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全氟化合物(Perfluorinated compounds, PFCs)是氢原子全部被氟原子取代的碳氢化合物,具有热稳定性、疏水疏油的优良特性,被广泛应用于工业和消费品等生产生活领域。PFCs所含有的氟原子电负性高、原子半径小,较高的碳氟键能使其具有高度稳定性,在自然环境中不易被生物降解,在各种环境介质中均有所残留[1]。作为PFCs前体的最终降解物质,PFOS在自然环境中检出率最高,其主要通过工业废水和市政废水释放到天然水体中,威胁水生生物的健康安全[2],通过食物链的传递可富集到人体内,对肝脏、内分泌、免疫性能等方面产生毒性危害[3]。因此,其污染控制技术成为研究热点。
目前,有关 PFOS 去除的研究主要集中在物理吸附和化学催化降解方面[4-5]。其中物理吸附成本低、可操作性强,易于推广。有研究表明,PFOS 在颗粒状活性炭上的吸附能力大于560 mg·g−1[6];通过硝酸盐、碳酸盐、氯离子改性的砾石对PFOS的去除率高达99.7%[7]。人工湿地因低能耗、低成本,广泛应用于污水处理,通过湿地系统中植物吸收富集、填料吸附截留和微生物降解作用,不仅可以去除氮磷等营养盐物质,还可以去除金属离子、新兴污染物[8-9]。CHEN等[10]研究表明,人工湿地对水体中PFOA和PFOS的去除率分别为77%~82%和90%~95%。
铝污泥是给水处理过程中的副产品,在给水厂中大量产生,其含有大量的铝和聚合物,可以吸附污染物[11],将铝污泥与沸石、钢渣等材料混合烧制成颗粒状填料,可改善填料的理化性质,提升污染物的吸附性能[12]。将改性后的铝污泥填料应用于人工湿地中,其含有的铝、铁等元素可强化湿地的吸附、沉淀作用,而且有利于系统内部微生物的生长附着和植物根系的穿透[13]。
目前,铝污泥人工湿地对含氟水体的净化效果研究较少。本文基于前期的研究成果[13-14],以普通人工湿地为对照,将铝污泥填料置于人工湿地装置内,构建铝污泥人工湿地,通过动态实验探究了其对复合污染水体中C、N、P和PFOS的去除效果,以期为人工湿地在生态修复工程中的应用提供参考。
铝污泥人工湿地对含氟水体主要污染物的去除效果及分布特征
Removal effect and distribution characteristics of main pollutants in fluorine-containing water by aluminum sludge constructed wetland
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摘要: 全氟化合物(PFCs)作为一种典型的新兴污染物,在自然环境中不断检出,其暴露水平、来源影响及去除方式备受关注。本文选取铝污泥人工湿地和普通人工湿地,通过动态实验探究了其对复合污染水体中C、N、P和PFOS的去除效果及各污染物在系统中的空间分布特征。结果表明,2种人工湿地可以协同去除水体中的C、N、P和PFOS,但C、N、P的去除效果会受到PFOS的抑制作用,并且去除率的降幅随着PFOS质量浓度的增大而增大。当初始PFOS质量浓度为250 µg·L−1时,铝污泥人工湿地对C、N、P的去除率分别为(52.47±2.21)%、(65.79±1.87)%和(68.68±1.47)%;铝污泥人工湿地中植物对氮磷去除贡献率为28.81%,比无PFOS时提高5.27%;铝污泥人工湿地对PFOS的去除率为(73.24±2.56)%,比普通人工湿地高8.46%,填料中PFOS质量占比在2种类型的湿地系统中分别为(56.23±1.27)%和(40.28±2.55)%。铝污泥人工湿地对含氟水体中污染物的削减作用较好,且C、N、P的去除效果受PFOS胁迫作用较小。Abstract: As a typical new pollutant, perfluorinated compounds (PFCs) has been widely detected in water. Their exposure levels, source effects, and removal methods have raised many concerns. In this study, aluminum sludge constructed wetlands and common constructed wetlands were selected to study their removal effects and spatial distribution characteristics of C, N, P and PFOS in the complex pollution water through dynamic experiments. The results showed that the two constructed wetlands could synergistically remove C, N, P and PFOS, but the removal effects of C, N and P were inhibited by PFOS, and the decrease of removal rate increased with the increase of PFOS concentration. When the initial PFOS concentration was 250 µg·L−1, the removal rates of C, N and P in al sludge constructed wetland were (52.47±2.21)%, (65.79±1.87)% and (68.68±1.47)%, respectively. The contribution rate of plants to nitrogen and phosphorus removal in aluminum sludge constructed wetland was 28.81%, being 5.27% higher than that without PFOS. The removal rate of PFOS in aluminum sludge constructed wetland was (73.24±2.56)%, being 8.46% higher than that in common constructed wetland. In the two wetland systems, the weight proportions of PFOS in fillers were (56.23±1.27)% and (40.28±2.55)%, respectively. Aluminum sludge constructed wetland has a better reduction effect on the pollutants in fluorine-containing water, and the removal effect of C, N and P was less affected by PFOS stress.
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表 1 不同PFOS质量浓度下C、N、P的去除率
Table 1. Removal rates of C, N and P at different mass concentrations of PFOS
PFOS质量
浓度/(µg·L−1)COD/% 氨氮/% TN/% TP/% 0 62.11±2.48 67.43±2.33 73.57±2.78 72.35±0.95 1 60.15±1.92 68.64±1.85 72.41±2.04 71.33±1.22 250 52.47±2.21 59.58±2.56 65.79±1.87 68.68±1.47 5 000 43.62±2.18 51.52±2.01 57.45±1.77 62.17±1.49 表 2 不同人工湿地对C、N、P的去除率
Table 2. Removal rates of C, N and P by different constructed wetlands
% 工况 COD 氨氮 TN TP P0 53.28±2.14 64.25±2.25 67.48±1.88 65.98±1.58 P1 42.57±1.87 52.35±1.51 57.02±3.02 59.25±1.84 L0 62.11±2.48 67.43±2.33 73.57±2.78 72.35±0.95 L1 52.47±2.21 59.58±2.56 65.79±1.87 68.68±1.47 表 3 各介质对N、P的去除贡献率
Table 3. Contribution rate of each part to N and P removal
% 污染物种类 植物 微生物降解+填料吸附 N P N P 普通
人工湿地C、N、P 23.54 54.33 76.46 45.67 C、N、P、PFOS 33.93 58.75 66.07 41.25 铝污泥
人工湿地C、N、P 20.88 36.79 79.12 63.21 C、N、P、PFOS 25.57 39.64 74.43 60.36 -
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