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Quiz & test questions Grade 11 Engineering & Design

Vesper Flats Utility: A Grade 11 Water Engineering Unit Test

A grade 11 engineering assessment mixing multiple-choice, short-answer, and computation items on treatment-train design, detention time, chlorine dosing, and pressure.

Objectives

  1. Students will apply treatment-plant sizing formulas to find detention time, chlorine feed, and removal efficiency.
  2. Students will judge treatment and pressure results against real regulatory and service ranges.

Vocabulary

Detention time
Detention time is how long water stays inside a tank or basin before flowing out. Water must stay long enough for each treatment step, like settling or disinfecting, to finish its job.

Also: treatment train, pounds formula, removal efficiency, service pressure

Teacher overview

This 40-minute unit test is worth 30 points and checks whether students can apply water-treatment engineering to a working plant. It mixes two multiple-choice items, two short-answer items, and four computation items, all set at the fictional Vesper Flats regional utility. Two of the computation items also ask students to judge the result against a real regulatory or service range.

Vesper Flats Utility: A Grade 11 Water Engineering Unit Test — Grade 11 Engineering & Design
Name: ____________________________ Date: ______________

Assessment

All items describe the fictional Vesper Flats utility.

  1. (2 points) Which sequence gives the correct order of a conventional treatment train?
    • A) Filtration, coagulation, sedimentation, disinfection
    • B) Coagulation, sedimentation, filtration, disinfection
    • C) Sedimentation, filtration, coagulation, disinfection
    • D) Disinfection, coagulation, sedimentation, filtration
  2. (2 points) In your own words, explain what detention time in a sedimentation basin measures.
  3. (4 points) A Vesper Flats settling basin holds 500,000 gallons, and the plant runs at 5,000 gpm. Find the detention time in hours.
  4. (4 points) An operator wants a chlorine dose of 2.0 mg/L at a flow of 5 MGD. Use the pounds formula, feed (lbs/day) = dose × flow (MGD) × 8.34, to find the chlorine feed rate in pounds per day. Explain whether the residual this dose leaves in the distribution system could exceed the 4.0 mg/L maximum residual disinfectant level.
  5. (4 points) Raw water enters at 15 NTU of turbidity and leaves the settling basin at 4.5 NTU. Find the removal efficiency as a percent, using (influent − effluent) ÷ influent × 100.
  6. (2 points) A conventional plant must keep finished water at or below which turbidity value in 95 percent of its monthly samples?
    • A) 0.3 NTU
    • B) 3 NTU
    • C) 15 NTU
    • D) 30 NTU
  7. (4 points) A Vesper Flats storage tank holds water 120 feet above town. Using 0.433 psi per foot of head, find the pressure delivered, in psi, and state whether it falls inside the usual 40-to-80 psi service range.
  8. (8 points) Vesper Flats' filters are running at 6.5 gpm per square foot, above the usual 2-to-6 range. Explain one problem this overload can cause for finished-water quality, and describe one engineering change that would bring the loading rate back into range.

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) Coagulation, sedimentation, filtration, disinfection. Coagulation clumps particles, sedimentation settles them, filtration strains what remains, and disinfection finishes the water; the order cannot be rearranged because each stage prepares the next.
  2. Answer: The average time water spends in the basin. Detention time measures how long, on average, a volume of water stays in the basin, which is the settling time available for particles to drop out. Accept any answer capturing time spent in the basin for settling.
  3. Answer: 1.7 hours. Detention time = 500,000 gallons ÷ 5,000 gpm = 100 minutes; 100 ÷ 60 = 1.67, about 1.7 hours.
  4. Answer: 83.4 lbs/day. Feed = 2.0 × 5 × 8.34 = 83.4 pounds per day. Chlorine demand only lowers the residual below the dose, so a 2.0 mg/L dose cannot leave a residual above the 4.0 mg/L MRDL, which applies to the residual measured in the distribution system rather than to the dose.
  5. Answer: 70 percent. Removal efficiency = (15 − 4.5) ÷ 15 × 100 = 10.5 ÷ 15 × 100 = 70 percent.
  6. Answer: A) 0.3 NTU. A conventional filtration plant must keep finished water at or below 0.3 NTU in 95 percent of monthly samples; the higher options exceed the standard.
  7. Answer: 52 psi. Pressure = 120 feet × 0.433 psi per foot = 51.96, about 52 psi, which falls inside the usual 40-to-80 psi service range.
  8. Answer: Running filters above the design range pushes water through too fast, so fine particles can break through and finished-water turbidity rises, weakening the barrier against microbes. Adding filter surface area, building an additional filter, or lowering the flow through each filter would bring the loading rate back inside the 2-to-6 range. Full credit requires one quality problem and one workable engineering fix.

Differentiation

Support

Provide the detention-time, pounds, and removal-efficiency formulas on a reference strip, and allow a calculator for every computation item. For item 1, give the four stage names in a word bank so students order them rather than recall them.

Extension

Ask students to find the largest flow, in gpm, at which the 500,000-gallon basin from item 3 would still provide a 2-hour detention time, and to connect that limit to the filter-overload problem in item 8.

ELL supports

Provide a labeled treatment-train diagram for reference during item 1, and sentence frames for the short-answer items, such as "Detention time measures how long ___." Allow computation answers to be shown as labeled steps rather than in full sentences.