Methods of Water Treatment


Water Contaminants

Acidic Water
Aluminum
Ammonia
Arsenic
Bacteria
Barium
Benzene
Bicarbonate
Borate (Boron)
Bromine (Bromide)
Cadmium
Calcium
Carbon Dioxide
Carbon Tetrachloride
Chloride
Chlorine
Chromium
Color
Copper
Cryptosporidium
Cyanide
Fluoride
Giardia Lamblia
Hardness
Hydrogen Sulfide
Iron
Lead
Legionella
Magnesium
Manganese
Mercury
Methane
Nickel
Nitrate
Nitrite
Odor
Organics
Pesticides
pH
Potassium
Radium
Radon
Selenium
Silica
Silver
SOC's
Sodium
Strontium
Sulfate
Taste
THM's
TOC
Total Dissolved Solids
Turbidity
Uranium
Viruses
VOCs

Carbon Dioxide

Source
Free carbon dioxide (C02) exists in varying amounts in most natural water supplies. Most well waters will contain less than 50 ppm. Carbon Dioxide in water yields an acidic condition. Water (H2O) plus carbon dioxide (C02) yields carbonic acid (H2C03). The dissociation of carbonic acid yields hydrogen (H) and bicarbonate alkalinity (HCO3). The pH value will drop as the concentration of carbon dioxide increases, and conversely1will increase as the bicarbonate alkalinity content increases.

H20 + CO2 <===> H2CO3 <==> H+ + HCO3

Water with a pH of 3.5 or below generally, contains mineral acids such as sulfuric or hydrochloric acid. Carbon Dioxide can exist in waters with pH values from 3.6 to 8.4, but will never be present in waters having a pH of 8.5 or above. The pH value is not a measurement of the amount of carbon dioxide in the water, but rather the relationship of carbon dioxide and bicarbonate alkalinity.

Treatment
Free CO2 can be easily dissipated by aeration. A two-column deionizer (consisting of a hydrogen form strong acid cation and a hydroxide form strong base anion) will also remove the carbon dioxide. The cation exchanger adds the hydrogen ion (H+), which shifts the above equation to the left in favor of water and carbon dioxide release. The anion resin removes the carbon dioxide by actually removing the bicarbonate ion. A forced draft degasifier placed between the cation and anion will serve to blow off the CO2 before it reaches the anion bed, thus reducing the capacity requirements for the anion resin. The CO2 can be eliminated by raising the pH to 8.5 or above with a soda ash or caustic soda chemical feed system.