Well Management Level 2 Training Module. Prairie Farm Rehabilitation Administration of Agriculture
and Agri-Food Canada, Alberta Environment, Alberta Water Well Drilling Association and Alberta Agriculture,
Food and Rural Development
 Water Wells that last for Generations. Alberta Agriculture, Food and Rural Development; Alberta Environment; Prairie Farm Rehabilitation Administration of Agriculture and Agri-Food Canada
 Water Well Management Level 2 Training Module. Prairie Farm Rehabilitation Administration of Agriculture and Agri-Food Canada, Alberta Environment, Alberta Water Well Drilling Association and Alberta Agriculture, Food and Rural Development
 Chemical Cleaning, Disinfection and Decontamination of Water Wells. John Schnieders. Published by Johnson Screens Inc. St. Paul, MN
Ohio State University article on the concentration of chlorine necessary to act as an effective disinfectant, and the effects of the water's pH and temperature: See http://ohioline.osu.edu/b795/b795_7.html for details.
Water Quality Association
P.O. Box 606
4151 Naperville Road
Lisle, IL 60532
National Sanitation Foundation
P.O. Box 130140
789 N Dixboro Road
Ann Arbor, MI 48113-0140
(734) 769-8010, (800) NSF-MARK
U.S. Environmental Protection Agency
(to visit in person)
Office of Water Resource Center
1200 Pennsylvania Avenue, NW
Ariel Rios Building
Washington, DC 20460
Phone: (202) 260-7786, email: email@example.com
The Safe Drinking Water Hotline
The hotline operates from 9:00 AM to
5:30 PM (EST)
The hotline can be accessed
on the Internet at
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Crystal Clear Supply provides portable ceramic water filter purifiers and portable reverse osmosis water treatment equipment - see http://www.crystalclearsupply.com/category_s/7.htm
Handbook of Disinfectants and Antiseptics, Joseph M. Ascenzi (Editor), CRC, 1995, ISBN-10: 0824795245 ISBN-13: 978-0824795245 "The evaluation of chemical germicides predates the golden age of microbiology..." -
This well-focused, up-to-date reference details the current medical uses of antiseptics and disinfectants -- particularly in the control of hospital-acquired infections -- presenting methods for evaluating products to obtain regulatory approval and examining chemical, physical, and microbiological properties as well as the toxicology of the most widely used commercial chemicals.
Potable Aqua® emergency drinking water germicidal tablets are produced by the Wisconsin Pharmacal Co., Jackson WI 53037. 800-558-6614 pharmacalway.com
Principles and Practice of Disinfection, Preservation and Sterilization (Hardcover)
by A. D. Russell (Editor), W. B. Hugo (Editor), G. A. J. Ayliffe (Editor), Blackwell Science, 2004. ISBN-10: 1405101997, ISBN-13: 978-1405101998.
"This superb book is the best of its kind available and one that will undoubtedly be useful, if not essential, to workers in a variety of industries. Thirty-one distinguished specialists deal comprehensively with the subject matter indicated by the title ... The book is produced with care, is very readable with useful selected references at the end of each chapter and an excellent index. It is an essential source book for everyone interested in this field. For pharmacy undergraduates, it will complement the excellent text on pharmaceutical microbiology by two of the present editors."
The Pharmaceutical Journal: "This is an excellent book. It deals comprehensively and authoritatively with its subject with contributions from 31 distinguished specialists. There is a great deal to interest all those involved in hospital infection ... This book is exceptionally well laid out. There are well chosen references for each chapter and an excellent index. It is highly recommended." The Journal of Hospital Infection.: "The editors and authors must be congratulated for this excellent treatise on nonantibiotic antimicrobial measures in hospitals and industry ... The publication is highly recommended to hospital and research personnel, especially to clinical microbiologists, infection-control and environmental-safety specialists, pharmacists, and dieticians."
New England Journal of Medicine: City Hospital, Birmingham, UK. Covers the many methods of the elimination or prevention of microbial growth. Provides an historical overview, descriptions of the types of antimicrobial agents, factors affecting efficacy, evaluation methods, and types of resistance. Features sterilization methods, and more. Previous edition: c1999. DNLM: Sterilization--methods.
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