聚丙烯酰胺降解细菌的筛选及其在脱水污泥生物干化中的应用研究

发布时间：2018-06-18 18:51

  本文选题：聚丙烯酰胺 + 脱水污泥　； 参考：《西北大学》2016年博士论文

【摘要】：脱水污泥含水率高是我国污泥处置目前普遍存在的问题,直接影响脱水污泥的后续处理。造成这一问题的原因有多种,其中之一是由目前在污水与污泥处理中大量使用的,以聚丙烯酰胺(PAM)为代表的高分子有机絮凝剂引起的。在污泥脱水过程中,被PAM吸附絮凝的污泥颗粒聚集后会形成胶状物聚合体,造成脱水后的污泥不易分散,内部水分蒸发困难,使得自然条件下污泥干化需要更长时间。本研究为解决这一问题,筛选可降解PAM的菌株,研究其降解特性,并以固体菌剂的形式对脱水污泥干化过程进行生物强化,降解脱水污泥中的PAM,加快污泥干化速度。主要有以下结论：从四个来源的脱水污泥中分离出11株可在PAM培养基上生长的菌株,经过重金属耐受性和耐盐性实验,筛选出一株菌株H13以PAM为唯一营养源生长,7 d内PAM降解率可达35.9%。结合形态学特征、全自动微生物分析系统仪鉴定及16S rRNA基因序列分析,确定为恶臭假单胞菌(Pseudomonas putida)。对菌株的生长和PAM降解的影响因素进行了研究。凝胶过滤色谱(GPC)分析显示微生物降解后PAM的分子量下降,培养21 d后,聚合物重均分子量从6.44×10~6 Da减小到1.85×10~4 Da。PAM中的高分子量组分经过生物降解变为中低分子量组分,进一步作为菌株生长所需的碳源被转化利用。红外光谱(FT-IR)分析显示,微生物生长过程中,PAM侧链酰胺基转化为羧基,水解的氨基作为生长所需的氮源被微生物吸收利用。液质联用分析(LC-MS)分析显示,PAM降解前和降解后的产物中,含CH_3-C=C-CHO基团及其衍生基团的化合物较多。经SDS-PAGE分析,通过硫酸铵沉淀、DEAE-Sepharose FF离子交换层析和SephadexG-200分子筛层析纯化得到了PAM诱导产生的胞外酰胺酶。酶的最适温度为44℃C,最适pH为7.8,低浓度的Mg~(2+)、Ca~(2+)、Mn~(2+)对酶活性有激活作用,Fe~(2+)、Zn~(2+)、Cu~(2+)、Ni~(2+)等金属离子会抑制酶活性,碘乙酸可使酶彻底失活。该酶对短链的脂肪族酰胺类化合物也具有水解能力,对腈类化合物则没有水解能力。通过CODEHOP方法针对该酶氨基序列保守区域设计简并引物,克隆并鉴定了酰胺酶的基因片段,确定分离酶为脂肪族酰胺水解酶。通过单因素实验及正交分析,确定了菌株的固体菌剂发酵最适营养源及条件。污泥生物干化的实验室实验及小试实验显示,菌剂可有效降低污泥中PAM浓度,促进污泥含水率下降,缩短了干化所需时间。在污水厂实地进行了脱水污泥的生物干化及好氧发酵中试实验,结合好氧发酵设备,可在15d内将污泥转化为符合国家标准的有机肥料产品,所需时间远少于传统污泥堆肥,是一套具有参考意义的污泥稳定化、资源化示范工艺。
[Abstract]:High moisture content of dewatered sludge is a common problem in sludge disposal in China, which directly affects the subsequent treatment of dewatered sludge. There are many reasons for this problem, one of which is caused by the high molecular organic flocculant, which is widely used in sewage and sludge treatment and represented by polyacrylamide (PAM). In the process of sludge dewatering, the flocculated sludge particles adsorbed by PAM will form a colloidal polymer, which results in the sludge being difficult to disperse and the internal water evaporation difficult, which makes it take longer for the sludge to dry under natural conditions. In order to solve this problem, the strain that can degrade PAM was screened, its degradation characteristics were studied, and the drying process of dewatered sludge was biostrengthened in the form of solid bacteria agent, the PAM in dewatered sludge was degraded, and the drying rate of sludge was accelerated. The main conclusions are as follows: 11 strains which can grow on PAM medium were isolated from dewatered sludge from four sources and tested for heavy metal tolerance and salt tolerance. A strain H13 with PAM as the sole nutrient source was screened. The degradation rate of PAM could reach 35.9g within 7 days. Combined with morphological characteristics, automatic microbiological analysis system and 16s rRNA gene sequence analysis, Pseudomonas putida was identified as Pseudomonas putida. The factors affecting strain growth and PAM degradation were studied. Gel filtration chromatography (GPC) analysis showed that the molecular weight of PAM decreased after microbial degradation. After 21 days of culture, the average molecular weight of PAM decreased from 6.44 脳 10 ~ (-6) Da to 1.85 脳 10 ~ (4) Da.PAM. It is further used as a carbon source for the growth of the strain. FT-IR analysis showed that PAM side chain amide group was converted to carboxyl group during microbial growth and hydrolyzed amino group was absorbed by microorganism as the nitrogen source for growth. LC-MS analysis showed that the compounds containing CH3-CnC-CHO group and their derivatives were more in the products before and after the degradation of PAM. By SDS-PAGE, the extracellular acylase induced by PAM was purified by DEAE-Sepharose FF ion exchange chromatography and Sephadex G-200 molecular sieve chromatography. The optimum temperature of enzyme is 44 鈩，

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