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sludge cake handling is sometimes overlooked in the design. If a conveyor or live-
bottom (conveying) storage bin breaks down, a "bottleneck" may result and the shut
down the dewatering system. Although most sludge handling equipment, such as
conveyors, are reliable and the cost of dual or additional equipment may be considered
unwarranted, the consequences of a shutdown of the dewatering system can be
substantial. Therefore, additional handling equipment or provisions for an alternative
handling or disposal option, such as an alternative conveyor that leads to a temporary
storage container or trucks or direct discharge into storage receptacles, should be con-
Sludge Cake Transport. Sludge cake is normally transported at the treat-
ment facility by conveyor belts. However, other systems, such as augers and pumps,
can also be used. In all cases when selecting a sludge cake transport system, the
designer must consider minimizing agitation to reduce changing the thixotropic or plastic
characteristics of the sludge, odor control, and housekeeping, such as spillage.
The subparagraphs that follow provide an overview of design considerations
for conveyor, auger, and pumping systems for sludge cake transport. More detailed
information is presented in Design of Municipal Wastewater Treatment Plants--Manual
of Practice No. 8 (WEF 1992).
2-4.9.1 Conveyor Systems. Conveyor systems are most commonly used to
transport sludge cake for filter presses. Located beneath the filter press, conveyors can
transport the discharged sludge cake to a storage hopper, to a truck loading facility, or
to an additional onsite disposal or treatment process (i.e., incineration). Conveying
systems may involve horizontal, inclined, or cross-collection transfer. For horizontal
conveyor transfer, a flat conveyor belt located beneath the filter press that is equipped
with side skirts or troughs is used. A narrow feed chute from the press discharge to the
conveyor should be used to direct the sludge cake to the belt discharge point.
2-188.8.131.52 The inclined belt transfer involves conveyor belts equipped with cleats or
corrugations to ensure that the cake is moved without slipping or rolling. Potential
problems with this type of conveyor include inadequate scraping and cleaning of the
belt. Inclined drag flight (chain) conveyors can also be used; however, these conveyors
can be a potential maintenance problem because of wear to chain and flights and
2-184.108.40.206 The cross-collection conveyor can be either horizontal or inclined.
2-220.127.116.11 Cake conveyor systems are typically a major housekeeping concern. The
conveyor design should consider minimizing transfer points to avoid the accumulation of
sludge. The design of the conveyor system should also provide additional rollers for
those areas where the sludge drops onto the conveyor.
2-4.9.2 Auger Systems. Augers can move dewatered sludge horizontally, on an
incline, or vertically. These systems move dewatered sludge by the pushing action of a
helical blade attached to a center shaft. The blade and shaft of the auger are mounted