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This question is about water - AQA - GCSE Chemistry - Question 5 - 2022 - Paper 2
Question 5
This question is about water. Sewage is waste water. Sewage contains organic matter. Describe how sewage is treated to remove organic matter. [4 marks] Sea wate... show full transcript
Worked Solution & Example Answer:This question is about water - AQA - GCSE Chemistry - Question 5 - 2022 - Paper 2
Step 1
Describe how sewage is treated to remove organic matter.
Answer
Sewage is treated through a series of processes to effectively remove organic matter:
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Screening: This initial step involves removing large solids from sewage using screens or grates.
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Sedimentation: The sewage is allowed to sit in a tank, where heavier solids can settle at the bottom as sludge.
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Anaerobic Digestion: The settled sludge undergoes anaerobic digestion, where bacteria break down organic matter without oxygen, producing biogas and reducing the volume of sludge.
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Aerobic Treatment: Finally, the liquid effluent is treated aerobically. This involves aerating the liquid to support aerobic bacteria that further break down any remaining organic matter.
Step 2
Step 3
Explain why the concentrations of sodium ions and of chloride ions in the ground water in Table 5 are unchanged by Process 1.
Answer
The sodium ions and chloride ions pass through the filter during Process 1 because they are dissolved in solution and are smaller than the filter pores. Therefore, they are not trapped or removed by the filtration process.
Step 4
Explain why the ground water in Table 5 requires Process 2 before the water is safe to drink.
Answer
The ground water may contain harmful microbes that can pose health risks. Process 2, which involves the addition of ozone, sterilizes the water by destroying these microbes, making it safe for drinking.
Step 5
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