of time (about 30 days) after PCP solutions had been

introduced, and then the degradation appeared to cease.

Upon addition of an additional 0.5 ml of sludge supernatant

at t=60 days (to #304, #305, and #309) the degradation

activities resumed for another period of time and stopped

again. There were only negligible amounts of organic carbon

in the sludge supernatant, so the degradation should result

solely from biological activities. This degradation pattern

suggests that the microorganisms can degrade PCP but cannot

rely on PCP as a sole source of energy and carbon, i.e., the

microorganism populations were first in stationary phase

then in endogenous phase. Dehydrogenase activity (DHA)

tests on these PCP degradation study samples were performed

two months after the study ended and showed DHA only at

background levels, indirectly confirming the hypothetical

degradation pattern. Chu and Kirsch (1973) found one

bacteria culture was capable of utilizing PCP as a single

source of carbon and energy for growth. However, Stanlake

and Finn (1982) suggested that sporadic or continuous

addition of PCP-adapted cells to the treatment system might

be necessary because yields were low when bacteria utilize

PCP as the sole carbon source. Kaufman (1978) also reported

in his review that PCP was removed by respiring cells but

did not support growth. The degradation pattern shown in

Figures 5-12 and 5-13 agreed with the latter two

observations.