Screening of organic contaminants in urban snow

Snowmelt is known to cause peak concentrations of pollutants, which may adversely affect receiving water quality. High concentrations of metals and suspended solids in snow have been reported, whereas studies on organic pollutants are rare. This study aims at investigating the occurrence of anthropogenic organic compounds in urban snow in Gothenburg (Sweden). The most frequently detected organic pollutants in the collected snow samples were polycyclic aromatic hydrocarbons (PAHs), high molecular-weight phthalates, 4-nonylphenol and 4-t-octylphenol. Brominated flame retardants and chlorinated paraffins were only sporadically detected. In several snow samples, the concentrations of specific PAHs, alkylphenols and phthalates were higher than reported stormwater concentrations and European water quality standards. Pollutant source identification and sustainable management of snow are important instruments for the mitigation of organic contaminants in the urban environment.     

Resource recovery from source separated domestic waste(water) streams; full scale results

A major fraction of nutrients emitted from households are originally present in only 1% of total wastewater volume. New sanitation concepts enable the recovery and reuse of these nutrients from feces and urine. Two possible sanitation concepts are presented, with varying degree of source separation leading to various recovery products. Separate vacuum collection and transport followed by anaerobic treatment of concentrated black water (BW) demonstrated on a scale of 32 houses preserve 7.6 g/N/p/d and 0.63 gP/p/d amounting to respectively 69 and 48% of the theoretically produced N and P in the household, and 95% of the retained P was shown to be recoverable via struvite precipitation. Reuse of the anaerobic sludge in agriculture can substantially increase the P recovery. Energy recovery in the form of biogas from anaerobic digestion of concentrated BW, fits well in new concepts of sustainable, zero energy buildings. Nutrient recovery from separately collected urine lowers the percentage of nutrient recovery in comparison with BW but can, on the other hand, often be implemented in existing sanitation concepts. Theoretically 11gN/p/d and 1.0 g P/p/d are produced with urine, of which 38-63 and 34-61% were recovered in practice on a scale of 8-160 inhabitants in Sweden. New sanitation concepts with resource recovery and reuse are being demonstrated worldwide and more and more experience is being gained.     

Anaerobic degradation of palm oil mill effluent (POME)

The biodegradation characteristics of palm oil mill effluent (POME) and the related microbial community were studied in both actual sequential anaerobic ponds in Malaysia and enrichment cultures. The significant degradation of the POME was observed in the second pond, in which the temperature was 35-37 °C. In this pond, biodegradation of major long chain fatty acids (LCFA), such as palmitic acid (C16:0) and oleic acid (C18:1), was also confirmed. The enrichment culture experiment was conducted with different feeding substrates, i.e. POME, C16:0 and C18:1, at 35 °C. Good recovery of methane indicated biodegradation of feeds in the POME and C16:0 enrichments. The methane production rate of the C18:1 enrichment was slower than other substrates and inhibition of methanogenesis was frequently observed. Denaturing gradient gel electrophoresis (DGGE) analyses indicated the existence of LCFA-degrading bacteria, such as the genus Syntrophus and Syntorophomonas, in all enrichment cultures operated at 35 °C. Anaerobic degradation of the POME under mesophilic conditions was stably processed as compared with thermophilic conditions.     

Experimental study of a novel hybrid constructed wetland for water reuse and its application in Southern China

A new type of hybrid constructed wetland (CW), consisting of both vertical-baffled flow wetland (VBFW) and horizontal subsurface flow wetland (HSFW), has been deployed in Southern China to naturally accelerate the removal of organic matter and nitrogen. The hybrid CW system is characterised by a combination of continuous baffled flow vertical wetland and 'S' pattern horizontal subsurface flow wetland with natural aeration ditches to increase the concentration of dissolved oxygen in the HSFW bed. An internal circulatory system from the HSFW effluent back to the VBFW may optionally be operated to enhance the biological denitrification effect. Cyperus alternifolius is the main macrophyte in the wetland bed. The performance of the hybrid CW was studied with a pilot-scale system and three full-scale systems for municipal sewage treatment in Southern China. The results suggest that this new hybrid CW can achieve removal efficiencies of chemical oxygen demand, suspended solids, ammonia nitrogen, total nitrogen, and total phosphorus of better than 83.6, 95.0, 71.7, 64.5 and 68.1% respectively, with a specific wetland bed area of 0.70-0.93 m(2) PE(-1). The mean effluent concentrations of these parameters would meet the regulatory discharge limits for wastewater treatment systems (GB18918, 2002) and reuse in the context of agricultural irrigation solutions in China.     

Exploring the potential synergistic effects of chemical disinfectants and UV on the inactivation of free-living bacteria and treatment of biofilms in a pilot-scale system

The main objective of this study is to explore possible synergistic or additive effects of combinations of chemical disinfectants (sodium hypochlorite, peracetic acid, hydrogen peroxide, chlorine dioxide) and UV in their efficacy in inactivating free-living bacteria and removing biofilms. In contrast to most studies, this study examines disinfection of municipal water in a pilot-scale system using a mixed bacterial suspension, which enables a better simulation of the conditions encountered in actual industrial environments. It was shown that the combination of either hypochlorite, hydrogen peroxide, peracetic acid, or chlorine dioxide with UV yielded additive effects on the inactivation of free-living bacteria. Actual synergy was observed for the combination of UV and 5 ppm hydrogen peroxide. Regarding biofilm treatment, additive effects were observed using the combination of hydrogen peroxide and UV. The promising results obtained in this study indicate that the combination of UV and chemical disinfectants can considerably reduce the amount of chemicals required for the effective disinfection and treatment of biofilms.     

数据结构课多媒体CAI课件的制作

本文介绍了利用多媒体开发工具Authorware制作数据结构CAI课件的开发过程,重点讨论了开发过程的设计思想和关键技术。     

用空心钢锭制造的压力容器大型环段锻件

水岛工厂把杂质含量低的熔融金属同偏析少的大型空心钢锭结合起来,已能生产重达320t的高质量钢靛。250t的实验性空心钢锭已经制造出来,目的是模拟相同尺寸空心钢锭的内部质量。1300MW压水堆压力容器零件和1100MW沸水堆压力容器零件锻造的环段,也已经用氧气顶吹转炉冶炼-RH脱气-空心钢锭浇注的方法制成。由于空心钢锭的均匀性,环段锻件偏析较少,而且内表面完好无缺陷。本文不仅概述了环段锻件的制造资料,而且概述了制造设备,包括4400t压力机、立车以及自动无损探伤设备。     

核电站用的大型低压转子锻件的制造和质量

本文阐述了用420t钢锭制造整体低压转子锻件的生产过程及其质量。为了使整个转子都具有良好的和均匀的机械性能,利用了电子计算机来确定热处理条件。这种方法称为电子计算机辅助热处理工艺设计(CAHT)。实践证明,采用电子计算机辅助热处理工艺设计,对预计整体转子的机械性能是非常有效的。整体转子锻件的机械性能试验结果是令人满意的。锻件中心孔试验表明,其室温断裂韧性已超过200MPam~(1/2)。     

挤压的热平衡及温度变化

温度是挤压工艺的最重要的参数之一。提高温度,金属变形抗力减小,但同时易于导致局部温度过高,引起低熔点共晶和多相组织熔化,以及制品表面粗糙,限制了最大挤压速度。挤压过程中温度的变化取决于:锭坯加热湿度,锭坯向挤压筒的热传导以及变形和摩擦热效应。     

由纵波和转换波资料估计横波速度

Tessmer和Behle(1988)指出,如果能获得正常的P波和转换波(P-SV)资料,就可以从地面地震资料估计横波速度。Tessmer和Behle关系式为 V_(sv)=V_(p-sv)~2/V_p (1)式中,V_(sv)为横波速度,V_p,为纵波速度,y_(p-sv)为转换波速度。公式(1)是用来求随深度改变的速度的,转换波资料的增长部分对公式(1)的有效性提供了主要的验证。