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Reading passage Grade 5 Science

The Cleanup Crew at Kemsley: Microbes That Eat Waste

A grade 5 informational passage about an operator who keeps trillions of microbes fed and full of air at a fictional water reclamation plant, with six questions.

Objectives

  1. Students will quote accurately from the passage to answer questions about the treatment steps.
  2. Students will explain how microbes turn waste in water into settled solids and gas.
  3. Students will draw a labeled model showing where the matter in the waste ends up.

Vocabulary

Floc
Floc is the fluffy clumps of dirt and treatment chemicals that form in the water during cleaning at a treatment plant. Floc looks like tiny snowflakes drifting in the water.
Biosolids
Biosolids are the nutrient-rich solid material left over after sewage sludge has been treated and made safe. Many farms use treated biosolids as fertilizer for their fields.

Also: microbe, reclamation, settle

Teacher overview

This passage follows one operator through the biological stage of the water reclamation plant in the fictional town of Kemsley, where living microbes do most of the cleaning. Teachers can assign it during a unit on matter cycling through ecosystems, since the microbes act as decomposers that turn dissolved waste into solids that settle out and gas that leaves the water. A common error in this topic is picturing a wastewater plant as a giant strainer that filters everything out; the passage is written so that students see the screen catch only the large objects, while the dissolved waste is handled by something alive.

The Cleanup Crew at Kemsley: Microbes That Eat Waste — Grade 5 Science
Name: ____________________________ Date: ______________

Passage

Nadia Prell starts work before the sun comes up. She is an operator at the Kemsley Water Reclamation Facility, in the small town of Kemsley. Nearly all the water the town uses indoors ends up at her plant. It comes from sinks, showers, washing machines, and toilets, and it arrives through one large pipe.

The first steps use machines. A steel bar screen catches rags, sticks, and other trash that should never have gone down a drain. Then the water moves slowly through a long tank. Sand and grit sink to the bottom there.

What is left looks like dirty water, and that is the hard part. The waste in it is dissolved or broken into tiny bits. No screen can catch it. So Kemsley hands the job to something alive.

The next tank is as big as a swimming pool. Its surface rolls and bubbles all day. The bubbles come from blowers that push air through pipes in the floor of the tank. Living in that water are trillions of microbes. Microbes are bacteria and other tiny creatures, far too small to see without a microscope.

The microbes eat the waste. That is the whole idea. They use the waste as food and they use the oxygen from the bubbles to break it down. Waste that was floating in the water becomes part of the microbes themselves. Some of it leaves the tank as gas.

Nadia's main job is keeping the microbes healthy. She checks the air, the flow, and the temperature. Twice a shift she carries a jar of tank water to the lab and puts one drop under a microscope. She looks for certain slow creatures with waving hairs. When she sees plenty of them, the tank is doing well. When they disappear, something is wrong, and she has only a few hours to fix it before the whole tank suffers.

The microbes clump into brown flakes called floc. In the next tank the water sits still, and the flakes settle to the bottom like snow. Clear water flows off the top. Nadia pumps some of the settled microbes back into the bubbling tank so the crowd there stays large. The rest is thickened and dried into biosolids, which farmers can spread on fields.

Before the clear water leaves for Tarrow Creek, it passes under lamps that give off ultraviolet light. That light stops any germs left in the water from making copies of themselves.

Nadia says the plant does not clean the water by itself. Her job is to keep the microbes fed, warm, and full of air, so that they can do the cleaning for her.

Questions

  1. What does the steel bar screen catch at the start of the plant? Quote the words from the passage that tell you.
  2. Where do the microbes in the big tank get the oxygen they need?
  3. The passage uses the word "floc." According to the passage, what is floc?
  4. Why does Nadia pump some of the settled microbes back into the bubbling tank instead of sending all of them away?
  5. Nadia says the plant does not clean the water by itself. Quote one sentence from the passage that supports what she means, then explain the sentence in your own words.
  6. Draw a diagram with arrows that shows where the matter in the waste goes at Kemsley. Start with waste in the water, and include the microbes, the settled flakes, and the gas that leaves the tank. Label each part.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: Rags, sticks, and other trash. The passage says the steel bar screen "catches rags, sticks, and other trash that should never have gone down a drain."
  2. Answer: From bubbles of air. The passage explains that blowers push air through pipes in the floor of the tank, and the microbes use the oxygen from those bubbles to break down the waste.
  3. Answer: Brown flakes of clumped microbes. The passage says the microbes clump into brown flakes called floc, and that those flakes settle to the bottom of the next tank.
  4. Answer: So the bubbling tank keeps enough microbes to eat the waste that keeps arriving. The passage says she returns some settled microbes so the crowd there stays large, which means the plant does not have to grow a new population every day.
  5. Answer: Any accurate quotation showing the microbes doing the work, such as "The microbes eat the waste." A student explanation should say that the machines only remove the large trash and the grit, while the living microbes remove the waste that is dissolved in the water.
  6. Answer: A labeled diagram with arrows running from waste in the water, to the microbes in the bubbling tank, and then to two ends: flakes of floc that settle and become biosolids spread on fields, and gas that leaves the tank. Accept any drawing that shows the matter moving from the water into the microbes and then out in those two forms.

Differentiation

Support

Read the passage aloud once while students follow along, pausing after each section to name the step in one phrase. Give these students a partly drawn diagram for question 6 with the boxes already labeled, so they only add the arrows.

Extension

Ask these students to write a short paragraph explaining what would happen at the fictional Kemsley plant if the blowers failed for a full day, using at least two details from the passage as support. Have them predict what Nadia would see under the microscope.

ELL supports

Pre-teach "microbe," "waste," "settle," and "floc" with simple sketches, and provide a picture sequence of the four tanks in order. Allow students to answer questions 2, 3, and 4 in short phrases, and let them label their diagram for question 6 in their first language before adding English words.

Extensions

Have students look at pond water or a soil-and-water mixture under a classroom microscope and sketch what they find. The teacher collects the pond water, and students wash their hands after handling it. The creatures they see are relatives of the ones Nadia counts, and the sketch gives students a reason to believe that a tank can hold trillions of living things nobody can see from the walkway.