Influence of short- and long-term exposure on the biodegradation capacity of activated sludge microbial communities in ready biodegradability tests

The output of ready biodegradability tests (RBTs), that are extensively used to screen the potential of chemicals to be biodegraded, can be influenced by exposure of microbial communities to organic chemicals.

Monod-based ‘single-data’ strategy for biodegradation screening tests

Environmental contextObtaining biodegradation data over time can be difficult, especially when dealing with environmental compartments of increasing complexity. We evaluated the possibility of obtaining a full biodegradation depletion curve from a single biodegradation-time experimental measurement, and found that environmental information related to potential chemical persistence can be derived. The applicability of this ‘single-data’ strategy is illustrated using simulated and experimental data for several compounds. AbstractInformation obtained from biodegradability tests, e.g. half-life (t50) or kinetics parameters, is relevant in environmental risk assessment of new chemicals. In these tests, the removal of the tested compound is measured over a prefixed period of time (e.g. 28 days in ready biodegradability tests) to derive a substrate depletion curve. The implementation can be time-consuming, costly and difficult, especially when the complexity of the environmental compartment increases. In this work, the possibility of obtaining a full biodegradation depletion curve from a single biodegradation-time experimental data point (‘single-data’ strategy) was evaluated. Monod kinetics are assumed to avoid the limitations related to first-order kinetics (only valid for very low substrate concentrations). Experimental and simulated data were used to illustrate the potential of the proposed strategy. The effects on the estimates of several variables (e.g. Monod kinetics parameters, compound concentration or variability in biodegradation data) and the errors introduced to some of the variables were also evaluated. The results suggest that the proposed strategy can be used as a rapid (based on data measured at day 7) and low-cost screening approach to anticipate the result of a biodegradability test for new chemicals. The applicability and practical limitations of the ‘single-data’ strategy have been illustrated using experimental data for several compounds ranging from readily biodegradable (e.g. benzoic acid, acetylsalicylic acid, p-toluic acid) to potentially persistent compounds (e.g. bupivacaine, p-phenitidine, phtadinitrile).