AAO系统对四环素的去除特性及微生物群落结构变化研究

发布时间：2018-07-18 14:28

【摘要】：抗生素（antibiotics）在临床和畜牧饲养业中应用广泛，其中，四环素（tetracycline）是使用量较大的抗生素之一。大部分的四环素未经人体或动物充分吸收，直接排出体外，由于其在自然水体中难以降解，持续的四环素压力使得四环素耐药细菌和四环素耐药基因不断增殖，给人体健康带来严重威胁。厌氧-缺氧-好氧（Anaerobic-Anoxic-Oxic，AAO）水处理工艺是一种传统的污水处理方法，在城市污水处理厂的应用范围广泛，运行技术成熟，目前对四环素类抗生素在污水处理厂的去除影响因素及对微生物群落的影响机制尚不明确。本研究以四环素作为研究对象，研究了不同工况下四环素在AAO系统中的去除情况，采用响应面法对实验进行模拟和优化，考察系统操作参数对四环素去除的影响以及四环素在活性污泥中的吸附特性；然后研究了四环素对AAO系统微生物种群的影响，采用宏基因组高通量测序对样品进行测序，考察微生物群落多样性及四环素耐药基因的变化，同时，通过硝化细菌的演变情况来探究四环素对AAO系统硝化作用的影响。 结果表明：AAO系统的水力停留时间（hydraulic retention time，HRT）和污泥龄（sludge retention time，SRT）分别对四环素的去除有显著的影响，然后由响应面法分析得出，污泥龄和四环素初始浓度及其交互作用对四环素去除率的影响极为明显，污泥龄、水力停留时间及四环素初始浓度的二次项对四环素去除率有一定影响。随着污泥龄的增大，四环素去除率逐渐提高。在最佳实验条件SRT：15.5d，HRT：9.9h，CTC, in：283.3μg/L下对建立的四环素去除率数学模型进行验证实验，发现实验值与预测值具有较高的一致性，说明所建立的四环素去除率模型具有可靠性和准确性。不同初始浓度的四环素在活性污泥上的吸附动力学符合伪二级模型，化学吸附是控制整个吸附速率的最重要的因素。不同温度下，四环素在活性污泥上的吸附呈现不同的特点：10℃和25℃条件下，吸附较符合Langmuir模型；40℃条件下，吸附较符合Henry模型，活性污泥对四环素的吸附是吸热反应，在高温条件下的吸附性能好于低温条件。 在此基础上，对优化条件下的AAO系统中的微生物种群结构进行对照试验，结果表明加入痕量四环素会改变系统微生物的群落结构，并在缺氧、厌氧及好氧环境下都能增大微生物群落多样性；tet(A)，tet(B)，tet(C)，tet(E)，tet(M)，tet(S)和tet(O)的浓度随着四环素的加入都是增大的。所测试的八种四环素耐药基因之间具有较强的相关关系，其中tet(A)，tet(B)，tet(C)，tet(E)，tet(M)，tet(S)和tet(O)之间的相关性显著（P 0.05），而tet(X)与其他检测到的四环素耐药基因的相关性最弱（P 0.05）。另外，活性污泥中的外排泵基因tet(A, B, C, E)的浓度最高，远远超过核糖体保护类和降解四环素酶类两类基因。四环素对AAO反应体系TN的去除以及硝化细菌活性并未产生抑制作用，反而起到一定的促进作用。
[Abstract]:The antibiotic (antibiotics) has been widely used in clinical and animal husbandry, among which tetracycline (tetracycline) is one of the most widely used antibiotics. Most of the tetracycline is not fully absorbed by humans or animals and is discharged directly from the body. Because it is difficult to degrade in natural water, the constant pressure of tetracycline causes the proliferation of tetracycline resistant bacteria and tetracycline resistant genes. It poses a serious threat to human health. Anaerobic-Anoxic-Oxicic-AAO (Anaerobic-Anoxic-Oxicic-AAO) water treatment process is a traditional wastewater treatment method. At present, the factors affecting the removal of tetracycline antibiotics in wastewater treatment plants and the mechanism of affecting microbial communities are not clear. In this study, the removal of tetracycline in AAO system under different operating conditions was studied, and the response surface method was used to simulate and optimize the experiment. The effects of system operating parameters on the removal of tetracycline and the adsorption characteristics of tetracycline in activated sludge were investigated, and then the effects of tetracycline on the microbial population of AAO system were studied, and the samples were sequenced by macrogenome high-throughput sequencing. To investigate the diversity of microbial community and the changes of tetracycline resistance genes, and to explore the effect of tetracycline on nitrification of AAO system through the evolution of nitrifying bacteria. The results showed that the HRT (HRT) and (sludge retention time (SRT) of the two systems had significant effects on the removal of tetracycline, respectively, and the response surface method was used to determine the effect of HRT on the removal of tetracycline. The effects of sludge age, initial tetracycline concentration and their interaction on the removal rate of tetracycline were very obvious, and the secondary terms of sludge age, hydraulic retention time and initial concentration of tetracycline had a certain effect on the removal rate of tetracycline. With the increase of sludge age, the removal rate of tetracycline increased gradually. The mathematical model of tetracycline removal rate was verified under the optimal experimental conditions, SRT: 15.5dh HRT: 9.9hCTC, in:283.3 渭 g / L, and the experimental value was found to be in good agreement with the predicted value. The model of tetracycline removal rate is reliable and accurate. The adsorption kinetics of tetracycline on activated sludge with different initial concentrations was in accordance with the pseudo-secondary model, and the chemical adsorption was the most important factor to control the adsorption rate. At different temperatures, the adsorption of tetracycline on activated sludge showed different characteristics. At 10 鈩，

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