【作者】 池勇志；

【导师】 季民； 李玉友；

【作者基本信息】 天津大学 ， 环境工程， 2010， 博士

【摘要】 厌氧消化工艺在处理剩余污泥时由于同时具有资源化、稳定化和无害化的优点,长期以来一直在剩余污泥处理中扮演着重要角色。然而在实际应用中,厌氧消化工艺也存在着对有机物处理效率低和处理速度慢等问题。本研究采用微波结合碱解预处理技术通过破坏剩余污泥(Waste Activated Sludge,WAS)絮体结构和菌体细胞壁而提高WAS中有机物的溶解性和可生化性,从而改善WAS厌氧消化性能。研究具体分为以下三个部分,即微波结合碱解预处理试验、静态高温和中温厌氧消化试验——生物化学甲烷势(Biochemical Methane Potential,BMP)试验和动态高温和中温厌氧消化试验。首先,在微波结合碱解预处理试验中利用均匀设计法得到的数据分别建立了以WAS中的COD、SS和VSS溶解率为目标,以微波加热温度、加热时间和氢氧化钠投加量为影响因素的回归方程。在本试验边界条件下,该回归方程预测在加热温度=210℃,加热时间=35min,加碱量=0.2 g-NaOH/g-SS时,WAS最大VSS溶解率可达85%,且与试验结果能很好吻合。其次,采用BMP试验研究了12种预处理对WAS静态高温和中温厌氧消化过程中的甲烷累计产量、沼气累计产量、相对甲烷累计产量和甲烷产生速率的影响。利用修正的Gompertz方程求解得到的动力学参数表明:经过预处理后WAS的甲烷累计产量势(P)和最大甲烷产生速率(R)均高于对照。在高温BMP试验中其P和R的峰值分别为333 mL-CH4@STP·g-1-VS投入(mL-CH4 @STP·g-1-VS投入指在BMP试验中投入1g VS的甲烷累计产量在标准状态下的毫升数,其中@代表at,STP(Standard Temperature and Pressure)代表标准状态(0℃和101.325 kPa))和73 mL-CH4@STP·g-1-VS投入·d-(1mL-CH4@STP·g-1-VS投入·d-1指在BMP试验中每天每投入1g VS的甲烷累计产量在标准状态下的毫升数),分别比对照提高41%和28%。在中温BMP试验中其P和R的峰值分别为426 mL-CH4 @STP·g-1-VS投入和56 mL-CH4@STP·g-1-VS投入·d-1,分别比对照提高64%和75%。经综合考虑后确定最佳预处理条件为加热温度=170℃,加热时间=1 min,加碱量=0.05 g-NaOH/g-SS。最后,分别以WAS和未经中和处理的微波结合碱解预处理WAS为基质(预处理条件为:加热温度=170℃,加热时间=1 min,加碱量=0.05 g-NaOH/g-SS),研究了在水力停留时间为30 d的工况下,完全混合型的高温和中温厌氧消化反应器的厌氧消化性能及其消化污泥的脱水性能,并采用16S rDNA(ribosomal Deoxyribonucleic Acid,核糖体脱氧核糖核酸)克隆分析技术分别对高温和中温厌氧消化污泥进行了微生物解析。研究表明:WAS经微波结合碱解预处理后与对照相比,高温和中温厌氧消化工艺对WAS中的VS、总化学需氧量、总碳水化合物和总蛋白质的去除率均有不同程度的提高。其中高温和中温厌氧消化工艺对VS的去除率分别相对提高27%和21%,高温和中温厌氧消化污泥中的溶解性COD浓度分别相对提高51%和71%,高温和中温厌氧消化工艺甲烷产率(L-CH4 @STP /g-COD投入)分别相对提高13%和14%,高温和中温厌氧消化工艺所产沼气中甲烷的百分含量相对提高8%。16S rDNA克隆分析技术对高温和中温厌氧消化污泥中微生物种群结构的分析表明:高温和中温厌氧消化污泥的微生物多样性指数分别为53.2和138.0,即中温厌氧消化污泥的微生物多样性大于高温厌氧消化污泥的微生物多样性。高温和中温厌氧消化污泥脱水试验表明:WAS经微波结合碱解预处理后再经厌氧消化处理将使得高温和中温厌氧消化污泥的脱水性能下降。更多还原

【Abstract】 Anaerobic digestion (AD) plays an important role for its ability to produce energy-rich biogas, to stabilise the waste activated sludge (WAS) and to destroy pathogens. However, AD has several limitations: (a) the treatment efficiency of organic compounds is low, and (b) the processing speed is not high. In this study, a combined microwave/NaOH pretreatment (MNP) process was studied which focused on destruction of floc structures and lysis of microbial cells to release biodegradable organic materials and render them more accessible to AD for improving the anaerobic digestion performances of WAS. The study consisted of three parts: MNP, biochemical methane potential (BMP) tests and semi-continuous anaerobic digestion experiments.Firstly, in the MNP tests, uniform design was successfully applied to determine the relationship of WAS solubilization of COD, SS and VSS to environmental conditions (target temperature, microwave holding time, and NaOH dose) and to establish the quadratic model describing the solubilization ratios to changes in these variables. Within the design boundaries, the predicted maximum solubilization ratio of VSS (85%) occurred at target temperature of 210℃, holding time of 35min, and NaOH dose of 0.2g-NaOH/g-SS. The results showed that the predicted values inosculated with the experimental values very well.Secondly, thermophilic and mesophilic BMP tests were studied in order to investigate the effects of 12 kinds of MNPs on cumulative methane production, cumulative biogas production, relative cumulative methane production and methane production rate. The kinetic parameters achieved from the modified Gompertz equation showed the cumulative methane production potential (P) and the maximum methane production rate (R) of the pretreated WAS were higher than those of the controls. In the thermophilic BMP tests, compared with the control, the peak values of P and R of the pretreated WAS were 333 mL-CH4 @STP·g-1-VSadded (at the standard temperature and pressure (STP) conditions of 0℃and 101.325 kPa) and 73 mL-CH4@STP·g-1-VSa dded·d-1,respectively, which were improved by 41% and 28%, respectively. In the mesophilic BMP tests, compared with the control, the peak values of P and R of the pretreated WAS were 426 mL-CH4 @STP·g-1-VSa dded和56-CH4 mL@STP·g-1-VSadded·d-1,respectively, which were improved by 64% and 75%, respectively. After we considered various factors comprehensively, 170℃with 1 min holding time and 0.05 g-NaOH/g-SS were suggested for MNP of WAS.Thirdly,to evaluate anaerobic digestion performances and the dewatering performances of the anaerobic digested sludges, the continuous stirred thermophilic anaerobic digestion process (TADP) and mesophilic anaerobic digestion process (MADP) were operated at HRT (hydraulic retention time)=30 d to treat raw WAS and pretreated WAS (pretreated at 170℃with 1 min holding time and 0.05 g-NaOH/g-SS), respectively. Then the microbial community structures in the thermophilic and mesophilic anaerobic digested sludges were analyzed with 16S rDNA (ribosomal Deoxyribonucleic Acid) cloning techniques. The results showed, compared with the controls, removal efficiencies of VS, TCOD (total chemical oxygen demand) total carbohydrate and total protein were improved in TADP and MADP treating pretreated WAS. The VS removal efficiencies of TADP and MADP treating preteated WAS increased by 27% and 21% respectively as compared with their controls. Compared to the corresponding controls, the SCOD (soluble COD) levels of thermophilic and mesophilic anaerobic digested sludges were enhanced by 51% and 71%, respectively. The methane production rates (L-CH4 @STP /g-CODadded) of TADP and MADP treating preteated WAS improved 13% and 14% repectively when compared to their controls. Both methane contents in the biogas of TADP and MADP treating preteated WAS increased by approximately 8% compared with those of their controls. The analysis results of the microbial community structures analyzed with 16S rDNA cloning techniques showed, the microbial diversity indexes were 53.2 and 138.0 for thermophilic and mesophilic anaerobic digested sludges, respectively. This meant that the microbial community of TADP had less diversity than that of MADP. The results of dehydration experiments showed, the dewaterabilities of digested sludge from TADP and MADP treating preteated WAS were lower than that from the controls.更多还原