Handbook of Civil Engineering Calculations

FIGURE 9. Sludge handling system.

generally located so as to have a suction head as shown in Fig. 9. A schematic of a rotary
lobe pump is shown in Fig. 10.
The required flow rate for the sludge pump using the 4 h/d, 7 d/wk operation scheme
is:

6,230 gal/day

Flow rate (gal/min) = (4 ^ 60 ^ - 26 ga./min (1.64 L/s)

2. Compute the headless in the piping system
   The head loss through the piping system is calculated using the Hazen-Williams formula:

/ 100 \i.85/ Q

185

\i L \

tf=(0.2083)( —) (^-)(-M)

where H = Dynamic head loss for clean water, ft (m)
C = Hazen-Williams constant (use 100)
Q = Flow rate in pipe, gal/min (L/s)
D = Pipe diameter, in (mm)
L = Equivalent length of pipe, ft (m)

Note: There is an SI version of the Hazen-Williams formula; use it for SI calculations.

DISCHARGE

SUCTION

FIGURE 10. Rotary-lobe pump schematic.

Aerobic

Digester

Rotary Lobe

Sludge Pump

Sludge

Holding

Tank

Sludge Dewatering

Facility (Centrifuge)

To Off Site

Disposal

3" Pipe

10 feet (3m)