Activated sludge treatment of synthetic wastewater containing pentachlorophenol.

Activated sludge treatment of a pentachlorophenol (PCP)-containing synthetic waste was examined. With a waste containing some sugars, and 40-120 mg/L PCP, laboratory activated sludge required about seven days for acclimation. However, the prior addition of a quasipure culture of PCP-metabolizing Arthrobacter resulted in immediate acclimation. Even with acclimated sludge, however, the system was upset for two days by a simple step change from 40 to 120 mg/L of PCP. The stability of the system to such a shock load was considerably improved when a chemostat culture of the PCP-metabolizing Arthrobacter was fed slowly into the mixed liquor. Kinetic models were developed to describe the dynamic response of the system in terms of growth parameters, hydraulic detention time, sludge age, and bleed-in rate from the chemostat.