A settling tank for a municipal water supply is 2.5 m deep, and 20°C water flows through

Question:

A settling tank for a municipal water supply is 2.5 m deep, and 20°C water flows through continuously at 35 cm/s. Estimate the minimum length of the tank which will ensure that all sediment (SG =2.55) will fall to the bottom for particle diameters greater than
(a) 1 mm and
(b) 100 μm. Fig P7.72