Common chemical parameters include pH, nitrates and dissolved oxygen. Measuring O2 (or DO) is an important gauge of water quality. Changes in dissolved oxygen levels indicate the presence of microorganisms from sewage, urban or agriculture runoff or discharge from factories.
A right level of ORP minimizes the presence of microorganisms such as E. coli, Salmonella, Listeria. Levels of Turbidity below 1 NTU indicates the right purity of drinking water.