Lab / experiment Grade 10 Engineering & Design

Settling Column Test: A Grade 10 Sedimentation Design Lab

A grade 10 lab where students test how a coagulant changes how fast cloudy water clears, then connect the result to sedimentation basin design.

Grade: Grade 10
Subject: Engineering & Design
Material: Lab / experiment
Time: 55 min
Prep: Moderate prep
Materials: Two clear tall jars or 1-liter graduated cylinders per group (used as settling columns), Powdered alum, sold as pickling alum (a small pinch per column with coagulant), Clean soil or silt (about 2 tablespoons per column), Tap water (about 1 liter per column), Stopwatch or phone timer, Ruler marked in centimeters, Cloudiness comparison card with a 1-to-5 scale (1 = clear, 5 = very cloudy), Stir stick, safety goggles, and towels for spills, Measuring spoons: a tablespoon for the soil and a small scoop for the alum, Waste container for the settled water and sludge

Standards

HS-ETS1-3 NGSS

Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics as well as possible social, cultural, and environmental impacts.

How this material aligns: In analysis question 6 students use their own clearing times to weigh a coagulant dose against a larger basin, naming chemical cost and extra sludge on one side and land and construction cost on the other, the prioritized trade-offs this standard names.

All materials for HS-ETS1-3 →

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: Analysis questions 3 and 4 carry depth and time units through a settling-rate calculation in centimeters per minute and a detention-time conversion from hours to minutes.

All materials for HSN-Q.A.1 →

Download Word file

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 test how a coagulant changes how fast cloudy water clears in a settling column.
Students will calculate a settling rate and connect their results to sedimentation basin detention time.

Vocabulary

Sedimentation: Sedimentation is the step where water sits almost still in a big basin so the heavy clumps of dirt can sink to the bottom. The cleaner water on top then moves on to the filters.
Floc: Floc is the fluffy clumps of dirt and treatment chemicals that form in the water during cleaning at a treatment plant. Floc looks like tiny snowflakes drifting in the water.
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: coagulant, settling rate

Teacher overview

Before a treatment plant filters water, it lets the heaviest particles settle out in a large basin, and adding a coagulant makes fine particles clump into larger flocs that fall faster. This lab lets students test that idea directly: they compare how quickly cloudy water clears in a plain column and in a column dosed with a pinch of coagulant. The investigation question is testable: does adding a coagulant speed up how fast the water clears? A classroom column is far smaller than a real basin, so students also connect their timing to the 2 to 4 hours water typically spends in a real sedimentation basin.

Settling Column Test: A Grade 10 Sedimentation Design Lab — Grade 10 Engineering & Design

Name: ____________________________ Date: ______________

Procedure

Step 1 (safety, before starting): Put on goggles. Powdered alum is a mild irritant, so handle it with the scoop, do not eat or taste it, and do not drink any water in this lab. Wipe up spills right away and keep the columns steady so they do not tip.

Step 2 (form your hypothesis): Your group will prepare two settling columns. Column A gets cloudy water only. Column B gets the same cloudy water plus a small pinch of coagulant. Write a one-sentence hypothesis predicting which column will clear faster, and why.

Step 3 (identify your variable): The one thing you change between the columns is the coagulant. This is your independent variable. Keep everything else the same: the same amount of water, the same amount of soil, the same column size, and the same starting stir. These are your controls.

Step 4 (make the cloudy water): Add about 1 liter of tap water and about 2 tablespoons of soil to each column. Stir both the same way until the water looks evenly cloudy.

Step 5 (rate the start): Use the 1-to-5 card to rate each column's cloudiness right after stirring, and record both as the "start" rating. Measure and record the depth of water in each column in centimeters.

Step 6 (dose Column B): Add a small pinch of coagulant to Column B and give it one gentle stir. Do not stir Column A again. Start the timer for both columns at the same moment.

Step 7 (record over time): At 5, 10, and 15 minutes, rate each column's cloudiness on the 1-to-5 card without stirring, and record the ratings. Also record the time, in minutes, when each column first reaches a rating of 2 or better.

Step 8 (clean up): Pour the settled water and sludge into the container your teacher provides. Rinse the columns and dry your station.

Data & Analysis

Column	Start rating (1-5)	5-min rating	10-min rating	15-min rating	Time to reach rating 2 (min)
A (no coagulant)
B (with coagulant)

For Column B (with coagulant), how many minutes did it take to reach a clarity rating of 2 or better?
Compare the 15-minute ratings of Column A and Column B. Which column was clearer, and by how many rating points?
Suppose Column B reached a rating of 2 in a column of water 30 centimeters deep after 8 minutes. What was the average settling rate of the clarity front in centimeters per minute?
Water typically spends 2 to 4 hours in a sedimentation basin. Convert 3 hours to minutes, and explain why a real basin gives particles far more time to settle than your column did.
A coagulant makes fine particles clump into larger, heavier flocs. Using your own data, explain how adding it changed how fast the water cleared.
Based on your results, would adding a coagulant or building a larger basin (more surface area and detention time) do more to improve settling, and what trade-off, such as chemical cost or extra sludge, would an engineer weigh?

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: varies by group's own data.
Report the recorded time, in minutes, when Column B first reached a rating of 2 or better. Most groups will find Column B reaches it sooner than Column A.
Answer: varies by group's own data.
The clearer column is the one with the lower 15-minute rating; the difference is the two ratings subtracted. Most groups will find Column B is clearer by one or more rating points. Accept any answer that matches the group's data.
Answer: 3.75 centimeters per minute.
Settling rate = 30 centimeters ÷ 8 minutes = 3.75 centimeters per minute.
Answer: 180 minutes.
3 hours × 60 minutes/hour = 180 minutes. A real basin holds the water for hours, so particles have far longer to settle than the 15 minutes the classroom column allowed, which is why a plant removes much more than a short column can.
Answer: varies by group's own data.
Accept any answer that uses the group's ratings to describe faster clearing in the coagulant column, explaining that the coagulant clumped fine particles into larger flocs that settled more quickly than the loose particles in Column A.
Answer: varies by group's own data.
Accept any answer that names a choice supported by the data and states a real trade-off, such as a coagulant clearing the water fastest but adding chemical cost and more sludge to handle, while a larger basin needs more land and construction cost.

Differentiation

Support (below grade level)

Prepare one dosed column as a class demonstration before groups build their own, and give a simplified data table that records ratings at only the start and 15 minutes instead of every interval.

Extension (above grade level)

Have groups run a third column that changes a second variable, such as a larger coagulant dose or a warmer water sample, and compare its clearing time with Columns A and B, then explain which single change made the biggest difference.

ELL supports

Provide picture cards for each step (stir, dose, time, rate) and label the 1-to-5 clarity scale with a sketch for each level. Provide a sentence frame for the hypothesis in Step 2: "I predict Column ___ will clear faster because ___."