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Caring for Earth
The Wet Treatment, Part 2



The Wet Treatment, Part 2
Reading Level
     edHelper's suggested reading level:   grades 7 to 9
     Flesch-Kincaid grade level:   9.07

Vocabulary
     challenging words:    digesters, effluent, hydrologists, power-generation, sedimentation, settles, sludge, solid-waste, wastewater, wastewater-treatment, sewage, killing, slow-moving, organic, scum, destination
     content words:    Wet Treatment


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The Wet Treatment, Part 2
By Trista L. Pollard
  

1     In The Wet Treatment, Part 1, we explored the destination of our wastewater and the beginning of the water treatment process. Let us continue our exploration by moving on to the fourth step. Removing sludge is the next part of the treatment for our wastewater. Sludge, which is the organic part of sewage, settles to the bottom of the tanks and is pumped to large tanks called digesters to be processed. A small part of water is removed during this step. This is called thickening. Removing scum is the fifth step in the treatment process. Scum is grease, oils, plastics, and soaps that are in the wastewater. When the sludge settles to the bottom of sedimentation tanks, lighter materials float to the surface of the water. The scum is skimmed from the surface of the water using slow-moving rakes. The scum is thickened and sent to the digesters with the sludge.
 
2     Wastewater-treatment plants also use a filtration process to treat the sewage. Once the solids are removed, the liquid sewage is filtered through a substance, usually sand, by gravity. The filtration process helps to remove almost all of the bacteria, odor, and the remaining solid waste from the wastewater. It also reduces the color of the wastewater and the amount of iron in the water. In some plants, the water may be filtered through carbon particles to remove organic material particles. Now people can buy carbon filters for their homes to remove bacteria and other materials from their tap water.
 
3     The sixth step in the treatment process focuses on killing bacteria. The wastewater flows into a tank called a chlorine contact tank. Once the water is in the tank, chlorine is added to kill the bacteria. Remember, bacteria in our water can cause serious health problems like diseases. As the bacteria are destroyed, most of the chlorine is removed. Any chlorine that remains must be neutralized by adding other chemicals. This protects the fish and other marine animals when the treated water is released back into the environment.

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