Aquatic Biodegradation Behavior of Pentachlorophenol Assessed Through a Battery of Shake Flask Die-Away Tests

Abstract

The aerobic aquatic biodegradability of pentachlorophenol (PCP) was studied in standard Organization for Economic Cooperation and Development/International Organization for Standardization shake flask screening tests for ready biodegradability and in more environmentally realistic surface water die‐away tests with low chemical concentrations. Screening tests were conducted with either activated sludge or supernatant from settled activated sludge. Concentrations of activated sludge were 30 and 0.3 mg suspended solids per liter. Sludges were either freshly collected or initially preexposed to PCP. With supernatant, only low inoculum levels were used (0.5 ml/L). Some surface water tests were carried out with sediment amendment. Added chemical concentrations ranged from 1 to 74,000 μg/L. At nontoxic concentrations, PCP was rapidly biodegradable after an adaptation period of about 10 to 20 d. At concentrations below about 10 μg/L, degradation rates decreased, and the shape of the degradation curves indicated a shift from growth‐linked degradation to non‐growth‐linked degradation. Addition of sediment to surface water reduced the acclimation periods but did not influence the subsequent degradation rate. Preexposure of activated sludge to PCP drastically eliminated the acclimation period and increased the tolerance of the sludge to PCP toxicity. With PCP used as a model compound, the results show that a battery of simple shake flask tests is suitable for provision of a detailed characterization of the biodegradability chemical compounds.

Evaluation of the OECD 314B Activated Sludge Die-Away Test for Assessing the Biodegradation of Pharmaceuticals

“…OECD 314B provides the low test material concentration, high biomass concentration, nongrowth, first-order kinetics conditions for measuring primary, and ultimate biodegradation for measuring the differences in biotransformation between pharmaceuticals that are not necessarily observed in the ready test − . It is also a batch test run without the detailed operation, resource needs, and costs of other simulation tests, such as OECD 303 and OPPTS 835.3220 .…”

“…To characterize the biotransformation processes that occur during sewage treatment, a method that uses biomass concentrations representing STP conditions (2000 mg/L), test concentrations more relevant to environmental concentrations (µg/L-ng/L) and chemical specific end points are needed. OECD 314B (16) provides the low test material concentration, high biomass concentration, nongrowth, first-order kinetics conditions for measuring primary, and ultimate biodegradation for measuring the differences in biotransformation between pharmaceuticals that are not necessarily observed in the ready test (17)(18)(19)(20)(21). It is also a batch test run without the detailed operation, resource needs, and costs of other simulation tests, such as OECD 303 and OPPTS 835.3220 (22).…”

Prediction of the Formation of Biogenic Nonextractable Residues during Degradation of Environmental Chemicals from Biomass Yields

“…However, after some time for adaptation microbes can "learn" to degrade recalcitrant compounds. 16 A third reason for persistence is that chemicals are poor growth substrates because they do not provide energy, carbon or nutrients to microbes under the specific environmental conditions. For example, alkanes have persisted over millions of years in reservoirs where no suitable electron acceptor (oxygen) was available.…”