【作者】 孙雪菲；

【导师】 王曙光；

【作者基本信息】 山东大学 ， 环境工程， 2011， 博士

【摘要】 随着社会经济生活的不断发展,水环境污染问题日益严重,废水生物处理技术是解决水污染问题的重要手段之一。与传统的絮体活性污泥相比,好氧微生物颗粒由于其优异的沉降性能和良好的生物活性而受到普遍关注。重金属污染指由重金属或其化合物造成的环境污染,已经十分普遍。在微生物生长代谢过程中,微量的重金属是微生物生活所需物质,但是过量反而抑制微生物的生长代谢甚至引起死亡。因此研究微生物颗粒与金属之间的相互作用对于维持生物系统的稳定运行具有重要意义。本论文从好氧微生物颗粒的界面吸附特性研究出发,探讨了好氧微生物颗粒与金属离子相互作用的界面过程,解析了重金属对好氧微生物颗粒生理生化特性的影响,并在量化计算的指导下对微生物颗粒表面进行修饰强化了微生物颗粒与重金属的相互作用界面行为。主要研究内容和研究结果如下：1.研究了好氧微生物颗粒与分子染料之间相互作用,评价了好氧微生物颗粒的表面特性。研究结果表明好氧微生物具有很强的结合分子染料的能力,其最大结合常数为56.818 mg/g SS;利用染料分子探针结合单分子层模型判定含水好氧微生物颗粒比表面积为72.32 m2/g SS;热力学分析表明好氧微生物颗粒对染料的吸附是自发、吸热过程。2.考察了二元金属体系中好氧微生物颗粒与金属离子之间的界面作用过程和作用机理。研究发现金属离子与好氧微生物颗粒最大结合系数分别为55.25 mg/g Co (pH7)和62.50 mg/g Zn (pH5);二元金属的添加导致了金属之间的竞争,减少了金属与颗粒的结合量；二级动力学速率方程能够很好的拟合试验数据,推断颗粒与金属的相互作用的速率限制步骤为电子交换或共用电子引起的化学反应过程；好氧微生物颗粒与Co(Ⅱ)相互作用的初始反应速率大于与Zn(Ⅱ)作用速率；光谱和能谱分析显示好氧微生物颗粒界面上的官能团(如羟基和羧基)是颗粒界面上发生反应的主要活性位点。3.采用傅里叶红外光谱(FTIR)和X射线光电子能谱(XPS)技术,深入探讨了不同来源的微生物颗粒胞外聚合物(EPS)与金属离子的界面作用机理。研究发现好氧微生物颗粒分泌的紧密束缚型EPS (Tightly bound EPS, TB-EPS)含量高于松散束缚型EPS (Loosely bound EPS, LB-EPS),其主要成分都为多糖和蛋白质；对Zn2+和Co2+, LB-EPS与金属离子之间比TB-EPS具有更大的结合能力,且两种类型的EPS与金属离子相互作用都符合单分子层作用模型；与一元金属体系相比,二元金属的加入引发了金属之间对活性位点的竞争减少了金属与EPS之间的结合量：光谱及能谱分析显示,EPS表面羟基,氨基和羧基基团参与了与金属离子的相互作用。LB-EPS与金属相互作用时,LB-EPS不仅起到了络合剂的作用,同时絮凝作用强化了LB-EPS与金属的相互作用能力。4.解析了金属离子的长期加入对好氧微生物颗粒微生物活性和群落多样性的影响。结果表明,Cu(Ⅱ)的加入大大降低了好氧微生物颗粒生物质的浓度,生物活性以及生物多样性；而Ni(Ⅱ)对好氧微生物颗粒生物多样性的毒性作用比较小,且好氧微生物颗粒体系提高了微生物对镍离子的耐受水平。即使在镍浓度为15 mg/L时,Ni(Ⅱ)仍然一定程度上刺激了好氧微生物颗粒的生物产量和生物活性。微生物颗粒对金属耐受性的提高主要是因为微生物颗粒为微生物提供了一个缓冲区使得微生物可以逐渐适应高的金属浓度,使得微生物得以继续生长或者微生物的重新分布以满足其微环境的需求；同时高的生物量和高的EPS含量都有利于降低金属离子对好氧微生物颗粒的毒性。5.在密度泛函理论的指导下,强化了金属离子在好氧微生物颗粒表面的界面行为,探讨了聚乙烯亚胺修饰和好氧微生物颗粒与金属离子之间的作用机理。密度泛函理论计算结果显示游离的Cu2+或是水合铜离子,都更倾向作用于氨基的N位；聚乙烯亚胺表面修饰强化了好氧微生物颗粒与金属离子的相互作用,其最大结合参数分别为71.239 mg/g Cu(Ⅱ)和348.125 mg/g Cr(Ⅵ); FTIR分析显示氨基参与了表面修饰的好氧微生物颗粒与金属离子的相互作用；XPS结果显示好氧微生物颗粒表面存在Cr(Ⅲ)离子,说明微生物颗粒与Cr的相互作用不但包括表面修饰的好氧微生物颗粒与Cr(Ⅵ)的结合,还包括相互作用过程中Cr(Ⅵ)被还原为Cr(Ⅲ), Cr(Ⅲ)以固体相的形式沉积在好氧微生物颗粒表面。更多还原

【Abstract】 Biological treatment is one of the most widely used wastewater treatment processes. Aerobic microbial granules play an important role in the field of biological wastewater treatment due to their advantages over the conventional sludge floes, such as a denser and stronger aggregate structure, better settleability and ensured solid-effluent separation, higher biomass concentration, and greaterability towithstand shock loadings. Heavy metals can be stimulatory, inhibitory, or even toxic in biochemical reactions depending on the metal concentration and speciation, the state of microbial growth, and the biomass concentration. Therefore, study was conducted to investigate the interaction machnisms of aerobic microbial granules and metal ions. The work could provide useful information for the the design and operation of biological systems. In this paper, the binding capacities and mechanisms of aerobic granule with metal ions was investigated. The effects of long-term addition of metal ions on the biochemical properties of aerobic granules were examined. The mechanism and binding sites involved in the interaction of metal ions with modified aerobic granules were also evaluated. Main contents and results are as follows:1. Batch experiments were conducted to study the binding characteristics of a eationic dye, Malachite Green (MG), onto aerobic granules. The Langmuir isotherm was found to provide the best theoretical correlation of the experimental data for the biosorption of MG. The monolayer biosorption (saturation) capacities were determined to be 56.8 mg/g. The aerobic granule had a specific surface of 72.32 m2/g SS. Thermodynamic analysis show that biosorption follows an endothermic path of the positive value ofΔH0 and spontaneous with negative value ofΔG0.2. The interaction process of cobalt(Ⅱ) and zinc(Ⅱ) and aerobic granules was characterized. Single component and binary equimolar systems were studied at different pH values. The equilibrium was well described by Redlich-Peterson adsorption isotherm. The maximal binding capacity of the granules, in single systems (55.25 mg/g Co; 62.50 mg/g Zn) compared with binary systems (54.05 mg/g Co; 56.50 mg/g Zn) showed reduction in the accumulation of these metals onto aerobic granules. The kinetic modelling of metal sorption by granules has been carried out using Lagergren equations. The regression analysis of pseudo second-order equation gave a higher R2 value, indicating that chemisorption involving valent forces through the sharing or exchange of electrons between sorbent and sorbate may be the rate limiting step. The initial biosorption rate indicated that aerobic granules can adsorb Co(Ⅱ) more rapidly than Zn(Ⅱ) from aqueous solutions. Meanwhile, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses revealed that chemical functional groups (e.g., alcoholic and carboxylate) on aerobic granules would be the active binding sites for biosorption of Co(Ⅱ) and Zn(II).3. The interacting mechanisms of metallic cations (Zn2- and Co2+) to active chemical groups on the extracellular polymeric substances (EPS) of the aerobic granules, including loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS), were examined by XPS and FTIR spectroscopy. For Zn2+ and Co2+, LB-EPS showed stronger binding properties than TB-EPS and the process of them was described well by the Langmuir isotherm. Compared to the single-metal system, binary-metal addition induced competitive binding between the Zn2+ and Co2+ with reduction of the maximal binding capacity for both EPS. The main chemical groups involved in the interactions between contaminants were apparently alcohol, carboxyl and amino. These groups were part of the EPS structural polymers, namely, polysaccharides, proteins, and hydrocarbon-like products. When biosorption and flocculation occurred at the same time, the LB-EPS were used not only as chelate sorbents but also as flocculants to further enhance their sorption capacity.4. This part investigated the individual toxic effects of long-term addition of Cu(Ⅱ) and Ni(Ⅱ) on the biochemical properties of aerobic granules in sequencing batch reactors (SBRs). The biochemical properties of aerobic granules were characterized by EPS content, dehydrogenase activity and microbial community biodiversity. One SBR was used as a control system, while another two received respective concentration of Cu (Ⅱ) and Ni(Ⅱ) equal to 5 mg/L initially and increased to 15 mg/L on day 27. Results showed that the addition of Cu (Ⅱ) drastically reduced the biomass concentration, bioactivity, and biodiversity of aerobic granules. The toxic effect of Ni(Ⅱ) on the biodiversity of aerobic granules was milder and the aerobic granular system elevated the level of Ni(Ⅱ) toxicity tolerance. Even at a concentration of 15 mg/L, Ni (Ⅱ) still stimulated the biomass yield and bioactivity of aerobic granules to some extent. The elevated tolerance seemed to be owed to the concentration gradient developed within granules, increased biomass concentration, and promoted EPS production in aerobic granular systems.5. According to quantum chemistry calculation, it is investigated that copper ions and hydrated copper ions are preferred to interact with amine groups. Porous aerobic granules were grafted with polyethylenimine (PEI), due to the presence of a large number of amine groups in the PEI molecule. The biosorption characteristics of cations and anions from aqueous solution using modified aerobic granules were investigated. FTIR and XPS analysis exhibited the presence of PEI on the granule surface. Compared with the raw granule, the modified aerobic granules with PEI showed a significant increase in sorption capacity for both metal ions. The monolayer biosorption capacity of granules for Cu(Ⅱ) and Cr(Ⅵ) ions was found to be 71.239 and 348.125 mg/g. The optimum solution pH for adsorption of Cu(Ⅱ) and Cr(Ⅵ) from aqueous solutions was found to be 6 and 5.2, respectively. The biosorption data fitted better with the Redlich-Peterson isotherm model. FTIR showed chemical interactions occurred between the metal ions and the amide groups of PEI on the biomass surface. XPS results verified the presence of Cr(Ⅲ) on the biomass surface, suggesting that some Cr(Ⅵ) anions were reduced to Cr(Ⅲ) during the sorption.更多还原