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Quiz & test questions Grade 11 Science

Morrant Well PFAS Treatment: Removal and Regulation Quiz

A grade 11 science quiz on PFAS chemistry, the 4.0 ppt limit, and treatment, mixing multiple-choice, computation, and evaluation items around a fictional town's well.

Objectives

  1. Students will identify PFAS chemistry, the drinking-water limit, and common treatment methods.
  2. Students will calculate removal efficiency and evaluate two treatment options for a contaminated well.

Vocabulary

PFAS
A large family of human-made chemicals used in things like nonstick pans, waterproof fabric, and firefighting foam. They are called forever chemicals because they take a very long time to break down.
Maximum contaminant level (MCL)
A maximum contaminant level, or MCL, is the highest amount of a certain substance that federal rules allow in drinking water. Water systems test regularly to prove their water stays under each limit.
Granular activated carbon
Small black grains of specially treated carbon that grab contaminants as water flows through them. Utilities use big tanks of it to remove PFAS, bad tastes, and odors.
Reverse osmosis
Reverse osmosis cleans water by pushing it through a membrane with holes so tiny that salt and most other dissolved things cannot fit through. It can even turn seawater into fresh water.

Also: removal efficiency

Teacher overview

This 30-minute quiz is worth 22 points and checks whether students understand why PFAS are difficult to remove, what the drinking-water limit is, and how treatment performance is measured. It uses the fictional town of Morrant, which found PFAS in a well and must decide how to treat it. The items mix three multiple-choice questions, three computation questions, and two written questions, including one that asks students to evaluate two treatment options against each other.

Morrant Well PFAS Treatment: Removal and Regulation Quiz — Grade 11 Science
Name: ____________________________ Date: ______________

Assessment

Use the fictional town of Morrant where a scenario is given. The maximum contaminant level for PFOA and PFOS is 4.0 ppt each.

  1. (2 points) PFAS are often called "forever chemicals" mainly because:
    • A) they are radioactive
    • B) they contain very strong carbon-fluorine bonds that resist breakdown
    • C) they evaporate almost instantly
    • D) they are living organisms
  2. (2 points) The EPA maximum contaminant level for PFOA and PFOS in drinking water is about:
    • A) 4.0 ppt each
    • B) 4.0 mg/L each
    • C) 15 ppb each
    • D) 0.3 NTU each
  3. (2 points) Which treatment is commonly used to remove PFAS from drinking water?
    • A) Adding more chlorine
    • B) Granular activated carbon
    • C) Raising the pH
    • D) Ordinary sand filtration alone
  4. (3 points) Morrant's well measures 88 ppt of PFOA entering a granular activated carbon unit. After treatment the water measures 6 ppt. Using removal efficiency = (influent - effluent) / influent x 100, calculate the percent removal. Round to the nearest whole percent.
  5. (3 points) Does the 6 ppt treated water meet the 4.0 ppt limit? State by how much it clears or misses the limit.
  6. (3 points) Morrant needs the treated water at or below 4.0 ppt. Starting from the 88 ppt influent, what percent removal is required to reach exactly 4.0 ppt? Round to the nearest tenth.
  7. (3 points) Explain why PFAS is harder to remove than many other contaminants, connecting your answer to its chemical structure.
  8. (4 points) Granular activated carbon and reverse osmosis can both lower PFAS, but reverse osmosis also produces a concentrated waste stream and uses more energy. Morrant must choose one. Give one advantage and one disadvantage of each, then state which you would recommend and why.

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: B.
    PFAS resist breakdown because of their very strong carbon-fluorine bonds, which is why they persist in the environment and earn the "forever chemicals" nickname.
  2. Answer: A.
    The maximum contaminant level for PFOA and PFOS is 4.0 ppt each. The other options use the wrong unit (mg/L), the lead action level (15 ppb), or the turbidity standard (0.3 NTU).
  3. Answer: B.
    Granular activated carbon adsorbs PFAS onto its surface and is a common treatment. Adding chlorine or adjusting pH does not remove PFAS, and ordinary sand filtration alone does not capture these dissolved molecules.
  4. Answer: 93%.
    Removal efficiency = (88 - 6) / 88 x 100 = 82 / 88 x 100 = 93.18, which rounds to about 93 percent.
  5. Answer: no, it misses the limit by 2.0 ppt.
    The treated water is 6 ppt, which is above the 4.0 ppt limit by 6 - 4.0 = 2.0 ppt, so it is not yet compliant and needs further treatment.
  6. Answer: 95.5%.
    Required removal = (88 - 4.0) / 88 x 100 = 84 / 88 x 100 = 95.45, which rounds to about 95.5 percent.
  7. Answer: its strong carbon-fluorine bonds resist breakdown.
    Accept any answer explaining that PFAS molecules are held together by very strong carbon-fluorine bonds, so conventional treatments that rely on breaking contaminants down do little. PFAS must instead be physically captured, for example by adsorption onto activated carbon, which is slower and more demanding.
  8. Answer: a reasoned choice with trade-offs for each.
    Accept any answer that gives a real advantage and disadvantage for each option, for example: granular activated carbon is simpler and lower energy but the carbon must be replaced and disposed of; reverse osmosis removes many contaminants at once but uses more energy and creates a concentrated waste stream that must be managed. A full-credit answer states a recommendation and justifies it with these trade-offs.

Differentiation

Support

Provide the removal-efficiency formula already written with labeled blanks for influent and effluent, and work one example with different numbers before students reach item 4. Allow a calculator for all computation items.

Extension

Have students calculate how much the required removal from item 6 would change if Morrant's influent were twice as high, and write a short explanation of why a higher starting concentration demands a higher percent removal to reach the same limit.

ELL supports

Pre-teach PFAS, maximum contaminant level, removal efficiency, and activated carbon with short definitions and a simple picture of contaminant molecules sticking to carbon. Provide a sentence frame for items 7 and 8, such as "PFAS is hard to remove because its ___ bonds are very strong."