【作者】 王宝；

【导师】 张虎元；

【作者基本信息】 兰州大学 ， 环境科学， 2010， 博士

【摘要】 采矿废弃物中的硫化矿物在遇到空气和水后会氧化产生酸性矿山废水(Acid Mine Drainage, AMD)。酸性矿山废水的pH非常低,且其中含有大量的重金属和硫酸盐。酸性矿山废水对矿区周围环境的污染已经成为全世界采矿工业共同面临的严峻问题。目前,解决酸性矿山废水污染问题的方法主要包括两大类,一类是从源头上控制酸性矿山废水的产生；另一类是对已产生的酸性矿山废水进行生物或化学处理。从源头上控制酸性矿山废水的产生是现在解决酸性矿山废水污染问题的优先选择。顶部覆盖、加碱混合处置、喷洒灭菌剂抑制细菌活动等都是常用的酸性矿山废水源头控制方法。分选出产酸能力极强的采矿废弃物,并利用设置了完备衬垫系统的包封设施对它们进行填埋处置,是一种新的酸性矿山废水源头控制方法。现在,用于包封采矿废弃物的衬垫系统主要有压实粘土衬垫(Compacted Clay Liner, CCL)、土工合成粘土衬垫(Geosynthetic Clay Liner, GCL)和土工膜(Geomembrane, GM)。“还原屏障”是由兰州大学提出的针对采矿废弃物处置场开发的新型屏障系统。它是一种具有微生物活性、内部处于强烈还原状态的低渗透性屏障。它不仅可以通过极低的渗透系数来限制重金属污染物的迁移,还可以利用自身内部微生物呼吸作用所导致的强烈还原环境实现对重金属污染物的固定。本研究的目标是评价城市污水处理厂污泥作为还原屏障制作材料的可行性以及污泥还原屏障在采矿废弃物处置场底部使用的可靠性。在本研究中,通过批式吸附试验和厌氧微生物培养试验两种方法揭示了污泥对重金属的阻滞机制。批式吸附试验结果表明污泥对重金属具有较强的吸附能力,其对Zn2+和Cd2+的吸附量分别达到了13.62 mg·g-1和15.60 mg·g-1。厌氧微生物培养试验的结果表明,微生物呼吸作用可以将污泥悬液由氧化态驱动到强烈还原态,进而促使污泥悬液体系内硫酸盐还原反应发生,最终导致污泥悬液内重金属离子浓度降低。使用柔性壁渗透仪对污泥试样的渗透系数进行了测定。试验结果表明,污泥试样的渗透系数小于1.0×10-7 cm/s,达到了采矿废弃物处置场的防渗设计标准。污泥试样内的微生物活动会降低自身的渗透系数。通过渗透试验研究了污泥试样与酸性孔隙液之间的相容性。试验结果表明,在酸性孔隙液的渗透作用下,污泥试样的渗透系数会逐渐增大。本研究的结果表明,污泥是还原屏障合适的制作材料。污泥还原屏障的强烈还原状态有助于全面降低重金属的活动性,实现固定重金属的环境工程目标。在酸性孔隙液作用下,污泥还原屏障渗透系数有增大的趋势。因此,污泥还原屏障在用于AMD控制时,需要通过添加其它碱性物质来弥补其长期酸缓冲能力的不足。更多还原

【Abstract】 Acid mine drainage (AMD) generated from the natural oxidation of mine wastes and rocks enriched in metals sulfide minerals. This waste water is characterized by a low pH and elevated concentration of heavy metals and sulfates, all of which have a detrimental effect on the ecosystems of mining districts. AMD from mine waste is a serious environmental problem associated with mining industry around the world.Strategies for mitigating the contamination resulted from AMD include source control and treatment of the contaminate water through chemical or biological methods. Prevention of the formation of AMD is generally a favorable option. Past prevention efforts generally include covering the mine wastes, co-disposal with alkaline material, inhibiting the growth of bacterial by spraying batericides, and so on. Segregating the most hazardous material and then disposal of them in a lined contained facility is an innovative technique to preclude the formation of AMD. Liner systems that have been widely used to contain mine waste include compacted clay liner (CCL), geosynthetic clay liner (GCL) and geomembrane (GM), and so on.Reduced liner (RL) is proposed by Lanzhou University, China as a new type containment system for mine wastes. It does not only have a low hydraulic conductivity as traditional hydraulic barrier but also posses strong reducing environment, where favor the formation of precipitation of metal sulfide. The objective of this study is to investigate the potential of municipal sewage sludge as construct material for RL and to assess the long-term integrity of the RL serving at mine waste dump site.Batch sorption test and anaerobic microbial incubation test were conducted to investigate the retardation mechanisms of heavy metals maybe occurred in sewage sludge suspensions. The results of batch sorption indicated that sewage sludge possessed strong adsorption capability for Zn2+ and Cd2+, which of 13.62 mg·g-1 and 15.60 mg·g-1, respectively. Anaerobic microbial incubation test results showed that microorganisms occurring in sewage suspensions can induce the redox condition of sewage sludge suspensions changed from oxidized state to strong reduced state and then promote the formation of sulfide mineral. The strong reducing condition established in sewage sludge suspension promoted the concentrations of heavy metals decrease to a lower level.The hydraulic conductivity of compacted sewage sludge was determined using flexible-wall permeameters. The measured hydraulic conductivity of compacted sewage sludge was lower than the regulatory specifications of 1.0×10-7cm/s for landfill site. Microorganism activity occurred in sewage sludge has the ability to decrease the hydraulic conductivity of compacted sewage sludge.The compatibility of the compacted sewage sludge with acidic pore water spiked with heavy metals was assessed through hydraulic conductivity test. Test results indicated that the permeation of acidic pore water tend to increase the hydraulic conductivity of compacted sewage sludge.The results of this study suggest that sewage sludge is a suitable material for constructing RL. Compacted sewage sludge can provide overall anaerobic reduction condition which decrease the mobility of heavy metals, displaying a potential application in pollution control engineering. With respected to the increase in hydraulic conductivity due to acidic pore water, further research clearified that the addition of alkaline material is needed to enhance the acid compatibility of compacted sewage sludge if used to control AMD.更多还原