Waste Water Treatment

Question 1

where does sewage water and waste water come from?

Answer 1

-agricultural systems e.g. waste water from nutrient run off and slurry from animals
-flushing water down the drain e.g. after having a bath or going to the toilet
- industrial processes also produce alot of waste water which can contain some harmful chemicals

Question 2

what has to happen before sewage is is put back into fresh water sources?

Answer 2

it has to be treated to remove any organic matter or harmful microbes

Question 3

what are the processes involved in treating waste water at sewage treatment plants?

Answer 3

1) Sewage is screened to remove large materials e.g. plastic bags
2) Sedimentation in a sediment tank separates solids (sludge) from liquid (effluent).
3) Effluent undergoes biological aerobic digestion to break down organic matter and microbes
4) Sludge goes through anaerobic digestion to break down any organic matter or other microbes
5) Additional stages may involve chemical treatment or UV treatment for toxic substances from industrial processes

Question 4

what is anaerobic digestion?

Answer 4

a process in which organic matter in sludge is broken down toget rid
-it releases methane gas which can the be used as an energy source while the remaining digested waste can be used as a fertiliser

Question 5

what the advantage of sewage treatment?

Answer 5

it uses less energy than desalination of water so can be used as an alternative in areas where there is not much fresh water

Question 6

what are the disadvantages of sewage treatment?

Answer 6

-it requires more processes than treating fresh water
-people may not like the idea of drinking water that used to be sewage