Page 265 - Materials Chemistry, Second Edition

248 Practical Design Calculations for Groundwater and Soil Remediation

6.5.2 Design of an Aboveground Biological System
For the trickling-filter type of bioreactors, the following empirical equation
is often used [2]:

C out −0.5
= exp  −  kD QA(/ )   (6.25)
C in
where
C = COC concentration in the reactor effluent, mg/L
out
C in = COC concentration in the reactor influent, mg/L
k = rate constant corresponding to the packing depth of D, (gpm) /ft
0.5
D = depth of the filter, ft
Q = liquid flow rate, gpm
A = cross-sectional area of the packing material, ft 2

The hydraulic loading rate to a bioreactor is often small, at 0.5 gpm/ft or
2
less. If the hydraulic loading rate is known, Equation (6.27) can be used to
determine the cross-sectional area of the bioreactor:
Q
= (6.26)
A bioreactor
surfaceloading rate
When a rate constant determined from a different packing depth is used,
the following empirical formula should be applied to adjust the rate constant:

 D 1  0.3
k 2 = k 1    (6.27)
 D 2
where
k = rate constant corresponding to a filter of depth D 1
1
k = rate constant corresponding to a filter of depth D 2
2
D = depth of filter #1
1
D = depth of filter #2
2
The following procedure can be used to size an attached-growth
bioreactor:
Step 1: Select a desirable packing depth, D. Adjust the rate constant to
the selected packing depth, if necessary, by using Equation (6.27).
Step 2: Determine the hydraulic loading rate of the bioreactor by using
Equation (6.25).
Step 3: Determine the required cross-sectional area by using Equation
(6.26). Calculate the diameter of the bioreactor corresponding to
this area. Round up the diameter value to the next half or whole
foot. If the calculated cross-sectional area is too large, select a
larger packing depth and restart from Step 1.