Natural continuous influent nitrifier immigration effects on nitrification and the microbial community of activated sludge systems

Two sequencing batch reactors (SBRs) were operated for 100 days under aerobic conditions, with one being fed with unsterilized municipal wastewater (USBR), and the other fed with sterilized municipal wastewater (SSBR). Respirometric assays and fluorescence in situ hybridization (FISH) results show that active nitrifiers were present in the unsterilized influent municipal wastewater. The maximum ammonia utilization rate (AUR) and nitrite utilization rate (NUR) of the unsterilized influent were 0.32 ± 0.12 mg NH4+-N/(L·hr) and 0.71 ± 0.18 mg NO2?-N/(L·hr). Based on the maximum utilization rates, the estimated seeding intensity for the ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) of the USBR was 0.08 g AOB/(g AOB·day) and 0.20 g NOB/(g NOB·day) respectively. The fraction of nitrifiers/total bacteria in the influent was 5.35% ± 2.1%, the dominant AOB was Nitrosomonas spp., Nitrosococcus mobilis hybridizated with Nsm156, and the dominant NOB was Nitrospira hybridizated with Ntspa662. The influent nitrifiers potentially seeded the activated sludge of the bioreactor and hence demonstrated a mitigation of the acclimatization times and instability during start-up and early operation. The AUR and NUR in the USBR was 15% and 13% higher than the SSBR respectively during the stable stage, FISH results showed that nitrifiers population especially the Nitrospira in the USBR was higher than that in the SSBR. These results indicate that the natural continuous immigration of nitrifiers from municipal influent streams may have some repercussions on the modeling and design of bioreactors.     

堆肥对土壤中石油烃的去除及微生物群落的影响

为研究堆肥对石油污染土壤中不同组分烃的去除作用及土壤微生物群落结构变化的影响,利用重量法和GC-MS测定土壤中总石油烃、烷烃和多环芳烃的含量,采用高通量测序技术研究了堆肥对土壤微生物群落结构和多样性的影响作用.结果表明,向石油污染土壤中施加堆肥进行42d的修复处理,土壤中石油烃、烷烃、多环芳烃去除率分别为（12.4±0.01）%、（10.2±0.01）%、（9.38±0.02）%;自然放置的土壤中3种烃去除率分别为（3.21±0.02）%、（-3.00±0.01）%、（-6.59±0.02）%.自然放置的土壤香农指数、ACE指数和Chao1指数分别为4.30、3489.3和2691.0,加入堆肥进行修复处理后,土壤香农指数、ACE指数和Chao1指数分别增加为5.80、4684.7和3851.8.油污土壤中放线菌门（Actinobacteria）所占丰度由47.3%降低为28.2%,拟杆菌门（Bacteroidetes）丰度由0.78%增加至16.2%.变形菌门（Proteobacteria）丰度为37.4%,修复结束后几乎不变.属水平上,油污土壤中的优势菌属包括原小单孢菌属（promicromonospora）、微小杆菌属（Exiguobacterium）、诺卡氏菌属（Nocardioides）、分支杆菌属（Mycobacterium）、柠檬酸细菌属（Citrobacter）.施入堆肥使土壤中的这些优势菌属丰度降低,土壤中出现氮单胞菌属（Azomonas）、藤黄单胞菌属（Luteimonas）、假鞘氨醇杆菌属（Pseudosphingo bacterium）、紫单胞菌属（Parapedobacter）等新菌属.研究结果表明,与自然放置的土壤相比,向石油污染土壤中施入有机堆肥可有效去除土壤中的石油烃、烷烃和多环芳烃.并使土壤微生物群落结构发生明显变化.     

侧流污泥返送到缺氧池对A2/O系统效能影响研究

为了探究侧流化学磷回收后生物污泥返送对主流系统的影响,连续85d对A²/O系统厌氧池混合液中的磷进行侧流化学回收,并将侧流生物污泥回流到缺氧池,考察了系统整体的磷、氮、有机物的去除,及生物除磷途径与污泥性能的变化.结果表明,刚开始系统除磷效果有所提高,出水PO₄^3-浓度为（0.07±0.04） mg/L;20d后污泥沉降性能开始变差,除磷性能恶化,但对氮和有机物去除一直无显著影响;厌氧释磷速率和好氧吸磷速率下降,但缺氧吸磷速率却增加,缺氧反硝化聚磷和好氧聚磷的除磷比例由43.20%上升为53.38%,反硝化聚磷除磷得到了加强;污泥微生物胞内PHA和糖原的代谢模式无变化,但厌氧段合成的PHA量逐步下降;侧流磷最大回收量占进水磷量的24.75%,能够实现可观的磷回收效果;系统发生崩溃后,停止侧流化学磷回收,系统各功能就会逐渐得到恢复,可实现系统连续运行.     

考虑环境因素的城镇污水处理投资效率——基于三阶段DEA的方法

运用三阶段DEA模型对剔除环境因素和随机误差因素影响前后的城镇污水处理效率进行测算和比较.研究结果表明：经济、社会和水资源禀赋等环境因素对城市污水处理投资效率具有显著影响,且高估了污水处理的综合技术效率.我国当前城镇污水处理综合技术效率水平不高,仅为0.797;从区域来看,东部和中部综合技术效率较高,西部地区综合技术效率较低.从纯技术效率和规模效率来看,多数省份处于低高型阶段,说明多数省份存在管理技术不足,规模冗余的现象,且我国污水处理率低于污水处理投资效率.因此,在提高污水处理的管理技术水平的同时也要提高污水处理量和污水处理规模的建设.     

Algae functional group characteristics in reservoirs and lakes with different trophic levels in northwestern semi-humid and semi-arid regions in China

In order to study the differences in algae species and their biomass in water bodies in a region, three reservoirs and two lakes at the center of Guanzhong Plain were chosen to identify algae functional groups, measure biomass, and assess water quality, from January2013 to December 2014. The water bodies represented different trophic levels: one oligotrophic, three mesotrophic, and one eutrophic. Based on the Reynolds' functional groups, they had 10 groups in common—B, P, D, X1, M, MP, F, S1, J, and G, but the algae biomasses and proportions were different. In the oligotrophic reservoir, functional group B reached a peak biomass of 576 × 10~4 L~(-1), which accounted for 31.27%. In the eutrophic lake,functional group D reached a peak biomass of 3227 × 10~4 L~(-1), which accounted for only13.38%. When samples collected from other water bodies with similar trophic levels were compared, we found differences in the algae species functional groups. The potential reasons for the differences in algae functional group characteristics in the different water bodies in the region were water temperature and nutritional states.     

袋式除尘器声波反吹清灰方式的研究

在不同的声波作用下，测定了除尘器内的残余阻力和清灰周期，阐明了声波反吹清灰效果与声波频率和声压的关系。通过实验证明，延长反吹时间、增大反吹风速、多次反吹以及增加清灰次数都不是改善反吹袋式除尘器清灰效果的理想办法，声波反吹清灰能有效地降低残余阻力和残留粉尘负荷，并能明显地延长清灰周期，因而是一种理想的清灰方式。本文还对反吹与声波的作用次序进行了实验，结果表明，在反吹清灰的过程中间鸣喇叭，清灰效果最好     

絮凝体形态学和密度的探讨——Ⅰ.从絮凝体分形构造谈起

常规混凝操作条件下形成的随机型絮凝体具有分形的特征，其分形维数Ｄｆ和絮凝体密度函数ｐｅ∝ｄｐ－Ｋｐ的指数Ｋｐ之间具有Ｄｆ＝３－Ｋｐ的关系。通过建立分布成长絮凝体模型，讨论了在絮凝过程中逐次导入颗粒间的空隙率对絮凝体密度和的影响。模型参数的分析结果进上步证明了分布成长的絮凝体是一个典型的分形，其分形，其分形维数取决于颗粒间空隙比ε和颗粒结合个数ｍ，降低ε或提高ｍ均有利于提高Ｄｆ，使絮凝体由松散同致密     

Urban stormwater disinfection, quality variability during storage and influence on the freshwater algae: Implications for reuse safety

Stormwater reuse is one of the most important ways to mitigate water resource shortage. However, urban stormwater contains many bacteria species, which threaten the reuse safety. Therefore, stormwater disinfection is highly needed. Although disinfection has been widely conducted in the drinking water and reclaimed water, it is rarely carried out for stormwater. This study collected the roof stormwater and undertook chlorination disinfection. Two typical bacteria, Escherichia coli (E. coli) and Staphylococcus aureus (S.aureus) were selected in this study to investigate the disinfection efficiency. It is found that bacteria species present in the stormwater had an important influence on disinfection efficiency while the original stormwater quality did not show an obvious affect. However, when the disinfected stormwater was stored, the stormwater quality was highly variable during its storage process and the variability was affected by bacteria species. The S.aureus containing stormwater showed a high variability of quality and S.aureus significantly regrew. However, the E.coli containing stormwater quality had a relatively low variability and E.coli did not significantly regrew. Additionally, it is noted that after storage, the dissolved form of stormwater was more positive to the freshwater algae's growth while the particulate form (including bacteria and other particulate matters) was less. This implies that a further treatment such as filtration is needed before the stored stormwater is recharged into receiving waters in order to remove particulate forms. These research outcomes can provide useful insight to effective stormwater disinfection and ensure reuse safety.     

New insight into scale inhibition during tea brewing: Ca2+/Mg2+ complexing and alkalinity consumption

Scale not only affects the taste and color of water, but also increases the risks of osteoporosis and cardiovascular diseases associated with drinking it. As a popular beverage, tea is rich many substances that have considerable potential for scale inhibition, including protein, tea polyphenols and organic acids. In this study, the effect of tea brewing on scale formation was explored. It was found that the proteins, catechins and organic acids in tea leaves could be released when the green tea was brewed in water with sufficient hardness and alkalinity. The tea-released protein was able to provide carboxyl groups to chelate with calcium ions (Ca²⁺), preventing the Ca²⁺ from reacting with the carbonate ions (CO₃²⁻). The B rings of catechins were another important structure in the complexation of Ca²⁺ and magnesium ions (Mg²⁺). The carboxyl and hydroxyl groups on the organic acids was able to form five-membered chelating rings with Ca²⁺ and Mg²⁺, resulting in a significant decrease in Ca²⁺ from 100.0 to 60.0 mg/L. Additionally, the hydrogen ions (H⁺) provided by the organic acids consumed and decreased the alkalinity of the water from 250.0 to 131.4 mg/L, leading to a remarkable reduction in pH from 8.93 to 7.73. It further prevented the bicarbonate (HCO₃⁻) from producing CO₃²⁻ when the water was heated. The reaction of the tea constituents with the hardness and alkalinity inhibited the formation of scale, leading to a significant decrease in turbidity from 10.6 to 1.4 NTU. Overall, this study provides information to help build towards an understanding of the scale inhibition properties of tea and the prospects of tea for anti-scaling in industrial applications.     

A simple,explicit formula for the critical pressure of homogenous two-phase nozzle flows

The critical pressure ratio of the homogeneous two-phase nozzle flow model known as the Omega method is expressed in function of the Omega Parameter as the exact numerical solution of a transcendental equation. A well fitting, easy to use, explicit approximation for flashing and non-flashing flows is presented here. The validation against the exact numerical solution proves that this new formula is better fitting than the other ones in the technical literature for both single and two-component flows.