Page 155 - Materials Chemistry, Second Edition

138 Practical Design Calculations for Groundwater and Soil Remediation

Solution:
(a) For the 4-m reactor,
3
the residence time = V/Q = 4 m /(0.04 m /min) = 100 min
3
3
Q, C in Q, C out
4 m 3

Use Equation (4.20) to find the final effluent concentration:

C out C out 1
= =
+
C in 1,800 1(0.1)(100)
C = 164 mg/kg (It exceeds the cleanup level.)
out
3
(b) For the two 2-m reactors,
3
3
the residence time = V/Q = 2 m /(0.04 m /min) = 50 min each
Q, C 0 Q, C 1 Q, C 2
2 m 3 2 m 3

Use Equation (4.28) to find the final effluent concentration:

 C 2   C 2   C 1   1   1 
C 2
=   =     =    
×
+
+
C 0  1,800  C 1   C 0   1(0.1)(50)   1(0.1)(50) 
C = 50 mg/kg (It is below the cleanup level.)
out
(c) The residence time of the first reactor = 1 m /(0.04 m /min)
3
3
= 25 min
The residence time of the second reactor
= 3 m /(0.04 m /min) = 75 min
3
3
Q, C 0 Q, C 1 Q, C 2
1 m 3 3 m 3

Use Equation (4.28) to find the final effluent concentration:

 C 2   C 2   C 1   1   1 
×
C 2
=   =     =    
+
+
C 0  1,800  C 1   C 0   1(0.1)(25)   1(0.1)(75) 
C = 60.5 mg/kg (It is below the cleanup level.)
out