污染沉积物生物沸石覆盖修复过程中氮迁移转化机制

Controlling eutrophication of lakes and reservoirs is a difficult task globally. In situ capping of contaminated sediment is one of research focus. Previous research indicated that biozeolite capping could be an effective technique for controlling nitrogen release from sediment. However, the mechanisms of nitrogen transportation and transformation in remediation process are not clear, and its studies are urgently required. . In this project, the mechanisms of nitrogen transportation and transformation from sediment to interstitial water, to biozeolite, to overlying water in remediation process of sediment using In situ capping with biozeolite would be examined through a series of dynamic incubation experiments in the laboratory. The nitrogen transportation and transformation effects of C/N ratio, dissolved oxygen concentration, hydraulic retention time and thickness of capping layer would be studied. Successive changes of microbial community structure and dominant microflora on the biozeolite would be discussed. The nitrogen transportation and transformation effects of the competitive process between indigenous bacteria and isolated bacteria would be revealed. The mathematical models of ammonia nitrogen and nitrate nitrogen transportation and transformation would be constructed, and the effective time of controlling nitrogen using biozeolite capping would be estimated. Consequently, the mechanism of controlling nitrogen release from sediment through biozeolite capping technique would be illuminated, and the technique would be further optimized. . The research results can provide a theoretical basis and technological support for the practical application of remediation technique of nitrogen contaminated sediment using In situ capping with biozeolite in controlling eutrophication of lakes and reservoirs.

湖泊水库富营养化是当今水环境污染治理的难题，污染沉积物原位覆盖修复方法是研究热点之一。前期研究成果表明，生物沸石覆盖技术能有效控制沉积物氮释放，但修复过程中氮迁移转化机制尚不明确，亟需进一步研究。. 本项目拟采用室内水槽动态模拟试验，研究沉积物生物沸石覆盖修复过程中不同形态氮从沉积物→间隙水→生物沸石→上覆水迁移转化机制，重点考察碳氮比值、溶解氧浓度、水力停留时间和覆盖层厚度对氮迁移转化的影响；探讨沸石上微生物群落演替规律和优势菌群动态变化过程，揭示高效菌和土著菌相互竞争过程对氮迁移转化的影响；建立氨氮和硝氮迁移转化数学模型，预估生物沸石覆盖控氮的有效时间；从而探明生物沸石控氮机理，进一步优化技术方法。. 研究成果可为氮污染沉积物生物沸石覆盖修复技术在控制湖泊水库富营养化的实际应用中提供理论依据和技术支撑。

水体富营养化是当今水环境污染治理的难题。污染底泥原位生物活性薄层覆盖修复方法是研究热点之一。研究了污染底泥生物活性薄层覆盖修复过程中氮迁移转化机制，重点讨论了覆盖厚度、碳氮比值和溶解氧浓度对氮迁移转化的影响，探讨了沸石上微生物群落演替规律和优势菌群动态变化过程，揭示了高效菌和土著菌相互竞争过程对氮迁移转化的影响，从而探明了生物沸石控氮机理。研发了以净水厂污泥资源化制备除磷底泥覆盖材料，提出了一种以活性覆盖材料和沉水植物联合修复污染底泥方法。.（1）上覆水体最佳DO浓度为1~4 mg/L；生物沸石覆盖强度越大，控制效果越好，应结合底泥污染程度、控制效果要求及成本等设计覆盖强度；碳源减少使生物脱氮效果降低。.（2）生物沸石上硝化细菌数量随着碳源的减少而减少，反硝化细菌随着碳源的减少及上覆水体DO浓度增加（大于3 mg/L）而减少；高效菌一直存在生物沸石上，且都是优势菌，高效菌与土著菌存在竞争，土著优势菌的种类不断更替，新增土著优势菌中，沙雷氏菌和代夫特菌具有脱氮功能，细菌形态从球杆状变为杆状。.（3）C-WTPS最佳煅烧温度为400℃、煅烧时间为3h。与WTPS相比，C-WTPS对磷的吸附量增长48.2%，氨氮和有机物释放量大大减小。投加C-WTPS对溶液pH变化是有益的，即在酸性条件下反应后，pH会上升，中性和碱性条件下pH会下降；酸性条件下有利于C-WTPS对磷的吸附，但pH≧10时，磷吸附量显著下降，甚至出现磷释放；C-WTPS对磷有较强的结合能力，吸附的磷在溶液pH为3~10范围内较为稳定，再释放风险小，但当水体pH≧11时，吸附磷易再释放水体，再释放风险大。C-WTPS覆盖能完全控制底泥中磷释放，是非常有效的除磷材料。.（4）黑藻与煅烧改性净水厂污泥组合系统对间隙水中正磷酸盐和TP削减率分别为66.8%和59.8%，对底泥中铵态氮削减率分别为46%，对底泥TP削减率分别为7.9%，能将底泥中不稳定态无机磷（Fe-P和Al-P）转化为稳定态无机磷（Ca-P）。黑藻和煅烧改性净水厂污泥组合系统不仅有效削减底泥氮磷释放，而且能有效抑制底泥再悬浮。