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Regardless of any other factors, water piped into the home must be potable. To be potable it should be completely free of disease organisms. Water is the breeding ground for an almost unbelievably large variety of organisms. Water does not produce these organisms. It merely is an ideal medium in which they can grow. These organisms gain entry into the water through a variety of sources. They enter the water from natural sources, surface drainage, and sewage. Many of the organisms in water are harmless. In fact, they are extremely beneficial to man. Others have a mild nuisance value. And still, others are a source of disease.

In general, those organisms which are potential disease-producers are of primary concern. These are of five types:

  1. bacteria,
  2. protozoa,
  3. worms,
  4. viruses, and
  5. fungi.

The presence of certain organisms of these various types can lead to such infectious diseases as typhoid fever, dysentery, cholera, jaundice, hepatitis, giardiasis, undulant fever, and tularemia, as well as other diseases which spread through drinking unsafe water.

Tremendous strides have been made in the control of these diseases within recent years. Much of the credit must go to sanitary engineers for their careful, consistent control of public water supplies. As proof, outbreaks of typhoid fever in either this country or Canada are rare. Natural disasters can play havoc with water supplies, but under routine conditions, typhoid is no longer a serious threat. Paradoxically, the freedom from typhoid and other similar water-borne diseases makes necessary even greater vigilance today. For now, whole generations have grown up without the opportunity to develop a natural immunity to such diseases. Thus a failure in the protective system could result in far more people succumbing to the disease than in the past.

As was previously indicated, many water­borne organisms are extremely beneficial to man. Bacteria, protozoa, and fungi that purify polluted water are essential to our well-being. Many of these organisms set into motion the chain reactions that result in purification.

We can classify living organisms in many ways and into many groups. Modern taxonomy categorizes living organisms into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia. Monera includes single-celled bacteria and photosynthetic blue-green algae. They differ from all other organisms in that their more primitive cell structures lack a nuclear membrane as well as other membrane-bound organelles. They are called prokaryotes.

All other organisms are eukaryotes, that is organisms with cells that have distinct nuclei surrounded by nuclear membranes, as well as a variety of other well-defined membranous organelles. Organelles are specialized parts of cells (as mitochondria, chloroplasts, or endoplasmic reticulum) performing functions analogous to those of organs in many-celled plants and animals.

Members of the kingdom Protista are known as protists. They are solitary, single-celled eukaryotes (but some species form loose aggregations of cells called colonies). Animal-like protists are the protozoa; they are generally larger than bacteria and are mobile. Plant-like protists include several divisions of algae; these contain chlorophyll and carry on photosynthesis.

The Fungi are a diverse group of eukaryotes that are plant-like but that cannot carry on photosynthesis. They serve as decomposers, absorbing nutrients from dead leaves or other organic matter in soil and water. Fungi produce spores during the reproductive process. They consist of slime molds, such as the slimy masses found on decaying leaves and wood, and the true fungi, such as molds, yeasts, mildews, and mushrooms.

Plantae (plant) and Animalia (animal) kingdoms consist of the multicellular and well-developed plants and animals we are all familiar with. Plant cells contain photosynthetic pigments, such as chlorophyll, and plants carry out photosynthesis. Animal cells lack photosynthetic pigments, so animals must obtain nutrients by eating other organisms. (-->Next)

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