The Basic Types of Contaminants Found in Water

Dissolved Inorganics

Inorganic salts freely dissociate in water to form positive and negative ions. Calcium and magnesium, the minerals commonly associated with "hard" water, are two examples of dissolved inorganics. Heavy metals are another.

Dissolved Organics

Dissolved organic substances typically found in water include both man-made substances and the by-products of vegetative decay. Increasingly, they include tannins, humic acid, pesticides and chloramines. These chemical contaminants can interfere with the analysis of other constituents. They also tend to "foul" resin beds, filters and other water treatment equipment rendering them inoperable.

Suspended Particles

Suspended particles include silt, pipe scale, dust, fragments of valve material, undissolved minerals and organics, and the products of wear and abrasion. These suspended solids, colloids and large molecular weight organics can cause problems for a laboratory in at least three ways: first, they affect the reliability and performance of analytical instruments by clogging precision moving parts. Second, they shield bacteria from disinfection. Third, they can interfere with light transmission and measurements that require optical clarity.


Microorganisms include bacteria and by-products of bacteria called endotoxins or pyrogens. Bacteria can cause problems in the laboratory by:

Pyrogens are mainly lipopolysaccharides from the outer cell walls of gram-negative bacteria. If even trace amounts get into the blood stream of humans, they can trigger an immune response and cause fever.