Debate kit Grade 12 Science
Mandating Nutrient Removal Upgrades for Harlow Lake Plants
A grade 12 debate kit on requiring nutrient removal upgrades at plants discharging to a fictional lake, weighing water quality against ratepayer cost.
Objectives
- Students will evaluate real and illustrative evidence on both sides of a nutrient-removal mandate resolution.
- Students will construct and deliver a rebuttal grounded in cited evidence, distinguishing documented facts from illustrative testimony.
Vocabulary
- Biological nutrient removal (BNR)
- Biological nutrient removal uses specially managed bacteria to strip extra nitrogen and phosphorus out of wastewater before it is released. Removing these nutrients helps prevent algal blooms in the rivers and lakes that receive the treated water.
- Eutrophication
- Eutrophication is what happens when a lake or bay gets overfed with nutrients: algae grows out of control, and when it dies and rots, the water loses the oxygen that fish need.
Also: affordability, mandate
Teacher overview
This is a two-team structured debate for a 60-minute block, with prep time extending into a second session if needed. Students argue for or against a state mandate requiring every wastewater treatment plant discharging to the Harlow Lake watershed, a fictional lake used for this debate, to install biological nutrient removal (BNR) upgrades within ten years. The resolution has genuine tension between protecting the lake's water quality and limiting the cost increases that fall on the households who pay their local sewer bills.
Resolution & Background
Resolution: "The state should require every wastewater treatment plant discharging to the Harlow Lake watershed to install biological nutrient removal upgrades within ten years, even though the upgrades will raise local sewer rates."
Background: Most plants already provide standard secondary treatment. That standard requires effluent BOD and TSS of 30 mg/L or less. It targets organic matter and solids, not nutrients specifically. Nitrogen and phosphorus can pass through secondary treatment largely intact. Once discharged, they feed algae growth in a receiving lake, a process called eutrophication. When that algae later dies and decomposes, the decomposition uses up dissolved oxygen. Most fish need dissolved oxygen above 5 mg/L to survive. Biological nutrient removal is an added treatment stage, beyond standard secondary treatment. It uses specific microbial communities to strip nitrogen and phosphorus from wastewater before discharge. Installing it costs money. A widely used rule of thumb treats combined water and sewer costs above roughly 4.5 percent of household income as a high financial burden. The figure comes from adding two EPA benchmarks based on a community's median household income, 2.5 percent for drinking water and 2 percent for wastewater; EPA has no single official cutoff. That threshold matters because combined water and sewer bills nationally have already risen about 24 percent from 2019 to 2024, and about 5.1 percent more in 2025.
Evidence File
Case for the mandate:
- Most fish need dissolved oxygen above 5 mg/L. Algae blooms fueled by nutrient-loaded water can crash oxygen levels well below that threshold once the algae dies and decomposes. That directly threatens Harlow Lake's fish populations. (Source: standard water-quality benchmark, EPA/USGS.)
- The standard secondary treatment requirement of 30 mg/L BOD and TSS does not specifically target nitrogen or phosphorus. A plant can fully meet its legal discharge requirements while still contributing significant nutrient loading to the lake. (Source: EPA secondary treatment regulation, 40 CFR 133.)
- A fictional environmental group, the Harlow Lake Watershed Alliance, testifies for this debate. The group says that in comparable lakes where BNR upgrades were mandated, visible summer algae coverage declined within a few years of installation. It argues that voluntary upgrades alone have not happened fast enough to protect the lake. (Illustrative testimony created for this debate, not a documented figure.)
Case against the mandate:
- A widely used rule of thumb, built from two EPA benchmarks, treats combined water and sewer costs above roughly 4.5 percent of household income as a high burden, and EPA's 2024 affordability assessment measured high burden at both 3 percent and 4.5 percent. A mandated upgrade would raise local rates further, risking pushing already-burdened households over that line. (Source: EPA Water Affordability Needs Assessment, December 2024.)
- Combined water and sewer bills nationally have already risen about 24 percent from 2019 to 2024, and about 5.1 percent more in 2025. Ratepayers are absorbing significant increases before any new nutrient-removal mandate is even considered. (Source: Bluefield Research / industry rate surveys.)
- A fictional plant manager from the Cordray Creek treatment plant, one of the facilities that would be affected, testifies for this debate. The manager says a ten-year mandate does not allow enough time to design, finance, and construct BNR upgrades without triggering emergency rate increases, and argues for a fifteen-year phase-in instead. (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 to the resolution | Cites at least two pieces of evidence and explains how each supports the team's position | Cites multiple pieces of evidence, distinguishes documented facts from illustrative testimony, and explains their relevance |
| 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 between points are unclear | Argument follows a clear claim-evidence-conclusion structure | Argument is clearly structured, confidently delivered, and directly responsive to the resolution throughout |
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 such as "Our opponents claim ___, but the evidence shows ___."
Extension (above grade level)
Ask students to research, using only the Evidence File provided and not outside sources, what a fifteen-year phase-in proposed by the Cordray Creek plant manager might mean for water quality in the interim, and incorporate that reasoning into a stronger rebuttal for either side.
ELL supports
Pre-teach "biological nutrient removal," "eutrophication," "affordability," and "mandate" with simple definitions and a labeled diagram showing nutrients flowing from a treatment plant into a lake, feeding algae. Allow students to deliver rebuttals from written notes rather than extemporaneously.