The apparent losses due to metering errors: a proactive approach to predict losses and schedule maintenance

The effects of water meter age and private tanks on the apparent losses due to metering errors were evaluated by experimental and theoretical analyses. A monitoring campaign on a small district metered area (DMA) was carried out to determine the causes of apparent losses and implement a numerical model. Metering errors are affected by the flow rate passing through the meter, which is dependent on the network pressure and water level of the private tank. A node model that reproduces the effect of private tanks was coupled with EPANET and was applied to the DMA. The proposed modelling approach was used to identify where apparent losses are higher and to schedule maintenance. The model predicted the results of the installation of a device that minimises the effect of private tanks on apparent losses, the unmeasured flow reducer (UFR), the economic impact of losses and substitution programmes.     

A composite indicator for water meter replacement in an urban distribution network

In water supply management, volumetric water meter are typically used to measure users' consumption. With water meters, utilities can collect useful data for billing, assess the water balance of the system, and identify failures in the network, water theft and anomalous user behaviour. Despite their importance, these instruments are characterised by intrinsic errors that cause so-called apparent losses. The complexity of the physical phenomena associated with metering errors in aging water meters does not allow meter replacement to be guided by single parameters, such as the meter age or the total volume passed through the meter. This paper presents a meter replacement strategy based on a composite ‘Replacement Indicator’ (RI) that aims to reduce apparent losses. The performance of a meter during its operating life was analysed by means of this indicator, which signals when the meter needs to be replaced. To test the reliability and robustness of the proposed indicator, a Monte Carlo uncertainty analysis was performed. The methodology was applied to a real case study: a district metered area (DMA) in the Palermo city water distribution network (Italy). The analysis showed that ranking based on the composite indicator is better than common ranking procedures based on typical variables (e.g., the meter error curve or the meter age): the proposed indicator can better select the meters to be replaced and favourably affect the associated costs.     

供水企业产销差控制工作的策略与实践

产销差控制是国内外供水企业普遍重视的工作之一。以佛山市水业集团有限公司旗下A供水分公司2012年产销差控制的实践工作为例,对该公司产销差控制工作进行了总结与分析。分析表明,A公司产销差控制工作取得了一定成效,但仍存在一些问题需要进一步研究与探讨。     

Key control handles in integrated urban wastewater systems for improving receiving water quality

ABSTRACT

There is an increasing interest in modelling and control of integrated urban wastewater systems (UWS). Nevertheless, given the multiple interactions between the sub-systems – catchment, sewer system, wastewater treatment plant (WWTP) and receiving water system – the selection of effective control handles for improving receiving water quality is a major challenge. In this paper, a systematic study to identify the most important control handles in an UWS is presented. The Benchmark Simulation Model for Urban Wastewater Systems (BSM-UWS) is selected as a virtual case-study. Morris screening is used to perform global sensitivity analysis. Results indicate that, for the BSM-UWS layout, while river dissolved oxygen quality (T_exc,DO) is influenced by multiple control handles both in the sewer system and WWTP, river un-ionized ammonia quality (T_exc,NH3) is mainly influenced by WWTP control handles. The study highlights the need to perform simulations for at least 1 year when determining key control handles for UWS.     

A resilience assessment method for urban water systems

Infrastructure planning for Urban Water Systems (UWSs) is challenged by, inter alia, increasing uncertainty in both demand and availability of water and aging infrastructure, and this is already impacting the climate-proofing of cities. In this context, the idea of resilience has been gradually embraced by the water sector, but the term itself is not yet universally defined, nor operationalised. Here, we propose a methodology to assess the resilience of a UWS, defining it as the degree to which the UWS continues to perform under increasing stress. A resilience assessment method is then proposed as a ‘stress-test’ of UWS configurations, under increasingly more stressful scenarios. We then demonstrate a toolbox assembled for the proposed analysis using, as a proof of concept, a semi-synthetic case study. Results are promising, suggesting that the approach could assist in the uptake and evolution of resilience thinking in strategic water infrastructure decision making, leading to water-wiser cities.     

Assessment of the integrated urban water quality model complexity through identifiability analysis

Urban sources of water pollution have often been cited as the primary cause of poor water quality in receiving water bodies (RWB), and recently many studies have been conducted to investigate both continuous sources, such as wastewater-treatment plant (WWTP) effluents, and intermittent sources, such as combined sewer overflows (CSOs). An urban drainage system must be considered jointly, i.e., by means of an integrated approach. However, although the benefits of an integrated approach have been widely demonstrated, several aspects have prevented its wide application, such as the scarcity of field data for not only the input and output variables but also parameters that govern intermediate stages of the system, which are useful for robust calibration. These factors, along with the high complexity level of the currently adopted approaches, introduce uncertainties in the modelling process that are not always identifiable. In this study, the identifiability analysis was applied to a complex integrated catchment: the Nocella basin (Italy). This system is characterised by two main urban areas served by two WWTPs and has a small river as the RWB. The system was simulated by employing an integrated model developed in previous studies. The main goal of the study was to assess the right number of parameters that can be estimated on the basis of data-source availability. A preliminary sensitivity analysis was undertaken to reduce the model parameters to the most sensitive ones. Subsequently, the identifiability analysis was carried out by progressively considering new data sources and assessing the added value provided by each of them. In the process, several identifiability methods were compared and some new techniques were proposed for reducing subjectivity of the analysis. The study showed the potential of the identifiability analysis for selecting the most relevant parameters in the model, thus allowing for model simplification, and in assessing the impact of data sources for model reliability, thus guiding the analyst in the design of future monitoring campaigns. Further, the analysis showed some critical points in integrated urban drainage modelling, such as the interaction between water quality processes on the catchment and in the sewer, that can prevent the identifiability of some of the related parameters.     

Review of multi-criteria decision aid for integrated sustainability assessment of urban water systems

Integrated sustainability assessment is part of a new paradigm for urban water decision making. Multi-criteria decision aid (MCDA) is an integrative framework used in urban water sustainability assessment, which has a particular focus on utilising stakeholder participation. Here MCDA is reviewed in the context of urban water management used in a decision making framework. Three other commonly used integrated approaches in urban water management (cost-benefit analysis, triple bottom line and integrated assessment) are compared with MCDA. Generic types of shortcomings associated with MCDA are discussed to provide an understanding of MCDA's limitation in urban water management decision making; including 1) preferential independency, 2) double counting and under-counting, and 3) transparency of MCDA methods and results.     

Contaminant flows in urban residential water systems

A contaminant balance for urban residential water systems has been performed for 12 pollutants. The characteristics of the residential site were based on Ellenbrook, a suburb of Perth, Australia. The sources of contaminants were identified and characterised using published literature values. A water balance was used to estimated flow data, and these results were used in conjunction with the contaminant source characteristics to calculate contaminant loads. The contaminants examined were total nitrogen, ammonia, total phosphorus, copper, zinc, lead, cadmium, suspended solids, dissolved solids, chemical oxygen demand, polycyclic aromatic hydrocarbons and oil and grease. Diagrams of contaminant flows through the water, wastewater and stormwater systems are presented. By identifying the sources of contaminants, the diagrams are a useful reference when considering the fate of contaminants in alternative urban water system configurations or how to better handle or reduce these contaminants.     

Estimation of the benefits yielded by pressure management in water distribution systems

The occurrence of water losses in Water Distribution Systems is inevitable. Knowing that most of the real losses take place in distribution mains and in service connections, the methodology proposed in this paper is based on several leakage-assessment approaches from literature and on water distribution network modeling. This allows assessment of the benefits that can be achieved by pressure management in Water Distribution Systems, particularly in terms of water production reduction. Moreover, this approach can be useful for cost benefit analysis to help establish the level after which there is no more economic interest in reducing water losses (Economic Level of Leakage). Finally, the results from hypothetical case studies are presented and discussed, assuming the installation of Pressure Reducing Valves at District Metered Areas entry points.     

基于GIS和BP神经网络的洪灾损失评估模型的研究

本文在分析已有洪灾损失评估模型的基础上,构建了一种基于GIS和BP神经网络的洪灾损失评估模型,包括选取洪水致灾、地形条件、防洪能力、社会经济等因子;然后以鄱阳湖区为例进行了洪灾损失评估系统应用。结果表明建立的基于GIS和BP神经网络的洪灾损失评估模型具有较好的可行性和实用性。     

Assessment of treatment options of recycling urban stormwater recycling via aquifers to produce drinking water quality

With the release of the Australian Guidelines for Water Recycling: Managed Aquifer Recharge (MAR), aquifers are now being considered as a treatment barrier when assessing the human health risk of recycled water systems. An MAR research site recharging urban stormwater in a confined aquifer was used in conjunction with a quantitative microbial risk assessment to assess the microbial pathogen risk in the recovered water for drinking. The assessment involved undertaking a detailed assessment of the treatment steps and exposure controls, including the aquifer, to achieve the microbial health-based targets.     

可持续发展的城市交通系统评价指标体系

介绍了城市交通可持续发展的评价内容、过程及目标，并在此基础上建立了城市交通可持续发展系统的指标体系，以期为该体系的健全起到一定的作用。     

Quality performance gaps and minimal electricity losses in East Africa

The electricity sector in East Africa is characterized by high levels of electricity losses. The literature has extensively focused on investments and policy reforms that can potentially reduce losses. In this paper, we follow another approach by nonparametrically estimating the minimal losses given the actual inputs, outputs and electricity generation process. Minimal losses are then compared to actual losses to construct quality performance indicators. Using a tailored database for six East African countries over 10 years, we show that electricity losses could be reduced by 8%, representing savings of approximately $60 million per year.     

混凝土坍落度损失的原因分析及解决方法

从水泥成分、环境条件、混凝土外加剂等多方面分析了混凝土坍落度损失的原因，提出了相应的解决方法。     

Valuing flexibilities in the design of urban water management systems

Climate change and rapid urbanization requires decision-makers to develop a long-term forward assessment on sustainable urban water management projects. This is further complicated by the difficulties of assessing sustainable designs and various design scenarios from an economic standpoint. A conventional valuation approach for urban water management projects, like Discounted Cash Flow (DCF) analysis, fails to incorporate uncertainties, such as amount of rainfall, unit cost of water, and other uncertainties associated with future changes in technological domains. Such approach also fails to include the value of flexibility, which enables managers to adapt and reconfigure systems over time as uncertainty unfolds.     

富水黄土隧道坍体处理

结合具体工程实例,分析了富水黄土隧道坍体的情况及原因,介绍了该土家湾隧道坍体的处理方案及措施,重点就坍体施工开挖与衬砌进行了探讨,积累了富水土质坍体的处理经验。     

引气剂与消泡剂对混凝土表观质量的影响

通过试验和图像分析方法,研究不同引气剂种类与掺量、不同消泡剂掺量的聚羧酸减水剂复配过程对新拌混凝土和易性、含气量及硬化后表观质量的影响.合适比例的引气剂与消泡剂的减水剂复配有利于改善新拌混凝土的和易性和表观质量.结果表明,0.2％的ZY-EA1型引气剂与0.6‰的消泡剂在本试验条件下所得混凝土新拌状态与表观质量最优.     

光氧老化对沥青表观粘度的影响

介绍了沥青的光氧老化机理,研究了四种沥青室内、外光氧老化后表观粘度的变化,以表观粘度为参数建立了沥青一级光氧老化动力学模型,并用该动力学模型对这四种沥青的抗光氧老化性能进行了研究,求得了动力学参数。     

青岛市水资源承载力预测评价研究

水资源承载力的评价对发展地区经济具有重要意义,因此水资源的可持续利用理应受到人们的关注.通过对比水资源承载力的各评价方法,建立了综合评价模型,确立了评价的指标体系,利用均方差决策综合分析方法计算了评价指标的权重.最后,对青岛市水资源承载力按照不同时间段进行了预测评价分析,并根据当地实际,提出了提高当地水资源承载力的对策.     

机械加工精度对小功率电机机械耗的影响

阐述了机械加工精度对电机机械耗的影响 ,并从理论和试验两方面进行了分析 ,提出了在小功率电机的生产过程中 ,对电机的尺寸公差和形位公差一定要控制到位