多环芳烃及其衍生物在SBR/MBBR工艺中的分布与去除

多环芳烃(PAHs)是一类重要的持久性有毒有机污染物,而其衍生物SPAHs的毒性更高.通过对青岛市城阳污水处理厂采样,分析在其SBR/MBBR工艺中16种PAHs及硝基PAHs(NPAHs),甲基PAHs(MPAHs)以及氧基PAHs(OPAHs)的分布与去除.结果表明,16种PAHs及13种SPAHs均有检出,进水中,PAHs与SPAHs的总质量浓度分别为3 835. 14 ng·L~(-1)与6 889. 46 ng·L~(-1),其浓度远远高于其他地区的污水处理厂.在出水中,PAHs与SPAHs的总质量浓度为1 148. 18 ng·L~(-1)与1 724. 57 ng·L~(-1),去除率分别为70. 06%与74. 97%,可见SBR/MBBR工艺能有效去除PAHs与SPAHs.水相中PAHs的去除主要是针对低环多环芳烃(LMW-PAHs)的生物降解;而颗粒相中PAHs的去除主要依靠初沉池对LMW-PAHs的吸附沉淀以及生物单元对高环多环芳烃(HMW-PAHs)的生物吸附.对于SPAHs,MPAHs去除效果最好,去除率达89. 15%,颗粒吸附以及生物降解是其主要的去除机制;其次是OPAHs,去除率为63. 36%,在水相中主要依靠一级处理的颗粒吸附去除,在颗粒相中则主要在二级处理的生物吸附去除; NPAHs的去除率为48. 85%,主要在生物池中去除. SPAHs在SBR/MBBR工艺中的去除机制不尽相同,污水处理厂应根据不同处理工段PAHs与SPAHs的分布特征采取相应控制措施,而污泥中富集的PAHs与SPAHs远高于出水的排放量,因此,还应加强污泥中PAHs与SPAHs的管理.

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 3835.14 ng·L^-1 and 6889.46 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 1148.18 ng·L^-1 and 1724.57 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.