汞和甲基汞在CASS工艺中的迁移和转化

The Migration and Transformation of Mercury and Methyl Mercury in CASS Process

汞及其衍生物甲基汞具有极强的生物毒性,是生态环境研究的热门之一。本次实验以鹤山市某CASS工艺污水厂为研究对象,对该工艺各处理单元中进出水及污泥中汞和甲基汞的浓度进行测定并初步探讨汞和甲基汞在污水处理厂中的迁移与转化。结果表明:1) 就整个CASS (周期循环活性污泥法)工艺过程而言,存在明显的上下总汞迁移趋势,上层颗粒相与下层沉积相总汞变化率均于缺氧–厌氧段最大;2) 由于氧含量的增加导致汞的去甲基化,在曝气–厌氧阶段下层沉积相中甲基汞的变化程度要大于上层颗粒相;3) 甲基汞占总汞含量的变化趋势与甲基汞含量的变化趋势相近,说明总汞含量不会对甲基汞的含量变化趋势造成影响。

Mercury (Hg) and its derivative methyl mercury (MeHg) have high biotoxicity. And the study of mercury (Hg) and methyl-mercury (MeHg) is one of the hotspots in the ecological environment research. Our experiments select a waste water treatment plant (WWTP) with CASS ((Cyclic Acti-vated Sludge System)) process in Heshan City to determine the concentration of Hg and MeHg in each processing unit and study its migration and transformation in WWIP. The results showed that: 1) The trend of the total Hg migrating from shallow to deep is obvious in the whole CASS process, and the change of total Hg in granular phase and sedimentary facies reach maximum in anaerobic stage;2) Because of the demethylation caused by the increase of the dissolved oxygen, the decrease degree of MeHg in sedimentary facies is more significant than the MeHg in granular phase;3) The change of the concentration of MeHg and the proportion of MeHg in total Hg is similar, which means the concentration of total Hg have no effect on the change of MeHg’s concentration.