Quiz & test questions Grade 11 English Language Arts
Recovering Phosphorus at Selport: A Reading Analysis Quiz
A 30-point grade 11 quiz pairing an original explainer on nutrient recovery at a fictional plant with a concentration table students read and write from.
Objectives
- Students will locate stated values in a concentration table and report them with their units.
- Students will explain why a treatment process is applied to a concentrated side-stream rather than to the whole flow.
- Students will write an accurate paragraph tracing a substance through a multi-stage process.
Vocabulary
Key words: phosphorus, struvite, side-stream, digester, scale, slow-release fertilizer
Teacher overview
This 35-minute quiz is worth 30 points and pairs an original explainer about nutrient recovery at a fictional treatment plant with a table of phosphorus concentrations. It mixes three multiple-choice items, four short-answer items, and two constructed responses, so recall, table reading, and extended explanation are all assessed. The misconception the quiz is built to surface is the assumption that a treatment plant removes a pollutant once and permanently; students who hold it will miss why a substance released inside the plant can circle back to the head of the process and why the same compound can be a maintenance problem in one place and a product in another.
Assessment
Read the explainer and the table, then answer the items that follow. Point values are shown in parentheses.
Recovering Phosphorus at Selport
Phosphorus is a nutrient that plants need and that rivers can have too much of. When a river receives more than it can absorb, algae grow quickly, then die and decay, and the decay consumes oxygen from the water. Most fish need dissolved oxygen above 5 mg/L, so a bloom can leave a stretch of river unable to support the fish that lived there.
The fictional Selport Water Reclamation Facility treats the sewage of a mid-sized city. Most of the phosphorus arriving with that sewage is taken up by the microorganisms that do the treating, and it leaves the main flow inside the settled solids. Those solids go to a digester, a heated sealed tank where other microorganisms break them down and produce methane. Digestion also releases phosphorus back into the liquid, and that liquid, called a side-stream, is normally returned to the front of the plant. The phosphorus then travels the whole process again.
Returning the side-stream causes a second problem. Under the conditions inside digester piping, phosphorus combines with magnesium and ammonium and crystallizes on pipe walls as a hard mineral called struvite. The crystals narrow pipes, foul pump impellers, and eventually have to be chipped or dissolved out, which takes equipment offline.
Selport now sends the side-stream through a recovery reactor before returning it. The reactor adds magnesium, adjusts the acidity, and stirs the liquid so that struvite forms on purpose, as small round pellets suspended in the vessel rather than as scale on a pipe wall. Operators harvest the pellets, dry them, and sell them to a fertilizer blender, since struvite dissolves slowly in soil and releases its nutrients over a season. The reactor turns a maintenance problem into a product and sends much less phosphorus back to the front of the plant.
Total phosphorus at four points in the fictional Selport plant.
| Sampling point | Total phosphorus (mg/L) |
|---|---|
| Raw influent arriving at the plant | 6.2 |
| Digester side-stream entering the reactor | 620 |
| Digester side-stream leaving the reactor | 88 |
| Final effluent to the Embersley River | 0.4 |
- (2 points) What does the Selport reactor recover from the digester side-stream?
- A) Chlorine
- B) Phosphorus
- C) Dissolved oxygen
- D) Methane
- (2 points) According to the explainer, why does phosphorus in the side-stream cause a problem inside the plant, before any of it reaches the river?
- A) It lowers the temperature of the digester.
- B) It crystallizes as struvite on pipe walls and pump parts.
- C) It kills the microorganisms that treat the sewage.
- D) It makes the final effluent cloudy.
- (2 points) Using the table, state the total phosphorus concentration of the side-stream entering the reactor.
- (2 points) Using the table, state the total phosphorus concentration of the same side-stream after it leaves the reactor.
- (3 points) Explain in one or two sentences why Selport treats the digester side-stream rather than the plant's whole flow.
- (4 points) Which statement is best supported by the explainer and the table together?
- A) The raw influent carries the highest phosphorus concentration found anywhere in the plant.
- B) The reactor removes all phosphorus from the side-stream.
- C) The side-stream is far more concentrated than the raw influent, which is what makes treating it there worthwhile.
- D) The final effluent carries more phosphorus than the raw influent does.
- (4 points) The explainer connects algae growth to a benchmark for fish. State the benchmark and explain the sequence that links a bloom to it.
- (5 points) In one paragraph, explain to a reader who has never toured a treatment plant how phosphorus travels through Selport, from raw sewage to either the river or a bag of fertilizer. Use at least two figures from the table.
- (6 points) The explainer describes struvite as both a maintenance problem and a saleable product. Explain how one substance can be both, and identify what Selport changed in order to make the difference.
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: B) Phosphorus. The explainer states that the reactor grows struvite deliberately in order to capture phosphorus from the side-stream; methane is produced by the digester, not by the reactor.
- Answer: B) It crystallizes as struvite on pipe walls and pump parts. The explainer says the crystals narrow pipes and foul pump impellers, which takes equipment offline for cleaning.
- Answer: 620 mg/L. The table lists this value for the digester side-stream entering the reactor.
- Answer: 88 mg/L. The table lists this value for the same side-stream after the reactor.
- Answer: Because the side-stream is a small flow carrying a very high concentration, so a reactor sized for that stream captures most of the recirculating phosphorus. Treating the entire plant flow would mean handling a far larger volume to reach the same material. Award full credit for any answer naming both the concentration and the smaller volume.
- Answer: C) The side-stream is far more concentrated than the raw influent, which is what makes treating it there worthwhile. The table shows 620 mg/L in the side-stream against 6.2 mg/L in the raw influent, and choice B fails because the concentration leaving the reactor is 88 mg/L rather than zero.
- Answer: The benchmark is dissolved oxygen above 5 mg/L, which most fish require. Excess phosphorus feeds rapid algae growth; the algae die and decay; the decay consumes oxygen; and the oxygen can fall below what fish need, leaving that stretch of river unable to support them.
- Answer: Accept a paragraph that traces the path in order and uses at least two table figures accurately. A full-credit response follows phosphorus from the raw influent at 6.2 mg/L into the settled solids, into the digester where it is released into the side-stream at 620 mg/L, through the reactor that lowers the side-stream to 88 mg/L while forming harvestable pellets, and out through the final effluent at 0.4 mg/L to the river.
- Answer: Accept an explanation resting on where and how the crystals form rather than on what they are made of. Struvite forming uncontrolled on pipe walls is scale that must be chipped out, while the same compound formed on purpose in a stirred vessel makes round pellets that can be harvested, dried, and sold as slow-release fertilizer. What Selport changed was adding a reactor that controls magnesium and acidity so the crystals form where the plant wants them.
Differentiation
Support
Provide the explainer with its four stages already labeled in the margin, so students can locate the side-stream stage before answering items 5 and 8. Give item 8 as a four-box sequence organizer with the stages named and the figures blank. Allow items 3 and 4 to be answered by circling the table rows, and permit item 7 to be answered as a numbered chain of events rather than in sentences.
Extension
Ask students to write the two-sentence caption that would appear beside a photograph of the harvested pellets in the utility's annual report, one sentence stating what the pellets are and one stating what their recovery prevents. The constraint is that the caption may not use the word struvite, which forces precise paraphrase of a technical term.
ELL supports
Pre-teach "nutrient," "digester," "side-stream," "crystallize," and "scale" with a labeled process diagram showing sewage entering, solids settling, the digester, the side-stream loop, and the reactor. Provide a glossary card distinguishing the everyday meaning of "scale" from its meaning here. Allow the constructed responses to be drafted as labeled sequence diagrams that students then convert to sentences with a provided transition bank.
Extensions
Have students compare their item 9 responses and identify which explanations relied on the location of the crystals and which relied only on the intention behind them. The distinction matters, because a plant cannot decide to stop making scale without changing the conditions under which the crystals form, and the difference is visible in the strongest student answers.