Science of Water : Concepts and Applications

138 The Science of Water: Concepts and Applications
Viruses are diffi cult to destroy by normal disinfection practices, requiring increased disinfectant
concentration and contact time for effective destruction.
√ Note: Viruses that infect bacterial cells cannot infect and replicate within cells of other organisms.
It is possible to utilize the specifi city to identify bacteria, a procedure called phage
typing.
ALGAE
You do not have to be a water 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 fi lamentous algae like
Caldophora breaks loose in a pond or lake and washes ashore, algae makes its stinking, noxious
presence known.
Algae are a form of aquatic plants and are classifi ed by color (e.g., green algae, blue-green algae,
golden-brown algae, etc.). Algae occur in many shapes and sizes (see Figure 5.8). Although they are
not pathogenic, algae do cause problems with water/wastewater treatment plant operations. They
grow easily on the walls of troughs and basins, and heavy growth can plug intakes and screens.
Additionally, some algae release chemicals that give off undesirable tastes and odors.
As mentioned, algae are usually classifi ed by their color. However, they are also commonly classifi
ed based on their cellular properties or characteristics. Several characteristics are used to classify
algae including (1) cellular organization and cell wall structure; (2) the nature of the chlorophyll(s);
(3) the type of motility, if any; (4) the carbon polymers that are produced and stored; and (5) the
reproductive structures and methods.
Many algae (in mass) are easily seen by the naked eye—others are microscopic. They occur
in fresh and polluted water as well as in salt water. Since they are plants, they are capable of using
energy from the sun in photosynthesis. They usually grow near the surface of the water because
light cannot penetrate very far through the water.
Algae are controlled in raw waters with chlorine and potassium permanganate. Algae blooms
in raw water reservoirs are often controlled with copper sulfate.
√ Note: By producing oxygen, which is utilized by other organisms including animals, algae play
an important role in the balance of nature.
FUNGI
Fungi are of relatively minor importance in water operations (except for biosolids composting,
where they are critical). Fungi, like bacteria, are also extremely diverse. Most fungi are found in the
FIGURE 5.8 Algae.
Euglenoids Blue green
Diatom