Lesson plan Grade 7 Science

Brightwater Plant Tour: Ordering the Drinking Water Treatment Stages

A 50-minute grade 7 science lesson where students read how a treatment plant works and build a flowchart placing the six stages in the correct order.

Grade: Grade 7
Subject: Science
Material: Lesson plan
Time: 50 min
Prep: Low prep
Materials: Printed stage cards (one set per group of 3), Chart paper, Markers, A clear glass of tap water and a jar of cloudy river water (teacher display only), Index cards

Standards

RST.6-8.7 Common Core ELA

Integrate quantitative or technical information expressed in words in a text with a version of that information expressed visually (e.g., in a flowchart, diagram, model, graph, or table).

How this material aligns: The card-sort and flowchart in the procedure ask students to turn the plant's written stage descriptions into a visual flowchart, the exact word-to-diagram integration this standard names.

All materials for RST.6-8.7 →

MS-ESS3-3 NGSS

Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment.

How this material aligns: The card sort, flowchart, and exit ticket have students place each treatment barrier and name what it removes, including the 0.3 NTU turbidity check after filtration, the method for monitoring and minimizing contamination in drinking water this standard requires.

All materials for MS-ESS3-3 →

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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 place the six drinking water treatment stages in their correct order.
Students will explain what each stage removes or changes in the water.
Students will build a flowchart that turns a written process into a visual model.

Vocabulary

Coagulation: Coagulation is the first cleaning step at a drinking water plant. Operators quickly mix in a chemical that makes tiny bits of dirt stop pushing each other away so they can start sticking together.
Flocculation: Flocculation is the slow, gentle stirring step at a water plant that lets tiny sticky particles bump into each other and clump into bigger pieces called floc, heavy enough to settle out of the water.
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.
Filtration: Filtration is the step where water passes through layers of sand, gravel, or other materials that trap the small particles still left in it. It works like a very fine strainer.
Disinfection: Disinfection is the step that kills or disables germs in water so it is safe to drink. Water plants usually disinfect with chlorine, ultraviolet light, or ozone.
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.

Teacher overview

A drinking water plant does not clean water in a single step; it moves water through a series of stages, each of which removes a different kind of material. This lesson uses a fictional plant, the Brightwater Regional Treatment Plant, to give students a written description of each stage, which they then sort into the correct order and turn into a flowchart. The lesson builds the science-literacy skill of translating a technical description in words into a visual model.

Procedure

Hook (5 min): Show a clear glass of tap water and a jar of cloudy river water side by side. Ask students to list, on scrap paper, the steps they think happen between the two. Collect two or three ideas aloud without confirming them, so you can return to their guesses at the end.

Direct instruction (15 min): Walk through the six stages of conventional treatment in order, describing what each one does. Screening removes large debris such as sticks and leaves. Coagulation adds a chemical that makes tiny particles clump. Flocculation gently mixes the water so the clumps, called floc, grow larger. Sedimentation lets the heavy floc settle to the bottom of a basin. Filtration passes the water through sand and gravel to catch what is left. Disinfection adds chlorine to kill germs before the water enters storage. Note that after filtration a plant must keep turbidity at or below 0.3 NTU in nearly all of its samples, which is why the settling and filtering stages matter so much.

Card-sort and flowchart (15 min): In groups of three, hand each group a shuffled set of six stage cards, each printed with a stage name and its description but no numbers. Groups arrange the cards in order, then copy the sequence onto chart paper as a flowchart, drawing an arrow from each stage to the next and adding a one-word label on each arrow for what leaves the water at that step.

Share and check (10 min): Groups post their flowcharts. Lead a quick gallery walk, then reveal the correct order. As a formative check, ask each group to hold up the number of cards they placed correctly; if most groups miss the coagulation-flocculation-sedimentation sequence, reteach that trio using the clumping-then-settling idea.

Exit ticket (5 min): On an index card, students answer two questions: put these four stages in order (filtration, coagulation, disinfection, sedimentation), and name what disinfection removes that filtration does not. Collect and scan before dismissal.

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: The correct full order is screening, coagulation, flocculation, sedimentation, filtration, disinfection. Coagulation must come before flocculation and sedimentation because particles have to clump before they can grow and settle.
Exit ticket, ordering: The four listed stages in order are coagulation, sedimentation, filtration, disinfection. This mirrors the full sequence with screening and flocculation removed.
Exit ticket, disinfection: Disinfection kills germs such as bacteria and viruses. Filtration removes particles and much cloudiness, but it does not reliably kill the microscopic organisms that can make people sick, which is why chlorine is added.

Differentiation

Support

Give these groups stage cards that are already numbered on the back, so students can self-check after arranging them face up. Provide a word bank of the six stage names for the flowchart labels.

Extension

Ask students to add a seventh box to their flowchart for what happens after disinfection (storage and distribution to homes) and to explain why keeping a small amount of chlorine in the water all the way to the tap matters.

ELL supports

Pair each stage card with a simple icon (a screen, a chemical being added, a mixing paddle, settling dots, a filter, and a chlorine drop) and pre-teach the six vocabulary terms with those icons. Allow students to explain their flowchart orally to you or a partner instead of in writing.