Determining the right method of treatment is crucial to the life of the well.
By Michael Schnieders, PG, PH-GW
Water treatment efforts on residential or private wells and small community-managed groundwater systems are typically focused on aesthetic issues such as taste or discoloration, or water quality contaminants such as arsenic.
Water treatment efforts of this nature act as a barrier to harmful or undesirable contaminants that impact the delivery of clean, potable water for use and consumption.
Groundwater sources generally provide higher quality water than surface water resources, requiring fewer treatment steps. Typically, water quality challenges within a region are known at the time of construction. These challenges may include arsenic, nitrates, or other regulated contaminants.
Some issues may develop or worsen over time as the well ages, such as iron or the sediment load, or because of damage to the well, such as with coliforms.
The four basic steps of water treatment are coagulation and flocculation, sedimentation, filtration, and disinfection—typically conducted in that order in larger, municipal water treatment facilities.
For smaller well systems, the most common types of treatment are filtration, reverse osmosis, softening, and disinfection.
Filter systems remove problematic constituents by means of physical, chemical, or biological processes. Filtration is a broad category, including the removal of sand and sediment as well as protozoa and larger microorganisms. It can include a variety of methods such as gravity flow through filter media, membrane filtration, and reverse osmosis.
Reverse osmosis (RO) is in reality a multi-step filtration process that is used to remove a large majority of contaminants by pushing the water, under pressure, through a semi-permeable membrane.
Softeners use an ion exchange process for removal of chemical elements that cause hardness in water, such as calcium and magnesium. Softening can also remove metals and other contaminants like nitrates. Softeners are commonly employed to reduce hard water deposits on fixtures or to extend the life of appliances and piping.
Disinfection may use a physical process or chemical additive to target the amount of bacteria present. Ultraviolet (UV) treatment systems have a high rate of effectiveness in removing bacteria and viruses when maintained and operated correctly.
Oftentimes, different aspects of the water treatment process are put to use in tandem or in sequence to improve the quality of water at a location. Treatment may occur at the point-of-use (POU) such as a kitchen sink, or at the point-of-entry (POE) where the water source enters a residence.
Determining the Method
To characterize what method of treatment is necessary or desired, the water source should be tested to correctly identify the presence of problematic constituents. Collected samples should accurately reflect the downhole environment during regular use. This is an important aspect—one that could translate into thousands of dollars if done incorrectly. Samples should be collected at the wellhead to differentiate the groundwater from problems existing within the home’s plumbing.
New wells should be sampled following development and active use. The testing should be conducted after the well has stabilized to present an accurate evaluation of the regularly produced water quality. For example, an early sample caught before development is complete may identify a higher sediment load in the water than is present after development.
In older well systems, the well should be cleaned, disinfected, and actively pumped prior to sampling. This helps to eliminate any fouling that may have occurred because of stagnation or natural ageing that has occurred.
Additionally, if any modifications are necessary, they should be completed prior to testing so that the “new normal” is referenced in the results. For example, if the well has a sump or lower blank extension, it could impart hydrogen sulfide, higher iron, or microbial contaminants that would be addressed with cleaning.
Unfortunately, there remains a great misunderstanding in the role of water testing and the definition of a contaminant. Contaminants include many harmful substances as well as many harmless constituents.
Low levels of trace minerals, metals, and salts are all naturally present in groundwater. At low concentrations, these contaminants are harmless; some may even be desirable—such as a preference for hard, mineralized water. Other contaminants are the result of industrial spills or improper disposal, and undesirable at any concentration.
It is important to differentiate the need for required testing for human health and the role of testing for water treatment and operation. For example, understanding the absence of hexachlorocyclopentadiene or pentachorophenol in a water sample is important for classifying a new well as being free of industrial contamination, but it doesn’t help in identifying hard water and properly sizing a water softener.
Generally, a full water profile is conducted before the well is approved for potable use. This data may not fully provide the needed information for water treatment or for management of the well over time. Discuss the goals of your testing with the laboratory prior to sample collection.
More Than Costs
Selection of a treatment system should be based on more than just cost. A knowledge of the raw water quality is important, as is the understanding of the finished water and system byproducts.
For example, removal of calcium and magnesium from a water source will reduce the development of hard water deposits. However, it may also increase the corrosivity of the water. This could increase the vulnerability of appliances and old pipes to corrosion and structural decay.
Waste streams from reverse osmosis or ion exchange units can be quite concentrated with regards to their water chemistry. While this may not impact the potability of the water, it could alter the use and stability of onsite septic systems. These changes should be considered when selecting a system.
Much like a well, home water systems require routine maintenance. Also, like wells, regular and preventative maintenance of these systems is necessary to prevent impacts on water quality, reduce system failure, and help save the owner money.
Maintaining a home or small system treatment unit calls for a basic understanding of the requirements for that specific system as well as a commitment. The run-to-failure model often seen in well ownership is even more pervasive in home treatment systems unless a service company is brought in for system management.
The treatment device should be segregated from other systems and unobstructed, allowing easy access for maintenance and regular visual inspections. Flush or backwash the system as recommended and install new filter cartridges or media as necessary.
Set up a schedule to conduct routine testing to ensure the system is meeting the intended water treatment goals.
Irregular or frequent fouling of treatment systems, or a failure for them to meet the intended level of treatment, may indicate the water source has been compromised. This could be a major event or the result of natural fouling and well ageing that is more gradual.
A common example is the occurrence of iron bacteria. Iron bacteria will often migrate beyond the well and into the system, regardless of the size, impacting produced water quality. Once a filtration unit or water softener is breached, iron staining and gelatinous iron deposits can become visible in sinks and toilets.
Systems should be decided on that are cost effective, easy to operate, and meet the needs of the water resource and the owner. It is important that wells, as the raw water source, be factored into every aspect of the selection and employment of water treatment systems.
Finally, please note this article is by no means a complete guide to water treatment but more of a means of educating the industry. As with most well projects, each water source should be evaluated independently with the help of a qualified expert.
Michael J. Schnieders, PG, PH-GW, is a professional geologist serving as the principal hydrogeologist and president of Water Systems Engineering Inc. in Ottawa, Kansas. Schnieders’ primary work involves water resource investigation and management, specializing in the diagnosis and treatment of fouled well systems. Schnieders served as The Groundwater Foundation’s 2017 McEllhiney Distinguished Lecturer in Water Well Technology. He can be reached at firstname.lastname@example.org.