Water Treatment
Hardness
Water hardness is often best understood by its effects on soap usage. Harder water makes it “harder” to form foam or suds but often leaves the skin feeling dryer/cleaner. Softer water does the reverse: it makes it easy to use soap but can leave the skin feeling greasy or slimy.
The EPA defines water as moderately hard when it has 61-120 mg/L of hardness (measured as calcium carbonate), as hard when it has 121-180 mg/L, and as very hard when it has more than 180 mg/L.
Many water softener manufacturers recommend softening water as much as possible, but many people do not like the feeling of extremely soft water. Because of this, we try to find a balance and follow a general rule of thumb of trying to keep the amount of hardness under 100 mg/L. This results in water that will not cause excessive scaling but also does not feel too “slimy.”
There are two kinds of hardness: temporary & permanent. Temporary is the one that most people see scaling and crusting on shower heads, kettles, water heaters, and more. It is called temporary because it precipitates or comes out of the water easily. The crusting caused by hard water can damage appliances over time. Permanent hardness, though, does not precipitate out easily and is less problematic.
Hardness is caused by two specific minerals: calcium & magnesium. These minerals combine with soap to create soap scum, which can stain showers and sinks. To “soften” the water, we remove these minerals through ion exchange.
Alkalinity & pH
pH is a measure of the relative amount of free hydrogen and hydroxyl ions in water. Water that has more free hydrogen ions is more acidic, and water that has more free hydroxyl ions is more basic.
The range goes from 0 to 14 with 7 being neutral. pH units are logarithmic, meaning that each number represents a tenfold change in the acidity/basicness of water. Thus, water with a pH of 5.0 is ten times more acidic than water having a pH of 6.0.
pH can be affected by chemicals in the water, so it is an important indicator of chemical changes in water. It affects the solubility of different chemical constituents, including nutrients and heavy metals.
High pH causes a bitter taste and can lead to deposits on water pipes and other appliances. It also reduces the effectiveness of chlorine disinfection. Low pH causes corrosion of metals and other substances, including copper pipes.
Alkalinity is not the same thing as pH. Rather, alkalinity measures the acid-neutralizing capacity of a solution. It is essentially the buffering ability of water to neutralize acids and bases and maintain a fairly stable pH level.
TDS
TDS or total dissolved solids measures just that: all of the mineral content dissolved in the water. This usually consists of calcium, magnesium, sodium, potassium, carbonate, bicarbonate, silica, chloride, sulfate, and nitrate.
High TDS can be an indicator of other water quality issues, such as hard water, heavy metals, or high salinity. It can also lead to an unpleasant taste, mineral accumulation in plumbing and appliances, staining, corrosion, and restricted use for irrigation. Concentrations above 500 mg/L often give water a salty taste. However, high TDS itself is not a health concern.
High TDS is a result of groundwater’s contact with rocks and sediments in the aquifer. The longer that groundwater has been in contact with these, the higher the possibility of these dissolving into the groundwater. Still, geology, climate, and human activity all play a considerable role in the amount of solids dissolved in groundwater.
Iron, Manganese & Sulfide
Iron is a heavy metal that is naturally occurring in groundwater. It exists in water in two forms: ferrous iron [iron (II)] and ferric iron [iron (III)]. In high enough quantities (over 0.3 mg/L), both lead to reddish-brown or orange staining over time, especially in bathroom fixtures.
Iron does not precipitate or come out of water easily if the pH is below 7.0. Unfortunately, much of the water in our area that has high amounts of iron also has low pH, leading to a need for at least a two-step treatment system and higher costs.
Manganese is a heavy metal that is naturally occurring in groundwater. It is an essential nutrient and is found in much of the food we eat. In large amounts over a long period of time though, it can be toxic and affect the central nervous system. In high enough quantities (over 0.05 mg/L), it leads to brown-black staining over time, especially in sinks and bathroom fixtures.
Manganese does not precipitate or come out of water easily if the pH is below 8.0. Unfortunately, as with iron, much of the water in our area that has high amounts of manganese also has low pH, leading again to a need for at least a two-step treatment system and higher costs.
Sulfide is a gas. It dissolves easily in water and appears as tiny bubbles. Sulfide also stinks, literally. It is known by its characteristic smell of rotten eggs and/or sewage. Though it is toxic in large amounts, the amount dissolved in groundwater is minuscule and harmless. However, humans are extremely sensitive to the smell, so it is an unpleasant but merely aesthetic problem.
Sulfide can be converted to a less smelly ion called hydrosulfide. This requires raising the pH above 8.5, ideally above 9.0. As with iron and manganese, much of the water in our area that has high amounts of sulfide also has low pH, leading once again to a need for at least a two-step treatment system and higher costs.
Color
Pure water is not completely clear and colorless but actually has a slight blue tint. However, groundwater is not truly pure water. It contains dissolved minerals and often suspended materials in it, and these can impart color.
Tannins are a class of dissolved organic matter that comes from leaves, roots, and plant remains. It has a slightly bitter taste and creates a yellow or brown tint in water. They are difficult to filter out completely because there are many different types, and each responds differently to filter media. Iron can create a similar reddish-brown tint in water but is much easier to remove.
Suspended materials can include fine particles of clay and algae. These can be filtered out through physical filters or simply giving them time to settle to the bottom of a tank.