I think the BOD question was something along the lines of describing the test for BOD and evaluate its effectiveness for control and monitoring eutrophication...
I'm not sure how many marks i'll get but i basically defined BOD and then described the test:
Using a DO sensor on day zero and then again after placing the sample of water in a brown capped bottle in the dark at 20C for 5 days. The BOD is the difference in the two DO values.
I then talked about how when algal blooms, present because of eutrophication, die, the decomposers use up oxygen in the water to in order to break them down... Thus water that has been plagued by algal blooms has a very high BOD. Therefore BOD can be used as an indicator for algal blooms and eutrophication as the higher the BOD the greater the extent of eutrophication.
I finished off by saying although its useful as a test for monitoring eutrophication it should not be used alone as high BOD's can be due to other factors such as sewage contamination. Therefore further tests to determine nitrogen and phosphate concentration of the water should be carried out.
Briefly, thats how I interpreted the question anyway, any one else get anything similar?
and Halaby's congrats on ur first post