Alkalinity of Drinking Water Explained
Grasping the Concept of Alkalinity in Potable Water
Alkalinity refers to the capacity of water to resist acidic compounds. This characteristic within water is linked to the presence of ions such as hydroxides, carbonates, and bicarbonates. Hydroxide ions are naturally present in water, albeit usually in negligible amounts. High concentrations of hydroxides are rarely detected in natural water bodies but may emerge after certain treatments. Carbonates may sporadically be found in untreated water, generally below 3 to 4 grains per gallon (gpg), and may also originate from lime soda water softening processes. Bicarbonates are the primary contributors to a water’s alkalinity, detectable in virtually all natural water sources, with quantities ranging from 0 to about 50 gpg. Essentially, water’s alkalinity is its capability to neutralize acids, with alkaline substances like hydroxides or bases identifiable by their bitter taste and their ability to turn red litmus paper blue. Phosphates and silicates are scarcely present in considerable concentrations in natural water bodies, though they play roles in diverse water treatment procedures. A balanced level of alkalinity is advantageous for the majority of water sources to combat acidity, yet an overabundance can result in various problems. These ions are neutralized by cations such as acidity, magnesium, and sodium or potassium. The alkaline impact of bicarbonate ions is typically unnoticeable unless they are highly concentrated, whereas even minute amounts of carbonate and hydroxide ions are perceptible. Water with high alkalinity may exhibit an unpleasant "soda" flavor, and the Environmental Protection Agency’s Secondary Drinking Water Regulations impose limits on alkalinity based on total dissolved solids (500 ppm) and pH levels.
Water that is overly alkaline can cause excessive drying of the skin by removing natural oils. Alkalinity can be diminished through reverse osmosis, a process that also eliminates other dissolved solids. Although distillation and deionization are alternative methods to remove dissolved solids, they are less feasible for residential applications due to their cost and space requirements when compared to under-sink or countertop reverse osmosis systems.
Other methods to decrease alkalinity include lime softening, which can precipitate alkalinity but is predominantly utilized in industrial and municipal contexts. Anion resin treatment can eliminate most anions but may result in elevated chloride ion levels and release nitrates when the resin is exhausted. Neutralizing alkalinity with mineral acids transforms bicarbonates and carbonates into carbonic acid, necessitating a mechanism for the carbon dioxide gas to be released. Nevertheless, handling strong acids requires precise control and caution.