Some understanding of basic chemistry is needed to understand water chemistry, but the only background needed to begin this course is the ability to recognize the symbols of the elements – C for carbon, H for hydrogen, Ca for calcium, etc. The rest is explained in what follows.

The various impurities that can be found in water can be categorized in several different ways: Are they dissolved, particulate, or colloidal? Are they organic or inorganic? Are they biological or mineral? Are they ionized or not? Are they aesthetic contaminants, health-related contaminants, or just process nuisances? Each of these will be discussed, along with the concepts of oxidation/reduction, adsorption, and chemical equilibrium, which will be explained and demonstrated with the pH scale and the alkalinity continuum.