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.     

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.     

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.     

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。     

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.     

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.     

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。     

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.     

Experience in using the acoustic emission method when constructing hydraulic tunnels

Conclusions  1. The curve of AE intensity in a hole with observance of certain recording conditions adequately reflects the structure and stage of regions being deformed in the vicinity of workings. 2. Both recording parameters and geometric characteristics of the section of observations (form of the contour of the working, presence of interfaces, etc.) affect the value of the recorded AE intensity. 3. The results of using the AE method at the site of the Zhinvala hydrostation and Dnestr pumped-storage station showed its high effectiveness for determining the structure and state of the rock mass as part of the set of static and dynamic methods of investigation. Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 1, pp. 17–19, January, 1998.     

贵州山区输水管道局部水头损失计算方法探讨

针对贵州高原山地地区地形条件较复杂,管线走向蜿蜒曲折、起伏较大,按沿程水头损失的5%～10%进行局部损失计算,容易出现富裕水头较小、输水建筑物布置不满足要求等问题。以塘坎上水库输水管道水头损失计算为例,结合长距离输水典型工程水力分析成果进行论证分析。结果表明:地形条件复杂、管线拐弯点多且角度大的输水工程,管道局部水头损失占沿程水头损失的比例远大于10%。实践设计时,应结合工程布置和建筑物结构,选择科学方法进行分析,确保计算结果更贴近实际,为工程顺利施工建设和功能效益发挥提供重要技术支撑。     

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...     

Flow regime and head loss in a drip emitter equipped with a labyrinth channel

Labyrinth channels are widely adopted in emitter designs to regulate the water flow.The flow regime and the head loss of labyrinth channels have significant impacts on the hydraulic performance of emitters.In this study,the flow behavior of water passing through an emitter channel is observed using the micro particle image velocimetry(PIV),and the head loss during the flow is analyzed for an emitter with a triangular labyrinth channel.The results show that the flow regime is consistent with the classical theory of hydraulics governing straight channels,even when the cross-sectional area is very small(as small as 0.5 mm×0.5 mm).The critical Reynolds number from laminar to turbulent flows in a labyrinth channel is approximately in a range between 43 and 94.The local head loss factor decreases as the Reynolds number increases for labyrinth channels with smaller cross-sectional areas,such as 0.5 mm×0.5 mm and 1.0 mm×1.0 mm.The local head loss factor is not related to the Reynolds number and is only a function of the boundary conditions of the labyrinth channel when the Reynolds number exceeds approximately 1 000(for cross-sectional areas of 1.5 mm×1.5 mm and 2.0 mm×2.0 mm).The ratio of the local head loss to the total head loss total( /)j fh h first increases and then remains nearly constant as the Reynolds number increases in the labyrinth channel.The head loss in the labyrinth channel is almost equal to the local head loss,and total( h_j/h_(ftctal))is approximately 0.95 for cross-sectional areas of greater than 1.0 mm×1.0 mm.These results can be used for optimizing the design of emitter channels.     

管流与明渠层流的总流机械能方程及机械能损失计算

管流与明渠流同属流体力学中的内流,其总流机械能方程在水力学中称为总流能量方程。现有水力学中的总流能量方程是以理想不可压缩液体的伯努利方程为基础得到的,无法得到总流机械能损失的表达式。该文作者曾直接从黏性不可压缩流体运动的控制方程出发分别得到了管流及明渠流的总流机械能方程,解决了以上问题。考虑到层流条件下明渠流自由表面的变形特点,该文在前述工作基础上,将管流及明渠流在层流条件下的总流机械能方程进行了统一,同时还分别计算了管流(圆管、不同长短半轴比的椭圆管、不同宽高比的矩形管和不同内外径比圆环管)及明渠流(不同宽深比的矩形明渠)在层流条件下的总流机械能损失系数。结果表明:在同一雷诺数条件下,圆管层流的总流机械能损失系数比椭圆管层流、矩形管层流、圆环管层流及较大宽深比的矩形明渠层流的机械能损失系数要小。     

高层商住楼初期灭火流量水头损失探讨

通过计算高层商住两用楼高位消防水箱在火灾初期供应消防流量时产生的水头损失,分析了为扑救初期火灾消防给水系统需要的压力,探讨了高位水箱设置高度与增压设施设置的科学性与必要性。得出普通高层商住楼高位消防水箱安装高度利用屋顶机房等架空可以不需要设置增压设施,高级高层商住楼则需要设置自动喷水灭火系统增压设施,以满足火灾初期流量与喷头工作压力的要求。最后结合工程实践,检验了建议的可行性。     

Cs-137在浙江省水土流失背景值监测中的应用

Cs-137系全球分布的一种人工放射性核素,自大气沉降至地表后立即被土壤胶体颗粒强烈吸附,并主要是伴随着土壤颗粒的机械运动而迁移,根据Cs-137在土壤剖面中的分布规律便可判断采样点是受侵蚀还是沉积。水土流失背景值的测定是开发建设项目水土保持工作中的重要内容,水土流失预测是编制开发建设项目水土保持方案中的重要依据,也是水土保持监测中的一项重要内容。以宁波市周公宅水库水土保持监测为例,探讨Cs-137在开发建设项目水土流失背景值监测中的应用。