200

180

160

Sand—DOC
Concentration (mg/L)
140
120
100
80
60
40
20
0
Karri bark—DOC
Pine wood chips—DOC
Pine sawdust—DOC
Sand—TOC
Karri bark—TOC
Pine wood chips—TOC
Pine sawdust—TOC
0
2
4
6
8
Time (days)
14

12

Nitrate (as N) (mg/L)
10
Sand

8

Karri bark
Pine wood chips
6

Pine sawdust

4

2

0

0
50
100

Distance along column (cm)

120
Permeable Reactive Barrier
FIGURE 7.6
Concentration of nitrate (as N) along the length of each column experiment.
FIGURE 7.7
Concentration of soluble organic carbon and total organic carbon from the four columns.
as well as a strong organic odor, which corroborates the high concentrations
of DOC. As the amount of DOC in the effluent of the denitrification PRB was
a concern, owing to potential passivation of the ZVI, it was decided that the
shredded aged Karri bark was not appropriate for the PRB system and was
omitted from further testing.
As the carbon source will degrade over the life span of the PRB, it is important that some sand is used in the PRB’s construction to provide long-term
structural integrity of the barrier. A second round of column tests was