Removal of radionuclides from Estonian groundwater using aeration, oxidation, and filtration
Removal of radionuclides from Estonian groundwater using aeration, oxidation, and filtration
复制标题
DOI：
10.3176/proc.2012.1.08
复制
发表时间：
2012-01-01
影响因子：
0.9
通讯作者：
Eensalu, Toivo
中科院分区：
文献类型：
--
作者：
Lumiste, Liie;Munter, Rein;Eensalu, Toivo
对塔林东北郊区的地下水进行了分析，以确定铁、锰、硫化物、氨和放射性核素（Ra-226、Ra-225）的含量以及总放射性。已经确定，寒武纪文迪安水层的几口威尔斯井的年有效剂量将超过欧盟饮用水准则（0.1 mSv/yr）。目的是找到一种同时净化地下水的技术，使其不含铁、锰、硫化物、氨和某些放射性核素（Ra-226、Ra-228）。由文丘里型曝气单元GDT（Gas-Degas Technology，Mazzei Corp.，USA）、氧化槽和两级过滤柱。测试了几种非催化（Everzit Special Plus，砂）和催化过滤材料（Filtersorb FMH，Pyrolox）。沿着从过滤器到II级过滤器出口的流程，主要通过分光光度法（哈赫DR/2000）监测pH值、溶解氧和二氧化碳、浊度、铁、锰和氨的含量。爱沙尼亚辐射中心使用液体闪烁计数法和γ-光谱法测定水样的放射性。据确定，通过对地下水进行密集曝气，然后进行一定接触时间的氧化，并适当选择不同性质的过滤材料，可以与铁和锰一起去除镭同位素。该过程的总效率是90%的总阿尔法和70%的总β活性去除地下水。由于井水中的铀含量很低，而氡在脱气分离器中几乎完全被去除（99%），因此总有效剂量由Ra-226和Ra-228计算。它约为0.067 mSv/年，低于欧盟DWD指南（0.1 mSv/年）。通过检查洗涤水，验证了放射性核素在第一个过滤步骤中已被Fe（OH）（3）絮凝物去除的理论假设。测定含沉淀物的洗涤水和过滤洗涤水的放射性。结果显示，在含有沉淀物的水中，总α活性高4.6倍，总β活性高5.3倍。在共沉淀过程中，MnO 2和Fe（OH）（3）絮凝起着重要作用，导致同时去除镭同位素。镭与MnO_2的共沉淀比与Fe（OH）（3）的共沉淀更有效。
Groundwater in the north-eastern suburb of Tallinn was analysed to determine the content of iron, manganese, sulphides, ammonia, and radionuclides (Ra-226, Ra-225) and total radioactivity. It was established that for several wells of the Cambrian Vendian water layer the annual effective dose would exceed the EU guideline for drinking water (0.1 mSv/yr). The purpose was to find a technology for simultaneous purification of groundwater from iron, manganese, sulphides, ammonia, and some radionuclides (Ra-226, Ra-228). A pilot plant consisting of a Venturi-type aeration unit GDT (Gas-Degas Technology, Mazzei Corp., USA), an oxidation tank, and two-stage filtration columns was constructed. Several non-catalytic (Everzit Special Plus, sand) and catalytic filter materials (Filtersorb FMH, Pyrolox) were tested. Along the flow sheet from the aerator to the II stage filter outlet the pH, dissolved oxygen and carbon dioxide, turbidity, the content of iron, manganese, and ammonia were monitored, mainly by using spectrophotometry (HACH DR/2000). Radioactivity of water samples was determined by the Estonian Radiation Centre using the liquid scintillation counting method and y-spectrometry. It was established that by intensive aeration of groundwater followed by oxidation for a certain contact time and appropriate selection of filter materials of different properties, it was possible to remove together with iron and manganese also radium isotopes. The total effectiveness of the process was 90% removal of gross-alfa and 70% removal of gross-beta activity of groundwater. Since the uranium content in the well water was marginal and radon was almost totally (99%) removed in the degas separator, the total effective dose was calculated by Ra-226 and Ra-228. It was about 0.067 mSv/yr, which is lower than the EU DWD guideline (0.1 mSv/yr). The theoretical assumption that radionuclides were already removed with Fe(OH)(3) flocks in the first filtration step was verified by examining wash water. The radioactivity of wash water containing precipitate and the filtered wash water were measured. Results showed 4.6 times higher gross-alfa and 5.3 times higher gross-beta activity in the water containing precipitate. The co-precipitation process, where MnO2 and Fe(OH)(3) flocks played an essential role, resulted in simultaneous removal of radium isotopes. Co-precipitation of radium with MnO2 was more effective than with Fe(OH)(3).