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AP Environmental Science 8.11: Sewage Treatment

Practice AP Environmental Science questions on primary, secondary, and tertiary sewage treatment, aeration, bacteria, and disinfection.

Syllabus
Effective Fall 2025
Course
AP Environmental Science

Exam points

  • distinguish primary, secondary, and tertiary sewage treatment by physical, biological, and chemical processes

Covered syllabus points

STB-3.N—Describe best practices in sewage treatment

8.11 Sewage Treatment question 1

[Maximum number: 4]

Read the following article from the Fremont Daily Times and answer the questions that follow.

Fremont Daily Times

Scientists Discuss Threats from Plastic Pollution

In testimony before the United States Senate Committee on Environment and Public Works, Dr. Duke Ewoldsen, an eminent toxicologist, discussed a new water pollutant that threatens aquatic life: microbeads. Ewoldsen noted that while posing a different threat than more conventional water pollutants such as nitrates, phosphates and PCBs, tiny beads of plastic contained in many products, especially cosmetics, now threaten plankton and small fish that ingest the particles because they mistake them for food. The microbeads cannot be digested and can fill or block the digestive tracts of the fish, leading to starvation. In addition, surfaces of these small spheres can adsorb organic pollutants such as PCBs and dioxin.

When asked about steps to reduce this threat, Ewoldsen noted that the beads are so small that they are not easily removed by wastewater treatment plants and thus often enter aquatic ecosystems in wastewater discharges.

Figure for Question 8.11 Sewage Treatment question 1 — AP Environmental Science

Question (a)

(a)

While wastewater treatment plants are ineffective at removing microbeads, they are very effective at removing large pieces of plastic waste and other pollutants.

[ 4 ]

Question (i)

(i)

Identify one way large pieces of plastic are removed from wastewater during primary treatment.

[ 1 ]

Question (ii)

(ii)

Prior to discharge, wastewater is often disinfected. Identify one technique commonly used to disinfect wastewater.

[ 1 ]

Question (iii)

(iii)

Sludge or biosolids produced during the wastewater treatment process can be spread on agricultural fields. Identify one advantage and one disadvantage of this practice.

[ 2 ]
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