Well Water Disinfection

Many of us live with the false confidence that our well water is safe
because it is filtered by the earth.  And to some extent that is true.

Many of us live with the false confidence that our well water is safe because it is filtered by the earth.  And to some extent that is true.  The earth’s crust can filter larger particles, but what happens if the water table is under a pasture or a field that has been fertilized with manure just prior to raining?  E-coli, which is found in manure, may not be removed by seepage and can find its way into the water table.  In many cases, depending on the composition of the earth, this water table is not dormant.  It may in fact be flowing. So the contaminated water you are drinking may be coming from a source miles from your well.

There are two types of water sources, groundwater and surface water.  Groundwater is that water that is pulled from aquifers many feet under the earth’s surface, where surface water is water that is open to the atmosphere such as lakes, ponds, rivers or reservoirs.  Surface water has a greater likelihood of containing water-borne pathogens because of run-off conditions and decomposing organic matter. That was the case of the Cholera epidemic in Latin America that began in January 1991 and by 1997 had spread to all but one Latin American country killing 12,000 and causing illness in 1.3 million others.

Today about 12 million households depend upon private wells to provide their drinking water, that’s roughly 15 per cent of the U.S. population.  Public utilities today are required to meet EPA minimum standards for safe drinking water.  Private citizens are not.  With the exception of protozoan parasites such as Cryptosporidium parvum and oocysts and Giardia lamblia cysts, disinfection of drinking water will render it safe for human consumption. 

So the big question before us today is why do so many private well owners and farms choose not to chlorinate their water wells?  And, why do so many resist chlorinating the drinking water of their livestock?

Several reasons come to mind. First, the negative or untrue information regarding the use of chlorine as a disinfectant. Second, the presumed initial high cost of equipment that needs to be purchased. Third, the “I don’t like the taste of chlorine” excuse.

As for the first objection, while it is true that adding chlorine into the water can produce byproducts such as iron oxide, magnesium oxide, or calcium oxide it can also produce (THMs) trihalomethanes including the most often reported THM member, chloroform.

According to the EPA, the health risks from these (THM) byproducts at the levels at which they occur in drinking water are extremely small, especially when compared to the risks associated with inadequate disinfection.  However, should a concern remain regarding these contaminants, inexpensive equipment is available that will further lower the levels of these contaminants.

As for the second objection, cost is negligible compared to the expenses incurred from equipment maintenance and losses due to water-borne pathogens in the form of medical expense, lost productive time, and loss due to death.  Chlorine is available in one of three forms: gas, solid or liquid.

Gas has advantages where large volumes of water are produced, but that advantage is lost when your water demands drop below several hundred thousand gallons per day. Gas cylinders should be housed in a separate room with direct emergency access to outside air, fitted with an exhaust fan ventilation system.  Personnel require specialized training in the event of a leak.  Remember, Chlorine in its gaseous form is lethal at concentrations as low as 0.1 per cent of air by volume.

The second type of chlorine is in a solid, also known as calcium hypochlorite.  This is a white solid that contains 65 per cent available chlorine and dissolves easily in water. 

While there are advantages, such as long-term stability, there are disadvantages.  Calcium hypochlorite is a corrosive, and as anyone who has a swimming pool can tell you it has a strong odour and requires proper handling.  What you may not know, however, is that it must be kept away from organic materials such as wood, cloth and petroleum products because reactions between calcium hypochlorite and organic materials can generate enough heat to cause a fire or an explosion. 

Calcium hypochlorite is extremely effervescent, absorbing moisture and in the process forming chlorine gas.  Therefore shipping containers must be emptied completely or resealed carefully  Also, after  dissolving the concentrate in water the user must purchase a chemical injector to place the concentrate in the water supply.

The last type of chlorine is in liquid form known as sodium hypochlorite. This form is available from 5.25 per cent (household bleach), to 15 per cent available chlorine.  The major disadvantage is the cost of the liquid form compared to the gaseous form.

However, when the flow requirements are less than several hundred thousand gallon per day, that cost is offset.  The advantages, however, are numerous.  First, as a liquid it is easier to handle and more readily available than either of the other two sources.  The equipment to inject liquid chlorine is by comparison inexpensive to purchase with a variety of non-electric chemical injectors available to handle this task. Installations can be made at the well water source using commercially available PVC fittings.  With the exception of controlling spillage, there are no special safety requirements or equipment to contend with.

At this point I want to mention the amount of chlorine that I would expect a well owner to be injecting.  Without water testing to determine just what is in the water there is no real way to accurately project how much chlorine needs to be added to the water to make it safe.  You must keep in mind that chlorine is an oxidizer and unlike the other methods of disinfection it is depleted as it is used.  Depletion depends upon the type of contaminate and the total amount.  What is important to remember is that what you want at the end of the day is what we refer to as chlorine residual. 

Generally speaking, water that has a residual of 0.2 to 0.4 PPM of free chlorine has adequate residual to kill any bacteria or viruses that may re-enter the water supply given 20 to 30 minutes of contact time.  On the other hand, 1 PPM or greater free chlorine will kill those same pathogens on contact. Once your water has reached a point where there is 1 PPM of free chlorine, you have effectively oxidized most minerals and killed most pathogens.  Your water is now relatively safe for consumption. 

The last of the objections that I routinely hear is that of the taste. But, it is not practical to try and provide bottled water for our livestock.  There are inexpensive steps that can be taken to remove not only the byproducts of chlorine but also the suspended mater that occurs naturally within the water supply. 

Two such steps are filtration systems that are placed at the point of entry (POE) to the home or the housing facility. Activated charcoal filtration will remove chlorine but it will not remove THMs, PCBs, radon, arsenic, or Cryptosporidium cysts.  For that you need to use a green sand filter.  Used in conjunction with activated charcoal filtration, you can be very confident that you have removed all foreign matter from your drinking water.

This type of filtration can be used as either a point of use (POU) or a POE filtration.  POU filtration is the cartridge type that is placed close to or at the point of need, and requires scheduled changing to maintain the best filtration possible.  POE types are typically canister types which are placed outside the home or at the well source and have life expectancies of up to five years before media replacement is necessary. There are advantages and disadvantages to both that can only be determined by the specific use that you have.

I would be remiss if I did not mention that there are other types of liquid disinfection available.  These include hydrogen peroxide (H2O2), iodine, bromine, chloramines, ozone, and chlorine dioxide (Cl2O2).  Ultraviolet has found a following and is effective providing there is no suspended matter in the water being treated.  Any suspended matter will cause the UV light to diffuse and diminish its effectiveness. However, chlorine is the only one that leaves a residual with secondary disinfection capabilities.
When the water is properly treated prior to use you can cut the cost of pharmaceuticals that need to be used and make the pharmaceuticals that must be used more effective.  By stopping the pathogens before they enter the body you reduce the need to treat the sickness, thus saving thousands of dollars.  By reducing or removing the organics that are suspended in the water you enable the pharmaceuticals that must be used to be more effective when treating your livestock.  You will also reduce the amount of time required to fix or replace equipment that leaks due to oxides that have built up on your drinkers. 

Clean, safe drinking water should always be thought about as being the first step in a biosecurity program. n

This paper was presented at the Midwest Poultry Federation Convention in March 2007 by Frank Daniels, president of Chemilizer Products, Inc., manufacturer of non-electric liquid chemical injectors.  www.chemilizer.com