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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 treatment involves several processes to effectively remove organic matter. Initially, the sewage undergoes screening or grit removal to eliminate larger solid particles. Then, it is subjected to sedimentation, allowing heavier solids to settle out as sludge. Following this, the sludge undergoes anaerobic digestion, where bacteria break down organic matter in the absence of oxygen, effectively reducing its volume and treating it. Finally, the treated liquid effluent enters the aerobic biological treatment, where oxygen is added to further break down any remaining organic matter, ensuring the water is cleaner and safer for discharge or further treatment.
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 remain unchanged because these ions pass through the filter during the reverse osmosis process due to their small size. Since they are in solution, they are not trapped or removed by the filter, which is designed to separate larger particles.
Step 4
Explain why the ground water in Table 5 requires Process 2 before the water is safe to drink.
Answer
Ground water in Table 5 requires Process 2, which involves adding ozone, because it contains microbes that are harmful to health. Ozone treatment is effective in killing these microbes, ensuring that the water is purified and safe for consumption.
Step 5
Step 6