23 JULY 2003
tion of the press. Once the press is selected, the calculations for supporting equipment
can be done, as demonstrated in Examples no. 1 and 2.
Assumptions. The following assumptions and criteria are used for the design
of the sludge-dewatering system.
The characteristics of ground water to be treated are as follows.
5-22.214.171.124 Assumed type of ground water contamination is landfill leachate containing
heavy metals (i.e., chromium) and organics (i.e., volatiles and semivolatiles). Specific
Chromium (hexavalent) = 10 mg/L (required effluent 0.02 mg/L)
BOD5 = 900 mg/L (required effluent 30 mg/L)
COD = 1,600 mg/L
5-126.96.36.199 Design influent flow is 6.3 L/s (100 gpm).
5-4.1.2 This example assumes that the contaminated ground water is first treated to
remove the metals by a reduction, flocculation, and clarification process, which
generates a metal hydroxide sludge. Following metals removal, the ground water is then
treated to remove organics contamination by an activated sludge process, which
generates biological sludge. The two separate sludge streams are then sent to separate
filter presses. Fixed-volume recessed plate filter presses will be used.
5-4.1.3 This example assumes that treatability testing has been done and the
following data were obtained.
5-188.8.131.52 Metal Hydroxide Sludge.
a. Sludge Feed Characteristics.
Concentration of solids = 1%
Solids production = 70 mg/L
Specific gravity = 1.0
b. Sludge Cake Characteristics.
Cake thickness = 32 mm (1.25 inches)
Wet cake density = 1200 kg/m3 (75 lb/ft3)
Minimum solids = 30%
c. Optimum Chemical Conditioning.