1.1: Water Resources and Origin of Contaminants

Learning Objectives

• Explain the water sources and the water cycle
• Discuss water contaminates

This chapter presents a brief introduction to the water sources that are available for potable supply; detailed information is presented in Water 032 (Water Supply). Understanding the water sources used for potable application is important to appreciate the variety of contaminants that can be present in water, and assess their characteristics.

Water Sources

Figure 1.1.1 shows that our planet’s water sources are limited. Freshwater is much easier to use for potable applications because it requires more simple treatment. However, it represents only a very small fraction of the Earth’s water portfolio. A large proportion of the freshwater is locked in glaciers, and is therefore difficultly accessible. As a result, less than 1% of the water present on the planet is groundwater and surface water that can be used as potable water source.

Figure \(\PageIndex{1}\): Distribution of the Earth’s Water by Timothy Bralower is licensed under CC BY-NC-SA 3.0

The origin of a water source (e.g., seawater, groundwater, surface water, or groundwater under the direct information of surface) determines its characteristics and the presence of specific contaminants. The concentration and composition of contaminants in the water are also driven by the movements of water, which is illustrated by the water hydrologic cycle (Figure 1.1.2).

Figure \(\PageIndex{2}\): Water Hydrologic Cycle - The Water Cycle by the USGS is in the public domain

Classifications of Contaminants

Pure water (i.e., H2O) only exists in the vapor state. As water condensates, and runs off as surface water or percolates into the ground, it accumulates contaminants. Contaminants in water can be classified in various ways. The most basic classification is based on the fact that contaminants in water can be solid particles, ions, or dissolved gases.

Contaminants can be found in water in the gas, dissolved, or solid phase

Another classification scheme refers to the causes of contamination:

• Natural contaminants come from soil geology, erosion of soils, etc. Examples of contaminants include fluoride and arsenic.
• Man-made contaminants (also called anthropogenic contaminants):

• • Industrial contaminants vary widely and are specific to the industries that generate them. Examples of industries that generate contaminants often found in water include chemical, mining, metal, textile, food processing, petrochemical, and pulp and paper industries.
  • Agricultural contaminants can be separated into two broad groups:
    • Contaminants that originate from crops, such as pesticides, fertilizers, nutrients, and sediments
    • Contaminants that are derived from animal products, which include a variety of organic contaminants, nitrogenous chemicals, microorganisms, salts; fats, and oils and grease
  • Domestic contaminants can be separated into two groups:
    • “Conventional” contaminants, which include microorganisms, organics, nitrogen, phosphorus, inorganics, metals, detergents, and pesticides
    • Pharmaceuticals and personal care products, which have been gaining attention in the water industry

What is the difference between a contaminant and a pollutant?

• A contaminant is a substance that is not normally expected;
• A pollutant is a substance found at a concentration that has reached a level that adversely affects the suitability of the water for its intended purpose.

For this course, the classification that will be used is the following:

• Chemical contaminants, which can be separated in the following subgroups:
  • Physical parameters or aesthetic characteristics
  • Inorganic materials and minerals
  • Organic materials
• Microorganisms

This classification is also used for water treatment strategies, which include physical treatment processes (e.g., clarification, filtration), chemical processes (e.g., oxidation, precipitation, adsorption), and biological processes (i.e., bacteriologically-mediated reactions). Drinking water regulations are also separated according to these three groups (see Chapter 8 – review chapter # as needed).

Review Questions

1. Outline the water cycle highlighting water sources.
2. List the major contaminates of water in the environment.

Chapter Quiz

1. How much water on planet earth is easily treated for drinking water?
   1. 96%
   2. 20.9%
   3. 32%
   4. < 1.0%
2. Most of the water on earth is found in the ___________.
   1. Atmosphere
   2. Ocean
   3. Ground
   4. Rivers
3. Which of the following is not a major contaminant of water?
   1. Physical contaminants
   2. Nitrogen
   3. Chemical
   4. Biological
4. Anthropogenic contaminants refers to ___________.
   1. Turbidity
   2. Geological contaminants
   3. Inorganic contaminants
   4. Manmade contamination
5. Which of the following contaminants depletes dissolved oxygen in water?
   1. Minerals
   2. Pathogens
   3. Organic matter
   4. Inorganic matter
6. ___________ is(are) an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases the primary productivity of the ecosystem.
   1. Evapotranspiration
   2. Eutrophication
   3. Sublimation
   4. Turbidity
7. The ___________ is(are) essential for the maintenance of most life and ecosystems on the planet.
   1. Climate
   2. Water cycle
   3. Esthetic characteristic of water
   4. Atmospheric circulation
8. Over time, water returns to the ___________, to continue the water cycle.
   1. Ocean
   2. Ground
   3. Aquifers
   4. Plants
9. The ___________ drive(s) the water cycle.
   1. Types of precipitation
   2. Oxygen concentration
   3. Nutrient levels
   4. Sun
10. What portion of surface water is found in the permafrost and ice?
    1. 69%
    2. 68.7%
    3. 96.5%
    4. 30.1%