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The treatment of drinking water for an urban supply consists of a number of stages - Leaving Cert Chemistry - Question 9 - 2006
Question 9
The treatment of drinking water for an urban supply consists of a number of stages. In the case of any three of the stages in the treatment process, state the treatm... show full transcript
Worked Solution & Example Answer:The treatment of drinking water for an urban supply consists of a number of stages - Leaving Cert Chemistry - Question 9 - 2006
Step 1
State the treatment involved and why it is carried out.
Answer
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Screening: This process involves removing large debris and encouraging the coagulation of suspended solids. It is crucial because it ensures that larger particles do not clog the filtration system.
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Sedimentation: Also referred to as settling, this stage allows suspended solids to settle at the bottom of the tank. This is important for the initial processing of water, so that less solid waste enters the subsequent treatment stages.
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Chlorination: This stage disinfects the water by killing pathogens. This is vital as it ensures that the treated water is safe for consumption.
Step 2
1. Write in your answer book the omitted words corresponding to each of the numbers 1 to 5.
Answer
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Solid: In primary treatment, sewage is passed through grids and over grit channels to remove dense solid material.
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Sedimentation: The sewage is then transferred to sedimentation tanks where suspended solids are allowed to settle.
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Biological: In secondary treatment, the sewage is broken down by biological digestion.
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Nitrates: Tertiary treatment removes phosphates and nitrates. These nutrients can cause eutrophication if their concentrations build up in lakes and rivers.
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Eutrophication.