- Microorganisms.
- Pyrogens, endotoxins, DNase and RNase.
- Dissolved non-ionized solids and gases.
- Dissolved ionized solids and gases.
The first 3 groups of contaminants are all essentially "particulate matter" in one form or another, and can be "filtered" out by passing the water through a sieve that has a pore size that is smaller than the matter to be removed. Dissolved non-ionized solids and gasses include natural organic remains, man-made organic chemicals, and oxygen, resulting from exposure of the water to ecological contaminants.
Dissolved ionized solids and gasses come from exposure to rock and minerals in the earth, such as sodium chloride, calcium carbonate (limestone), calcium magnesium carbonate (dolomite), and other soluable chemicals that occur either naturally or as a result of man-kind's contamination of the water supply. The main ionized gas is carbon dioxide. These contaminants contribute to the hardness, conductivity, alkalinity and pH of the water.