Review It
Remember, authors must support their claims with evidence and such support may come in the form of pros and cons that help the reader gain a balance and complete understanding of the topic. As you examine the evidence, think about the facts and statistics being presented. Notice how the author explains the evidence and how it relates to the claim begin made. Such an explanation is called reasoned judgment. The more logical and well-thought-out the reasoning, the more likely the reader will be to accept and understand the author’s claim. Evaluating the evidence and reasoning that support the claim will ensure that you have the skills necessary to be a critical reader.
This reverse osmosis unit in a desalination plant helps to change saltwater into drinking water.
To review this skill, read the “How to Deal with Leftover Water” section of the article, and then complete the activity below. Think about how the author is continuing to support the claim about the effects of desalination.
How To Deal With Leftover Water
6 The second major environmental concern with desalination is discharge water. Most desalination plants take in two times more seawater than the fresh water they produce. To produce 50 million gallons per day of fresh water, Carlsbad will draw in 100 million gallons of seawater. The leftover water is returned to the ocean as discharge water, but with its salinity — its salt level — doubled.
7 The discharge water is so salty that it does not dissolve well in the ocean.
8 “It’s like oil and vinegar — they stay separate,” Whitney said. “You end up with these very large dead zones … where you have really salty water just sitting on the ocean bottom.”
9 Carlsbad will deal with this problem by mixing the salty water with cooling water discharged from a nearby power plant. As a result, the discharge water will be only about 20 percent saltier than the ocean.
10 Another approach is to use spray nozzles to spread the discharge water under the ocean surface. This helps the salty discharge mix with the ocean water. The water board currently recommends this approach. MacLaggan from Poseidon says, however, that the force of such sprayers is so great that it can kill some sea life.
— Newsela Opens a new window, December 4, 2014
What evidence best supports the idea that desalination is dangerous to sea life? Refer to the details in the article. You may use the highlighter tool to highlight the details, or print the excerpt document Opens a new window and highlight on paper. Next, click Show Answer to see if you are correct.
