Question : Explain the changes that can be observed in the characteristics of river water when sewage is discharged into it and a few weeks after the discharge with respect to : (i) level of dissolved oxygen(ii) population of fresh water organisms.

Question : Explain the changes that can be observed in the characteris

1.	Question : Explain the changes that can be observed in the characteristics of river water when sewage is discharged into it and a few weeks after the discharge with respect to : (i) level of dissolved oxygen(ii) population of fresh water organisms.
Answer» PEAK A- Sharp increase in BOD, disappearance of clean water organisms Peak B- Increase in dissolved oxygen, reappearance of clean water organisms Peak A- Increase in dissolved oxygen, reappearance of cleanwater organisms Peak B- Sharp increase in BOD, appearance of clean water organisms Peak A- Sharp increase in BOD, appearance of clean water organisms Peak B- INCREASED number in dissolved oxygen, disappearance of clean water organisms Peak A- Increased number of anaerobic BACTERIA, disappearance of clean water organisms Peak B- Sharp decline in dissolved `O_(2)`, reappearance of clean water organisms Solution :N//A