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Difficulty: HardWeakening Arguments

To reduce municipal water treatment expenses, Metro City's utility department plans to install bio-filters containing specialized bacterial strains in the main reservoir. Laboratory tests demonstrated that these bacteria rapidly break down microplastics, which currently clog standard filtration membranes at downstream treatment facilities. Department officials conclude that implementing these bio-filters will significantly decrease overall water treatment operating costs across the city. Which of the following, if true, most seriously weakens the utility department's conclusion?

  1. The bacterial strains release acidic organic compounds during microplastic digestion that severely corrode plant intake pumps, creating new repair costs that exceed membrane maintenance savings.Answer
  2. B
    Standard filtration membrane replacement currently accounts for the single largest line-item maintenance expenditure across all downstream facilities.
  3. C
    Several neighboring municipalities have recently expressed interest in licensing bio-filter technology for their own industrial wastewater treatment units.
  4. D
    Downstream purification plants currently report higher overall water filtration efficiency during cold winter months than during summer months.
  5. E
    Microplastics are not the only type of particulate pollutant present in Metro City's central reservoir that requires filtration.

Answer

The statement regarding the release of acidic organic compounds during microplastic digestion that corrode intake pumps and create costs exceeding membrane savings most seriously weakens the argument.
The correct answer weakens the argument by demonstrating an unintended negative consequence of the proposed solution. If the bacterial digestion process releases corrosive byproducts that damage intake pumps and incur replacement costs higher than the savings from reduced membrane clogging, the net financial impact will be negative, directly refuting the conclusion that overall expenses will decrease.

Step-by-Step Solution

1
Identify the premise and conclusion of the argument.
Premise: Lab tests show specialized bacteria digest microplastics that clog downstream membranes. Conclusion: Deploying these bio-filters will significantly decrease overall city water treatment operating costs.
Understanding the logic chain reveals the underlying assumption that microplastic removal will yield net financial savings.
2
Identify the unstated assumption in the plan.
The argument assumes that deploying the bacterial bio-filters will not introduce new hidden operational expenses or side effects that outweigh the cost savings from clogging reduction.
A plan-based argument is vulnerable to evidence showing unexpected negative side effects or implementation barriers.
3
Evaluate the choices to find new information that shatters this assumption.
The choice describing corrosive acidic compounds proves that implementing the bio-filters introduces a new repair expense that exceeds the savings gained from reduced membrane clogging.
This directly invalidates the conclusion that overall water treatment operating costs will decrease.

Key Concept

Weakening a Plan-to-Goal Argument via Implementation Side Effects
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Topics

Weakening Arguments

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