5.3 Water pollution

Learning objectives

After reading this module, students should be able to

• understand the major kinds of water pollutants and how they degrade water quality
• understand how and why the lack of safe drinking water in some parts of the world is a major problem
• know what sewage treatment does and why it is important
• know why it is more difficult to remediate groundwater pollution than surface water pollution
• understand how we can work toward solving the crisis involving water pollution

The water pollution crisis

The Module Water Cycle and Fresh Water Supply described one aspect of the global water crisis, the water shortages that afflict many arid and densely populated areas. The global water crisis also involves water pollution, because to be useful for drinking and irrigation, water must not be polluted beyond certain thresholds. According to the World Health Organization, in 2008 approximately 880 million people in the world (or 13% of world population) did not have access to improved (safe) drinking water ( World Health Statistics, 2010 ) (See Figure Proportion of Population by Country Using Improved Drinking Water Sources in 2008 ). At the same time, about 2.6 billion people (or 40% of world population) lived without improved sanitation (see Figure Proportion of Population by Country Using Improved Sanitation Facilities in 2008 ), which is defined as having access to a public sewage system, septic tank, or even a simple pit latrine. Each year approximately 1.7 million people die from diarrheal diseases associated with unsafe drinking water, inadequate sanitation, and poor hygiene, e.g., hand washing with soap. Almost all of these deaths are in developing countries, and around 90% of them occur among children under the age of 5 (see Figure Deaths by Country from Diarrhea Caused by Unsafe Water, Unimproved Sanitation, and Poor Hygiene in Children Less than 5 Years Old, 2004 ). Compounding the water crisis is the issue of social justice; poor people more commonly lack clean water and sanitation than wealthy people in similar areas. Globally, improving water, sanitation, and hygiene could prevent up to 9% of all disease and 6% of all deaths. In addition to the global waterborne disease crisis, chemical pollution from agriculture, industry, cities, and mining threatens global water quality. Some chemical pollutants have serious and well-known health effects; however, many others have poorly known long-term health effects. In the U.S. currently more than 40,000 water bodies fit the definition of “impaired” set by EPA (See Figure Percentage of Impaired Water Bodies in a Watershed by State in USA Based on US EPA Data in 2000 ), which means they could neither support a healthy ecosystem nor meet water quality standards. In Gallup public polls conducted over the past decade Americans consistently put water pollution and water supply as the top environmental concerns over issues such as air pollution, deforestation, species extinction, and global warming.