Water quality is determined by the presence of contaminants, physical and chemical factors such as pH and conductivity, and the number of minerals present. Water chemistry begins with a very simple formula – H2O –two hydrogen and one oxygen elements. Pure water is colorless, tasteless, and odorless. What makes water “good” is the lack of impurities.
Impurities in water are measured and commonly referred to as “Total Dissolved Solids” (TDS) as a measure of the total ions in solution. These electrically charged dissolved particles (ions) make ordinary water a good conductor of electricity. Pure water has a high electrical resistance, and resistance is frequently used as a measure of its purity.
Electrical conductivity is a measure of the capacity of water to conduct electrical current, it is directly related to the concentration of salts dissolved in water, and therefore to the TDS. Salts dissolve into positively charged ions and negatively charged ions, which conduct electricity. Electrical Conductivity is actually a measure of the ionic activity of a solution in term of its capacity to transmit current. In dilute solution, such as water, TDS and EC are reasonably comparable.
Hardness- Water hardness is measured by the amount of “grains per gallon,” of calcium and magnesium ions specifically. In one gallon of water, one grain of hardness translates to 64.8 milligrams of calcium or 17 ppm present. Less than one grain per gallon is considered “soft” water, more than 7 grains per gallon (gpg) is considered “hard” water. Most people enjoy drinking water at approximately 4 grains of hardness.
pH measures the strength of an acid or base: The pH scale reads 1.0 to 6.9 is considered acidic, 7.0 is neutral and 7.1 to 14.0 is alkaline. Absolutely pure water has a pH of exactly 7.0, putting it directly in the middle of the pH scale, it contains no acids, no bases, and no (zero) alkalinity and essentially no taste.
Humans largely influence all the factors related to water quality, as we discharge waste in water and add substances and contaminants to water that are not naturally present. Pollutants such as metals, oils, pesticides, and fertilizers run off from land into the waters, causing excess algae growth and other harmful impacts to water quality.
Many inorganic water impurities exist as ions in water, the most common of these ions are:
Cations (Positively Charged Ions): calcium, magnesium, sodium, iron, manganese
Anions (Negatively Charged Ions): sulfate, chloride, biocarbonate, nitrate, carbonate