【作者】 刘翔；

【导师】 陈建民；

【作者基本信息】 复旦大学 ， 环境科学， 2009， 博士

【摘要】 污水处理最常用的活性污泥和生物膜法中,微生物的胞外聚合物(EPS)的性质与污泥性能有着密切的联系。了解活性污泥与生物膜之间的EPS的性质差异,以及EPS对生物膜量和污泥性能的影响情况,对改善反应器运行具有现实意义。本课题对活性污泥、生物膜以及活性污泥一生物膜共存的三种生物处理系统分别开展了EPS性质与污泥性能的比较研究。为了完整考察EPS不同层面的聚合物对于污泥性质的影响,提出了分层提取低速离心粘附物(LSCP)、溶解型EPS(SEPS)和结合型胞外聚合物(BEPS)的方法,并通过实验选择加热法作为实验提取BEPS的方法,该方法提取的EPS的量较多,提取的DNA在各组分中所占比重最小。对BATH用于测定污泥表面相对疏水性的标准条件进行了实验讨论,确定600nm为实验波长,反应静置时间为20min,推荐使用辛烷和PUM(phosphate-urea-magnesium)缓冲液分别作为疏水相和水相,采用1／10作为疏水相和水相的体积比H／A的取值,并提出了推荐实验步骤。考察了贫有机底物条件下营养条件的变化对活性污泥反应器中污泥性能和EPS的影响,发现COD／N比例从120／5降至120／24,污泥的沉降性能变好,SVI从164下降到105,但ESS(出水SS)从5mg／L上升到18mg／L,絮凝性能有所下降。EPS中的蛋白质成分下降,而多糖和腐殖质成分均加倍；COD／P比例从120／1上升到120／0.2,SVI很快上升到200以上,污泥发生膨胀。EPS中蛋白质含量基本不变,腐殖质含量加倍,多糖含量下降。分析微生物菌群结构后证实了,适应该种营养条件的丝状菌成为优势种群。在各工况中,活性污泥的EPS总量中的蛋白质和腐殖质分别与污泥的沉降和絮凝性能呈负相关性。各层面EPS组分对于污泥沉降、絮凝性能的影响表现在微生物胞外最外层的LSCP中的多糖成分,其对沉降性能有着正面的贡献,但与絮凝性能负相关。在贫有机底物水质条件下,考察中试规模实验装置中四种材质、形状的填料的EPS性质后,发现斜柱型悬浮填料挂膜最好,其生物膜的EPS总量最大。蛋白质为不同填料上生物膜的EPS中差别最大的一种组分。考察生产规模条件下的同一个悬浮填料生物反应池内两种悬浮填料的表面性质后发现,填料A比填料B表面更具亲水性和更高的表面电势。但填料A上的单位面积膜量不如填料B,同时填料A上的生物膜的EPS大于填料B的。两种填料EPS总量的差别,主要由BEPS中的蛋白质的量的差别引起的。比较反应池中的活性污泥和悬浮填料上的生物膜的EPS后发现,同一池内的生物膜EPS的量远大于活性污泥的EPS的量,从组分含量来看,生物膜中的蛋白质含量是活性污泥的1.5倍。污泥的EPS的总量、蛋白质以及BEPS中的蛋白质和DNA含量与污泥表面相对疏水性呈正相关性,说明了生长在填料上的微生物的粘附能力大于活性污泥中微生物的粘附能力。即使采用的是相同表面性质的组合填料,三个生产规模的废水处理站水质条件的影响使粘附在填料表面生长的生物膜的EPS存在差异。尽管如此,三种生物膜上的蛋白质组分,却表现出了差不多的含量,均为50mg／g-VSS左右。组合填料上的生物膜的SEPS层面的腐殖质和DNA含量也表现出了与生物膜相对疏水性正相关的关系。给水厂弹性立体填料上的生物膜的EPS含量远小于污水厂生物膜的。更多还原

【Abstract】 In wastewater treatment, the extracellular polymeric substances (EPS) of microorganism in both the activated sludge and biofilm systems are closely related to sludge characteristics. With respect to improving the operation of a bioreactor, it is important to understand the differences of EPS properties between the activated sludge and biofilm, and the effects of EPS on sludge characteristics and the quantity of biofilm. This study thus compared the EPS properties with the sludge characteristics in three systems--activated sludge, biofilm, and their concurrent system.This study firstly proposed extractions for low speed centrifugation products (LSCP), soluble EPS (SEPS) and Bound EPS (BEPS) in order to examine the effects of different layers of EPS on sludge characteristics. Heating extraction was chosen for the BEPS extraction because of the greater quantity of the BEPS extracted and because of the lowest DNA proportion.The evaluation of test parameters on bacterial adhesion to hydrocarbons (BATH) method using sludge samples was conducted. Results showed that the relative hydrophobicity (RH) of activated sludge was more stable at a wavelength of 600 nm, and a minimum standing time of 20 min gave stable results. N-octane and phosphate-urea-magnesium (PUM) buffer were found suitable as the hydrophobic and aqueous phase respectively. The volume ratio of the hydrophobic to the aqueous solution is suggested to be 1/10. An optimized procedure is then recommended.Feeding with poor organic substance synthetic wastewater in an experimental equipment, the effects of nutrients (COD/N/P) on the composition of EPS and sludge characteristics were studied. When the COD/N ratio changed from 120/5 to 120/24, the activated sludge performed better with the sludge volume index (SVI) value lowering from 164 to 105. Meanwhile the effluent suspended solids (ESS) increased from 5mg/L to 18mg/L, indicating that the bioflocculation of sludge became worse. A decreasing content of protein and a doubling content of humic and polysaccharide in EPS were found in this period. Phosphorus depleted conditions (COD/P=120/0.2) resulted in a rapid increase in SVI, indicating sludge bulking. Both doubling content of humic and decreasing content of polysaccharide in EPS were detected. The analysis of the microbial community structure of the activated sludge showed that the filamentous bacteria were dominant under this condition. A larger amount of protein content in total EPS was associated with poorer settleability, and the humic content in total EPS had significant negative correlation with the bioflocculation of sludge. Thus it can be concluded that the polysaccharide in LSCP had a positive correlation to the settleability and a negative one to the bioflocculation of the sludge, suggesting an important effect of the outermost layer EPS of the cell on sludge characteristics.Different performance of four carriers with various structures and materials were shown in a pilot-scale equipment. The amount of total EPS of biofilm in the inclined columnar type carrier was the greatest, with the greatest quantity of biofilm. Furthermore among the EPS of different layers for the four carriers, the protein was the composition showing the greatest variation.In the investigation of the surface properties of two carriers in a full-scale suspended carrier bioreactor, carrier A exhibited more hydrophilic surface and carried higher surface potential than carrier B. The amount of EPS of biofilm on carrier A was greater than that on carrier B, and the difference of EPS of the two biofilms was mostly caused by the significant difference of protein composition. The EPS of biofilm on suspended carriers was much greater than that of activated sludge in the same chamber. The protein content of biofilm EPS was 1.5 times of that of activated sludge. Results showed that sludge relative hydrophobicity (RH) increased with protein content and the total content of EPS of biofilm in suspended carriers, and the same relationship was true between the RH and the content of protein and DNA in BEPS. These result confirmed that the microorganisms on carrier had better adhesive properties than those in activated sludge.Although using the same combined packing, the EPS of biofilm coming from the three treatment stations were quite different due to the different kinds of wastewater. Nonetheless almost the same content of protein of three biofilm on combined packing were detected--approximately 50mg/g-VSS. Humic and DNA content of SEPS of biofilm in combined packings were also significantly correlated to RH of the sludge. Using the same elastic packing, the EPS of biofilm in wastewater treatment plant was much greater than that in the water treatment plant.更多还原