Dissolved Gases, Heavy Metals, & Dissolved Organic Compounds As Water Impurities
Dissolved carbon dioxide (CO2) associates with water molecules to form carbonic acid (H2CO3), reducing the pH and contributing to corrosion in water lines, especially steam and condensate lines. Carbonic acid, in turn, dissociates to bicarbonate (HCO3–) or carbonate (CO32-), depending on pH. Most of the CO2 found in water comes not from the atmosphere but from carbonate that the water has dissolved from rock formations.
Dissolved oxygen (02) can corrode water lines, boilers and heat exchangers, but is only soluble to about 14 ppm at atmospheric pressure.
The infamous “rotten egg” odor, hydrogen sulfide (H2S) can contribute to corrosion. It is found primarily in well water supplies or other anaerobic sources. H2S can be readily oxidized by chlorine or ozone to eliminate sulfur.
Radon is a water-soluble gas produced by the decay of radium and its isotopes. It is the heaviest gas known and occurs naturally in groundwater from contact with granite formations, phosphate and uranium deposits. Prolonged exposure may cause human health problems including cancer.
Heavy metals such as lead, arsenic, cadmium, selenium and chromium – when present above certain levels – can have harmful
effects on human health. In addition, minute concentrations may interfere with the manufacture and effectiveness of pharmaceutical products, as well as laboratory and industrial processes of a sensitive nature.
Dissolved Organic Compounds
Dissolved organic materials occur in water both as the product of material decomposition and as pollution from synthetic compounds such as pesticides.
Tannins, humic acid and fulvic acids are common natural contaminants. They cause color in the water and detract from the aesthetics of water but, unless they react with certain halogens, they have no known health consequences in normal concentrations. In the presence of free halogen compounds (principally chlorine or bromine), they form chlorinated hydrocarbons and trihalomethanes (THM’s), which are suspected carcinogens. Maximum allowable limits of THM’s in municipal systems have been imposed by the United States Environmental Protection Agency (EPA).
Synthetic Organic Compounds
A wide variety of synthetic compounds which are potential healthhazards are present in water systems due to the use of industrial and agricultural chemicals. These compounds are not readily biodegradable and leach from soil or are carried by runoff into water sources. Many are suspected carcinogens and are regulated by the EPA.