Fundamental Chemistry and Hydraulics - Mathematics and Statistics for the Environment - page 352

TABLE 14.4
Common Metals Found in Water

Metal Health Hazard

Barium Circulatory system effects and increased blood pressure

Cadmium Concentration in the liver, kidneys, pancreas, and thyroid

Copper Nervous system damage and kidney effects; toxic to humans

Lead Same as copper

Mercury Central nervous system (CNS) disorders

Nickel CNS disorders

Selenium CNS disorders

Silver Gray skin

Zinc Taste effects; not a health hazard

Source: Spellman, F.R., Handbook of Water and Wastewater Treatment Plant
Operations , 3rd ed., Lewis Publishers, Boca Raton, FL, 2013.

14.1.2.7.4 Dissolved Oxygen (DO)
Gases, including oxygen, carbon dioxide, hydrogen sulfide, and nitrogen, can be dissolved in water.
Gases dissolved in water are important. For example, carbon dioxide is important because of the
role it plays in pH and alkalinity. Carbon dioxide is released into the water by microorganisms and
is consumed by aquatic plants. Dissolved oxygen (DO) in water is of the most importance to water-
works operators because it is an indicator of water quality. We stated earlier that solutions could
become saturated with solute. This is also the case with water and oxygen. The amount of oxygen
that can be dissolved at saturation depends upon temperature of the water. However, in the case of
oxygen, the effect is just the opposite of other solutes. The higher the temperature is, the lower the
saturation level; the lower the temperature is, the higher the saturation level.

14 .1. 2 . 7. 5 M e t a l s
Metals are common constituents or impurities often carried by water. At normal levels, most metals
are not harmful; however, a few metals can cause taste and odor problems in drinking water. Some
metals may be toxic to humans, animals, and microorganisms. Most metals enter water as part of
compounds that ionize to release the metal as positive ions. Table 14.4 lists some metals commonly
found in water and their potential health hazards.

14.1.2.7.6 Organic Matter
Organic matter or organic compounds are those that contain the element carbon and are derived
from material that was once alive (i.e., plants and animals):

• Fats
• Dyes
• Soaps
• Rubber product
• Wood
• Fuels
• Cotton
• Proteins
• Carbohydrates

Organic compounds in water are usually large, nonpolar molecules that do not dissolve well in
water. They often provide large amounts of energy to animals and microorganisms.