Question

Fresh sludge has moisture content of 99%, after thickening its moisture content is reduced to 96%. The reduction in volume of sludge is ........

• A. 5%
• B. 75%
• C. 85%
• D. 97.5%

Hint:

To solve sludge problems, use a standard reference mass/volume (like 100 units) and track the constant solids before and after thickening.

Answer 1

The Correct Option is B

Assume initial volume of fresh sludge = 100 units
Moisture content = 99% $⇒$ Solids = 1 unit
After thickening, moisture content = 96%
Solids = 1 unit $⇒$ this forms 4% of total volume
So, new volume = $\frac{1}{0.04}$ = 25 units
Reduction in volume = 100 - 25 = 75 units
Percentage reduction = $\frac{75}{100} \times 100 = 75%$