Modelling of coliform removal in 186 facultative and maturation ponds around the world

The paper presents a very extensive evaluation of the coliform decay in facultative and maturation ponds, based on data from 186 different ponds in the world. The ponds encompass a very wide diversity in terms of physical and operating conditions, covering most situations encountered in practice. The median values for the coliform removal efficiencies were 1.8 log units (98% removal) for primary facultative ponds, 1.0 log units for secondary facultative ponds (90% removal) and 1.2 log units (94% removal) for each maturation pond in the series. Two equations to be used for design purposes were derived for estimating the die-off coefficient K(b) (dispersed flow, 20 degrees C) in facultative and maturation ponds. The first equation led to a slightly better fitting with the observed logarithm of the effluent coliform concentrations (R2 = 0.874), and related K(b) with the pond detention time t and depth H (K(b) = 0.682 H(-1.286) t(-0.103)). The other equation also led to a satisfactory fitting (R2 = 0.845), but was slightly simpler, depending only on the pond depth (K(b) = 0.549 H(-1.456)).     

英国跨国高等教育的发展动因及策略

英国发展跨国高等教育的动因主要有三个：获取丰厚的经济收入;推动本国高校教学和科研的国际化;巩固其国际高等教育领先地位。其发展策略主要是：政府制订国际教育发展战略;给予高校更多自主权;树立教育品牌;加快国内外学分、学历和学位互认等。     

英国GIS高等教育与城市规划实践

本文结合城市规划等行业对高等院校毕业生的GIS技能的需求对英国大学中GIS教学培训的情况作一简单介绍,并通过若干实例就英国大学地理规划类院校的GIS辅修课程的讲授范围及深度要求、地理及计算机等院校GIS专业的课程设置结构等方面提供一些具体信息,供中国有关大专院校参考。     

Tracer study and profiling of a tertiary lagoon in the United Kingdom: II

Monitoring data over a year showed that the performance of a tertiary lagoon system in the United Kingdom was very variable. Distinct seasonal patterns were seen for all the determinands. Tracer studies and profile sampling of one of the lagoons were carried out in order to investigate the factors affecting performance. The tracer studies, using sodium fluoride, indicated that the hydraulic regime was dispersed plug flow. The mean retention time was found to be 26 h, but the peak in tracer concentration occurred after 12 h, showing significant short-circuiting. During the profile sampling, the pH, temperature, DO and conductivity were measured down through the lagoon at 16 positions and four depths. E. coli, enterococci and total coliform numbers were measured in samples taken from the surface and the base of the lagoon. The results showed temperature decreased down through the lagoon, but the other parameters increased with depth, indicating that the short-circuiting was caused by the cooler influent sinking to the base of the lagoon.     

Comparison of ammonia volatilisation rates in algae and duckweed-based waste stabilisation ponds treating domestic wastewater

Quantification of ammonia volatilisation from wastewater stabilisation ponds is important in order to understand its significance for overall nitrogen removal in these widely applied low-cost treatment systems. Ammonia volatilisation rates were measured in pilot plant facilities consisting of one line of four algae-based ponds in series and a parallel line of four ponds with a floating mat of duckweed (Lemna gibba). Ammonia volatilisation was assessed during a period of one and a half years. The method applied is accurate, convenient and is proposed for analysis of a wide range of gasses emitted from stabilisation ponds and possibly other aquatic systems. The ammonia volatilisation rates in algae-based ponds (ABPs) were higher than in duckweed-based ponds (DBPs). This can be explained by the lower values of NH(3) in DBPs due to shading and lower pH values, since the volatilisation rate highly correlated with free ammonia concentration (NH(3)) in pond water. The duckweed cover appeared not to provide a physical barrier for volatilisation of unionised ammonia, because whenever NH(3) concentrations were equal in ABP and DBP also the volatilisation rates were equal. Volatilisation was in the range of 7.2-37.4 mg-Nm(-2)d(-1) and 6.4 -31.5 mg-Nm(-2)d(-1) in the ABPs and DBPs, respectively. Average influent and effluent ammonium nitrogen measurements showed that the ammonia volatilisation during the study period in any system did not exceed 1.5% of total ammonium nitrogen removal. Therefore this study confirmed results from simultaneous experimental work in our laboratory indicating that nitrification/denitrification, rather than ammonia volatilisation, is the most important mechanism for N removal in ABPs and DBPs.     

Comparison of model approaches for predicting coliform removal in waste stabilization ponds

This paper compares the two most frequently used approaches for the prediction of faecal coliforms in the effluent (FC_e) of waste stabilization ponds (WSPs): the continuous stirred reactor (CSTR) model and the dispersed flow (DF) model. On the basis of theoretical and practical analysis, it is concluded that, under most conditions usually found in practice, the DF model can be expected to predict unrealistically low FC_e. This trend is more pronounced the more the flow conditions in the pond(s) approach plug flow, and the higher the average retention time per pond. Model differences in FC_e prediction typically deviate from one another by up to 1–2 log units. This can lead to the design of substantially different pond sizes, with footprint differences between the two models of 30–50% not being exceptional. Consequently, on the basis of usually applied model parameters, for the time being it appears safer to use the CSTR model for FC_e prediction in WSP systems.     

Spatial policy in the United Kingdom: Regulatory experimentation in the after-Fordist era

Adopting insights from regulation theory and recent literature on re-scaling, this paper examines the historical development of British urban and regional policy in the United Kingdom. It is first shown that spatial policies in the post-war period can to some degree be considered as part of the Fordist mode of regulation. It is then argued that recent policy innovations can be analysed as attempts to make spatial policy compatible with other regulatory mechanisms and with the current round of accumulation. Thus, attempts are undertaken to create a `post-Fordist institutional fix', i.e., an ensemble of rules, institutions and discourses that can to a certain degree facilitate capital accumulation during a particular period. These attempts appear to be partially successful. On the one hand, new policy mechanisms seem to be in line with other neo-liberal or Third Way policies and some shortcomings of previous policies have been overcome. But on the other hand, spatial policy is characterised by new tensions and contradictions. The central state seems to overestimate its own ability to encourage local and regional governments to make use of `endogenous potential'. In addition, current policies do not sufficiently account for the detrimental effects of inter-territorial competition.     

GIS在英国等欧洲国家及中国城市规划管理中的应用

本文结合若干实例介绍了GIS技术在英国等欧洲国家的规划管理与设计工作中的发展与应用现状,并总结了其应用经验与教训。对于一些具有规划应用潜力的GIS相关技术,本文也予以简单评价。最后就一些与GIS在中国规划设计管理中应用的有关问题提出了一些个人看法。     

Effects of baffles on the performance of model waste stabilization ponds

The performance of three baffled laboratory-scale facultative stabilization ponds were compared with that of an unbaffled control pond. The hydraulic characteristics of the ponds were estimated from the results of tracer tests.The biochemical oxygen demand (BOD₅) removals achieved with the control pond and with the ponds having 3, 6 and 9 baffles were 79, 81, 86 and 89% respectively and the chemical oxygen demand (COD) removals were 81, 84, 84.2 and 84.2%. The reductions in total solids (TS) were respectively 43, 46, 51 and 64%. Dispersion indices of 0.161, 0.126, 0.112 and 0.096 were obtained for the control, 3, 6 and 9 baffle ponds respectively, which indicated a trend of decreasing dispersion index with increasing number of baffles.     

An experimental investigation of aeration performance in stepped spillways

Dissolved oxygen content is a prime indicator of water quality. The oxygen transfer across the air–water interface at a hydraulic structure, such as a weir or spillway, occurs by self‐aeration along the chute and by flow aeration in the hydraulic jump at the downstream end of the structure. Despite increased research activities in the field of stepped spillways, the aeration efficiency of stepped spillways is not yet known. This paper investigates the aeration efficiency of stepped spillways, in particular the effects of varying chute angle and step height. Empirical correlations predicting length of the nonaerated flow region and aeration efficiency were developed. The results indicate that stepped spillways are effective for oxygen transfer.     

Whole life cost performance of domestic rainwater harvesting systems in the United Kingdom

Rainwater harvesting (RWH) can be used to reduce the demand for potable mains water. At the single‐building scale, previous research has focused on water‐saving potential, while financial assessment has either been omitted or considered in an ad hoc manner. This paper reports on the application of a more rigorous financial analysis of domestic RWH systems than had been conducted previously. Whole life costing was selected as the most appropriate financial assessment technique. A total of 3840 domestic system configurations were assessed at a daily time step, taking into account various stakeholder perspectives and future cost scenarios. In each case, it was found that harvesting rainwater was significantly less cost effective than relying solely on mains‐only water. The domestic RWH systems generally resulted in financial losses approximately equal to their capital costs. Without significant financial support, domestic RWH is unlikely to be cost effective for all reasonably foreseeable scenarios.     

Potential of making—Over to sustainable buildings in the Kingdom of Bahrain

Two unique large buildings in the Kingdom of Bahrain were selected for make-over to sustainable buildings. These are the Almoayyed Tower (the first sky scraper) and the Bahrain International Circuit, BIC (The best world Formula 1 Circuit). The amount of electricity extracted from using renewable energy resource (solar and wind), integrated to the buildings—has been studied thoroughly.     

An introduction of a multi‐soil‐layering system: a novel green technology for wastewater treatment in rural areas

Multi‐soil‐layering (MSL) systems are designed for municipal wastewater, livestock wastewater and polluted river water treatments. They are mainly composed of soil mixture block layers and water‐permeable layers (PL). The MSL system overcomes many of the shortcomings of conventional soil treatment systems such as easy clogging, large land requirement and low hydraulic loading rate. This paper summarizes the structure, purification mechanism and practical application of the systems for different kinds of wastewater treatment. The paper also compares MSL systems with other decentralized systems such as wetland and compact filter systems in their respective structures and treatment efficiencies. Finally, the paper gives a rough evaluation of the lifespan and cost of an MSL system based on its material composition.     

Addition of an aerated iron‐rich waste‐activated sludge to control the soluble sulphide concentration in sewage

Hydrogen sulphide emission in sewers is associated with toxicity, corrosion and odour and also yields considerable costs. The purpose of this study was to evaluate whether the soluble sulphide concentration in raw sewage can be controlled by dosing an iron‐rich waste‐activated sludge (WAS) or an iron‐rich aerated waste‐activated sludge (AWAS). An average soluble sulphide elimination of 99% was achieved at an iron‐rich AWAS to sewage ratio (v/v) of 16%, whereas dosage of iron‐poor AWAS at the same ratio decreased the soluble sulphide in the raw sewage by only 53%. Our lab‐scale tests suggest that dosing iron‐rich AWAS to sewage did not affect the chemical oxygen demand (COD) and total ammonia nitrogen (TAN) removal as well as the nitrification efficiency in the receiving activated sludge system. The results indicate that iron‐rich AWAS dosage is a feasible technique to remediate the sulphide problem in sewers.     

垃圾土中水分运动的一维数值分析

运用Brooks-Corey模型拟合了垃圾土的土水特征曲线和非饱和渗透系数,运用饱和—非饱和渗流分析,研究了垃圾土的一维水分运动过程,通过数值模拟计算了垃圾土在降雨入渗过程前后的水分运动,展示了孔隙水压力随时间的变化,使得对垃圾土中的水分运动过程的认识更加直观清楚。     

山西省垃圾填埋场工程设计问题分析及对策

分析了山西省中小市县生活垃圾卫生填埋处理工程发展现状,指出了初步设计过程的几个关键共性问题,并提出了解决这些问题的技术方法和对策,为城市垃圾填埋场工程防洪、调节池及其封闭处理优化设计提供了一定的依据与经验.     

Performance assessment of solute transport upscaling methods in the context of nuclear waste disposal

Stochastic simulations of solute transport in heterogeneous log₁₀ K random fields were conducted at two different support scales to assess solute transport upscaling methods in the context of nuclear waste disposal. A very fine grid-scale is used to obtain a reference solution of the real problem, which is based on data from the Sellafield site. A coarse-scale model is obtained by upscaling the heterogeneous grid-blocks onto equivalent homogeneous hydraulic conductivity tensors calculated using the Simple Laplacian Technique. Random fields were designed with different degrees of heterogeneity such that the standard deviation of log₁₀ K ranged between 0 and 1. It is shown that the early arrival time of particles at a control location, reflected in the lower limit of the 95% confidence interval of the mass flux cumulative density function stochastic process, associated with the upscaled model is strikingly similar to the one associated with the real solution for all heterogeneities. This is encouraging for the application of upscaled stochastic models to the design of nuclear waste repositories where the design of a nuclear waste disposal facility relies on the estimation of the early travel time of radionuclides arriving at a control location. On the contrary, the late arrival time of particles at the control location is largely underestimated by the upscaled model.     

Numerical analysis of thermal process in the near field around vertical disposal of high-level radioactive waste

For deep geological disposal of high-level radioactive waste(HLW)in granite,the temperature on the HLW canisters is commonly designed to be lower than100fiC.This criterion dictates the dimension of the repository.Based on the concept of HLW disposal in vertical boreholes,thermal process in the nearfield(host rock and buffer)surrounding HLW canisters has been simulated by using different methods.The results are drawn as follows:(a)the initial heat power of HLW canisters is the most important and sensitive parameter for evolution of temperaturefield;(b)the thermal properties and variations of the host rock,the engineered buffer,and possible gaps between canister and buffer and host rock are the additional key factors governing the heat transformation;(c)the gaps width and thefilling by water or air determine the temperature offsets between them.     

Numerical analysis of thermal process in the near field around vertical disposal of high-level radioactive waste简

For deep geological disposal of high-level radioactive waste (HLW) in granite, the temperature on the HLW canisters is commonly designed to be lower than 100 °C. This criterion dictates the dimension of the repository. Based on the concept of HLW disposal in vertical boreholes, thermal process in the near field (host rock and buffer) surrounding HLW canisters has been simulated by using different methods. The results are drawn as follows: (a) the initial heat power of HLW canisters is the most important and sensitive parameter for evolution of temperature field; (b) the thermal properties and variations of the host rock, the engineered buffer, and possible gaps between canister and buffer and host rock are the additional key factors governing the heat transformation; (c) the gaps width and the filling by water or air determine the temperature offsets between them.     

The effects of reduction of the deposited waste on short‐term landfill leachate composition of a landfill: a case study in Norway

Municipal solid waste landfill leachate was sampled over from a landfill receiving varying amounts of municipal solid waste. The investigation aimed to provide information on expected leachate changes in the short term, either after closure of an active landfill, or after a strong decline in the amount of waste deposited at smaller landfills. It was found that during a two year period following a sudden decline in the amount of waste deposited, the levels of various chemical and physical parameters all dropped sharply. The reasons for the decline in discharge levels are thought to be aerobic decomposition taking place in the municipal solid waste just after landfilling, and thus the decline in the impact of this process when there were less fresh waste masses available, and formation of preferential flow paths for the leachate as the municipal solid waste stabilized in the landfill.