【作者】 方迪；

【导师】 周立祥；

【作者基本信息】 南京农业大学 ， 植物营养学， 2006， 博士

【摘要】 制革污泥是一种既含高浓度有毒金属铬（含Cr达1～4％），同时也富含有机质、氮磷等植物养分的有机废弃物。污泥无害化及资源化是多数制革企业当前面临的迫切选择。基于生物湿法冶金原理（biohydrometallurgy）的生物淋滤（bioleaching）技术在去除污染介质中重金属上获得的成功，为我们去除或回收制革污泥中高量的铬提供了全新的启示。本文以制革污泥为研究对象，对制革污泥生物淋滤工艺进行了有益的探索，主要研究三大内容：制革污泥生物淋滤工艺参数的优化；污泥中对生物淋滤细菌（Acidithiobacillus ferrooxidans LX5和Acidithiobacillus thiooxidans TS6）产生抑制的有机物鉴定；内源耐酸性酵母TS7的分离及其在加速制革污泥生物淋滤脱铬进程中的作用机制与效果验证。序批式试验表明，采用嗜酸性氧化亚铁硫杆菌A．ferrooxidans LX5和氧化硫硫杆菌A．thiooxidans TS6并少量添加能源物质硫粉的生物淋滤技术能高效脱除（溶出）制革污泥中的铬。淋滤反应8d，Cr的溶出率接近100％。且生物淋滤处理后的制革污泥沉降性能大大改善，污泥中氮磷等植物养分损失较少。硫粉投加量，污泥浓度，起始H₂SO₄添加量，温度以及污泥回流比等对制革污泥生物淋滤过程均有不同程度的影响。研究显示，硫粉加入量4g／L，污泥浓度4％～6％，起始H₂SO₄添加量0.185mL／g，温度28℃，污泥回流比1／2～2／3等条件对制革污泥中Cr的生物淋滤去除最为有利，且污泥淋滤过程中污泥pH值和Cr溶出率与反应时间（T）、硫粉投加量（S）、污泥浓度（C）、温度（W）、起始H₂SO₄添加量（H）之间的关系可以分别用表达式pH=-0.064S+0.063C-0.215W-21.95H-0.43T+16.09；Cr（％）=1.74S-1.90C+3.46W+289.56H+6.73T-144.99来反映。制革污泥中铬的生物淋滤脱除主要是靠污泥介质的酸化，即污泥pH值的降低来实现的，氧化作用贡献极小。研究发现，污泥中铬的大量溶出（80％以上）存在明显突变点：当污泥pH值≤2.0，才能使污泥中Cr的溶出率达到80％以上；pH值下降到1.5，Cr的溶出率接近100％。污泥DOM对嗜酸性硫杆菌A．ferrooxidans LX5和A．thiooxidans TS6氧化亚铁和氧化硫粉均存在明显抑制。通过对8种常见有机物对硫杆菌抑制作用的研究以及对污泥DOM中一元小分子有机羧酸的检测发现，污泥DOM对硫杆菌LX5（TS6）氧化Fe²⁺（S粉）所产生的抑制程度高低与污泥DOM中一元小分子有机酸含量大小密切相关。8.94mM甲酸和2.09mM乙酸是导致污泥150mg DOC L^-1的DOM-H对Fe²⁺（S粉）氧化的抑制率分别高达95％和79％的主要原因。试验还发现，与A．thiooxidans TS6相比，A．ferrooxidans LX5对葡萄糖，淀粉和柠檬酸等有机物更为敏感，而对小分子一元有机羧酸中的乙酸，丙酸和丁酸表现出更强的耐受力。作者从制革污泥中分离出一株以制革污泥DOM为碳源和能源且能耐受极端酸性环境的酵母TS7，将其复合作用于以嗜酸性硫杆菌（LX5和TS6）为主体的制革污泥生物淋滤过程。结果显示，83％的制革污泥DOM被酵母TS7消耗，一定程度上消除或减轻了DOM对硫杆菌的毒害，进而与未添加酵母TS7的对照相比，污泥中Cr的淋滤周期缩短4d，第6d，污泥pH值即下降到1.5，Cr的溶出率接近100％。280L气升式内环流（ALR）反应器中进行的制革污泥生物淋滤反应（硫杆菌与酵母菌配合）验证了污泥淋滤技术在中试规模下仍具有稳定的处理效果（淋滤作用3d，Cr的溶出率达到94％）。本文研究表明，利用嗜酸性硫杆菌或复合以耐酸性异氧菌的生物淋滤作用可以高效脱除制革污泥中高量的铬，是一门极具应用前景的污泥“洁净化”技术。更多还原

【Abstract】 Land application represents the most economical way for final disposal of tannery sludge as it combines the recycling of plant nutrients and sludge disposal at the same time. Unfortunately, the presence of high levels of poisonous metal Cr in tannery sludge often limits its use as a fertilizer. The Cr content in tannery sludge is about 1-4% on a dry weight basis, and in some cases, extremely high concentrations of up to 13% of Cr have been reported. A technologically feasible process called bioleaching was used to remove Cr from tannery sludge with Acidithiobacilli species in this study. The objective of the present study is （1） to optimize the key parameters; （2） to determine the possible inhibitory substance（s） present in tannery sludge, and further to evaluate their impacts on iron and sulfur oxidization by Acidithiobacillus ferrooxidans LX5 and Acidithiobacillus thiooxidans TS6, respectively; （3） to exploit the indigenous heterotrophic microorganisms present in tannery sludge to eliminate side effect of inhibitory substance and improve the heavy metal bioleaching efficiency; （4） to investigate a pilot-scale study for bioleaching of Cr from tannery sludge. Ultimately, the expected outcome from this work will contribute to the understanding of bioleaching strategies with an ultimate purpose of developing an appropriate method to facilitate optimization of bioleaching strategies.Batch experiments showed that almost 100% of Cr removal efficiency could be obtained after 8-10 days of bioleaching when 4 g l^-1 of elemental sulfur was added, in the presence of A. ferrooxidans LX5 and A thiooxidans TS6. 4g l^-1 of elemental sulfur; 4%-6% of solid content; 28℃; 0.185 ml sulfuric acid of the initial of addition to per dry sludge and 1/2 2/3 of recycled ratio of bioleached sludge were reported to be the most favorable for Cr bioleaching from tannery sludge. Although the bioleaching of Cr from tannery sludge was strongly influenced by various parameters such as sulfur concentration; temperature; solid content; the initial sulfuric acid addition; the recycled ratio of bioleached sludge etc, it was found that chromium required a sludge pH of 2-3 to initiate its solubilization and further at constant pH, metal solubiliztion was the same regardless of the above parameters. When sludge pH decreased 1.5, almost 100% of Cr could be removed from tannery sludge. Additionnally, the settling capability of decontaminated sludge was improved tremendously, and the nitrogen, phosphors and organic matter values of sludge samples were only marginally affected.Results obtained in batch cultures in flasks using sludges from three different wasterwater plants (tannery sludge from Haining Kasen Co. Ltd （Sludge H）, domestic sludge from Nanjing （Sludge N）, and municipal sludge from Wuxi （Sludge W）, demonstrated that sludge DOM of three origins significantly inhibited ferrous iron and sulfur oxidation by A. ferrooxidans LX5 and A. thiooxidans TS6, respectively. The toxicity of sludge DOM appeared when the concentration was higher than 150 mg DOC L^-1. Among the organic compounds tested, the monocarboxylic organic acids including formic acid, acetic acid, propionic acid, and butyric acid exhibited a marked toxicity to Acidithiobacillus species. Of these organic acids, formic acid was the most toxic one as indicating that iron and sulfur oxidation almost were entirely inhibited at a concentration of 1.67 mM. Moreover, it was found that A. ferrooxidans LX5 was more sensitive to glucose, starch, and citric acid than A. thiooxidans TS6, while the former seemed to be more acetic, propionic, and butyric acid resistant than the latter. In the selected 150 mg DOC L^-1 of DOM derived from Sludge-H, the concentrations of formic acid and acetic acid were 8.94 mM and 2.09 mM, respectively, being a contributing factor causing 95% inhibition of iron oxidation and 70% inhibition of sulfur oxidation.An acidophilic sludge DOM-degrading yeast TS7 was successfully isolated from tannery sludge and it could achieve optimum growth in potato dextrose agar （PDA） liquid media of pH 2-7. When yeast TS7 was inoculated in the medium containing 2007 mg DOC L-1 sludge DOM derived from tannery sludge, about 83% of sludge DOM was assimilated or decomposed within 72 hours. As a result, Cr bioleaching efficiency was enhanced when yeast TS7 was inoculated simultaneously with A. ferrooxidans LX5 and A. thiooxidans TS6 into tannery sludge. Compared with the 10 days required for maximum solubilizaiton of Cr for the control sludge, the bioleaching period was significantly shortened to 6 days for sludge receiving co-inoculation.A pilot-scale study for bioleaching of Cr from tannery sludge in 280L air lift reactor confirmed that the bioleaching process is a feasible and promising technology for removing heavy metals from tannery sludge.更多还原