23 JULY 2003
Figure 5-1. Schematic for sludge dewatering process design example no. 1.
5-188.8.131.52 Supporting Systems. Based on the specific filter press selected, require-
ments for sizing supporting systems such as precoating, air blowing, and media wash-
ing systems, along with utility requirements, will be determined from the information pro-
vided in Paragraph 2-4 and from equipment manufacturers or suppliers. However, for
this example these requirements will not be further defined.
Sludge Storage, Conditioning, and Feed Systems.
5-184.108.40.206 Development of System Components. The flow scheme, shown in Figure
5-1, involves sludge storage, conditioning, and feed systems. The associated
assumptions related to the design criteria presented below are primarily based on
information given in Paragraph 2-4.
a. A sludge storage tank will be located upstream of the sludge conditioning
b. A dry lime storage and mixing system will be used downstream of the
sludge storage tank. This system will have the capacity to store a 30-day supply of
hydrated lime, which will be provided in 45-kg (100-pound) bags of 96% purity. A
hydrated bagged lime system was selected because of the low quantity of lime required,
as described in Subparagraph 2-4.6.1. The dry lime will be fed in the required amount
into a dilution tank by two volumetric feeders. A 10% slurry of calcium hydroxide
(CaOH2) by weight will be mixed prior to being metered into the conditioning tank.
c. A ferric chloride storage and mixing system will be used downstream of the
sludge storage tank. This system will have the capacity to store a 30-day supply of 40%
ferric chloride solution. The ferric chloride will be diluted to obtain a 10% solution prior to
being metered into the conditioning tank.
d. A sludge transfer system will be used to pump the sludge from the sludge
storage tank to the conditioning tank. If required, the sludge will pass through an in-line
grinder prior to the sludge transfer pumping system. This in-line grinder will improve
sludge mixing and flow characteristics and protect downstream pumping and dewatering
e. The conditioning system will consist of a conditioning tank to which the
sludge and conditioning chemicals are added and assumed to be completely mixed.
The conditioned sludge will then be pumped to the filter press units.
f. The feed pump system will consist of pumps with the capacity to deliver the
sludge to the filter press at the following pressure stepping conditions, as described in
Subparagraph 2-4.3.1--30 minutes (1800 seconds) at 172 kPa (25 psig), 30 minutes
(1800 seconds) at 345 kPa (50 psig), 30 minutes (1800 seconds) at 517 kPa (75 psig),
and 1 minute (60 seconds) at 690 kPa (100 psig).