Rapid detection of sewer defects and blockages using acoustic-based instrumentation

Sewer flooding incidents in the UK are being increasingly associated with the presence of blockages. Blockages are difficult to deal with as although there are locations where they are more likely to occur, they do occur intermittently. In order to manage sewer blockage pro-actively sewer managers need to be able to identify the location of blockages promptly. Traditional closed-circuit television (CCTV) inspection technologies are slow and relatively expensive so are not well suited to the rapid inspection of a network. This is needed if managers are to be able to address sewer blockages proactively. This paper reports on the development of an acoustic-based sensor. The sensor was tested in a full scale sewer pipe in the laboratory and it was shown that it is able to find blockages and identify structural aspects of a sewer pipe such as a manhole and lateral connection. Analysis of the received signal will locate a blockage and also provide information on its character. The measurement is very rapid and objective and so inspections can be carried out at much faster rates than using existing CCTV technologies.     

矩形断面压力管道汇流口局部能量损失

采用水动力学基本理论,对矩形断面有压管道汇流口的水力特性进行分析研究,提出收缩系数及局部能量损失系数的综合表达式,并与试验结果进行了比较。研究结果表明:正确描述管道汇流口水流特性,必须考虑主管和支管的面积、流量的相对大小和交汇角的影响;局部能量损失随流量比增大而增大,随面积比增大而减小,随交汇角增大而增大。     

Long term monitoring of sewer sediment accumulation and flushing experiments in a man-entry sewer.

This paper presents continuous field experiments carried out during 4 years in a man-entry egg-shaped combined sewer in Lyon, France in order to contribute to the knowledge and the modelling of sediment accumulation and sediment removal by means of a Hydrass flushing gate. The 250 microm sediments are mainly mineral, and their physical and chemical characteristics appear as rather stable in time and space. Long-term sediment monitoring reveals: (i) a regular asymptotic increase of both the sediment mass and the slope of its longitudinal profile, (ii) a clear correlation between local sediment profile irregularities and sewer ancillaries but without significant influence on the global and long term accumulation. Simple sediment accumulation modelling shows: (i) a good suitability of a three parameters conceptual model to reproduce asymptotic sediment volume accumulation, and (ii) a good suitability of the Velikanov model to reproduce sediment profiles. Both models reproduce observations with an acceptable margin of uncertainty for operational management purposes but are very sensitive to input data and parameter values. The Hydrass flushing gate is efficient and it appeared that the mass of sediments moves downstream linearly with the number of flushes.     

用环形断面管流模拟多年生植物的人工湿地的水头损失

此项研究对填有石质介质和生长植物根系的两个水槽进行了连续4年的露天水流和孔隙率实验研究。石质介质分别为大颗粒的卵石和小颗粒豆粒砾石。为了更准确计算成熟人工湿地渗流的水头损失,利用环形断面管流的假设来改进欧根（Ergun）方程紊流项,再对人工湿地的石质介质和植物根系的水流水头损失进行模拟。研究结果表明：不考虑植物根系影响,只考虑孔隙率变化,Ergun方程的计算结果明显低于实测结果。改进后的欧根方程（M—E—p1）的计算结果可以较为准确预测水槽中石质介质的水头损失。其中豆粒砾石介质的预测结果较为理想,卵石介质的模拟结果略低于实验结果。     

高水头扬水工程岔管应力分析

针对克拉玛依市绿化扬水工程压力水头高、贴边岔管主管与支管垂直且连接处产生应力集中问题,通过有限元对贴边岔管进行应力计算分析。计算结果表明：1^#贴边岔管通过增加管壁厚度而不施加补强板的方式可满足应力要求,采用Q345C钢材,管壁厚为18 mm;2^#、3^#贴边岔管均可通过单层外贴补强板方式满足应力要求,采用Q390C钢材,主管、支管及补强板厚度28 mm,补强板宽度500 mm。分析结果证明：各贴边岔管单元开孔越大,则主管缺失部分越多,导致主、支管补强板夹角处的应力集中也越大。同时,补强板焊缝处应力也较大而管壁应力较小,通过提高焊缝施工质量,尽量避免产生局部过大拉应力。计算分析结果可为供水工程的安全运行提供参考。为了节省工程投资,可考虑相应主管与其支管建立整体有限元模型联合受力计算,进一步优化贴边岔管结构和布置形式。      

The acoustic attenuation and hydraulic roughness in a large section sewer pipe with periodical obstacles.

The acoustic attenuation, relative sound pressure levels and the equivalent Nikuradse wall roughness under variable flow conditions in a 600 mm concrete sewer pipe are experimentally investigated. The values of the acoustic attenuation are obtained in the case of airborne sound propagation in the dry pipe. A range of values of the equivalent wall roughness is artificially generated by deploying a periodical array of engineering bricks. A novel method of rapid evaluation of the acoustic attenuation is proposed. The method relies upon sound reflections from the adjacent manholes. The results demonstrate that the acoustic attenuation depends strongly on the value of the equivalent wall roughness. This work can pave the way to the efficient methodology for the in-situ, physical evaluation of the equivalent hydraulic roughness of new and existing sewer networks.     

Attenuation of an ultrasonic beam by suspended particles and range of acoustic flow meters in sewer networks

Ultrasonic flow meters are commonly used in wastewater management. Under certain circumstances, a reduction in the flow meter range may occur and cause significant error in the flow rate measurement. Attenuation due to suspended particles is one of the phenomena capable of reducing the flow meter range. The present paper examines attenuation resulting from re-suspended pond sediment over a wide range of concentration values. It appears that a formula established for sand suspensions provides a good estimate of ultrasound attenuation for these types of particles as well. Experiments conducted for wastewater under particle concentrations commonly encountered in sewer networks demonstrate that the attenuation by particles only contributes to a negligible extent towards intensity decay, in accordance with theoretical predictions. We also theoretically determine herein the operating conditions under which the range of an ultrasonic flow meter would be significantly reduced due to particle attenuation.     

瞬变流动中液体管道摩阻损失计算方法综述

综述基于拟恒定假设基础上瞬变流控制方程摩阻积分项的近似处理方法,指出传统的拟恒定摩阻模型不能十分准确地描述瞬变流动过程的真实物理现象。总结国外非恒定摩阻的计算模型及各种模型的计算思路与适用范围,指出非恒定摩阻模型的研究方向,期望结合特征线理论使液体管道水击计算更接近实际;提出了不考虑流动过程,应用测量数据辨识校正摩阻系数的新方法。     

三峡工程库首区地震监测

三峡工程库首区地震监测至今已有46年,在世界水电史上也是罕见的。46年的地震监测资料综合分析表明,蓄水前库首区是一个典型的低频度、强度小的弱震区,其震中在空间上主要分布于秭归盆地的东西两侧,其成因大部分属于天然构造地震。蓄水后,地震活动频度大幅增加,强度保持在蓄水前的本底水平,最大地震仅为ML2．4级。地震活动的空间分布与水库蓄水前相比,有较大的变化,其地震活动主要分布于巴东牛口至巫山培石库段。     

管路突然扩大时局部水头损失的数值模拟

选取了Spalart-Allmaras湍流模型,对Re＜5500时管路中突然扩大的局部水头损失进行了数值模拟.计算结果表明:模拟得到的测压管水头与试验值吻合较好,用断面平均速度计算速度水头时,若取动能修正系数为1.0,则会使局部水头损失的计算值较实际值偏小,速度水头计算方法的影响远大于突然扩大管路的沿程损失对局部水头损失系数的影响.     

Continuous monitoring in sewer networks an approach for quantification of pollution loads from CSOs into surface water bodies.

Different approaches for quantification of pollution loads discharged from combined sewer networks into surface water bodies have been observed over the last few years and decades, but a large number of unresolved problems still remain. Many monitoring campaigns have been based on manual or automated spot sampling - with the long known limitations of this method such as sampling errors and errors due to sample conservation, transport and preparation. On the other hand, only recently have sensors became available which are suitable for continuous application in sewer networks. A large number of practical problems still have to be solved before continuous monitoring in sewer networks will be successful. Additionally, most of the applicable sensors are based on surrogate methods which results in a considerable effort for reference measurements for sensor calibration. Finally, it has to be considered that, depending on the sewer network topography, deposition and remobilisation of pollutants varies considerably, which limits the generality of monitoring results and, subsequently, their applicability as a base for the design of storm water tanks or combined sewer overflows (CSO). A monitoring station for continuous monitoring of load discharges from a CSO has been installed and operated for more than one year. The design and equipment of the measurement station, operational experiences and results are given in this paper.     

施工监控量测在居甫渡水电站引水隧洞的应用

隧洞施工工艺选择不当,易造成围岩失稳甚至大塌方,给工程带来不可弥补的经济和时间损失。因此,监控量测是隧洞没计和施工中所必须的,对保证工程质量．施工安全具有重要作用。云南居甫渡水电站引水隧洞现场监控量测的断面佰置、数据采集,对节测数据的处理、分析及应用,可供其他类似工程参考。     

Evaluation of sewer infiltration/inflow using COD mass flux method: case study in Prague

The combined sewer system of the City of Prague, similar to other relevant locations, is strongly affected by infiltrating waters. The knowledge of their volume is one of the important parameters with respect to sewer system operation, maintenance and reconstruction. The methodology is based on the variation of diurnal chemical oxygen demand (COD) load and continuous water quality monitoring using in-line absorption spectrometry. This approach allows the identification of individual components of the diurnal wastewater hydrograph, in particular the contribution of parasitic water flow to wastewater discharge. The statistical relevance was tested using Monte Carlo simulations on a 7-year data series of flow rate. The results show that application of this methodology provides specific relevant information about individual sub-catchments within an entire sewer system, particularly in terms of absolute and relative values of I/I and structural state indicators. Processing of long-term data series gives clear information about the significance of the monitoring period length for the relevance of obtained results.     

Increased biogas production in a wastewater treatment plant by anaerobic co-digestion of fruit and vegetable waste and sewer sludge - a full scale study

Anaerobic digestion is a well established technology for the reduction of organic matter and stabilization of wastewater. Biogas, a mixture of methane and carbon dioxide, is produced as a useful by-product of the process. Current solid waste management at the city of Prince George is focused on disposal of waste and not on energy recovery. Co-digestion of fresh fruit and vegetable waste with sewer sludge can improve biogas yield by increasing the load of biodegradable material. A six week full-scale project co-digesting almost 15,000 kg of supermarket waste was completed. Average daily biogas production was found to be significantly higher than in previous years. Digester operation remained stable over the course of the study as indicated by the consistently low volatile acids-to-alkalinity ratio. Undigested organic material was visible in centrifuged sludge suggesting that the waste should have been added to the primary digester to prevent short circuiting and to increase the hydraulic retention time of the freshly added waste.     

GIS在水土流失监测预报中的应用

本文介绍了GIS技术的应用，结合影响水土流失的各种因素，利用GIS对空产数据处理和分析的特殊功能，实现水土流失监测预报系统数据与图形的有机结合，提高了水土流失监测预报的科学性，为减少水土流失提供可靠的信息资源。     

细沟作为坡面水土流失红线监测标志可行性探讨

水土流失红线为计入水土流失面积的土壤流失量控制线,容许土壤流失量是水土流失红线特征值,但缺乏水土流失红线监测的指示标志。解决水土流失监测对象问题是水土流失红线研究的首要任务。细沟是水力侵蚀作用下在坡面上产生的一种小沟槽地形,细沟形成是坡面水土流失由轻微转向强烈的最明显标志。根据细沟形态特征、侵蚀特点和发育条件,论证了细沟作为坡面水土流失红线监测标志的可行性,即细沟不仅具备坡面水土流失监测对象的条件,还可作为坡面容许土壤流失量判别的标志,而且可作为坡面水土流失治理效果评估的重要指标,更是坡面水系工程布局的依据。     

In situ measurements of shear stresses of a flushing wave in a circular sewer using ultrasound.

Deposits build up in sewer networks during both spells of dry weather and in connection with storm water events. In order to reduce the negative effects of deposit on the environment, different cleaning technologies and strategies are applied to remove the deposits. Jet cleaning represents the most widely used method to clean sewers. Another alternative cleaning procedure is flushing. On account of new developments in measurement and control panels, the flushing method is becoming more important. Therefore, in the last few years a number of new flushing devices have been constructed for application in basins, main sewers and initial reaches. Today, automatic flushing gates are able to accomplish cleaning procedures under economical and ecological conditions.The properties of flushing waves for cleaning sewers have been determined by several mathematical-numerical studies. These various investigations use altering numerical schemes, are based on different sets of physical equations and take one- or more dimensional aspects into account. Considering that bottom shear stress is the key value to evaluate the beginning of motion of any deposit, one may use this value that has to be determined by measurements. This paper deals with shear stresses caused by flushing waves which have been measured by an ultrasonic device that can determine the velocity in different depths of flow. Thus, it is possible, within certain limits, to calculate bottom shear stresses based on the log-wall law. Further discussion will deal with the requirements of measurements, its uncertainty and aspects in respect to the application of simulation of flushing waves.     

Towards full predictions of temperature dynamics in McNary Dam forebay using OpenFOAM

Hydroelectric facilities impact water temperature; low velocities in a reservoir increase residence time and enhance heat exchange in surface layers. In this study, an unsteady three-dimensional model was developed to predict the temperature dynamics in the McNary Dam forebay. The model is based on the open-source code OpenFOAM. RANS equations with the Boussinesq approximation were used to solve the flow field. A realizable κ-ε model that accounts for the production of wind turbulence was developed. Solar radiation and convective heat transfer at the free surface were included. The result of the model was compared with the field data collected on August 18, 2004. Changes in diurnal stratification were adequately predicted by the model. Observed vertical and lateral temperature distributions were accurately captured. Results indicate that the model can be used as a numerical tool to assess structural and operational alternatives to reduce the forebay temperature.     

高水头长压力管道抽水蓄能电站水力过渡过程计算分析

由于水泵水轮机转轮特殊的水力特性,抽水蓄能电站水力过渡过程较复杂,对水道系统的安全运行影响较大,需要专门对其水力过渡过程进行分析.根据某高水头长压力管道抽水蓄能电站水泵水轮机的转轮四象限特性曲线及输水系统布置,对电站输水发电系统的水力过渡过程进行计算机仿真模拟和分析.结果表明,该抽水蓄能电站水力过渡过程中大波动的各项指...