Viruses

Viruses are very different from the other microorganisms. Consider their size, for example. Relative to size, if protozoans are the Goliaths of microorganisms, then viruses are the Davids. Stated more specifically and accurately, viruses are intracellular parasitic particles that are the smallest living infectious materials known—the midgets of the microbial world. Viruses are very simple life forms consisting of a central molecule of genetic material surrounded by a protein shell called a capsid and sometimes by a second layer called an envelope. They contain no mechanisms by which to obtain energy or reproduce on their own; thus, to live, viruses must have a host. After they invade the cells of their specific host (animal, plant, insect, fish, or even bacteria), they take over the host's cellular machinery and force it to make more viruses.

ill!

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Elaborate, irregular

Geometric polyhedral

Long, slender rod

Geometric polyhedral

Figure 8.7 Elaborate shapes of virus.

In the process, the host cell is destroyed and hundreds of new viruses are released into the environment. The viruses of most concern to the waterworks operator are the pathogens that cause hepatitis, viral gastroenteritis, and poliomyelitis.

Smaller and different from bacteria, viruses are prevalent in water contaminated with sewage. Detecting viruses in water supplies is a major problem because of the complexity of the nonroutine procedures involved, although experience has shown that the normal coliform index can be used as a rough guide for viruses just as for bacteria. However, more attention must be paid to viruses whenever surface water supplies have been used for sewage disposal. Viruses are difficult to destroy by normal disinfection practices; increased disinfectant concentration and contact time are required for the effective destruction of viruses. Viruses occur in many shapes, including long, slender rods; elaborate, irregular forms; and geometric polyhedrals (see Figure 8.7).

Note: Viruses that infect bacterial cells cannot infect and replicate within cells of other organisms. It is possible to utilize this specificity to identify bacteria, a procedure called phage typing.

You do not have to be a water/wastewater operator to understand that algae can be a nuisance. Many ponds and lakes in the United States are currently undergoing eutrophication, the enrichment of an environment with inorganic substances (e.g., phosphorus and nitrogen), causing excessive algae growth and premature aging of the water body. The average person may not know what eutrophication means; however, when eutrophication occurs, and especially when filamentous algae such as Caldophora break loose in a pond or lake and wash ashore, algae make their stinking, noxious presence known.

Guide to Alternative Fuels

Guide to Alternative Fuels

Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future.

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