A Sonication Extraction Method to Determine PAHs in Activated Sludge (Supernatant and Solid) for the Monitoring of Aerobic Biodegradation

Abstract

A simple analytical method was developed and optimised for the determination of polycyclic aromatic hydrocarbons in activated sludge consisting of supernatant and solid, which collected from the aerobic reactor (aerated zone) of the biological treatment step in a wastewater treatment plant. The procedure accomplishes in feasible time of extraction and reasonable solvent volume without the need of any special technique to perform the extraction step. The method involves extraction of entire sample by sonication and mechanical shaking using n-hexane, preconcentration by solvent evaporation, and determination by high-performance liquid chromatography with diode array and fluorescence detectors. The developed method was optimised to give precise results in both low and high spiked samples: relative standard deviation lower than 10%, limits of detection lied between 0.2 and 5 μg kg $^{-1}$ , and recoveries were between 66% and 109%. This method allows the monitoring of the bioremediation efficiency of PAHs by the activated sludge, since it permits the extraction of both PAHs; those that adsorbed to the solid phase, and the other that presented in supernatant phase. The activated sludge could be valuable in the bioremediation of lighter PAH compounds mainly those which consist of two and three fused aromatic rings.