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Debate kit Grade 7 Science

Recycled Water or a New Reservoir? A Grade 7 Water-Supply Debate Kit

A grade 7 debate on whether a community should treat wastewater to drinking-water standards instead of building a reservoir, with evidence on cost and trust.

Objectives

  1. Students will evaluate evidence on both sides of a water-supply policy resolution.
  2. Students will construct and deliver an argument supported by named evidence.
  3. Students will respond to an opposing team's evidence with a direct rebuttal.

Vocabulary

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: advanced treatment, affordability

Teacher overview

This is a two-team structured debate for a 60-minute block, with preparation extending into a short second session if needed. Students argue for or against a growing community building a potable water reuse system, treating wastewater to drinking-water standards and returning it to the supply, instead of building a new reservoir. Both approaches are used by real water systems today, and each carries genuine costs and benefits, which makes this a resolution reasonable, informed adults could argue either way.

Recycled Water or a New Reservoir? A Grade 7 Water-Supply Debate Kit — Grade 7 Science
Name: ____________________________ Date: ______________

Resolution & Background

Resolution: "This community should build a potable water reuse system to meet its growing water demand, instead of building a new reservoir."

Background: As a community grows, it needs more water. One option is a new reservoir. A reservoir stores rain and river water. But building one means buying land. It also means building dams or pipelines. That can take years to permit and build. A second, newer option is potable reuse. This means treating wastewater with extra steps. Those steps make it meet drinking-water standards. The treated water then returns to the supply. Orange County's Groundwater Replenishment System uses this method. It treats and reuses 130 million gallons of water each day. That makes it the largest system of its kind in the world. Both options cost money. Utilities usually recover that cost through household rates. A widely used rule of thumb, built from two EPA benchmarks, sets a warning line for cost: combined water and sewer costs above about 4.5 percent of household income count as a high burden. EPA itself has no single official cutoff.

Evidence File

Case for potable reuse:

  1. Orange County's Groundwater Replenishment System already treats and reuses 130 million gallons of wastewater each day. This proves potable reuse can work for a large population. It is not just a small-scale experiment. (Source: Orange County Water District.)
  2. EPA's national assessment says $625 billion in drinking-water infrastructure investment is needed nationwide over the next 20 years. A reuse system can often be added onto a community's existing wastewater plant. That may cost less than buying land and building an entirely new reservoir. (Source: EPA Drinking Water Infrastructure Needs Survey and Assessment.)
  3. A fictional civil engineer, quoted for this debate, says a new reservoir here would take 8 to 10 years to build, since this community's hills make construction slow. Adding treatment steps to the existing plant could finish sooner. (Illustrative estimate created for this debate, not a documented figure.)

Case against potable reuse:

  1. Advanced treatment used in some reuse systems takes more energy than regular treatment. Regular treatment and delivery takes about 1 to 2 kilowatt-hours per 1,000 gallons. This means reuse can raise a utility's energy costs and its dependence on the electric grid. (Source: industry engineering references.)
  2. A widely used rule of thumb, built from two EPA benchmarks, sets a high-burden line at about 4.5 percent of household income for water and sewer costs. New treatment equipment costs money to build and monitor. Utilities usually recover those costs through rates, which could push rate-sensitive households over that line. (Source: EPA affordability benchmarks, as used in EPA's 2024 Water Affordability Needs Assessment.)
  3. A fictional residents' group, the Millbrook Clean Water Alliance, was created for this debate. It argues that many residents feel uneasy drinking treated wastewater, even when it is safe. The group says public trust takes years to earn, and a rushed rollout could hurt that trust. (Illustrative testimony created for this debate.)

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 its single strongest point, and give sentence starters for rebuttals: "Our opponents claim ___, but the evidence shows ___." Allow students to deliver their argument from written notes rather than extemporaneously.

Extension (above grade level)

Ask students to research, using only the Evidence File provided and not outside sources, how a community might combine both approaches, a smaller reservoir expansion paired with a partial reuse system, and to incorporate that compromise reasoning into a stronger closing rebuttal.

ELL supports

Pre-teach "potable reuse," "reservoir," "advanced treatment," and "affordability" with simple definitions and a labeled diagram comparing the two water-supply paths side by side. Allow students to deliver rebuttals by reading directly from prepared evidence cards rather than speaking from memory.