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Debate kit Grade 7 Social Studies & Civics

Toilet to Tap? A Grade 7 Debate on Water Recycling

A grade 7 debate kit on whether a fictional coastal town should build a water-recycling plant instead of a new reservoir, with evidence for both sides.

Objectives

  1. Students will evaluate evidence on both sides of a water-recycling policy resolution.
  2. Students will construct and deliver a rebuttal supported by named evidence.
  3. Students will explain how the same reverse-osmosis membrane technology is used in more than one type of water treatment.

Vocabulary

Reverse osmosis
Reverse osmosis cleans water by pushing it through a membrane with holes so tiny that salt and most other dissolved things cannot fit through. It can even turn seawater into fresh water.
Potable reuse
Cleaning used water so thoroughly that it becomes safe drinking water again. Special plants use several layers of treatment and constant testing to make sure it is safe.
Reservoir
A human-made lake, usually created by a dam, that stores water for later. Reservoirs supply cities and farms and help control floods.

Also: public perception

Teacher overview

This is a two-team structured debate for a class period, with prep time extending into a second session if needed. Students argue for or against a fictional coastal town, Sable Bay, building a reverse-osmosis water recycling plant that purifies wastewater into drinking water, instead of building a new reservoir to store more rainwater. Reverse osmosis, the same membrane technology used both to remove salt from seawater and to purify wastewater for reuse, sits at the center of a resolution with genuine tension between water security, cost, and public comfort with the idea of recycled water.

Toilet to Tap? A Grade 7 Debate on Water Recycling — Grade 7 Social Studies & Civics
Name: ____________________________ Date: ______________

Resolution & Background

Resolution: "Sable Bay (a fictional coastal town used for this debate) should build a reverse-osmosis water recycling plant. It should build this plant instead of a new reservoir, to secure its future water supply."

Background: Reverse osmosis is a water treatment step. It pushes water through a thin membrane. The membrane blocks salt, bacteria, and many other contaminants. This step is used in two ways. It removes salt from seawater at desalination plants. It also cleans used water at recycling plants. That cleaned water becomes safe to drink again. This second use has a name: potable reuse. One large example already works today. It sits in Orange County, California. It is called the Groundwater Replenishment System. It is the world's largest plant of this kind. It makes 130 million gallons of clean water each day. Reverse osmosis is one of its main steps. A reservoir works in a different way. It is a large basin. It stores rainfall and river water for later use. This is a much older way to secure water. Sable Bay's town council must pick one approach. It will fund that choice with its next big water budget.

Evidence File

Case for building the recycling plant:

  1. Orange County's Groundwater Replenishment System proves this technology works at a large scale. It makes 130 million gallons of clean water per day. (Source: Orange County Water District.)
  2. A fictional Sable Bay engineering report was written for this debate. It estimates a recycling plant would give the town a steady supply. This is because it uses the town's daily wastewater, not rainfall. Rainfall can vary sharply from year to year. (Illustrative estimate created for this debate, not a documented figure.)
  3. A recycling plant can often go on land the town already owns. This land sits near the town's existing wastewater plant. A new reservoir usually needs more land. That can force nearby property owners to move.

Case against building the recycling plant:

  1. Reverse osmosis takes more energy than regular treatment. Removing salt from seawater this way uses about 11 to 15 kilowatt-hours per 1,000 gallons, while regular water treatment uses only about 1 to 2. Purifying wastewater takes less energy than desalting seawater but more than regular treatment. A recycling plant would likely raise the town's energy costs. (Source: industry engineering references.)
  2. A fictional Sable Bay group, Sable Bay Neighbors for Clean Water, wrote testimony for this debate. The group says recycled wastewater has a public-perception problem. Some people call this the "yuck factor." The group wants public education and taste-testing first, before the town spends money on a plant residents may not trust. (Illustrative testimony created for this debate.)
  3. A new reservoir can offer other benefits a treatment plant cannot. These include recreational use and wildlife habitat. The town would get more than just water security for its money.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Rubric
Criterion Emerging Developing Proficient Advanced
Evidence use Repeats a claim with no cited evidence Cites one piece of evidence without explaining its relevance Cites at least two pieces of evidence and explains how each supports the team's position Cites multiple pieces of evidence, explains their relevance, and anticipates the opposing side's likely response
Rebuttal quality Does not respond to the opposing team's points Responds to an opposing point but without new evidence Directly rebuts a specific opposing point using evidence from the file Rebuts multiple opposing points and explains why the team's evidence outweighs them
Organization & delivery Argument is difficult to follow; no clear structure Argument has a structure but transitions are unclear Argument follows a clear claim-evidence-conclusion structure Argument is clearly structured, confidently delivered, and directly responsive to the resolution

Differentiation

Support (below grade level)

Provide a simplified evidence card for each side listing only the single strongest point, and give sentence starters for rebuttals ("Our opponents claim ___, but the evidence shows ___.").

Extension (above grade level)

Ask students to find one other real-world water recycling project besides Orange County's system, using a source the teacher has approved, and to draft one new evidence point about it in the same cited format used in the Evidence File.

ELL supports

Pre-teach "reverse osmosis," "potable reuse," and "reservoir" with a labeled diagram showing a membrane filtering water on one side and clean water passing through on the other. Allow students to deliver rebuttals from written notes rather than extemporaneously.