TOTAL DISSOLVED SOLIDS IN WATER

Ionic Contaminants and Other Contaminants in Solution and Suspended Contaminants

As we learned previously, many dissolved inorganic water contaminants or impurities exist as ions in solution, the most common of these ions are:

These electrically charged dissolved particles make ordinary natural water a good conductor of electricity. Coversely, pure water has a high electrical resistance, and resistance is frequently used as a measure of its purity.

Since only a few of these most common ionic water contaminants are health related, most natural water supplies are safe to drink from the standpoint of dissolved inorganic chemical contaminants. However, even though found more rarely -- and in much smaller quantities -- certain inorganic ions can be toxic. These contaminants are listed, along with their maximum allowable levels in the summary, which also includes maximum levels for radiological ionic contaminants, maximum levels for water turbidity (cloudiness), and maximum levels for coliform bacteria (which indicate the presence of human or animal fecal contamination). Turbidity and bacteria are examples of suspended water contaminants.

In addition, water supplies can contain dissolved organic chemical contaminants which are usually pollutants that enter water as a result of man's activities, such as insecticides, pesticides and herbicides. These are usually chronically, rather than acutely, toxic to man and other species in extremely small amounts. The trihalomethanes are dissolved organic contaminants, such as chloroform, which are formed in extremely small amounts by the reaction of chlorine used to disinfect water, with humic and fulvic acids from soil erosion. Other organics can enter both surface and groundwater through waste dumping, such as trichlorethylene, tetrachlorethylene (TCEs), polychlorinated biphenyls (PCBs), dioxin, etc. Many of the organic contaminants are probably carcinogenic (cancer-producing). The organics do not necessarily exist in water in the form of dissolved ions.

The Secondary Drinking Water Regulations control contaminants in drinking water that primarily affect the aesthetic qualities of water. Several of these -- chloride, sulfate, copper, iron, manganese, zinc, and total dissolved solids -­ are ionized contaminants.

Color and odor are contaminants which cause objectionable sensory responses to the water.

pH is a measure of the acid or alkaline strength of a water supply and corrosivity refers to the ability of a water supply to disintegrate pipes and containers.