【作者】 郑玉；

【导师】 柴立元；

【作者基本信息】 中南大学 ， 冶金工程， 2013， 博士

【摘要】 摘要：草类碱法制浆工艺产生的黑液,是一类难以处理的有机废水,含有大量的木质素,具有高COD浓度、高碱性、高色度及难降解等特点,一直以来都是国内外水处理研究的难点。本文针对国内外目前存在的草浆碱法造纸黑液处理技术瓶颈,利用从三国时期吴国竹简浸泡液中分离筛选出能有效降解造纸黑液的4株菌株;在对4株菌株黑液降解特性研究的基础上,系统研究了复合菌强化SBR反应器处理造纸黑液的核心工艺；基于芦苇浆造纸所产生的浓缩黑液的特点,提出碱析法-生物强化处理-生物微酸化-Fenton法深度处理的工艺流程,同时研究了生物强化处理作用下黑液木质素降解的机理。旨在从资源化和生物处理的角度为草浆造纸黑液治理提供新的处理技术和工艺。本文主要研究结果如下：(1)基于造纸黑液高pH和高COD浓度的特点,提出了碱析法预处理新思路。通过单因素和正交实验确定了预处理最佳条件：初始黑液pH为13、COD为78000mg/l、Ca2+投加量为4.5g/1,处理后黑液COD、木质素和色度的去除率分别为71.62%、83.21%、94.26%,黑液pH降低至11左右,COD降低至22300mg/1左右,同时析出可以回收利用的木质素,有利于后续生物法处理,克服了常规絮凝法或酸析法需要调节pH及容易造成二次污染等缺点。(2)从吴国竹简浸泡液中分离筛选出能在复杂造纸黑液环境中生长的3株细菌Pandoraea sp.B-6、Cupriavidus sp. B-8、Comamonas sp. B-9和1株霉菌Aspergillus sp. F-1。对4株菌株降解造纸黑液特性研究表明：各菌株均能在不外加碳氮源和微量营养元素的条件下对造纸黑液直接进行降解,降解条件为pH10～11, COD初始负荷为23000mg/1左右,生长温度为30-35。C,各菌株在高碱性条件下表现出很强的pH调节能力,黑液COD、木质素和色度去除率最高分别达到58.2%、46.7%、62.4%,并能分泌木质纤维素酶活,体现了菌株对高浓度造纸黑液的耐受性。(3)研究了生物强化处理草浆造纸黑液新工艺,采用生物强化处理与活性污泥法相结合,对木质素降解复合菌群进行了优化研究。在黑液初始COD为23000mg/1左右,pH为10,温度30℃,MLSS为4.5g/1,无外加碳氮源条件下,黑液COD、木质素和色度去除率最高可达到62.7%、48.1%、66.4%,高于单一菌株处理情况,说明了复合菌群组合强化活性污泥处理造纸黑液具有一定的协同作用。对生物强化处理与普通活性污泥法连续处理造纸黑液能力进行了比较研究,生物强化系统比普通活性污泥系统平均COD去除率高20%左右,平均木质素去除率高21%左右,色度去除率高22%左右,且反应启动时间大大缩短。生物强化系统进水COD从9000mg/1增加到24000mg/l,COD去除率仍然保持在50%,表明投加木质素降解复合菌群的生物强化系统耐冲击能力强。(4)采用傅里叶红外光谱、紫外光谱和气质联用等研究手段揭示了黑液中木质素的生物降解机理。可以初步认为在生物强化作用下,微生物首先直接利用黑液中的易降解的碳水化合物进行生长,并分泌一定的木质素纤维素酶活,促进木质素苯环之间的连接键的断裂,譬如Cα-Cβ断裂和p-0-4断裂,以及联苯之间的键的断裂,形成一系列的木质素单体结构,同时木质素单体逐渐脱除苯环上的甲氧基,由Lac和MnP进一步催化形成醌、苯氧自由基,并出现大量的羰基,且双键数量有所增加,甚至可以由LiP氧化生成开环产物,进入三羧酸循环。(5)采取碱析法-SBR生物强化-生物微酸化-Fenton法深度处理组合工艺对造纸黑液进行了连续处理,在15个运行周期中,造纸黑液初始pH13,COD约为78550mg/l左右,经组合工艺处理后,黑液COD、木质素和色度去除率分别达到98.5%、95.8%、99.8%。组合工艺实际应用到造纸黑液的处理是可行的。更多还原

【Abstract】 Abstract:In China, most pulping and paper industry takes the non-wood as material and large volumes of dark black liquor (BL) are generated as byproduct or waste. The BL contains high concentrations of lignocellulosic materials, phenolics, fatty acids and resinous compounds. The presence of the these compounds imparts extreme properties such as high pH (10-13) and high COD values (100000-250000mg/1) to the wastewater, making it one of the most difficult materials to handle in the world environmental protection.Based on the study of the four strains which were isolated from eroded bamboo slips (ancient writing tablets) for their ability of biodegrading BL, the bioaugmentation system in sequencing batch reactor (SBR) as corn treatment technology was systematically studied. According to the characteristics of BL, a novel integrated process is proposed:alkaline separating→bioaugmentation→microbiological acid-ification→Fenton process. The mechanism of bioaugmentation on degrading lignin was also studied. The study focuses on comprehensive utilization and bioprocess of BL and provides a theoretical and new technology support.The main results are as follows:According to the extreme properties of BL, a new pre-process on treatment of BL, alkali separating process is presented to remove lignin under high alkaline environment by adding Ca2+. Single-factor experiments combined with orthogonal experiment were carried out to determine the optimal conditions for removing COD concentration and lignin conten in BL. Under the following optimal conditions:pH was13, the dosage of Ca+was4.5g/l, the reaction temperature was60℃, the COD concentration was78000mg/l, the removal rate of COD, lignin and color achieved to71.62%,83.21%and94.26%, respectively, meanwhile the pH of BL decreased to about11, the COD concentration decreased to about22300mg/l and massive deposited lignin was produced, which is benefit to the subsequent biological treatment. The pre-processing is helpful to conquer the disadvantages of conventional flocculation methods or acidification which needs large amount of flocculent or acid consumption and facilitates secondary pollution.Three bacteria named Pandoraea sp. B-6, Cupriavidus sp. B-8, Comamonas sp. B-9and a fungus named Aspergillus sp. F-1were screened from the seven strains, which grew well on the culture contained BL. The optimal conditions in biotreatment of BL are as follows:initial pH was between10～11, COD was under22000mg/l, temperature was between30～35℃. Under the given conditions, the strains showed the strong abilities of pH adjustment and could secrete alkaline lingocellulolytic enzymes. The highest COD, color and lignin removal were about58.2%,62.4%,46.7%, respectively. The results showed the strains were well tolerated on the high alkaline environment. The results also showed adding other carbon, nitrogen sources and nutritional elements had no positive effects on biotreatment, which is much convenient in practical application.Detailed study was carried out on the bioaugmented activated sludge treatment of BL with multiple lignin-degrading microorganisms. The results showed that the best removal effeciency occured when the concentration of activate sludge was3.5g/l, initial pH was10, the COD concentration was about23000mg/l, the reaction temperature was30℃and the ratio of Pandoraea B-6, Comamonas B-9and Aspergillus F-1was2:1:2. The highest COD, color and lignin removal were about62.7%,66.4%,48.1%, respectively. The results illustrated that biaugmentation of multiple lignin-degrading microorganisms with activated sludge improved the treatment efficiency. In batch experiments, the bioagu-mentation system was investigated and the activated sludge process served as a control. The biaugmentation system was found to yield better COD, lignin and color removal efficiency over20%,21%,22%than those of the activated sludge process as a result of addition of the mixed special microorganisms. The reaction time was also shortened. When COD increased from9000mg/l to24000mg/l, COD removal efficiency could keep above50%in the biaugmentaiton system, which showed the biaugmentation system has a good shock load tolerance. The mechanism of lignin degradation in BL during bioaugmentaiton system treatment was also investgated by using Fourier transform infrared spectroscopy, UV spectroscopy and GC-MS method, etc. A preliminary analysis was made of the degradation mechanism as follows:the microorganisms directly utilized the carbon and nitrogen nutrient sources in BL for growth, then secreted lignocellulolytic enzymes and promoted the breakdown the benzene ring linkages. Meanwhile, lignin trimer and dimmers such as Cα-Cβ, β-O-4and β-β bond were gradually disappeared, demethoxylation and dehydroxylation reaction happened. Low-molecular-mass compounds such as aromatic aldehydes, aromatic acids and aromatic ketones were detected. Lignin monomers were gradually separated from the benzene ring, the quinone, benzene oxygen free radicals were formed by Lac and MnP secretion, and a large number of carbonyl group were produced as well as some double bonds, and even ring-opening products were formed into tricarboxylic acid cycle by LiP oxidation.On the basis of the previous experiments, the integrated processes were proposed. After15cycles’continuous operation, the BL was proved to be treated effectively. The initial conditions of treated BL were as follows:initial pH13.0, COD about78500mg/l. Under optimal conditions, the ultimate COD, color and lignin removal rate were98.5%,99.8%,95.8%, respectively.The study establishes the basis of the application of biaugmentation with multiple lignin-degrading microorganisms and provides a new possible method in BL treatment process, which also improves the disadvantages of BL process by multiple physicochemical methods.更多还原