either 2,4-DCP or to PCP itself. Phenol had an unclear role

in inducing the PCP degrading enzymes.


6.1.3 Column Biodegradation


 Column biodegradation were performed under nonsteady-

state conditions in continuously recirculating setups.

Biodegradation rates were obviously greater than in batch

experiments, with the rate increase for PCP degradation

being especially noticeable, partly because of larger

bacterial populations in the columns, and partly because the

dynamic flow conditions made the substrates more available

to the bacteria.

 A large percentage of input PCP was initially adsorbed

onto the soil but later desorbed and degraded completely.

When controlled under different environments, the column

which was kept under an aerobic environment by adding

hydrogen peroxide degraded all three phenolic compounds

fastest. In the anoxic conditions both the microbial

population build-up and the rate of phenolic compounds

degradation were the slowest among the three systems but not

by a wide margin.


6.1.4 Hydraulic Conductivity Tests


 Hydraulic conductivities of the soils in each column

were tested before and after the biodegradation experiments.

The bacterial growth in the columns did not have an impact

on the hydraulic conductivity, which suggested the