Evaluating the efficacy of water softening & conditioning technologies
What I love about the water treatment industry is that no two projects are exactly the same. Whether it is the influent water quality, the desired output water quality, or how that water will be used, each water quality improvement or management project depends on environmental, physical and personal variables.
To some people, “acceptable” water is water that is safe enough to drink; for others, it has to be purified to greater than 18 Mohm-cm resistance and contain no total organic carbon or pyrogens. When it comes to mission-critical applications, ASTM D1193, USP and European Pharmocopoeia offer water specifications for specific grades of water to ensure that there is no confusion in what we provide.
In less critical applications, the definition of acceptable often is left open to interpretation by the client, vendor and equipment supplier, which opens up the possibility of catastrophically failing in meeting the client’s expectations. I have seen adults get into shouting matches and professionals feud over the meaning of terms as simple as “soft water” or “water softener.”
At the most elementary level, most people understand that with hard water it is hard to get soap to lather, so it follows intuitively that water with which soap easily lathers should be called soft water.
As water professionals, we understand from the chemistry of calcium and magnesium reactions with soap that hard water contains high amounts of minerals that interact with soap. These minerals are responsible for the inhibitory effect on soap suds, as well as the formation of scale on pipe, faucets, fixtures, glassware and heating surfaces.
For almost a century, people typically have purchased water softeners to address one or both of the following issues. Soap interactions. Soap interacts with hard water minerals, causing significant negative effects to the user. Cleaning requires more soap and other products, glasses are cloudy, silverware is spotted, white laundry is gray and dingy, hair and skin are affected, and life in general is “harder.”
Mineral scale and precipitation. Hard water scale is easily recognized as the cloudiness on glasses, spots on silverware and crustiness on faucets, showerheads and other fixtures. Hidden scale and precipitation are harder for users to notice until electric water heater elements scale over, tankless water heaters lose flow, or gas-fired water heaters start to sound like Rice Krispies.
Physically removing calcium carbonate hardness ions to a level of approximately 2 grains per gallon is recognized by industry experts as water softening. Removing hardness ions from the water ensures that the soap and scale interactions cannot occur.
A traditional salt-based ion exchange water softener is currently the most cost-effective method on the market to address both scale and soap issues. However, there are some legitimate concerns about salt-based ion exchange systems.
Salt consumption, cost and inconvenience. Ion exchange systems use either sodium or potassium salt to regenerate. The easiest way to provide sodium or potassium to the softener is with cheap, ubiquitous chloride salt. The net environmental impact from harvesting, packaging, storage and transportation of salt typically is outweighed by the resource, labor and material savings these types of softeners provide. The resource efficiency of salt-based systems continues to improve thanks to resin matrix enhancements, upflow regeneration, improved brining and reserve algorithms, and the use of resin exhaustion sensor technologies.
Brine discharge. When a salt-based softener regenerates, a concentrated solution of calcium chloride and other ions is flushed to drain, along with associated backwash and rinse water. Municipal water systems have raised concerns about higher chloride concentrations in wastewater as a result of brine discharge. Softener bans in California have yet to show significantly beneficial results that justify the loss of convenience and energy and resource savings to homeowners or business owners who had to remove salt-based softeners.
Some homeowners do not like the feel of water produced by sodium-based water softeners (and, contrary to popular myth, that feeling does not come from the body’s natural oils). While relatively easily remedied with different regeneration strategies and various resins, some people will eschew purchasing a water softener because of this personal preference. Other homeowners simply do not want to deal with the hassle of hauling salt. There is an obvious need in the marketplace for salt-free alternatives to address scale and soap issues.
Salt-based ion exchange is not the only way to physically remove hardness ions. Membrane separation with nanofiltration or reverse osmosis membranes is a proven method of “softening” the water. Another method of hardness removal is electrodeionization (EDI), in which hardness ions are selectively removed using arrangements of ion exchange membranes that electrochemically regenerate instead of using salt. These are true salt-free softening technologies for which the efficacy easily can be tested by measuring the amount of calcium carbonate in the product water. Like salt-based softening technology, these alternative technologies have their strengths and weaknesses.
There are times when space, electrical supply, drainage availability or maintenance concerns prevent someone from being able to purchase a traditional water softener or other softening technology like EDI or membrane separation. To accommodate these customers’ needs, the free market has provided a plethora of products to compete for business.
I have yet to see a technology that truly softens water outside the realm of ion exchange or membrane separation. I am excited for the day when such a technology is developed; it will be one of the most significant technological breakthroughs of the century.
There are many salt-free devices for sale. They use various approaches like magnetism, radio frequency, ultrasonics, pressure modulation, heat modulation, organic acids, mono/bi/trimetallic reactions, phosphate compounds, chelating agents, and various iterations of media-assisted crystallization. Some do not work at all, salt-free scale control options are available in the marketplace that work well under certain chemical and operational conditions in reducing and even preventing hard water scale accumulation. However, there is a lack of consistent, repeatable, verifiable data on where, when and why these technologies will perform or not perform.
To make matters worse, due to loose definitions and overzealous marketers, some products are promoted as doing more than they really can. Playing fast and loose with terms like “softener” inevitably will lead to disappointed customers who might even feel they were deliberately deceived. If a device does not physically remove or sequester water hardness, then it is simply not a softener and should not be claimed as such.
Responsible companies are calling these appliances scale control devices or water conditioners to help minimize confusion in the marketplace. This step helps ensure consumer confidence and satisfaction, but more disclosure may be needed to help people know when something will work. “Just buy it and see how it works” is not an acceptable answer for dealers or their clients.
The next step in being a good corporate citizen is to be honest, scientific and objective about when, why and how a device will work. Much like the difference between nails and screws, each product has its strengths and weaknesses, and no one product is going to work perfectly in every application. Some salt-free devices work well in particular hardness ranges in some areas, but not in others, much to the frustration of plumbers and end users who are excited to adopt more efficient and economical technologies. Some manufacturers have not disclosed when and why their devices work or what the exact interference factors are.
This is an ongoing problem in the “alternative treatment technologies” realm, especially when it comes to delivering environmentally friendly, cost-effective solutions to customers. It can limit credibility in the marketplace.
A proposed Water Quality Research Foundation (WQRF) project aims to assess the capabilities of salt-free technologies by conducting third-party benchmarking tests. Potential outcomes of research on this topic could include the validation, creation or amendment of industry standards, as well as corresponding professional and consumer education. This study could measure salt-free technologies against the IAPMO Z601 standard and measure the scale reduction effects inside residential water heaters. It also could measure the scale buildup and ease of removal from glass shower doors and coffee makers. IAPMO currently is considering a new standard for scale reduction devices that proposes a low threshold for efficacy (60% scale reduction). The proposed WQRD study could address the consumer impacts of poor performance.
I am open to exploring all alternative technologies and not at all biased toward a salt-based ion exchange-only mindset. Just as with ion exchange or membrane separation technologies, I need to understand how something works, when it will and will not work, and how to measure its efficacy before I stake my reputation or client’s money on it.