Environmental Engineering Reference
In-Depth Information
Table 10.7 exPeCTed PerCenT
solids for CenTrifuge
deWaTered sludges
Type of sludge
Percent solids
Raw sludge
25-35%
Anaerobic digestion
15-30%
Activated sludge
8-10%
Heat treated
30-50%
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Conveyor
design
Relative conveyor speed
•
•
Type and condition
of sludge
Type and amount of chemical conditioning
•
•
Operating pool
depth
Relative conveyor speed (if adjustable)
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Centrifuge operators often find that the operation of centrifuges
can be simple, clean, and efficient. In most cases, chemical conditioning
is required to achieve optimum concentrations. Operators soon discover
that centrifuges are noise makers; units run at very high speed and
produce high-level noise that can cause loss of hearing with prolonged
exposure. When working in an area where a centrifuge is in operation,
special care must be taken to provide hearing protection.
Actual operation of a centrifugation unit requires the operator to
control and adjust chemical feed rates, to observe unit operation and per-
formance, to control and monitor centrate returned to treatment system,
and to perform required maintenance as outlined in the manufacturer's
technical manual. The centrifuge operator must be trained to observe
and recognize (as with other unit processes) operational problems that
may occur with centrifuge operation. Several typical centrifuge problems,
causal factors, and suggested corrective actions are provided below:
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symptom 1.
Centrate clarity is poor.
Causal factors:
Feed rate too high; wrong plate dam position; worn
conveyor flights; speed too high; high feed sludge solids concentra-
tion; improper chemical conditioning
Corrective actions:
Adjust sludge feed rate; increase pool depth;
repair or replace conveyor; change pulley setting to obtain lower
speed; dilute sludge feed; adjust chemical dosage.
•
symptom 2.
Solids cake is not dry enough.
Causal factors:
Feed rate too high; wrong plate dam position; speed
too low; excessive chemical conditioning; influent too warm
Corrective actions:
Reduce sludge feed rate; decrease pool depth
to increase dryness; change pulley setting to obtain higher
speed; adjust chemical dosage; reduce influent temperature.
