Worksheet Grade 10 Careers & CTE

Baymoor PFAS Cleanup: A GAC Treatment Technician Worksheet

A grade 10 careers worksheet where students act as a treatment technician at fictional Baymoor, checking PFAS levels against the MCL and reporting to the right precision.

Grade: Grade 10
Subject: Careers & CTE
Material: Worksheet
Time: 35 min
Prep: No prep
Materials: None

Standards

HSN-Q.A.3 Common Core Math

Choose a level of accuracy appropriate to limitations on measurement when reporting quantities.

How this material aligns: Items 6 and 8 have students report a treated PFAS value to the precision the lab method supports, the exact match-accuracy-to-instrument judgment this standard asks for.

All materials for HSN-Q.A.3 →

HSN-Q.A.1 Common Core Math

Use units as a way to understand problems and to guide the solution of multi-step problems; choose and interpret units consistently in formulas; choose and interpret the scale and the origin in graphs and data displays.

How this material aligns: Items 3, 4, and 7 carry ppt units through percent-removal and removal-efficiency calculations, keeping units consistent across the multi-step problem as this standard requires.

All materials for HSN-Q.A.1 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-23.

Objectives

Students will compare PFAS sample results to the federal maximum contaminant level.
Students will calculate percent removal and removal efficiency across a granular activated carbon unit.
Students will report a treated value to the precision the test method supports.

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.
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.
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.

Also: significant figures

Teacher overview

PFAS are a group of long-lasting chemicals that show up in some water supplies at very low levels, measured in parts per trillion. A federal rule sets the maximum contaminant level, or MCL, for two of them, PFOA and PFOS, at 4.0 ppt each. This worksheet puts students in the role of a treatment technician at the fictional Baymoor Water District, checking sample results against the MCL, figuring out how much a granular activated carbon unit removes, and reporting each result to the precision the test method actually supports. Real compliance samples go to certified labs that use EPA-approved methods, and those methods cannot reliably measure PFOA and PFOS as finely as the 0.1 ppt used here; that precision is set for this fictional scenario.

Baymoor PFAS Cleanup: A GAC Treatment Technician Worksheet — Grade 10 Careers & CTE

Name: ____________________________ Date: ______________

Student Worksheet

You are a treatment technician for the fictional Baymoor Water District. The town of Baymoor found PFOA in a raw well at 21 ppt and PFOS at 12 ppt. The federal MCL is 4.0 ppt each for PFOA and PFOS. This rule was set in April 2024 with compliance required by April 2029, and in May 2026 EPA proposed letting eligible systems apply for a two-year exemption to April 2031; the proposal was not final as of September 2026, so the rule is still in motion. The district installs a granular activated carbon (GAC) unit that removes 95% of the PFOA and 90% of the PFOS. Removal efficiency (%) = (influent minus effluent) / influent x 100. The district's contract lab method reads to the nearest 0.1 ppt.

By how many ppt does the raw PFOA level exceed the 4.0 ppt MCL?
By how many ppt does the raw PFOS level exceed the 4.0 ppt MCL?
The GAC removes 95% of the PFOA. What PFOA concentration, in ppt, leaves the GAC unit?
The GAC removes 90% of the PFOS. What PFOS concentration, in ppt, leaves the GAC unit?
Does the treated PFOA from item 3 meet the 4.0 ppt MCL? Does the treated PFOS from item 4? Explain in one sentence.
The lab reports PFOA to two significant figures. Write your item 3 answer to two significant figures.
Confirm the GAC's PFOA removal efficiency using the formula: (21 minus your item 3 answer) / 21 x 100.
The district's contract lab method reads to the nearest 0.1 ppt. Explain why reporting a treated value as "1.05000 ppt" would be false precision.
The rule remains in motion. Explain why a technician should track the proposed deadline exemption rather than assume the 2029 date is settled for the district.
A second Baymoor well reads PFOA at 3.5 ppt with no treatment. Is that well in compliance with the 4.0 ppt MCL, and by what margin?

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: 17 ppt. 21 ppt minus 4.0 ppt = 17 ppt above the MCL.
Answer: 8 ppt. 12 ppt minus 4.0 ppt = 8 ppt above the MCL.
Answer: 1.05 ppt. Removing 95% leaves 5%: 21 ppt x 0.05 = 1.05 ppt.
Answer: 1.2 ppt. Removing 90% leaves 10%: 12 ppt x 0.10 = 1.2 ppt.
Answer: Yes to both. Treated PFOA at 1.05 ppt and treated PFOS at 1.2 ppt are each below the 4.0 ppt MCL, so both meet the limit.
Answer: 1.1 ppt. To two significant figures, 1.05 ppt rounds to 1.1 ppt.
Answer: 95.0%. (21 minus 1.05) / 21 x 100 = 19.95 / 21 x 100 = 95.0%.
Answer: The lab method only resolves to the nearest 0.1 ppt, so digits beyond that, as in 1.05000 ppt, claim an accuracy the method does not have and are false precision.
Answer: Because the rule is still in motion, the district may or may not qualify for an exemption to 2031, and the proposal itself could still change. Planning, budgets, and reporting depend on the requirement that actually applies, so a technician should track the proposal rather than assume the original date holds.
Answer: Yes, by 0.5 ppt. 3.5 ppt is below the 4.0 ppt MCL, so the well is in compliance with a margin of 4.0 minus 3.5 = 0.5 ppt.

Differentiation

Support

Provide a filled-in example that removes 80% of a 10 ppt sample, worked step by step, before students try items 3 and 4. Give a short reminder card on how to count significant figures for item 6.

Extension

Ask students to find the smallest whole-percent removal the GAC would need to bring the raw PFOA sample down to or below the 4.0 ppt MCL, and to show the calculation that supports their answer.

ELL supports

Pre-teach "PFAS," "granular activated carbon," "maximum contaminant level," and "significant figures" with simple definitions and a picture of water passing through a carbon filter. Allow items 5, 8, and 9 to be answered with short phrases rather than full sentences.