典型离子型稀土矿区氮污染地下水原位微生物修复技术研究

In-situ Bioremediation Technology for Nitrogen-Contaminated Groundwater in Ionic Rare Earth Mining Area

针对离子型稀土矿区地下水高浓度氮污染,选择广东某离子型稀土矿历史遗留开采区作为试验场地,采用曝气-注液一体化装置,通过间歇性曝气以及微生物菌剂、零价铁、碱剂注液,开展原位硝化、反硝化修复试验。结果表明:原位曝气注碱有效改善了离子型稀土矿区地下水水化学条件,使DO浓度≥2mg/L、pH提至7~8,为微生物生长代谢创造有利条件,单次曝气增氧和碱剂注射的有效作用时间分别约为3和7d。通过间歇性曝气注液可动态调节地下水好氧/厌氧条件,实现同区域地下水硝化和反硝化反应的原位转换,逐步去除地下水中的氮污染。经过多轮次注射后,NH_(4)+-N浓度最低降至0.27 mg/L,最大去除率为99.5%,TN最大去除率为76.7%,可达到GB/T 14848-2017《地下水质量标准》Ⅲ类水质修复目标。研究显示,原位微生物修复技术能够有效修复离子型稀土矿区氮污染地下水,实际应用中应当采用间歇性曝气注液与多轮次注射的方式,以实现地下水水质稳定达标。

To address severe nitrogen pollution in groundwater in ionic rare earth mining area,a typical remaining mining area in Guangdong Province was selected as the test site.In-situ nitrification and denitrification tests were carried out using intermittent aeration and the injection of remediation agents through an integrated aeration-injection device.The results showed that the groundwater chemistry conditions were effectively improved,promoting the growth and metabolism of microorganisms through in-situ aeration and alkali injection.The DO concentration and pH in the groundwater increased to above 2 mg/L and 7-8,respectively,and remained stable for 3 and 7 d after a single injection.The in-situ nitrification and denitrification processes were able to react under dynamically adjusted aerobic/anaerobic conditions of groundwater during intermittent aeration and injections.After,multiple injections,the minimum concentration of NH_(4)+-N in groundwater was 0.27 mg/L,and the maximum removal rates of NH_(4)+-N and TN were 99.5%and 76.7%,respectively,which could reach Standard for Groundwater Quality(GB/T 14848-2017)ClassⅢ.The study revealed that in-situ bioremediation technology could effectively remove nitrogen contamination in groundwater in ionic rare earth mining area,and intermittent aeration injection and multiple rounds injection should be adopted in practical application to reach groundwater quality standards steadily.