The Use of Different Conveyance Calculations for Modelling Flows in a Compact Compound Channel

Flow measurements have been taken for steady and unsteady flows on a reach of a river having a compact compound channel. The 'single channel', 'divided channel' and 'lateral' distribution methods have been used to calculate conveyances for use in a one-dimensional unsteady flow model of the reach. Comparisons with measured flows show that the divided channel method and the lateral distribution method both underestimate floodplain flow depths. The lateral distribution method gives the closest accuracy in the relative depth range 0.15 ≤ Yr < 0.40. For large flow depths the single channel method becomes more accurate and slightly over-estimates flow depths.
The accuracy of unit width discharge distributions, calculated from the lateral distribution method are assessed by comparison with observed distributions for overbank flows.     

Nitrogen dynamics and removal in a horizontal flow biofilm reactor for wastewater treatment

A horizontal flow biofilm reactor (HFBR) designed for the treatment of synthetic wastewater (SWW) was studied to examine the spatial distribution and dynamics of nitrogen transformation processes. Detailed analyses of bulk water and biomass samples, giving substrate and proportions of ammonia oxidising bacteria (AOB) and nitrite oxidising bacteria (NOB) gradients in the HFBR, were carried out using chemical analyses, sensor rate measurements and molecular techniques. Based on these results, proposals for the design of HFBR systems are presented.The HFBR comprised a stack of 60 polystyrene sheets with 10-mm deep frustums. SWW was intermittently dosed at two points, Sheets 1 and 38, in a 2 to 1 volume ratio respectively. Removals of 85.7% COD, 97.4% 5-day biochemical oxygen demand (BOD₅) and 61.7% TN were recorded during the study.In the nitrification zones of the HFBR, which were separated by a step-feed zone, little variation in nitrification activity was found, despite decreasing in situ ammonia concentrations. The results further indicate significant simultaneous nitrification and denitrification (SND) activity in the nitrifying zones of the HFBR. Sensor measurements showed a linear increase in potential nitrification rates at temperatures between 7 and 16 °C, and similar rates of nitrification were measured at concentrations between 1 and 20 mg NH₄-N/l. These results can be used to optimise HFBR reactor design. The HFBR technology could provide an alternative, low maintenance, economically efficient system for carbon and nitrogen removal for low flow wastewater discharges.     

Mathematical analysis of oxygen and nitrate consumption in deep microbial films

The simultaneous diffusion and consumption of oxygen and nitrate into microbial films with aerobic and anaerobic layers was modeled by a system of differential equations and solved by numerical methods. Fickian diffusion was assumed. Models used Monod kinetics and zero-order kinetics, for growth limitation by oxygen and nitrate. Denitrification was assumed to be repressed by oxygen concentrations greater than a finite critical value. Both models indicate that oxygen concentration in the overlying water would have little effect on the nitrate uptake of thick films.     

聚丙烯纤维混凝土在泵站流道工程中的应用

泵站流道工程应用聚丙烯纤维混凝土，可充分利用纤维混凝土的抗裂、防渗特性，对易产生混凝土裂缝的泵站流道起防止裂缝病害的作用，试验研究了聚丙烯纤维混凝土的施工性，进行了纤维混凝土的配合比设计、施工作业和养护，保证了水泵站流道混凝土的抗裂防渗效果。     

Effects of inhibitors on nitrification in a packed-bed biological flow reactor

The individual effect of trivalent arsenic, hexavalent chromium and fluoride on nitrification is studied under continuous load in a packed bed biological flow reactor. The results show that Michaelis-Menten rate expression gives the best representation of nitrification data in the absence of inhibitors. However, in the presence of inhibitors, the system follows a non-competitive mode of inhibition with the following rate expression: The values of V_max and K_s are estimated as 1.466 mg l⁻¹ min⁻¹ and 2.349 mg l⁻¹ respectively. The inhibitor constant K_i is evaluated as 273 mg l⁻¹ for trivalent arsenic, 56 mg l⁻¹ for hexavalent chromium and 1185 mg l⁻¹ for fluoride.     

Modelling the fate of organic micropollutants in stormwater ponds

Urban water managers need to estimate the potential removal of organic micropollutants (MP) in stormwater treatment systems to support MP pollution control strategies. This study documents how the potential removal of organic MP in stormwater treatment systems can be quantified by using multimedia models. The fate of four different MP in a stormwater retention pond was simulated by applying two steady-state multimedia fate models (EPI Suite and SimpleBox) commonly applied in chemical risk assessment and a dynamic multimedia fate model (Stormwater Treatment Unit Model for Micro Pollutants — STUMP). The four simulated organic stormwater MP (iodopropynyl butylcarbamate — IPBC, benzene, glyphosate and pyrene) were selected according to their different urban sources and environmental fate. This ensures that the results can be extended to other relevant stormwater pollutants. All three models use substance inherent properties to calculate MP fate but differ in their ability to represent the small physical scale and high temporal variability of stormwater treatment systems. Therefore the three models generate different results. A Global Sensitivity Analysis (GSA) highlighted that settling/resuspension of particulate matter was the most sensitive process for the dynamic model. The uncertainty of the estimated MP fluxes can be reduced by calibrating the dynamic model against total suspended solids data. This reduction in uncertainty was more significant for the substances with strong tendency to sorb, i.e. glyphosate and pyrene and less significant for substances with a smaller tendency to sorb, i.e. IPBC and benzene. The results provide support to the elaboration of MP pollution control strategies by limiting the need for extensive and complex monitoring campaigns targeting the wide range of specific organic MP found in stormwater runoff.     

开采条件下海河流域平原区浅层地下水数值模拟研究

本文利用地下水数值模拟系统(GMS),建立了能反映海河流域平原区地下水含水层结构及其水流特性的大区域水文地质概念模型和地下水流模型,重点研究了在无开采井条件下地下水开采强度时空分布的特征,模拟了平原区1965~2005年41年间的地下水流场及漏斗的演变过程,综合分析了海河流域平原区浅层含水层长期开采条件下地下水系统的演变过程以及地下水开采带来的影响。同时,对所建立的地下水数值模型就流场、漏斗变化以及水文地质参数等多方面进行了识别和验证。采用经过率定和验证的模型,预测分析了水资源配置制定的地下水限采方案,为南水北调实施后对海河流域地下水的修复作用以及其它可能的影响提供了可靠的分析手段和措施。     

Importance of flow stratification and bubble aggregation in the separation zone of a dissolved air flotation tank

The importance of horizontal flow patterns and bubble aggregation on the ability of dissolved air flotation (DAF) systems to improve bubble removal during drinking water treatment were explored using computational fluid dynamics (CFD) modeling. Both analytical and CFD analyses demonstrated benefits to horizontal flow. Two dimensional CFD modeling of a DAF system showed that increasing the amount of air in the system improved the bubble removal and generated a beneficial stratified horizontal flow pattern. Loading rates beyond a critical level disrupted the horizontal flow pattern, leading to significantly lower bubble removal. The results also demonstrated that including the effects of bubble aggregation in CFD modeling of DAF systems is an essential component toward achieving realistic modeling results.     

用Koch 曲线模拟岩石结构面粗糙度的光弹试验

从分形几何的观点出发,根据结构面具有统计自相似特征,用Ｋｏｃｈ曲线在聚碳酸脂板上加工出不同粗糙度的结构面模型。对试件做了一系列单向压缩和压剪光弹实验,应用光弹理论分析了结构面在压剪载荷作用下应力场分布变化规律。结果表明,法向压力对不同粗糙度结构面上的抗剪强度有很大的影响     

Short-term variability of dissolved trace element concentrations in the Marne and Seine rivers near Paris

The concentrations of dissolved trace elements (Li, B, Mn, Cu, As, Rb, Sr, Mo, Cd, Ba, Pb) in the Marne and Seine rivers in the Paris urban area were monitored over a 2-year period. The resulting data indicated moderate contamination of waters by the most toxic elements (Cu, As, Cd and Pb). The River Marne upstream and the River Seine downstream of the city of Paris displayed similar concentrations. However higher fluxes of trace elements were observed in the Seine than in the Marne due to their different discharges. Li, B, Rb, Sr and Ba concentrations were correlated with river discharge and concentrations were higher during high river flow. This was interpreted as a dilution by discharge from a major natural or anthropogenic source. Mn, Cu, Mo, Cd and Pb concentrations were not correlated with discharge. Dissolved Mn, Cu and Cd increased rapidly in summer, whereas the concentration of Mo decreased. These variations were attributed to redox processes. During summer when the dissolved oxygen concentrations decrease, Mn, Cu, Cd and Pb are released into solution whereas Mo is immobilised. Like metals, variations in arsenic contents were not linked with discharge. Its similarity with phosphate distribution suggests similar controls involving phytoplankton uptake and release from sediments through organic matter mineralization.     

Recent developments in numerical modelling of subsurface flow constructed wetlands

Numerical modelling of subsurface flow constructed wetlands (CWs) gained increasing interest during the last years. The main objective of the modelling work is, on the one hand, to increase the insight in dynamics and functioning of the complex CW system by using mechanistic or process based models that describe transformation and degradation processes in detail. As these mechanistic models are complex and therefore rather difficult to use there is, on the other hand, a need for simplified models for CW design. The design models should be premium to the currently used design guidelines that are mainly based on rules of thumb or simple first-order decay models. This paper presents an overview of the current developments on modelling of subsurface flow CWs based on the modelling work and model developments presented at the WETPOL 2007 symposium. Three kinds of models have been presented: simple transport and first-order decay models, complex mechanistic models, and a simplified model that has been developed for design of CWs. The models are presented and selected results are shown and discussed in relation to the available literature.     

火灾中采用逆向通道连接的钢梁-钢管混凝土柱结构约束组件的数值模拟

利用有限元软件ABAQUS,采用三维块单元,模拟火灾中钢梁-钢管混凝土柱及其节点约束组件的性能。利用近期英国曼彻斯特大学的采用逆向通道连接的3组耐火试验,对模型进行验证。结果表明:有限元模型能成功进行模拟。利用有限元模型,初步研究改变连接构件以加强结构耐火能力的可行性。对连接方式进行改进,以期使连接梁的链式反应能更好发展。提出外伸-内缩式混合端板连接形式,连接的拉伸部分采用外伸端板,以提高延性;受压部分采用内缩式端板,提高韧性。结果表明:不需任何费用,只要用混合端板连接替代外伸端板连接,就能提高连接梁的耐火能力。     

Fatty acids production from hydrogen and carbon dioxide by mixed culture in the membrane biofilm reactor

Gasification of waste to syngas (H₂/CO₂) is seen as a promising route to a circular economy. Biological conversion of the gaseous compounds into a liquid fuel or chemical, preferably medium chain fatty acids (caproate and caprylate) is an attractive concept. This study for the first time demonstrated in-situ production of medium chain fatty acids from H₂ and CO₂ in a hollow-fiber membrane biofilm reactor by mixed microbial culture. The hydrogen was for 100% utilized within the biofilms attached on the outer surface of the hollow-fiber membrane. The obtained concentrations of acetate, butyrate, caproate and caprylate were 7.4, 1.8, 0.98 and 0.42 g/L, respectively. The biomass specific production rate of caproate (31.4 mmol-C/(L day g-biomass)) was similar to literature reports for suspended cell cultures while for caprylate the rate (19.1 mmol-C/(L day g-biomass)) was more than 6 times higher. Microbial community analysis showed the biofilms were dominated by Clostridium spp., such as Clostridium ljungdahlii and Clostridium kluyveri. This study demonstrates a potential technology for syngas fermentation in the hollow-fiber membrane biofilm reactors.     

Modelling the behaviour of mechanical biological treatment outputs in landfills using the GasSim model

The pretreatment of the biodegradable components of municipal solid waste (MSW) has been suggested as a method of reducing landfill gas emissions. Mechanical biological treatment (MBT) is the technology being developed to provide this reduction in biodegradability, either as an alternative to source segregated collection or for dealing with residual MSW which still contains high levels of biodegradable waste. The compost like outputs (CLOs) from MBT plants can be applied to land as a soil conditioner; treated to produce a solid recovered fuel (SRF) or landfilled. In this study the impact that landfilling of these CLOs will have on gaseous emissions is investigated. It is important that the gas production behaviour of landfilled waste is well understood, especially in European member states where the mitigation of gaseous emissions is a legal requirement. Results of an experiment carried out to characterise the biodegradable components of pretreated biowastes have been used with the GasSim model to predict the long term emissions behaviour of landfills accepting these wastes, in varying quantities. The landfill directive also enforces the mitigation of potential methane emissions from landfills, and the ability of landfill operators to capture gaseous emissions from low emitting landfills of the future is discussed, as well as new techniques that could be used for the mitigation of methane generation.     

Analysis of energy consumption in Finland based on the selected economics indicators

Energy is one of the main inputs of productions. Therefore, national policies have emphasised on accessibility, availability, and affordability of energy supply. This is very important for energy importers, in particular countries with high dependency on industrial products. Finland is one of such countries that has high-energy consumption due to its cold climate, energy-intensive industries, and low population density. Therefore, security of energy supply to respond domestic consumption is one of the main concerns of the Finnish government. To have a resilience energy supply, it is necessary to understand the energy system in Finland. Energy modelling is a tool that helps policy-makers and researchers to understand the fluctuations and changes in the energy system. This research is to investigate the relationship between energy consumption and selected macro-economic factors in Finland. Therefore, energy consumption in each sector is analysed and the importance of renewable energies is also considered. Finally, a regression model is presented to predict energy consumption.     

Distribution and transport of sediment-bound metal contaminants in the rio grande de tarcoles, costa rica (Central America)

A reconnaissance survey of the extent of metal contamination in the Rio Grande de Tarcoles river system of Costa Rica indicated high levels of chromium (Cr) in the fine-grain bed sediments (<60 μm) of tributaries downstream from leather tanneries (50–83 times Cr background or 3000–5000 μg/g). In the main channel of the river downstream of the San Jose urban area, Cr contamination in sediments was 4–6 times background and remained relatively constant over 50 km to the mouth of the river. Sediments from a mangrove swamp at the river mouth had Cr levels 2–3 times above background. Similar patterns of dilution were observed for lead (Pb) and zinc (Zn) sediment contamination, although the contamination levels were lower. The high affinity of Cr towards particulate phases, probably as Cr(III), allows the use of Cr contamination levels for delineating regions of deposition of fine-grained sediments and dilution of particle associated contaminants during transport and deposition.     

Modeling the removal of dissolved organic carbon by ion exchange in a completely mixed flow reactor

A mathematical model was developed to describe removal of dissolved organic carbon (DOC) by a macroporous, strong-base anion exchange resin in a completely mixed flow reactor with resin recycle and partial resin regeneration. The two-scale model consisted of a microscale model describing the uptake of DOC by the resin coupled with a macroscale model describing the continuous-flow process. Equilibrium and kinetic parameters were estimated from batch laboratory experiments. The model was validated using continuous-flow data from two pilot plant studies. Model predictions were found to be in good agreement with the observed pilot plant data.