December 2001: Volume 43, Number 12
Water Wells and Unique Treatment Needs
by Rick Andrew
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The vast majority of Americans get their water from either a municipal water source or privately owned water well. There are differences between municipal water supplies and private well water. Because of these differences, private well water can require more monitoring and a wider array of treatment methods than municipal water.
There are two main differences between municipal water supplies and privately owned well water: Municipal water supplies are frequently monitored for water quality by the municipality, and municipal water supplies are treated prior to distribution and consumption.
As a result, consumers of water supplied from a municipality can be quite confident that the water quality is within federal and state water quality guidelines. Information regarding water quality is available to municipal water supply consumers in annual reports. Typically, the only potential treatment issues with municipally supplied water are undesirable chlorine levels and detectable levels of trihalomethanes. Both of these issues result from the municipal treatment of the water and are normally dealt with through use of a simple water filter. Softening of municipal water may also be desired.
Privately owned well water
Typically, well water is required to be evaluated for microbiological contamination only at the time the well is installed, or when the property changes ownership. During routine operation, it’s up to the well owner to monitor the quality of well water. There are several basic tests that should be done at least annually to determine a basis for water treatment needs. These tests can be performed by a county health department, accredited testing laboratory or certified water treatment dealer. They include:
1. Total coliform count to determine possible sewage infiltration
2. Nitrate/nitrite testing to determine possible agricultural runoff impacts
3. Hardness to determine the recommended level of softening
There are additional tests that are recommended given the particular circumstances of the well. The quality of privately owned well water is influenced by many local and regional factors. Some of these factors are natural, and others are the result of human activity. Although there is a wide variety of possible factors—especially when various human industry is considered—the most common can be evaluated through the following tests:
-- If the area is known to have high arsenic levels in the groundwater, a test for arsenic concentration should be performed at least annually.
-- If there is a gas station nearby (within 1/4 mile), especially an older one, a BTEX and methyl tert-butyl ether (MTBE) analysis should be conducted. This is a volatile organic analysis to detect the presence of gasoline and/or the gasoline additive MTBE. This analysis should also be repeated annually.
-- If there is a rotten egg odor associated with the well water, a hydrogen sulfide and methane analysis should be conducted. This analysis should be repeated if the odors reoccur after treatment.
-- If there’s a musty or moldy odor with well water, an iron bacteria analysis should be conducted (this is often mistaken for hydrogen sulfide in the water). This analysis should be repeated if the odors reoccur after treatment.
-- If well water users are having problems with red staining of fixtures, the iron level of the well water should be analyzed. This analysis should be repeated if the staining reoccurs after treatment.
-- If the well water users are seeing brown staining of white laundry, the manganese level of the well water should be analyzed. This analysis should be repeated if the staining reoccurs after treatment.
Once analysis has been completed, the results should be evaluated to determine specific treatment needs and technologies for the well water.
Treatment of well water
The treatment of the well water will depend on the analysis. Some conditions, which will affect fixtures or result in odors, are best handled through point-of-entry treatment options. Still, other water conditions that may be costly to treat may be best handled through point-of-use devices. The overall analysis of the water should be evaluated when considering treatment options. For instance, a high level of arsenic may be treated by reverse osmosis (RO) with prechlorination; however, the RO membrane element will last much longer if hard water is softened prior to being treated by the unit. Keeping in mind that all aspects of water analysis must be considered in the overall design of a treatment system, Table 1 shows some treatment technologies that can be effective in treating specific well water conditions that are revealed through analysis.
Remember that other potential contaminants may be present in private water wells, especially when the well is near an industrial or commercial operation. Wells located near a dry cleaning establishment could potentially be impacted by tetrachloroethylene (PCE), or “perc.” Wells near metal plating facilities could potentially be impacted by the presence of degreasing solvents, cyanide or hexavalent chromium. Each of these situations should be researched in detail before the potability and potential treatability of the well water is evaluated.
Once a treatment system consisting of one or more treatment technologies has been developed for the well water based upon the analysis, it’s important to conduct follow-up analysis of the treated water to determine how well the system is working. The system may have to be adjusted depending upon its performance, as determined through the analysis of the treated water. This follow-up analysis should be conducted several times throughout the first year of treatment system operation, and after every adjustment made to the system.
The well water, treated or not, should be continually monitored at least annually. This continuing analysis will determine if the well water characteristics have changed, thus requiring a modification to the treatment system. It will also determine how well the system is functioning, and whether maintenance or component replacement is necessary.
When specifying components of a treatment system, it’s important to verify that the technology is safe and effective. One good way to assure that water treatment products are both safe and effective is to use certified water treatment devices. When you find the appropriate certification on the product or its packaging, you can be assured that the product has undergone rigorous testing according to the applicable ANSI/NSF standard. It means all materials have been determined by toxicologists to be safe for use with potable water, and that ongoing certification audits of manufacturing facilities are being conducted to verify ongoing continuity in manufacturing.
Private well owners don’t have the luxury of a municipal public works department to monitor the quality of water on an ongoing basis and provide treatment. It’s up to the private well owners and users to monitor the quality of the well water, and to treat it appropriately based on results of analysis. By conducting regular analysis of the source well water and treated well water, the owner can be confident that any treatment system in use is appropriate to the characteristics of the water and operating effectively.
About the author
Rick Andrew is a senior program representative in the Drinking Water Treatment Units Certification Program at NSF International. He has a bachelor’s degree and master’s degree in chemistry from the University of Michigan. Prior to joining NSF, he was a consulting environmental chemist for 12 years. He can be reached at (800) NSF-MARK or 673-6275 or firstname.lastname@example.org