2,4-DCP). PCP was resistant to biodegradation and the rates

of assimilation were not high enough to support bacterial

growth. The populations shifted into endogenous respiration

phase and eventually became extinct. Using indigenous soil

bacteria, the apparent degradation rates averaged 1.5 day-

(t /2= 0.5 days) for phenol, 0.1 day-1 (t/2= 7 days) for

2,4-DCP, and 0.006 day1 (t1/2= 120 days) for PCP. When

tested in multi-compound systems, phenol degradation rates

dropped off to 0.4 day-1 (tl/2= 1.7 days) but PCP

degradation rates increased to 0.008 day1 (t1/2= 86 days).

This increase was attributed to the effect of co-degradation

where bacteria utilized phenol as the primary carbon and

energy source to build up a larger population. Another set

of batch degradation experiments using different phenol to

PCP initial concentration ratios supported this hypothesis.

 Municipal wastewater sludge did not increase phenol

degradation rates but was a good source of a wide variety of

bacteria for aiding indigenous bacteria to degrade the other

two phenolic compounds. However, periodic addition of

sludge was required for more effective PCP removals. The

addition of sodium acetate and glucose as primary substrates

did not assist biodegradation in the sludge amended samples,

presumably because the effects were overshadowed by the

effects of sludge amendment. This result does not imply

that sodium acetate and glucose are not good substrates for

co-degradation. The enzymes required for PCP degradation

did not seem to be induced by exposing the bacteria to