Estimation of Biodegradation and Liquid-Solid Partitioning Coefficients for Complex PAHs in Wastewater Treatment

Batch testing was employed to estimate model parameters that are required for predicting the fate of polynuclear aromatic hydrocarbons (PAHs) in wastewater treatment. Linear partitioning was found to describe the partitioning of the PAHs to solids and was best described when the soluble phase of the PAHs was determined by centrifugation alone. The liquid-solid partitioning coefficients obtained for primary and secondary sludges were statistically different, with the latter being higher than the former for most of the PAHs examined in this study. Temperature had a significant impact on the estimated biodegradation rate coefficients (Kb). The biodegradation rate coefficients for anthracene and phenanthrene (3-ring PAHs) were statistically different from benzo(a)anthracene and chrysene (4-ring PAHs). The presence of a nitro-adduct on acenaphthene resulted in a substantial increase in the Kb relative to the unsubstituted anthracene and phenanthrene. A sensitivity analysis revealed that the removal of PAHs in a full scale wastewater treatment plant was most sensitive to the value of the liquid-solid partitioning coefficients. Approximately 60% of the PAHs were removed from the wastewater stream through partitioning to both primary and secondary solids, and subsequent discharge.