Respirometric evaluation and modeling of the impact of continuous benzo[a]anthracene feeding on activated sludge

BACKGROUND: This study evaluated the impact of continuous benzo[a]anthracene (B[a]A) feeding on the biodegradation of peptone/meat extract mixture by means of respirometric testing and modeling results, and microbial community analyses. A sequencing batch reactor (SBR) was operated at a sludge age of 10 days. At steady state, it was sustained with the peptone mixture feeding alone for 21 days. The following 21 days involved continuous dosing of 11 mg L⁻¹ of B[a]A together with peptone mixture. In the last period of 7 days, B[a]A feeding was stopped. Storage of poly-hydroxy alkanoates (PHA) occurred during substrate utilization. A compatible model was calibrated using the oxygen uptake rate (OUR) and PHA profiles characterizing each phase. RESULTS: Continuous exposure to B[a]A did not affect the microbial growth process, but slightly increased PHA storage rate and growth on stored PHA. Hydrolysis rates were increased at first exposure followed by a significant decrease. Substrate binding also occurred at first exposure and declined by the end of B[a]A feeding. A major change was observed in biomass composition due to continuous exposure to B[a]A. CONCLUSION: The major novelty of the study was to prove that B[a]A altered the composition of the enriched microbial culture, characterized by slightly different process kinetics, especially for hydrolysable COD fractions.