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Worksheet Grade 7 Careers & CTE

Reading a Sampling Log: A Water Testing Technician at Marlow Springs

A grade 7 careers worksheet where students read a water testing technician's field log and compare turbidity, chlorine, pH, and pressure readings to real limits.

Objectives

  1. Students will compare field readings to regulatory limits for turbidity, chlorine, pH, and pressure.
  2. Students will describe what a water testing technician does using evidence from a sampling log.

Vocabulary

Turbidity
Turbidity is a measure of how cloudy or murky water looks because of tiny particles floating in it. Clear water has low turbidity, and muddy water has high turbidity.
Chlorine residual
Chlorine residual is the small amount of chlorine still left in the water after it leaves the treatment plant. It keeps protecting the water from germs all the way to your faucet.

Also: sampling

Teacher overview

A water quality sampling technician spends the day collecting samples across a system and recording the results in a log. This worksheet gives students one day of a fictional technician's log and asks them to judge each reading against real regulatory limits. It practices reading a data table and comparing values to a standard, which is a central part of the testing job.

Reading a Sampling Log: A Water Testing Technician at Marlow Springs — Grade 7 Careers & CTE
Name: ____________________________ Date: ______________

Student Worksheet

Sofia is a water quality technician for the fictional Marlow Springs system. On one day she recorded these readings at four sites. Use this log and the limits below for every item.

Site Turbidity (NTU) Chlorine residual (mg/L) pH Pressure (psi)
1 (plant outlet) 0.10 1.4 7.5 —
2 (school) 0.15 0.9 7.7 58
3 (hilltop) 0.12 0.6 7.9 22
4 (edge of town) 0.28 0.3 8.0 45

Limits to compare against:

  • Water leaving the plant's filters must be at or below 0.3 NTU in at least 95 percent of monthly samples, and the fictional Marlow Springs system uses 0.3 NTU as its target at every site.
  • Chlorine residual in distribution is typically kept between 0.2 and 2.0 mg/L.
  • The secondary standard for pH is 6.5 to 8.5.
  • Most states require at least 20 psi of pressure at every connection; utilities usually aim for 40 to 80 psi.
  1. Which site had the highest turbidity reading, and is that reading still at or below the 0.3 NTU target?
  2. Site 3 sits on a hilltop with a pressure of 22 psi. By how many psi does that clear the 20 psi minimum?
  3. Between which two values do utilities typically keep the chlorine residual, and do all four sites fall inside that range?
  4. Site 4's chlorine residual is 0.3 mg/L. Is that inside the typical 0.2 to 2.0 mg/L range?
  5. The pH readings run from 7.5 to 8.0. Are all four inside the 6.5 to 8.5 secondary standard?
  6. Site 4's turbidity is 0.28 NTU and the target is 0.3 NTU. How far below the target is it?
  7. Site 4's turbidity of 0.28 NTU is what percent of the 0.3 NTU target, to the nearest whole percent?
  8. Site 3 on the hilltop has the lowest pressure. Explain why a hilltop site often reads lower pressure than sites lower in town.
  9. Sofia flags Site 3 for a second look even though it passes every limit. Explain why a reading that barely passes might still deserve attention.
  10. In one sentence, describe Sofia's job based on this worksheet.

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: Site 4, at 0.28 NTU. It is still at or below the 0.3 NTU target, so it passes.
  2. Answer: 2 psi. Site 3 reads 22 psi, and 22 − 20 = 2 psi above the minimum.
  3. Answer: Between 0.2 and 2.0 mg/L. All four readings (1.4, 0.9, 0.6, and 0.3 mg/L) fall inside that range.
  4. Answer: Yes. A residual of 0.3 mg/L is above 0.2 and below 2.0, so it is inside the typical range.
  5. Answer: Yes. Every pH reading from 7.5 to 8.0 falls between 6.5 and 8.5.
  6. Answer: 0.02 NTU. The target is 0.3 NTU and the reading is 0.28 NTU, so 0.30 − 0.28 = 0.02 NTU below the target.
  7. Answer: 93 percent. 0.28 ÷ 0.30 = 0.933, and 0.933 × 100 ≈ 93.3, which rounds to 93 percent.
  8. Answer: Accept answers noting that a hilltop is higher up, so there is less height of water above it, which means lower pressure than sites farther down the slope.
  9. Answer: Accept answers noting that a reading barely above the minimum leaves little margin, so a small change could push it out of range; watching it early prevents a future problem.
  10. Answer: Accept a one-sentence description such as: Sofia collects water samples across the system and records readings like turbidity, chlorine, pH, and pressure to check that each site meets its limits.

Differentiation

Support

Highlight the limit that goes with each column before students start, and let them mark each cell "pass" or "watch" before answering the written items. Provide the subtraction already set up for item 6.

Extension

Ask students to design a fifth site's readings that would all pass except one, state which limit it misses and by how much, and explain what Sofia should do about it.

ELL supports

Pre-teach "turbidity," "chlorine residual," and "sampling" with a labeled picture. Provide a sentence frame for items 8 and 9: "This site reads lower or needs a look because ___."