Standard and Industrial Water Softeners
Water softening is the process of removing calcium, magnesium, and other unwanted chemical and/or contaminant ions from hard water. By softening hard water, it is made more compatible with soaps; the process can also help extend the working life of plumbing by preventing the buildup of lime scale and reducing galvanic corrosion.
Most water softening devices utilize ion-exchange polymers or reverse osmosis processes. Other effective approaches involve precipitation methods and sequestration via the addition of chelating agents. There are many known fraudulent water softening techniques, as well, among them those claiming to use electricity or magnetism to soften water.
Many commercial and industrial water softener appliances use ion-exchange resin devices. In these water softening systems, “hardness ions” such as calcium and magnesium are exchanged for sodium or potassium ions.
Ion exchange resins generally take the form of small beads. Made from organic polymers, these beads contain anionic functional groups which bind more strongly to dications (calcium ions, for example) than they do to monocations (such as sodium ions). Certain inorganic materials, called zeolites, can also be used for ion-exchange processes; specialty resins are available to remove carbonate, bi-carbonate, and sulphate ions.
Lime softening is another common water treatment method, commonly used in the Midwest, Florida, Texas, and other areas. In lime softening, limewater (calcium hydroxide) is added to remove hardness ions via precipitation; it is also effective at removing iron, manganese, radium, and arsenic, as well as various other microorganisms and dissolved organic matter.
Standard water softeners are small and typically found in the basement of people’s houses. Huge companies like whirlpool make these. Industrial water softeners are much larger and are generally customized to a business’ needs. Generally these are made by smaller, private companies like Robert B. Hill.
Limewater reacts carbonatationally with CO2 to form calcium carbonate precipitate, reacts with multivalent ions to remove carbonate hardness, and reacts with anions to replace non-carbonate hardness caused by multivalent ions with non-carbonate hardness from calcium.
Recarbonation by the addition of carbon dioxide is required to lower pH levels, which are raised during the initial softening process. Adding lime to raw water raises pH levels and shifts the equilibrium of carbonate species in the water. Dissolved CO2 is changed into bicarbonate, then into carbonate, causing calcium carbonate to precipitate. Through double displacement reactions, magnesium can be precipitated as magnesium hydroxide.
Interestingly, in contrast to ion exchange softening methods—where sodium is exchanged for calcium and magnesium ions—both the calcium in the raw water and the calcium added in lime softening are precipitated. As such, lime softening provides a substantial reduction in total dissolved solids (or TDS); ion exchange softening provides no appreciable change in TDS levels.
As you can see there is a great deal of differentiation between an industrial water softener and a standard water softener. Either way, you can see the complexity that goes into water softening. Regardless, water softeners do have limitations to what they can remove.