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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 using several processes:
- Screening and Grit Removal: Large solids and grit are removed to prevent damage to equipment.
- Sedimentation: The sewage undergoes sedimentation, allowing solid materials (sludge) to settle at the bottom of the tank.
- Anaerobic Digestion: The solid sewage sludge is treated anaerobically, breaking down organic matter without oxygen, resulting in biogas and stabilized sludge.
- Aerobic Biological Treatment: The liquid effluent is then treated aerobically, promoting the growth of bacteria that consume remaining organic matter, thus purifying the water.
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 concentrations of sodium ions and chloride ions in the ground water remain unchanged during Process 1 because they pass through the filter. This occurs as the ions are in solution and are smaller than the filter pores, hence not trapped or removed.
Step 4
Explain why the ground water in Table 5 requires Process 2 before the water is safe to drink.
Answer
The ground water requires Process 2 because it contains microbes that are harmful to health. Process 2, which involves exposing the water to ultraviolet light, serves to sterilize the water by destroying these harmful microbes, ensuring it is safe for drinking.
Step 5
Step 6