Levels of hardness are referred to as follows:
|Soft Water||0 – 1 grains per gallon (gpg)|
|Slightly Hard Water||1 – 3.5 grains per gallon (gpg)|
|Moderately Hard Water||3.5 – 7 grains per gallon (gpg)|
|Hard Water||7 – 10.5 grains per gallon (gpg)|
|Very Hard Water||Over 10.5 grains per gallon (gpg)|
Waters which naturally contain very little hardness can also be problematic because they may be corrosive in some applications (see acidity).
For some applications, sequestering agents (Siliphos) are good for hardness conditions under 15 gpg. The only practical method for hardness removal above 15 gpg in residential applications is through cation exchange process employed by water softeners (also called conditioners).
Water which contains excess acidity tends to act aggressively towards plumbing and fixtures, causing corrosion and staining (i.e.-blue green stains on fixtures from copper pipes). Relative acidity/alkalinity is measured on the pH scale, ranging from 0- 1 4, where 7 is neutral, numbers lower than 7 are progressively more acidic, and numbers higher than seven are increasingly alkaline (basic). The pH value refers not to the quantity of acidity, but rather to the relative acidity/alkalinity of a particular sample.
Alkalinity acts as a buffer to deactivate the acidity, a process called neutralization. For example, limestone (calcium carbonate) is often applied to soil to offset the acidity which comes from acid rain and decaying organic material. The acceptable range for water is 6.5-8.5.
Acidity cannot be removed from water. However, it can be neutralized by raising the pH with alkalinity. This can be done by injecting a highly basic (alkaline) solution with a feed pump or by passing the water through a bed of processed limestone or similar material.
Iron concentration is measured in ppm or mg/l (milligrams per liter, where 1 ppm = 1 mg/l). Staining usually becomes a problem at concentrations greater than 0.3 ppm. Removal is through ion exchange (water softener) or oxidation/filtration (APIR).
Manganese is a metal similar to iron which causes a grey/black stain. It can cause staining in concentrations as low as 0.05 ppm. Manganese is removed in a manner similar to iron, although oxidation is more difficult, requiring a pH of at least 8.5.
Hydrogen Sulphide is a gas which smells strongly like rotten eggs. It results from the decay of organic matter with organic sulphur and the presence of certain types of bacteria. Even very low concentrations are offensive as well as highly corrosive (silver tarnishes almost immediately upon contact with H2S).
Because it is in a gaseous form, H2S cannot be collected in a sample bottle for laboratory analysis. Therefore, its presence must be reported when a sample is submitted for a treatment recommendation. It can be removed by
oxidation/filtration, aeration, or well sanitization.
Turbidity is a measure of suspended particles in water and can range from large particles which settle out of solution rapidly (such as sand), to extremely fine sediment which may stay suspended in solution even after standing for hours. Treatment depends upon size, which is measured in microns.
Most tastes and odours are caused by the presence of organic matter and chlorine. The vast majority of these can be removed with activated carbon.
The presence of toxic chemicals at various concentrations has been widely documented in many water supplies. Detection can be difficult as these contaminants often have no taste or odour. Treatment depends on type and concentration. These chemicals may be industrial solvents or agricultural pesticides and herbicides. One of the most common is Trihalomethane (THM) which is formed when chlorine in the water reacts with natural organic matter.
TDS is the sum of the mineral salts in water and if too high can result in objectionable taste, cloudy ice, interference with the flavor of foods and beverages and scale left behind in cookware. Generally speaking, the lower the TDS the more acceptable the drinking water. TDS of 1,000 ppm or more is unacceptable for drinking water. Reverse Osmosis (R0) process has proven itself as the most practical and cost effective method of correcting problems caused by high TDS.
Nitrates are inorganic chemicals dissolved in some water supplies as a result of feedlot and agricultural activities. Nitrate levels over 45 mg/L as actual NO3 (or 10 mg/L as Nitrogen, N) can be a serious health risk to infants and children. Reverse Osmosis has proven itself as an effective method of reducing Nitrates to safe levels.
The so-called heavy metals are toxic elemental metals such as Lead, Cadmium, Mercury, and Arsenic that find their way into water supplies from natural and industrial sources as well as home plumbing. These metals, especially Lead, can seriously affect the mental and neurological development of infants and children. Reverse Osmosis (R0) is recognized as the most practical method of reducing Lead to insignificant levels in drinking water. Carbon Block technology that incorporates ceramic ion exchange media is also an effective method of reducing lead.
Radium occurs in ground water due to the radioactive decay of Uranium in geologic formation. There is a health risk if the Radium level exceeds 20 pecocuries per liter (pCi/L). Cation exchange water softeners using proper regeneration procedures are effective in reducing Radium for POE applications. Reverse Osmosis systems are effective for reducing Radium for POU applications.
Particulate matter suspended in water is referred to as turbidity and is measured in Nephelometric Turbidity Units (NTU). A range of 0.5-1.0 NTU is the required limit for potable water. Higher levels of turbidity should be corrected with filtration.
Another measurement, the micron, is useful for measuring the size of particulate matter. A micron is one millionth of a meter or about 1/25,000 of an inch. Particles smaller than 30-40 microns cannot be seen with the naked eye and a 5 micron particle is about the size of a single grain of talcum powder.
Objectionable colour in water is expressed in APHA units. Typically, colour levels above 25 APHA are noticeable. At levels of 50-60 APHA the water typically requires treatment.
Objectionable odour from water is measured by the Threshold Odour Number (TON). The TON is the dilution factor required before an odour becomes minimally perceptible.
The pH Scale measures the relative acidity/alkalinity of a particular water sample. There are also several other contaminant measurement units with which you should be familiar. The first of these is pH, which measures the acidity or alkalinity of water due to dissolved substances.