Environmental Engineering Reference
In-Depth Information
Table 10.2 disTribuTion of WaTer
in TyPiCal aCTivaTed sludge
Water Type
% volume
Free water
75
Floc water
20
Capillary water
2
Particle water
2.5
Solids
0.5
Total
100
Source:
USEPA,
operational manual: Sludge
handling and Conditioning
, EPA-430/9-
78-002, U.S. Environmental Protection
Agency, Washington, D.C., 1978.
10.4 sludge PuMPing
ProCess ConTrol CalCulaTions
Wastewater operators are often called upon to make various process
control calculations. An important calculation involves sludge pumping.
The sludge pumping calculations the operator may be required to make
during plant operations (and should know for licensure examinations)
are covered in this section.
10.4.1 estimated daily sludge Production
The calculation for estimating the required sludge pumping rate
establishes an initial pumping rate and helps us to evaluate the ade-
quacy of the current withdrawal rate:
⎡
(Influent TSS Conc
.
−
Effluent TSS Conc.)
⎤
⎢
⎥
Estimated Pump
Rate (gpm)
×
Flow (MGD)
×
8.34 lb/g
al
(10.1)
⎣
⎦
=
% Solids in Sludge
×
8.34 lb/gal
× 0 min/day
144
Example 10.1
Problem:
The sludge withdrawn from the primary settling tank contains
1.4% solids. The unit influent contains 285 mg/L TSS, and the effluent
contains 140 mg/L TSS. If the influent flow rate is 5.55 MGD, what is the
estimated sludge withdrawal rate in gallons per minute (assuming the
pump operates continuously)?
Solution:
(285 mg/L
− × 5.55 MGD8.34lb/day
0.0148.34lb/gal
140mg/L)
×
Sludge Withdrawal Rate
=
×
×
1440
min/day
=
40 gpm
