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Question 18N.3.HL.TZ0.e

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Date November 2018 Marks available [Maximum mark: 2] Reference code 18N.3.HL.TZ0.e
Level HL Paper 3 Time zone TZ0
Command term Outline Question number e Adapted from N/A
e.
[Maximum mark: 2]
18N.3.HL.TZ0.e

The diagram shows an overview of the Henriksdal wastewater treatment process in Stockholm, Sweden.

Inside Y there are rotating paddles. Outline two reasons for these paddles being needed.

[2]

Markscheme

a. mixing substrate to increase contact with bacteria
OR
preventing sedimentation ✔

b. avoids formation of biofilms ✔

c. aeration for aerobic bacteria ✔

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