The correct answer is: A. 0 to 50
The sludge index is a measure of the consistency of sludge. It is determined by measuring the time it takes for a given volume of sludge to flow through a standard orifice. The sludge index is used to determine the type of treatment that is required for sludge, as well as the equipment that is needed to handle it.
For normal sludge, the value of sludge index for Indian conditions is 0 to 50. This means that the sludge is relatively thin and can be easily pumped or transported. Sludge with a sludge index of 50 or greater is considered to be thick and may require special handling.
The following are the different options and their brief explanations:
- Option A: 0 to 50. This is the correct answer. The sludge index for normal sludge is 0 to 50.
- Option B: 50 to 150. This is the sludge index for thick sludge.
- Option C: 150 to 350. This is the sludge index for very thick sludge.
- Option D: 350 to 500. This is the sludge index for extremely thick sludge.