23 JULY 2003
d. Compute filter volume required per cycle (assume a minimum of 1 cycle to
be performed each day).
Filter volume per cycle = [400 kg/d] / [(1 cycle/d) x (1120 kg/m3) x (0.30)] = 1.2 m3 (42 ft3) of
This is a rather large press for only one cycle per day; therefore, assume at
least two cycles per day. The filter press volume required would then be reduced by half
to 0.6 m3 (21 cubic feet).
Selection of Efficient Filter Press Unit.
5-18.104.22.168 Determine the Filter Press Sizes Available. From the manufacturer's
catalogs, determine the sizes of various filter press units. Using as the basis that the
most efficient and manageable filter press unit assembly is the one that has the fewest
operating units and provides nearly 100% operating capacity when one unit is out of
service, and about 25% extra capacity when all units are in operation, tabulate the filter
area available with and without the single largest unit for both sludge streams.
a. Metal Hydroxide Sludge. Based on this method, the proper unit to select
from information complied in Table 5-3 would be Item B. This selection has a total of
two units, including one operating unit and one standby unit. This assembly will provide
133% of the design daily requirement when one unit is not operating, and about 267%
of the design daily dewatering capacity when the standby unit is in operation.
b. Alternative Approaches. Because of the small amount of metal hydroxide
sludge generated, two potential alternatives for providing redundancy could be used.
The first approach would be to only provide redundancy for the biological sludge stream
and use the standby press for both sludge streams, or just providing two presses.
Another approach would be to obtain only the two presses required for the biological
sludge. Use one press as the primary press for the sludge and use the other as the
primary press for the metal hydroxide sludge (using a blanking plate to reduce the
volume) and as a standby press for the biological sludge stream. Using either of these
approaches would be a more economical way to satisfy the requirements.
c. Additional Calculations. Based on the information presented above,
additional calculations should be performed for sludge storage, conditioning, feed sys-
tems, sludge cake storage, and filtrate storage. These types calculations should follow
the example calculations shown in Examples no. 1 and 2. In addition to these
calculations, based on the specific filter press selected, requirements for sizing support-
ing systems, such as precoating, air blowing, and media washing, along with utility
requirements, will be determined from the information provided in Paragraph 2-4 and
from equipment manufacturers or suppliers.