Page 255 - Materials Chemistry, Second Edition

238 Practical Design Calculations for Groundwater and Soil Remediation

Step 3: Determine the required area of the activated-carbon adsorber
by using Equation (6.11).
Step 4: Determine the required height of the activated-carbon adsorber
by using Equation (6.12).
Step 5: Determine the COC removal rate or loading rate by using
Equation (6.14).
Step 6: Determine the amount of the COCs that the carbon adsorber(s)
can hold by using Equation (6.9).
Step 7: Determine the service life of the activated-carbon adsorber by
using Equation (6.15).
Step 8: Determine the optimal configuration when multiple adsorbers
are used.

Information needed for this calculation:

• The adsorption isotherm
• COC concentration in the influent liquid, C in
• Design hydraulic loading rate
• Design liquid flow rate, Q
• Bulk density of the activated carbon, ρ b

Example 6.10: Design an Activated-Carbon System
for Groundwater Remediation
Dewatering to lower the groundwater level for belowground construc-
tion is often necessary. At a construction site, the contractor unexpectedly
found that the extracted groundwater contained 5 mg/L toluene. The tolu-
ene concentration of the groundwater has to be reduced to below 100 ppb
before discharge. To avoid further delay of the tight construction sched-
ule, off-the-shelf 55-gallon activated-carbon units are proposed to treat the
groundwater. Use the following information to design an activated-carbon
treatment system (i.e., number of carbon units, configuration of flow, and
carbon change-out frequency):

• Wastewater flow rate = 30 gpm
• Diameter of carbon packing bed in each 55-gal drum = 1.5 ft
• Height of carbon packing bed in each 55-gal drum = 3 ft
• Bulk density of GAC = 30 lb/ft 3
• Adsorption isotherm: q(kg toluene/kg carbon) = [0.04C /(1+0.002C )],
e
e
where C is in mg/L
e