Distribution and Removal of Polycyclic Aromatic Hydrocarbons and Their Derivatives in SBR/MBBR Process

While polycyclic aromatic hydrocarbons (PAHs) are an important persistent toxic organic contaminant, the toxicities of substituted polycyclic aromatic hydrocarbons (SPAHs) are much higher than PAHs. Water and sludge samples were collected from the Qingdao Chengyang Sewage Treatment Plant (STP). The distribution and removal of 16 PAHs and nitro-PAHs (NPAHs), methyl-PAHs (MPAHs), and oxy-PAHs (OPAHs) in the SBR/MBBR process were analyzed. The results showed that 16 PAHs and 13 SPAHs were detected. In the influent water, the total concentrations of PAHs and SPAHs were 3 835.14 ng•L-1 and 6 889.46 ng•L-1, respectively, which were much higher than those of STPs in other regions. In the effluent, the total concentrations of PAHs and SPAHs were 1 148. 18 ng•L-1 and 1 724.57 ng•L-1, respectively, and the removal rates were up to 70.06% and 74.97%, respectively. The SBR/MBBR process presented a more effective removal capacity for PAHs and SPAHs. The removal of PAHs was mainly by the biodegradation of low-ring polycyclic aromatic hydrocarbons (LMW-PAHs)in the aqueous phase; while the removal of PAHsin the particle phase mainly relied on the adsorption and precipitation of LMW-PAHs in the primary sedimentation tank and the biosorption of high-ring polycyclic aromatic hydrocarbons (HMW-PAHs) in the bio-unit. For SPAHs, the removal efficiency of MPAHs (up to 89.15%) was the best under the functions ofparticle adsorption and biodegradation. The removal rate of OPAHs was 63.36%, which was mainly removed by the adsorption of primary particles in the aqueous phase and the biosorption from the biological treatment unit in the particlephase, and the removal rate of NPAHs was 48. 85% and largely occurred in the biological treatment unit. The removal mechanism of SPAHs in SBR/MBBR process was not the same. Therefore, STPs should take adequate control measures according to the distribution characteristics of PAHs and SPAHs in different treatment units. Additionally, the concentrations of PAHs and SPAHs in sludge were higher than those in the effluent. Thus, the management of PAHs and SPAHs in sludge should be improved. © 2019, Science Press. All right reserved.