Development and application of a quasi-static Langmuir isotherm for modelling selected resin acid fate in pulp mill wastewater treatment

Resin acids are pulp mill effluent contaminants that exhibit significant solubility, diffusivity, and surfactancy changes with pH within the range typically used for biological treatment. Such physical-chemical property changes which can influence removal during biological wastewater treatment, can be characterized by dynamic surface tension measurements. Dynamic surface tension measurements were made by the maximum bubble pressure method during batch treatment of selected resin acids in pulp mill effluent. Interpretation of dynamic surface tension data was made through the framework of a quasi-static Langmuir isotherm model that was derived as part of this investigation. The results suggested that under acidic conditions, resin acids form associations with other dissolved organic matter contained in pulp mill effluent, while under alkaline conditions, they behave as relatively soluble surfactants. A resin acid residuum, or threshold concentration, has been found to increase under acidic growth conditions. This residuum increase corresponded to an inferred reduction in resin acid bioavailability that was suggested from the isotherm modelling. The development of quasi-static isotherm adsorption models has application in computer simulation for design of adsorption based unit processes, and could potentially be utilized as an informative treatment process monitor.     

Ground water pollution by roof runoff infiltration evidenced with multi-tracer experiments

The infiltration of urban roof runoff into well permeable subsurface material may have adverse effects on the ground water quality and endanger drinking water resources. Precipitation water from three different roofs of an industrial complex was channelled to a pit and infiltrated into a perialpine glaciofluvial gravel-and-sand aquifer. A shaft was constructed at the bottom of the pit and equipped with an array of TDR probes, lysimeters and suction cups that allowed measuring and sampling soil water at different depths. A fast infiltration flow was observed during natural rainfall events and during artificial infiltration experiments. For a better understanding of the behaviour of contaminants, experiments were conducted with cocktails of compounds of different reactivity (ammonium, strontium, atratone) and of non-reactive tracers (uranine, bromide, naphthionate), which represent different classes of pollutants. The experiment identified cation exchange reactions influencing the composition of the infiltrating water. These processes occurred under preferential flow conditions in macropores of the material. Measuring concentration changes under the controlled inflow of tracer experiments, the pollution potential was found to be high. Non-reactive tracers exhibited fast breakthrough and little sorption.     

Lake George as a Sink for Contaminants Derived from the Kilembe Copper Mining Area, Western Uganda

Abstract  The copper mine at Kilembe in the Ruwenzori Mountains in western Uganda ceased to operate in 1978 but a steady flow of contaminants, including Cu, Co, Ni, Zn, Cd, and sulphate, continues to enter the Nyamwamba-Rukoki River, which passes through Queen Elizabeth National Park, and finally flows into Lake George. Lake George is quite shallow, alkaline, and highly eutrophic. Measuring mass-flow of contaminants, water, and suspended solids in the Rukoki River near Kasese allowed us to estimate their input into Lake George. Grid sampling of lake sediments indicated that the contaminants settle near the two mouths of the river; low concentrations in a drill core in the centre of Lake George indicate that further dispersion within the lake is small. Sequential extraction experiments on lake sediments and lake water analyses suggest low bioavailability of the heavy metals. We conclude that Lake George is a highly resilient system that efficiently immobilises contaminants. Though there is no health risk for the population under present environmental conditions, a reduction of the contaminant load is desirable.     

The effect of source motion on contaminant distribution in the cleanrooms

In the recent decades, cleanrooms have found growing applications in broad range of industries such as pharmacy and microelectronics. Concerns about negative effects of the contaminant exposure on the human health and product quality motivate many researchers towards understanding of the airflow and contaminant distribution though these environments. With an improvement in computational capacity of the computers, computational fluid dynamics (CFD) technique has become a powerful tool to study the engineering problems including indoor air quality (IAQ). In this research, indoor airflow in a full-scale cleanroom is investigated numerically using Eulerian-Eulerian approach. To evaluate the ventilation system effectiveness, a new index, called final efficiency, is introduced which takes all aspects of the problem into account. The results show that the contaminant source motion and its path have a great influence on the contaminant dispersion through the room. Based on the results, the contaminant distribution indexes, e.g. final efficiency and spreading radius, are improved when the source motion path is in the dominant direction of the ventilation airflow. Consequently, the efficiency of an air distribution system which provides a directional airflow pattern shows the least source path dependency. This study and its results may be useful to gain better understanding of the source motion effects on the indoor air quality (IAQ) and to design more effective ventilation systems.     

A novel method for industrial production of clean hydrogen (H2) from mixed plastic waste

This study describes a novel Hybrid Microwave Plasma Enhanced Gasification (HMPEG) method for converting plastic waste into hydrogen (H₂). Thermal processing of plastic waste is a low-cost method of producing H₂. Current methods, however, such as pyrolysis and gasification, are limited by inefficient heating and contaminants in syngas, resulting in a low H₂ yield. Our approach consists of a novel rotary pyrolysis reactor that employs an external microwave heater and an electrodeless microwave torch reformer, thereby addressing issues with current methods. In this study, pyrolysis of mixed plastic produces pyro-gas which is reformed at a temperature above 1500 °C by the steam plasma torch powered by microwave. The result is a 150 g/kg H₂ yield with a 67 vol.% higher production rate, an H₂/CO ratio of 7, and a conversion efficiency of 97.4%. Tar and dioxin concentrations in the syngas were found to be 0.078 g/Nm³ and 0.024 ng-TEQ/Nm³, respectively, much less than the legal limit. A novel microwave pyrolyzer cuts electrical power consumption by half, and the pure H₂ produced is suitable for direct use in hydrogen cars, power generation, and other applications. Once implemented, the energy-efficient HMPEG could aid in expanding H₂ commercial plants that use plastic waste as a raw input fuel.     

浅析助焊剂在使用过程中发生的物理化学变化

该文通过埘电子产品上异物的成分解析,分析了助焊剂在使用过程中所发生的物理化学变化。助焊剂在使用过程中,助焊剂中的活性剂如羧酸会与金属表丽的氧化物生成相应的羧酸盐,并珏由于金属离子本身的特性从而显示不同的颜色,同时经过试验验证了此变化的过程。     

Localized air-conditioning with occupancy control in an open office

Conditioning and ventilating open office spaces requires innovations as new buildings aim to be more intelligent, energy efficient and healthy. This paper explores the possibility of using a localized airflow to divide an open cubicle office into zones without partition walls. Computational fluid dynamics (CFD) model was used to simulate localized airflow in a cubicle office and both the energy and the indoor air quality concerns were addressed. The findings suggest that (1) localized airflow is plausible for zoning purposes, (2) localized airflow can result in both temperature and pollutant concentration segregations, (3) temperature segregations provide possible energy savings if coupled with occupancy-based HVAC control, and finally (4) limited air mixing between zones provide a novel way for better ventilation and indoor contaminant control.     

国际食品污染物监测体系理化指标监测介绍及思考

介绍了部分国家和国际组织食品污染物监测体系的监测历史、监测点选择、监测食品类别、污染物类别、采样原则、数据共享、数据利用,并将我国和发达国家这方面的工作进行了比较,找出差异和可以借鉴的方面,并提出了建议。     

A stochastic analysis of contaminant transport through a rough-surfaced fracture

A stochastic model for the calculation of flow and contaminant transport in a single fracture with variable apertures was presented. The spatially varying apertures of the fracture were generated using a geostatistical method, based on a given aperture probability density distribution and a specified spatial correlation length. Fluid flowed between two points in the fracture plane. The fluid potential at each node of the discretization mesh was computed and the steady state flow rates between all the nodes were obtained. Then the contaminant transport was calculated using a particle tracking method. The migration plumes of contaminant between the inlet and the outlet were displayed in contour plots and contaminant elution profiles were also plotted. Calculations showed that fluid flow occured predominantly in a few preferred paths. Hence, the large range of apertures in the fracture gives rise to flow channeling. Simulation results were correlated with the basic input parameters: standard deviation of a lognormal aperture distribution function and the spatial correlation length.