Remediation of contaminated dredged harbor sediments by combining hydrodynamic cavitation, hydrocyclone, and...

A pilot-scale hybrid treatment system consisting of hydrodynamic cavitation (HC), hydrocyclone separator (HS), and sodium persulfate (PS), was employed for removing polycyclic aromatic hydrocarbons (PAHs) from dredged harbor sediments. The effectiveness of PAH degradation was studied by varying the inlet pressure (0-2.0 bar), PS dosage (or Σ[PAH] to [PS] mole ratio of 1:1-1:10³) at HS inflow velocity of 2.85 m/s, slurry concentration of 10%, and reaction time of 60 min. The degradation rate of PAH in the overflow (OF) sediment was significantly lower than that of the underflow (UF) sediment. After an inlet pressure increase of 0.5 bar and ΣPAH: [PS] molar ratio of 1: 10, the PAH removal was 87% and 55% in the UF and OF, respectively, by the combined HC-PS-HS unit. Without PS, the PAHs removal was 46% and 40% in the UF and OF, respectively. The removal efficiency for 6-, 5-, 4-, 3-, and 2-ring PAHs was 100%, 93%, 93%, 92%, and 82% in the UF and 55%, 61%, 67%, 47%, and 36% in the OF by the combined HC-PS-HS system. FEEM spectroscopy clarified that aromatic protein-based components (tryptophan- and tyrosine-like combined) were gradually degraded and transformed into soluble microbial metabolites when organic matter content declined during the combined HC-PS-HS treatment. This study provides new insights into the combined HC-PS-HS system for PAH degradation in dredged sediments.