Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Water pollution and purification

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infectious microorganisms; Economic uses and benefits of

microorganisms; Growth and growth media; Public health,

current issues; Radiation mutagenesis; Water pollution and

purification; Water quality

WWater pollution and purificationATER POLLUTION AND PURIFICATION

With respect to microorganisms, water pollution refers to the

presence in water of microbes that originated from the intes-

tinal tract of humans and other warm-blooded animals. Water

pollution can also refer to the presence of compounds that pro-

mote the growth of the microbes. The remediation of polluted

water—the removal of the potentially harmful microorgan-

isms—or the reduction of their numbers to levels considered

to be acceptable for whatever purpose the water is used, rep-

resents the purification of water.

Microorganisms that reside in the intestinal tract find

their way into fresh and marine water when feces contaminate

the water. Examples of bacteriathat can pollute water in this

way are Escherichia coli, Salmonella, Shigella, and Vibrio

cholerae. Warm-blooded animals other than humans can also

contribute protozoan parasitesto the water via their feces. The

two prominent examples of health relevance to humans are

Cryptosporidium parvumand Giardia lamblia. The latter two

species are becoming more prominent. They are also resistant

to chlorine, the most popular purification chemical.

Normally, the intestinal bacteria do not survive long in

the inhospitable world of the water. But, if they are ingested

while still living, they can cause maladies, ranging from

inconvenient intestinal upset to life-threatening infections. A

prominent example of the latter is Escherichia coli O157:H7.

Pollution of the water with this strain can cause severe intes-

tinal damage, life long damage to organs such as the kidney

and—especially in the young, elderly and those whose

immune systems are compromised—death.

There are several common ways in which microorgan-

isms can pollute water. Runoff from agricultural establish-

ments, particularly where livestock is raised, is one route of

contamination. Seasonal runoff can occur, especially in the

springtime when rainfall is more pronounced. The feeding of

birds (e.g., ducks) is now recognized as a contributing factor.

For example, a large numbers of ducks that congregate can

contribute large quantities of fecal material to localized ponds

and lakes.

Once in the water, the growth of microorganisms can be

exacerbated by environmental factors such as the water tem-

perature, and by the chemical composition of the water. For

A wastewater treatment plant in Detroit, Michigan.

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