Writing prompt Grade 7 Health & Consumer Science
Ellet Creek's Drains and the Manrow River: An Explanatory Prompt
Students write a school website article tracing sink and toilet water through a fictional treatment plant and explaining why each step protects swimmers downstream.
Objectives
- Students will explain four wastewater treatment steps in order and what each step removes.
- Students will connect two treatment benchmarks to the health of people swimming downstream.
- Students will write an informative article with defined terms for a school audience.
Vocabulary
- Wastewater
- Wastewater is used water from sinks, showers, toilets, and businesses that goes down the drain. It travels through sewer pipes to a treatment plant to be cleaned before returning to nature.
- Effluent
- Effluent is the cleaned water that leaves a treatment plant at the end of the process. It is tested carefully before being released to a river, lake, or the ocean.
- Dissolved oxygen
- Dissolved oxygen is the oxygen gas mixed into water that fish and other underwater animals breathe. Cold, moving water holds more oxygen than warm, still water.
- Disinfection
- Disinfection is the step that kills or disables germs in water so it is safe to drink. Water plants usually disinfect with chlorine, ultraviolet light, or ozone.
Also: outfall
Teacher overview
The water that leaves a school's sinks and toilets reaches a treatment plant within hours, and in many towns it reaches a river that people swim in the same day. This prompt asks seventh graders to trace that path at a fictional school, from the drain to the plant to a river swimming spot, and then explain it for other students. One point is worth stating aloud before students draft. Treatment is often described as filtering, yet the central step is biological, because bacteria consume the organic material that would otherwise strip oxygen out of the river.
Prompt
Read the background, then write your article.
Background: where the water goes
Ellet Creek Middle School is a fictional school in a town of the same name. Every sink, shower, and toilet in the building drains into a sewer pipe under the street. That pipe carries the water about three miles to the Ellet Creek Water Reclamation Plant. The plant cleans the water and releases it into the Manrow River at a spot called the outfall. Two miles downstream is Vestry Landing, where families swim and float on inner tubes all summer.
The plant treats the water in steps.
Screening comes first. Bar screens catch rags, wipes, and trash. Anything that gets past this step can jam a pump.
Settling comes next. In a large quiet tank, heavy solids sink to the bottom and grease floats to the top. Both are scraped away.
Biological treatment is the heart of the plant. Billions of helpful bacteria are kept in a tank with the water and fed air. They eat the dissolved organic material that people wash and flush down drains.
Disinfection comes last, before the water leaves. This step kills the germs that could make a swimmer sick.
Numbers that show how well it works
Raw sewage arriving at a plant typically carries 100 to 300 mg/L of organic material, measured as BOD. Secondary treatment rules require the water leaving the plant to average 30 mg/L or less for both BOD and solids, and require the plant to remove at least 85 percent of each.
Those numbers matter downstream. When organic material reaches a river untreated, bacteria in the river use up the oxygen in the water while breaking it down. Most fish need dissolved oxygen above 5 mg/L. A river below a failing plant can drop under that line, and the same water carries germs that cause stomach illness in swimmers.
Your task. Write an informative article for the Ellet Creek Middle School website titled "Where Our Water Goes." Explain the four treatment steps in order and what each one removes. Use at least three specific numbers from the background. Define at least two terms for readers who do not know them. End with a short section telling students what they can do, such as what belongs in a trash can rather than a drain, and why that choice reaches the river. Write five to seven paragraphs. Do not argue a position, because this is an explanation.
Planning Organizer
Fill in every row before you draft. Each row becomes a paragraph or part of one.
| Part of the article | What I will write |
|---|---|
| Opening: what the article will explain | |
| Step 1, screening: what happens and why it matters | |
| Step 2, settling: what happens and why it matters | |
| Step 3, biological treatment: what happens and why it matters | |
| Step 4, disinfection: what happens and why it matters | |
| Number 1 from the background and what it shows | |
| Number 2 from the background and what it shows | |
| Number 3 from the background and what it shows | |
| Term I will define, and my definition | |
| Second term I will define, and my definition | |
| What students can do, and the reason | |
| Closing sentence |
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Exemplar & Rubric
Exemplar response
Where Our Water Goes
Every time someone at Ellet Creek Middle School washes their hands or flushes a toilet, that water starts a three-mile trip to the Ellet Creek Water Reclamation Plant. What the plant does with it decides whether Vestry Landing, two miles downstream, is a safe place to swim in July. Here is the path our water takes.
The first step is screening. Bar screens catch rags, wipes, and trash before the water goes any further. This step protects the pumps, because a wipe that gets through can wrap around a pump and stop it.
The second step is settling. The water sits in a large quiet tank where heavy solids sink and grease floats. Crews scrape both away. The water that leaves this tank looks much cleaner, but most of what matters is still dissolved in it.
The third step is biological treatment, and it is the heart of the plant. Operators keep billions of helpful bacteria in a tank, mix the wastewater in, and pump air through it. The bacteria eat the dissolved organic material from our drains. This step works by feeding the bacteria under careful control rather than by filtering.
The fourth step is disinfection. Before the water leaves, the plant kills the germs that could make a swimmer sick. Then the water flows out of the outfall into the Manrow River. Two terms are worth knowing. Effluent is the treated water leaving the plant. An outfall is the pipe where that water enters the river.
Two numbers show how much work the plant does. Sewage arriving at a plant usually carries 100 to 300 mg/L of organic material, measured as BOD, which stands for biochemical oxygen demand. The rules require the water leaving to average 30 mg/L or less, and the plant must also remove at least 85 percent of that organic material. A third number explains why that matters: most fish need dissolved oxygen above 5 mg/L, and organic material that reaches a river untreated pulls oxygen out of the water as it breaks down.
Students can help in two ways. Flush only toilet paper, because wipes labeled flushable still snag on the screens and on the pumps ahead of them. Also keep grease and leftover medicine out of the sink, because the bacteria in the treatment tank are living things that handle food waste well and handle medicine and cooking grease poorly. The water from our drains ends up at our swimming spot, so these choices matter there.
Rubric
| Criterion | Emerging | Developing | Proficient | Advanced |
|---|---|---|---|---|
| Topic and organization | Steps appear out of order or the article has no clear opening. | Opens the topic but the steps blur together. | Clear opening, four steps in order, and a closing section for students. | Also uses transitions that show how each step prepares the next. |
| Accuracy | Two or more steps are described incorrectly. | One step is described incorrectly or is left vague. | All four steps are described correctly, including biological treatment as bacteria consuming organic material. | Also explains why settling alone cannot finish the job. |
| Use of facts and terms | Uses no numbers from the background and defines no terms. | Uses one number, or defines a term inaccurately. | Uses three numbers correctly and defines two terms clearly. | Uses three or more numbers, defines two terms, and connects a number to swimmer health downstream. |
| Conventions | Errors make the article hard to follow. | Errors are frequent but meaning survives. | Few errors, and the writing suits a school website audience. | Clean conventions and a consistent informative voice throughout. |
Differentiation
Support
Give these students the four steps on cards to place in order before drafting, and a background sheet with the three numbers boxed and labeled. Allow a five-paragraph article, and provide the definition sentence frame: "___ means ___."
Extension
Ask students to add a paragraph explaining why cold water holds more oxygen than warm water, and what that means for a river receiving treated water in August rather than March. Have them state which month leaves less room for error at the plant.
ELL supports
Pre-teach "screening," "settling," "bacteria," and "outfall" with a simple four-box diagram of the plant, one box per step. Allow students to label the diagram first and write from their own labels, and provide a word bank of transition phrases for sequencing.
Extensions
Students can find out where their own community's wastewater is treated and where the treated water is released, then compare that map with the Ellet Creek scenario. A follow-up assignment asks them to write the label for a bathroom sign listing the three things that should never be flushed, in under forty words, so a reader finishes all of it.