Determination of Dissolved Oxygen in Water

High amount of Dissolved Oxygen in a lake indicate
If sample water does not contain enough microorganism then what needed to be done
Why is the Concentrated Sulphuric acid added to the sample after precipitates settle down?
According to drinking water specification provided by IS 10500 (2012), what should be range of DO of drinking water
The method used to measure Dissolved Oxygen in this experiment is