Treatment of municipal effluents: A conceptual model

Available treatment techniques for wastewater, municipal and industrial, are expensive either in terms of cost or in terms of energy or land requirement. Problems in running the system and the recurring expenditure involved in maintenance of the system are other aspects not appreciated when considering the available techniques. This leads to calls for an alternative technique which is compatible with the problems of a developing economy. It is attempted here to develop an integrated conceptual model which is less expensive, consumes relatively low energy, is easy to operate and maintain and would be acceptable to the community. End‐uses of the treated effluents are a beneficial aspect and can generate revenue to meet a reasonable part of the running expenses. The model could also be coupled with scientific land‐use planning which is very much needed in developing countries.     

分布式水文概念性模型及应用

在遥感与GIS支持下,建立地理空间信息库,提取了流域土地利用、土壤类型和植被类型等地理信息及相应的水空间参数,采用已有的水概念性模型,建立了一个分布式水概念性模型．模型结构简单,所需参数较少,易于率定,可操作性强．实例应用表明,该模型对雁栖河流域径流量的模拟是有效的,可用于评估流域水资源量、气候变化以及土地利用变化对水资源的影响．     

A conceptual model describing macromolecule degradation by suspended cultures and biofilms

Macromolecular (> 1,000 daltons) compounds such as proteins and polysaccharides can constitute a significant portion of dissolved organic carbon (DOC) in wastewater, but limited information is available on how these compounds are degraded in suspended and fixed-film biological wastewater treatment systems. Bacteria cannot assimilate intact macromolecules but must first hydrolyze them to monomers or small oligomers. Here, we summarize experiments performed in our laboratory which indicate that the enzymes responsible for hydrolysis are primarily those that remain attached to the cell. In biofilm cultures fed macromolecular substrates, for example, no more than 8% of total hydrolytic activity was found to be located m the cell-free bulk solution. These and other experiments support a generalized mechanism for macromolecule degradation by bioffims that features cell-associated hydrolysis, followed by the release of hydrolytic fragments back into bulk solution. The extent of fragment release is larger for proteins (bovine serum albumin) than for carbohydrates (dextrans).     

Capacity building for flood management systems: a conceptual model and case studies

How flood risks are affected by infrastructure and institutional arrangements differs among developed and developing countries. This paper compares flood management systems in Indonesia and Japan as they are affected by institutional, organizational and individual capacities. It uses a conceptual model and applies performance indicators to organize the measures of flood management effectiveness. The case studies show that institutional arrangements are essential for effective flood management, but their effectiveness depends on implementation capacity. While infrastructure may mitigate flood damage, its limitations must be recognized. Informed awareness of flood threats and management by the local community is critical.     

流域水生态承载力及其概念模型

通过对人类主导下的流域社会-经济-河湖复合生态系统基本特征的理论分析,在对水环境和水资源承载力等概念辨析的基础上,揭示了流域水生态承载力的"分区、分期、分级"属性以及"量、质、序"递进综合约束作用等基本内涵,并提出其广义和狭义的概念。在以二元水循环为驱动的"水资源-水环境-水生态-社会经济"互动机制基础上,建立了流域社会-经济-河湖复合生态系统概念模型和流域水生态承载力分区耦合概念模型,并以"人水和谐"思想为核心提出了水生态承载力承载度的综合评价基本思想,及其"分区、分期、强化耦合"的系统动力学模拟评价模型的实现思想。以太子河流域为例,进行了实例应用。     

The role of riparian woods in regulating nitrogen fluxes between the alluvial aquifer and surface water: A conceptual model

Conceptual models are proposed to explain nitrogen fluxes in the soils of riparian zones in relation to the different modalities of water logging and nitrate inputs. Non-submerged, temporarily submerged, and always submerged, sites are considered in both winter and summer. It is shown that capacities for epuration are elevated for nitrate loads from the alluvial aquifer during the lateral transfer of water from agricultural land to the river through the riparian zone. About 30 m of groundwater flow under the riparian wood studied is sufficient to remove all nitrate. Denitrification rates up to 50 mg N₂ per m² per day were observed in the field, but a potential for more denitrification exists. The efficiency of the riparian woods as natural filters regulating nutrient transfers to the river deserves more consideration in river management.     

Avoiding the water-poverty trap: insights from a conceptual human-water dynamical model for coastal Bangladesh

ABSTRACT

Water-related risks impact development opportunities and can trap communities in a downward spiral of economic decline. In this article, the dynamic relationship between water-related risks and economic outcomes for an embanked area in coastal Bangladesh is conceptualized. The interaction between flood events, salinity, deteriorating and poorly maintained water infrastructure, agricultural production and income is modelled. The model is used to test the effect of improvements in the reliability, operation and maintenance of the water infrastructure on agricultural incomes and assets. Results indicate that interventions can have non-marginal impacts on indicators of welfare, switching the system dynamic from a poverty trap into one of growth.     

Supplemental water releases for fisheries restoration in a Brazilian floodplain river: a conceptual model

Highly productive floodplain rivers in Brazil and elsewhere provide livelihood and recreational fishing for millions of people around the world, but damming and controlled water discharge are a threat to these valuable ecosystems. Supplemental water releases (SWRs) at a dam are increasingly used for restoring fisheries productivity in many floodplain rivers. We proposed a conceptual model for a hypothetical water release to enhance fisheries using Três Marias Reservoir (TMR) on the São Francisco River (SFR), Brazil. The information needed by the model follows: (i) Biologically, what is the best release date? (ii) How much water will be released? (iii) What is the pattern of impoundment and how much impounded water will be released? (iv) What is the lost revenue to the power plant associated with SWR? (v) What is the relationship between river discharge and the area of floodplain that is flooded? (vi) What is the relationship between SWR and fisheries value? Ichthyoplankton studies in the SFR showed a clear positive relationship between fish density and water level (WL). While the relationship between WL and floodplain area flooded and recruitment is not known, we concluded the best date for release is when there is a natural flood, which naturally triggers fish spawning and the SWR will add to the natural flood and cover a greater floodplain area. The released volume will range from 0.302 km³ to 2.192 km³, depending on SWR duration. In most years from 1976 to 2003, TMR impounded enough water for SWR only in the second half of the fish‐spawning season (January–March). Lost revenue at TMR depended on release volume and ranged from US$ 0.493 million to US$ 3.452 million for the actual power rate. However, SWR could increase commercial fisheries income an estimated US$ 4.468 million. We forecast that SWR can bring fisheries benefits that surpass the lost revenue. Published in 2007 by John Wiley & Sons, Ltd.     

Constructed wetlands for CSO treatment: an overview of practice and research in Germany.

Vertical flow treatment wetlands have been developed as very useful tools for treatment of combined sewage overflow. Several systems have been in operation for over 15 years. Based on recent research work, new technical guidelines now recommend systems with a drained filter of sand 0/2 mm and a throttled outflow. COD, NH4-N and SS removal rates of 85-99% can be expected from this type of filter. SS loadings that are too high and very long or frequent inundation affect the performance adversely. Information for successful long-term operation were derived from various existing plants.     

基于DPSIR概念模型的水资源系统脆弱性分析

从水资源复杂系统角度结合DPSIR概念模型,构建了水资源系统脆弱性评价指标体系。利用大样本数据、投影寻踪、粒子群算法、插值型曲线,建立了基于粒子群投影寻踪插值的水资源系统脆弱性评价模型。结合河北省南水北调受水区水资源系统的实例,从驱动力-压力-状态-影响-响应等5个方面计算分析了该系统的脆弱性。结果表明,以资源型缺水为主导的水资源基础条件薄弱已成为受水区水资源系统脆弱性的制约因素,且在未来很长一段时间内难以改变。     

Simulation of a subsurface vertical flow constructed wetland for CSO treatment.

Constructed wetlands (CWs) have proved to be a highly effective measure to reduce the ecological impact of combined sewer overflows (CSOs) on receiving waters. Due to the stochastic nature of the loading regime and the multitude of environmental influences, assessment of the performance of such plants requires detailed mathematical modelling. A multi-component reactive transport module (CW2D) was applied to simulate the flow, transport and degradation processes occurring in a CW for CSO treatment. CW2D was originally developed to simulate the treatment of municipal wastewater in subsurface flow CWs. Loading and operational conditions in CSO treatment differ fundamentally from the conditions occurring for wastewater treatment. Despite these differences, first results from the simulation of lab-scale experiments show, that the model is generally applicable to this type of plant. Modelling of adsorption, degradation processes, and influent fractionation, however, require further research.     

A conceptual market framework for water-bound nitrate pollution

The conversion of bottomland hardwood and swamp forests to irrigated agriculture has had problematic consequences for water bodies. Many of these problems can be linked to the use of synthetic nitrogen fertilizers to increase crop production. To date, there is little monitoring of nitrogen use in watersheds, which may be due to large fixed costs. Using market-based techniques which have addressed previous environmental challenges, with remotely sensed data to track a pollutant’s source, may be one alternative, by incentivizing nitrogen users to behave according to abatement costs traced back to the point of origin of a pollutant.     

核电厂水文地质概念模型与地下水监测井布设

为了做好核电厂附近地下水放射性监测,首先必须在分析厂址附近地形地貌、水文地质条件的基础上,初步确定厂址所在水文地质单元的边界条件和补、径、蓄、排关系,然后概化水文地质条件并建立水文地质概念模型,最后模糊判别地下水径流带,并以此指导厂址附近地下水找水方向和地下水放射性监测井位的布设。按上述思路,结合某核电厂址的水文地质条件,详述了水文地质概念模型的建立和地下水放射性监测井井位的布设原则及具体方案。     

概念性水文模型遗传算法多目标参数优选研究

简要介绍了概念性降水—径流模型的多目标参数优选方法,以新安江模型为例,从Pareto支配法（Pareto Domination Approach）原理出发讨论了四目标函数情形下Pareto最优参数空间（Pareto Optimal Set）的Pareto优先排序（Pareto Preference Ordering）求解策略。通过对汉江上游江口流域降水—径流的新安江模型的模拟检验,证明该方法能够为模型提供全局最优参数,好于传统的单目标参数优选结果。     

Assessment of CSO loads--based on UVIVIS-spectroscopy by means of different regression methods.

The use of UV/VIS-spectroscopy for water quality measurements is based on the solution of the correlation between the surrogate parameter absorbance and the resulting equivalence parameters. The coherence of absorbance and equivalence parameters (CODtot, CODsol, TSS) is solved in this paper with different regression methods. The correlation of absorbance and concentrations are analysed based on linear regression methods, model tree regressions, multivariate regression methods and support vector machines using sequential minimal optimisation algorithm. For this purpose the regression methods are calibrated on three 24hours measurement campaigns of a combined sewer measurement station situated in the combined sewer overflow chamber in Graz (Austria). The online measurement station has been conveying data for more than 2 1/2 years up to now. Finally, the load calculation based on the different regression methods and its comparison demonstrate that an apparently complex model does not inevitably lead to accurate concentration values due to possible model overfitting. Hence, the paper points out the possibilities and the drawbacks of spectroscopy measuring in sewers and the arising concentration values.     

河流排污权多目标优化分配模型研究

分析了目前排污权分配研究现状及存在问题,提出由河流环境保护部门确定河流总体排污权,依次向水功能区、排污者进行分配的两级分配模式,从生态环境保护和水资源可持续利用角度出发,以经济最优和水质最优为目标,以污染物浓度控制和总量控制为约束,同时考虑分配的公平性,排污者生产连续性等,建立河流排污权多目标优化分配模型。将此模型应用于举水河排污权分配并与不同方法之结果进行对比分析,证明本文提出的方法可给出的排序权总量较小,污染物综合处理费较少的方案,且水环境节余容量较多。     

基于纳污控制的流域初始排污权配置模式研究

面向纳污红线控制要求,结合我国流域纳污总量分解实践,以"纳污总量控制、兼顾公平和效益、尊重区域水环境容量差异、保障社会经济发展连续性"为配置原则,构建流域初始排污权多因素混合配置模式,并从配置模式的侧重点和功能角度,与现时经济活动量配置模式、非经济因子配置模式和排污绩效配置模式进行对比分析。以太湖流域为例研究结果表明:多因素混合配置模式集聚多种配置模式的优点,与水环境容量配置模式的配置方案比较接近,实现流域水环境纳污总量控制的有效分解,但适度提高了江苏省和上海市的COD、NH3—N和TP的初始排污权量,有利于促进经济的持续增长和社会公平。同时该配置模式操作简便,易于推广。     

Synthesis of a new conceptual model to facilitate management of ephemeral deflation basin lakes

Ephemeral deflation basin lakes are widespread throughout arid and semiarid regions of the Murray–Darling Basin in Australia. Although they are diverse, productive habitats, the water resources development has generally caused significant declines in their ecological condition. Managers are currently trying to protect or restore these systems, however, without an adequate theoretical framework on which to base management decisions. This is because the existing conceptual models provide little insight into the effects of any component of the flow regime except flooding. This paper reviews the effects of flooding and drying on lakes, using the information and conclusions therein to propose a conceptual model that identifies five stages in the flooding and drying cycle. This conceptual model incorporates elements of the Flood Pulse Concept, Trophic Cascade models and the Geomorphic–Trophic model, as they apply to these highly variable water systems.     

物理概念模型在水保效益评价中的应用

本文简述了文献［1］建立的具有物理过程基础的产流产沙概念模型及水土保持减水减沙效益计算方法，着重介绍了所建模型在水土保持减水减沙效益计算和水沙变化原因分析中的应用.计算及分析表明，模型法是可行的水土保持减水减沙效益评价方法，具有较好的应用前景。