Arrange a tour to the sewage-treatment plant that serves your ...

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Arrange a tour to the sewage-treatment plant that serves your community. Compare it with what is described in this chapter.
 
  Is the water being purified or handled in a way that will prevent cultural eutrophication? Are sludges being converted to, and used as, fertilizer? What improvements, if any, are in order? How can you help promote such improvements?

Question 2

A large number of fish are suddenly found floating dead on a lake. You are called in to investigate the problem. You find an abundance of phytoplankton and no evidence of toxic dumping. Suggest a reason for the fish kill.
 
  What will be an ideal response?

[cascooper22]

Answer to Question 1

Most communities will not have biological nutrient removal, nor will they have an alternative sludge treatment. Sewage treatment will stop at secondary treatment and, typically, the sludge will be land filled. Discussions concerning the economic and health costs and benefits of leaving the system as is or altering the system to include biological nutrient removal and/or treatment of the sludge prior to use as fertilizer would be the place to begin promoting improvement.

Answer to Question 2

A very likely reason for the fish kill is low oxygen level in the lake. A source for the nutrient enrichment should be located, as this was the first step in the process. Nutrient enrichment allow(ed) the rapid growth and multiplication of phytoplankton, increasing the turbidity of the water. The increasing turbidity shade(d) out the SAV that live in the water. With the die-off of SAV, there (was) a loss of food, habitats, and dissolved oxygen. . . . Thus, phytoplankton soon reache(d) a maximum population density. . . . Dead phytoplankton settle(d) out, resulting in heavy deposits of detritus on the lake or river bottom, which supported an abundance of decomposers, mainly bacteria. The explosive growth of bacteria, consuming oxygen via respiration, creates an additional demand for dissolved oxygen. Suffocation of the fish resulted.

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TYSM

[mohan]

Excellent