Effect of chemical dose on phosphorus removal and membrane fouling control in a UCT-MBR

Phosphorus removal was enhanced effectively by dosing aluminum sulfate and effluent phosphorus concentration was lower than 0.5 mg/L. Sludge activity was not inhibited but improved slightly with addition of aluminum sulfate. EPS concentrations both in mixed liquid and on membrane surface were decreased, contributing to the effective mitigation of membrane fouling. To enhance phosphorus removal and make the effluent meet the strict discharge level of total phosphorus (TP, 0.5 mg/L), flocculant dosing is frequently applied. In this study, the performance of aluminum sulfate dosing in a University of Cape Town Membrane Bioreactor (UCT-MBR) was investigated, in terms of the nutrients removal performance, sludge characteristics and membrane fouling. The results indicated that the addition of aluminum sulfate into the aerobic reactor continuously had significantly enhanced phosphorus removal. Moreover, COD, NH₄⁺-N and TN removal were not affected and effluent all met the first level A criteria of GB18918-2002. In addition, the addition of aluminum sulfate had improved the sludge activity slightly and reduced trans-membrane pressure (TMP) increase rate from 1.13 KPa/d to 0.57 KPa/d effectively. The membrane fouling was alleviated attributed to the increased average particle sizes and the decreased accumulation of the small sludge particles on membrane surface. Furthermore, the decline of extracellular polymeric substance (EPS) concentration in mixed sludge liquid decreased its accumulation on membrane surface, resulting in the mitigation of membrane fouling directly.     

Characteristics of two transferable aminoglycoside resistance plasmids in Escherichia coli isolated from pig and chicken manure

pRKZ3 is a non-conjugative IncQ plasmid, while pKANJ7 is a conjugative IncX plasmid. The optimal mating time of pKANJ7 varied under different conditions. Both of the two transferable ARPs had little impact on the growth of their hosts. A relatively high level of fitness cost was observed for pKANJ7. The fitness cost of ARPs depended on their hosts. Plasmid-mediated antibiotic resistance genes (ARGs) have recently become a more prominent concern in the global environment. However, the prevalence of aminoglycoside resistance plasmids in the livestock industry is under reported. In this study, two transferable aminoglycoside resistance plasmids, pRKZ3 and pKANJ7, isolated from pig and chicken manure, were characterized. Results showed that pRKZ3 (8236 bp) is a non-conjugative IncQ plasmid and contains genes encoding for plasmid replication and stabilization (repA, repB and repC), mobilization (mob), and antibiotic resistance (arr-3 and aacA). pKANJ7 (30142 bp) is a conjugative IncX plasmid which codes for a type IV secretion system (T4SS). Conjugative transfer experiments showed that the optimal mating time of pKANJ7 was 8 h under the starvation condition, but the number of tranconjugants increased with time under the nutrient condition. Statistical analysis indicated that the two plasmids had little impact on the growth of their hosts, but a relatively high level of fitness cost due to pKANJ7 was observed. We also found that the fitness cost of plasmids depended on their hosts. Compared with pKANJ7, the relative fitness cost index of pRKZ3 varied within a narrow range during the 10 days of competition. The low level of fitness cost of pRKZ3 might contribute to the persistence of the plasmid in the environment. Our study provides new information for understanding the characterizations of antibiotic resistance plasmids (ARPs) in manure sources and helps to clarify the transfer and persistence of ARPs in the environment following the application of manure.     

CAST工艺常规模式下脱氮性能研究

研究了有效容积为21.6 L的循环式活性污泥法反应器在常规模式下,处理模拟废水时,有机污染物和氮污染物的去除情况,并分析了反应器脱氮过程中的限制性因素。结果表明,在反应器的运行周期为4 h(进水曝气2 h,沉淀和排水各1 h)好氧区DO2 mg/L,污泥浓度MLSS稳定在4 000 mg/L时,污泥回流比为20%,COD和氨氮的去除率可达90%。对一个典型周期进行监测分析,氨氮去除彻底,出水主要是硝态氮,总氮去除率约为69%。静态试验测得氨氮氧化速率为8.0 mg NH4+-N/(g MLSS.h),硝态氮生成速率为3.3 mg NO3--N/(g MLSS.h)。从实验结果可以分析出,在上面运行条件下CAST工艺脱氮限制性因素是回流比和污泥龄。     

北京市交通道路空气中NOx的污染现状及时空变化规律研究

基于2008年及2009年分4个季节对北京市3种类型道路（开阔型、交叉路口型和峡谷型）空气中的NOx的现场监测结果,分析了3种类型道路空气中NOx的污染现状和时空变化规律及影响因素。实验结果表明,昼间北京市各类型街道空气中NOx浓度呈早晚浓度高、中午浓度低的变化规律,NOx浓度随季节和车流量变化较明显。交通道路空气中NO占NOx的分担率高,且有较好的相关性,而NO2分担率较低,与NOx相关性较差。     

北京市交通道路空气中NO_x的污染现状及时空变化规律研究

基于2008年及2009年分4个季节对北京市3种类型道路(开阔型、交叉路口型和峡谷型)空气中的NOx的现场监测结果,分析了3种类型道路空气中NOx的污染现状和时空变化规律及影响因素。实验结果表明,昼间北京市各类型街道空气中NOx浓度呈早晚浓度高、中午浓度低的变化规律,NOx浓度随季节和车流量变化较明显。交通道路空气中NO占NOx的分担率高,且有较好的相关性,而NO2分担率较低,与NOx相关性较差。     

再生水中NO_3~-—N、NO_2~-—N、NH_4~+-N在粉土介质中迁移转化的研究

通过土柱实验模拟再生水在粉土层下渗过程中NO3--N、NO2--N、NH4+-N的迁移转化规律。结果表明,实验温度为23.2～25.9℃时,土柱内发生反硝化反应,NO3--N的去除率为9.74%～39.16%,反应符合一级反应动力学方程,衰减系数为0.0968～0.5531m-1;实验温度低于19℃时,土柱内反硝化反应消失,说明低温是制约再生水在土柱内发生反硝化作用的主要因素。     

组合方法去除新型采油污水中有机污染物的研究

含聚丙烯酰胺采油污水的有效处理是近年来困扰油田三次采油生产的一个难题。研究采用移动床生物膜技术与O3/UV/H2O2高级氧化技术的组合方法来处理含聚丙烯酰胺采油污水。实验结果表明,移动床生物膜技术可以有效去除污水中的石油类有机物,但对聚丙烯酰胺几乎无效果。O3/UV/H2O2高级氧化技术可以降解污水中的聚丙烯酰胺。组合方法处理后的含聚丙烯酰胺采油污水水质可以达到污水综合排放标准中的一级要求。     

污泥厌氧消化液中碳酸盐对回收磷的影响

为探讨污泥厌氧消化液中碳酸盐对以磷酸钙盐形式回收磷的影响,以粉煤灰浸出液为钙源,考察了消化液中的碳酸盐对磷回收过程和磷回收产物性质的影响。实验结果表明,在反应pH为10、反应钙磷摩尔比为1.67、反应时间为10 m in的条件下,消化液碳酸盐浓度为2 400 mg/L(以CaCO3计)时,磷的回收率为78.53%,回收产物中磷含量(以P2O5计)为28.93%;对消化液进行盐酸预酸化使pH达到4及以下时,磷回收率接近100%,回收产物中磷含量(以P2O5计)达到43.08%。消化液中碳酸盐的存在易形成碳酸钙沉淀,从而降低了磷回收率、回收产物中磷含量以及回收产品的纯度;预酸化能够有效地去除消化液中的碳酸盐并降低了其对磷回收的不利影响。     

污泥焚烧中Cd形态转化的热力学平衡模拟

采用热力学平衡分析方法,结合典型污泥成分和焚烧条件预测了污泥焚烧过程中重金属Cd的转化和迁移规律。模拟计算中考虑了主量矿物质与Cl、S对Cd的形态转化的影响。研究结果表明,污泥焚烧过程中,在低温的条件下Cd主要以固体碳酸盐形式存在,随着温度升高,碳酸盐分解为固态CdO,随后有气态Cd(OH)2、Cd和CdO生成,并且在较高温度主要以气态Cd存在。焚烧体系中,矿物质SiO2对Cd的形态转化影响大于其他矿物质,SiO2能与Cd结合生成稳定的CdSiO3,从而可有效抑制含Cd气态污染物的排放。焚烧体系中Cl较易与Cd结合形成CdCl2而导致Cd的挥发,Cl含量的增加促进了Cd在焚烧体系中的挥发。在低温阶段,Cd易与S结合形成固态硫酸盐,抑制了金属的挥发;在高温阶段,金属的形态转化基本不受S的影响,但是可以影响气态金属Cd的生成温度。根据污泥在不同焚烧温度、Cl含量、S含量条件下Cd的不同产物形态,可以对Cd的污染进行有效控制。     

自来水污泥堆肥化研究

研究了自来水污泥脱水防粘预处理技术、高温好氧堆肥技术及其应用于园林种植效果。机械组成测定和电镜扫描结果表明,调理剂QS可以显著改善自来水污泥的粘结性及脱水性能;堆肥实验结果表明,预处理的自来水污泥与枯枝落叶按体积比3∶7混匀,加入尿素调节碳氮比,27 d后,可达腐熟,EM菌可以加快堆肥物料腐熟,19 d后,即可达腐熟要求;桉树盆栽实验结果表明,自来水污泥经堆肥化处理后,保水性提高,促进桉树生长,而且堆肥过程中添加EM菌可以进一步促进桉树生长。