23 JULY 2003
Calculate the volumetric capacity on the basis of the frequency, duration, and
overall quantity required for each specific application. The total pressure requirement is
calculated based on the total head requirements of the system, which includes the
summation of both the static and dynamic heads within the system. An additional safety
factor of 10 to 25% should be added to the dynamic pressure to reduce the effects
caused by the thixotropic characteristics of the sludge.
EQUALIZATION REQUIREMENTS AND VARIATION ALLOWANCES. The
objective of sludge flow equalization and variation allowances is to provide sludge that
contains similar characteristics for each filtration cycle.
. The design and equalization requirements and varia-
tion allowance for maximum conditions can be handled in several different ways.
However, these approaches are specific to an application and typically do not require
calculations. The first method would be to size the equipment and associated system
based on an average of 30 consecutive days of sustained flow and solids loading. In
general, this method would cause oversizing of equipment typically required. However,
if this approach uses several presses to process the sludge generated at the maximum
flow conditions, the number of presses operating during an average flow condition could
be reduced to handle only the average flow.
A second approach consists of basing the design on the average flow of an
average operating day and providing adequate storage for maximum flow conditions,
then processing the additional sludge with increased operating periods. To illustrate this
approach, assume the daily average flow was typically processed within 8 hours. To
process the sludge during maximum flow, an additional operating shift could be used to
process the sludge until average conditions resumed.
Minimum Conditions. Although typically the design of the filter press is
based on maximum or average requirements, and no calculations are based on
minimum flow conditions, the minimum flow condition should be considered. However,
several possible approaches can be used to address minimum flow conditions:
providing storage until enough sludge is generated to complete average flow filtration
cycle; reducing the number of filtration cycles over a typical operation period; using a
blanking plate to cut down the volume of sludge being dewatered if a single filter press
is being used; or cutting down on the number of units used if a multiple press system is
SUPPORT UTILITY REQUIREMENTS. Based on the initial selection of
equipment, requirements for ventilation, power, water, air, telephone, and other utilities
can be calculated. Although some of these calculations may be determined as
requirements for the entire treatment facility, incremental calculations may be required
that apply specifically to equipment or facilities required for filter press applications.