Reading passage Grade 4 English Language Arts
The Microbes That Clean Gorsebrook's Used Water
A grade 4 informational passage about the living microbes that clean used water at a fictional reclamation plant, with literal and inferential comprehension questions.
Objectives
- Students will identify what microbes do to the waste in used water at a reclamation plant.
- Students will explain why air is pumped into the tank, using details from the passage.
- Students will infer why operators send settled microbes back to the first tank.
Vocabulary
Key words: microbe, reclamation, settle, sludge, microscope
Teacher overview
The Gorsebrook Water Reclamation Plant is fictional, but the process the passage describes is the one most towns use to clean the water that leaves their drains. The passage introduces students to the idea that living things, not machines, do the main cleaning work, and that an operator's job includes keeping those living things fed and comfortable. It pairs well with a lesson on cause and effect, since almost every step in the plant exists because of something the microbes need. The misconception to name aloud is that all microbes cause disease, which leads students to expect a plant to kill them rather than feed them, and the second paragraph is written to address that directly.
Passage
The used water from every sink, shower, and drain in Gorsebrook flows to one building at the edge of town. It is called the Gorsebrook Water Reclamation Plant. The dirtiest water in town gets cleaned there. The cleaning is not done by people. It is done by microbes.
A microbe is a living thing far too small to see. Millions of them can fit in a single drop of water. Some microbes make people sick, but most do not. The ones at Gorsebrook eat the waste that people wash down their drains. They have been eating it for years.
The used water first flows into a long, deep tank. The tank looks like it is boiling, but the water is not hot. Pipes along the bottom blow air up through it. The bubbles keep the water moving, and they bring in something the microbes need. Microbes need air to breathe, just as a person does. Without the bubbles, the hungry microbes would slow down and stop eating.
Ms. Havel is an operator at the plant. Her main job is keeping the microbes healthy. She checks how much waste comes in each morning. If a lot arrives, she turns up the air. If the water gets cold, the microbes eat more slowly, so she watches the weather too. Once a week she puts a drop of the tank water under a microscope. She counts the shapes she sees. A healthy tank has a mix of shapes, and a sick tank does not.
After the eating tank, the water flows into a round, quiet tank. Nothing stirs it. The microbes clump together and sink slowly to the bottom. That thick layer at the bottom is called sludge. The water above it turns clear.
The plant does not throw all the sludge away. Pumps send part of it back to the first tank. The microbes in that returned sludge are already hungry, and they start eating the new water right away. Only the extra sludge leaves the plant. Some of it is dried and spread on farm fields, where it feeds crops.
The clear water still gets one last cleaning step before it leaves. Then it flows into the creek below town. Fish live in that creek. Ms. Havel says the fish are the real test of her work.
Questions
- Where does the used water at the Gorsebrook plant come from?
- What do the microbes in the first tank eat?
- Why do pipes blow air up through the first tank?
- Name two things Ms. Havel watches that change how fast the microbes eat.
- What is sludge, and where does it form?
- Why does the plant send part of the sludge back to the first tank instead of throwing all of it away?
- Ms. Havel says the fish in the creek are the real test of her work. What does she mean?
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Answer Key
- Answer: From every sink, shower, and drain in town. The first paragraph states that used water from the whole town flows to the plant.
- Answer: The waste that people wash down their drains. The second paragraph states this directly.
- Answer: Because microbes need air to breathe, and the bubbles also keep the water moving. The passage says the hungry microbes would slow down and stop eating without the air.
- Answer: Any two of these: how much waste arrives each morning, how cold the water is, and the weather. The passage names all three in the paragraph about Ms. Havel.
- Answer: Sludge is the thick layer of clumped microbes that sinks to the bottom of the quiet, round tank. The passage describes it forming after the eating tank.
- Answer: Because the microbes in the returned sludge are already hungry and start eating the new water right away. Accept any answer noting that returning them keeps the eating tank stocked with working microbes.
- Answer: Answers will vary but should connect that the cleaned water flows into the creek where fish live, so healthy fish show the plant cleaned the water well enough for living things downstream.
Differentiation
Support
Provide a simple four-box flow diagram, labeled used water, eating tank, quiet tank, and creek, for students to reference while answering questions 1 through 5. Allow question 7 to be answered aloud before it is written, and let students point to the sentence that supports each of their first three answers.
Extension
Ask students to write a short set of instructions a new operator would need for one cold week, using only what the passage says about temperature, air, and how much waste arrives. The instructions must have at least three numbered steps and must not add facts the passage does not supply.
ELL supports
Pre-teach microbe, settle, and sludge with a jar of muddy water that students watch separate over ten minutes, and use a photograph of bubbles rising in a tank for the air step. Allow questions 1 through 3 to be answered with short phrases, and provide a sentence frame for question 6.