Environmental Engineering FOURTH EDITION

174 ENVIRONMENTAL ENGINEERING

ide screen (not shown)

Figure 9-5. A comminutor used to grind up large solids.

Influent

lueni

Sludge

Figure 9-6. Rectangular settling tank.

to fill the tank. For example, if the tank volume is 100 m3 and the flow rate is 2 m3/min,
the retention time is 100/2 = 50 min.
The solids settle to the bottom of the tank and are removed through a pipe, while
the clarified liquid escapes over a V-notch weir, which distributes the liquid discharge
equally all the way around a tank. Settling tanks are also called sedimentation tanks