Water chlorination is the process of adding chlorine (Cl
2) or hypochlorite to water. This method is used to kill certain bacteria and other microbes in tap water as chlorine is highly toxic. In particular, chlorination is used to prevent the spread of waterborne diseases such as cholera, dysentery, and typhoid.
How To Use Chlorination Systems for Well & Spring Water
Water used for drinking and cooking should be free of odor, slime producing bacteria, and pathogenic (disease causing) microorganisms that cause such illnesses as typhoid fever, dysentery, cholera, and gastroenteritis.
Although several methods eliminate microorganisms and odors in water, chlorination is the most commonly used. Chlorination is effective against many pathogenic and non-pathogenic bacteria, but at normal dosage rates it does not kill all viruses, cysts, or worms. Often combined with filtration, chlorination is an excellent and cost-effective way to disinfect drinking water supplies, eliminate odors, and oxidize iron, and other metals.
The two most common methods of chlorination for residential well water systems are:
• Chlorine bleach (sodium hypochlorite)
• Solid bleach pellets and powders (calcium hypochlorite)
Questions to Ask When Choosing a Chlorinator:
• Have I had my water tested?
• What is the “chlorine demand” (based on my water test) of my water?
• What is the flow rate of my well pump in gallons per minute?
• How much contact time do I have after the chlorine is injected and will a contact tank be necessary?
• What is the line pressure in PSI, at the point where I plan to inject the chlorine?
Test Your Water
A general mineral analysis will provide a list of the common minerals. Important items to test for include:
• Coliform bacteria
• Alkalinity
• pH
• Hardness (calcium carbonate)
• Iron
• Manganese
• Total dissolved solids
Stains and Odors
If water is discolored, or has a strong odor, you may also want to test for:
• Iron Bacteria
• Tannin
• Hydrogen sulfide
Professional Analysis or Home Test Kit?
If there is an odor problem with the water supply, the first step is to determine the source. If the source is from the well directly a general mineral water analysis is critical to select the correct system.
To find a local lab, consult your county health department for recommendations.
The water sample should be drawn as close to the source as possible, before any filtration systems.
Allow water to run to 5 to 10 minutes, to make sure you are getting a sample that is coming directly out of the well, and has not been sitting in pipes or pressure tanks.
Estimate Chlorine Demand
When chlorine is added to water it not only reacts with bacteria, but also with other impurities, such as hydrogen sulfide, soluble metals, particles of organic matter and other microorganisms. The chlorine demand must first be satisfied, before a residual chlorine concentration can be established.
Once there is a residual chlorine concentration, this residual concentration has to be maintained during the required contact time to kill pathogenic microorganisms. To adequately disinfect the water it is therefore required to supply the water with a higher chlorine concentration than the concentration required to kill bacteria.
Chlorine demand is simply how much available or “free” chlorine in mg/L or PPM is needed to kill the bacteria, remove odor, and/or oxidize iron, in order to achieve your goals.
Amount of chlorine required to kill bacteria and oxidize iron, manganese and hydrogen sulfide:
* Based on CT Values recommended by USEPA. CT value is Concentration of chlorine multiplied by Time in retention. C x T = CT value. The less Concentration of chlorine you have, the longer the contact Time required.
Example: Common well water analysis and chlorine demand calculation:
Note, calculations for Chlorine Demand do not have to be exact. Once the system is up and running, a simple free-chlorine test after contact tank will let you know your chlorine demand. The chlorinator can be then be easily adjusted to put out more or less chlorine as needed.
Liquid bleach chlorinator
In-Line type solid chlorine pellet feeder
Pellet feeder mounted on top of well. Drops chlorine pellets when well pump runs
Water test kit with tests that can be on-site, giving immediate results. A mail-in sample bottle is available to send to lab for additional tests.
Laboratory analysis water test kit. Contains freeze pack with special bottles for sending by overnight UPS or FEDX to the lab. Extensive analysis for bacteria, general mineral, metals and chemicals are available for relatively low cost.
pH:
Chlorine is most effective if the water has a pH in the range of 6.0 to 7.5. At pH 8.0 much more chlorine is required to have the same effect than if the water had a pH of 7.0. At pH over 8.5 chlorine becomes ineffective
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