sewage and eutrophication

Question 1

why should sewage not be discarded in water bodies

Answer 1

untreated sewage should not be discharged into rivers or lakes as it may contain disease-causing organisms, which may infect a large number of people with diseases like cholera and typhoid

Question 2

how does eutrophication occur

Answer 2

1. untreated sewage or fertilisers contain phosphates and nitrates, which are nutreints for algae and water plants
2. this leads to excessive growth of algae and water plants, promoting bacteria growth
3. excessive algae and water plants on the surface of the water also results in water plants below in the seabed having a lack of oxygen.
   4, rate of photosynthesis in these water plants decrease rapidly, and they eventually die from a lack of food
   5, the excessive bacteria also can infect plants