Constrained Ant Colony Optimisation Algorithm for the layout and size optimisation of sanitary sewer networks

The incremental solution building capability of Ant Colony Optimisation Algorithm (ACOA) is used in this paper for the efficient layout and pipe size optimisation of sanitary sewer network. Layout and pipe size optimisation of sanitary sewer networks requires optimal determination of pipe locations, pipe diameters and pipe slopes leading to a highly constrained mixed-integer nonlinear programming (MINLP) problem presenting a challenge even to the modern heuristic search methods. A constrained version of ACOA equipped with a Tree Growing Algorithm (TGA) is proposed in this paper for the simultaneous layout and pipe size determination of sewer networks. The method is based on the assumption that a base layout including all possible links of the network is available. The TGA algorithm is used in an incremental manner to construct feasible tree-like layouts out of the base layout, while the constrained ACOA is used to optimally determine the cover depths of the constructed layout. Proposed formulation is used to solve three hypothetical test examples of different scales and the results are presented and compared with those produced by a conventional application of ACOA in which an ad-hoc engineering concept is used for layout determination. The results indicate the effectiveness and efficiency of the proposed method to optimally solve the problem of layout and size determination of sewer networks.     

Automated detection of sewer pipe defects in closed-circuit television images using deep learning techniques

Sanitary sewer systems are designed to collect and transport sanitary wastewater and stormwater. Pipe inspection is important in identifying both the type and location of pipe defects to maintain the normal sewer operations. Closed-circuit television (CCTV) has been commonly utilized for sewer pipe inspection. Currently, interpretation of the CCTV images is mostly conducted manually to identify the defect type and location, which is time-consuming, labor-intensive and inaccurate. Conventional computer vision techniques are explored for automated interpretation of CCTV images, but such process requires large amount of image pre-processing and the design of complex feature extractor for certain cases. In this study, an automated approach is developed for detecting sewer pipe defects based on a deep learning technique namely faster region-based convolutional neural network (faster R-CNN). The detection model is trained using 3000 images collected from CCTV inspection videos of sewer pipes. After training, the model is evaluated in terms of detection accuracy and computation cost using mean average precision (mAP), missing rate, detection speed and training time. The proposed approach is demonstrated to be applicable for detecting sewer pipe defects accurately with high accuracy and fast speed. In addition, a new model is constructed and several hyper-parameters are adjusted to study the influential factors of the proposed approach. The experiment results demonstrate that dataset size, initialization network type and training mode, and network hyper-parameters have influence on model performance. Specifically, the increase of dataset size and convolutional layers can improve the model accuracy. The adjustment of hyper-parameters such as filter dimensions or stride values contributes to higher detection accuracy, achieving an mAP of 83%. The study lays the foundation for applying deep learning techniques in sewer pipe defect detection as well as addressing similar issues for construction and facility management.     

试述山区城市污水管网系统的设计

结合编制某新城污水管网系统的初步设计,分析和研究了山区城市排水管网系统设计需要注意的几个问题,主要包括排水体制的选择、设计原则、系统管网布置、泵站设置、压力管道及重力自排管道的设计;重点阐述在管网布置时,应考虑地形及地质情况,优选重力流排水以节能,并且要兼顾考虑泵站的设置数量及管网建设的经济合理性;提出了确保管道稳定安全的防治措施。     

Prediction models for sewer infrastructure utilizing rule-based simulation

Management of infrastructure projects is becoming increasingly challenging due to inherent uncertainties. The most effeective way to deal with uncertainty is to collect supplementary information and knowledge. When expensive or infeasible, quantification of uncertainty may be performed using analytical or simulation techniques. The City of Edmonton, Canada has approximately 4600 km of sewer pipes in the combined, sanitary, and storm sewer local systems with uncertainty issues related to deterioration. The City has taken a proactive approach with respect to sewer rehabilitation, as it is more cost-effeective to repair a defective pipe prior to failure rather than after a collapse. This article demonstrates an approach for predicting the condition of a sewer pipe and the related cost of rehabilitation, given the limited data. Three models are described in this article that are developed to assist the City of Edmonton to effeectively plan maintenance expenditure. Each model uses a combination of rule-based simulation and probability analysis to assist in the planning of future expenditures for sewer maintenance, thereby producing an invaluable planning tool.     

Segmentation of Pipe Images for Crack Detection in Buried Sewers

Abstract:   Assessing the condition of underground pipelines such as water lines, sewer pipes, and telecommunication conduits in an automated and reliable manner is vital to the safety and maintenance of buried public infrastructure. To fully automate condition assessment, it is necessary to develop robust data analysis and interpretation systems for defects in buried pipes. This article presents the development of an automated data analysis system for detecting defects in sanitary sewer pipelines. We propose a three-step method to identify and extract cracks from contrast enhanced pipe images. This method is based on mathematical morphology and curvature evaluation that detects crack-like patterns in a noisy pipe camera scanned image. As cracks are the most common defects in pipes and are indicative of the residual structural strength of the pipe, they are the focus of this study. This article discusses its implementation on 225 pipe images taken from different cities in North America and shows that the system performs very well under a variety of pipe conditions.     

无锡市芦村污水处理厂进厂第四干管设计优化

介绍了无锡市芦村污水处理厂长为20.02 km的进厂第四干管的工程设计优化情况。在设计中充分考虑了系统布局的优化、与现状干管系统的匹配、管材的合理选用、管道与河道相交的做法并运用多种施工技术。在国内首次大规模将物联网技术应用于管网系统中,对同类型污水收集系统工程建设具有一定的借鉴作用。     

污水管网的优化设计

对于污水管网的优化设计,采用了图论中树形结构的理论来描述污水管网,提出用三叉树的形式来处理污水管网的网络结构,把管段当作树的节点作为研究对象;利用树的遍历中的后序法(即节点递归算法)进行水力计算,在优化计算时采取了枚举标准管径法来选取管径,可以提高运算速度;在优化程序中寻求造价最低、最优的同时考虑了管道费用和泵站费用.采用Delphi语言编制了污水管网优化程序,并且用天津某一小区的污水管网对此程序进行了实例考核.其优化设计思路可推广到雨水管道.     

Improved understanding of combined sewer systems using the Illinois Conveyance Analysis Program (ICAP)

Understanding the conveyance of sewer networks is vital, especially in cases of great variability in flow rates, such as in combined sanitary and storm sewer systems. Conventional conveyance studies in sewer systems often have extended computation times due to complexity of the solution, or alternatively make assumptions that ignore the water-surface profile within a pipe. In previous research, the hydraulic performance graph (HPG) was successfully used for open-channel capacity determination. The HPG summarizes the results of many backwater calculations for a reach so that these calculations do not need to be repeated. This article describes algorithms utilized by the Illinois Conveyance Analysis Program that uses the HPGs to describe the conveyance of a system, identify bottlenecks for varying conditions, conserve mass by tracking outflow and overflows under stepwise steady flow conditions. The software is freely available at https://github.com/obergshavefun/icap/wiki.     

Evaluation of uncertainties in sewer condition assessment

Closed Circuit Television Inspection is used since decades as industry standard for sewer system inspection and structural performance evaluation. In current practice, inspection data are helpful to support asset management decisions. However, the quality and uncertainty of sewer condition assessment is rarely questioned. This article presents a methodology to determine the probability to underestimate, overestimate or accurately estimate the real condition of a pipe using visual inspection. The approach is based on the analysis of double inspections of the same sewer pipes and has been tested using the extensive data-set of the city of Braunschweig in Germany. Results indicate that the probability to inspect correctly a pipe in poor condition is close to 80%. The probability to overestimate the condition of a pipe in bad condition (false negative) is 20% whereas the probability to underestimate the condition of a pipe in good condition (false positive) is 15%. Finally, sewer condition evaluation can be used to assess the general condition of the network with an excellent accuracy probably because the respective effects of false positive and false negative are buffered.     

Reliability-based layout design of sewage collection systems in flat areas

The sewer layout in flat areas significantly influences the final design which is desired to be optimized for the construction and operational costs. This study introduces a model for designing the layout of sewer networks considering their reliability. A reliability criterion is introduced and optimized using a simple simulated annealing scheme. The best layout with the maximum reliability represents an optimum sewer layout in which clogging in a sewer has the least effect on its upstream lines. A case study is solved using the proposed model. Then, for the obtained layout, the sewer specifications are designed using a dynamic programming model. The reliability somehow reflects the operational costs that can be taken into account in the system design by the proposed model. Furthermore, it is concluded that the network's reliability and construction cost are in conflict with each other such that more reliable layouts lead to more expensive designs.     

HDPE双壁缠绕管的定向钻牵引施工

广州市大坦沙污水处理厂(三期)新市涌至2号泵站管道工程(重力截污管道)有740m长的管道需敷设在广佛高速公路旁边，加之正上方有一条与之同线埋设的中国电信管线，因而采用了定向钻牵引法施工。结合该工程详细介绍了HDPE双壁缠绕管的牵引法施工要点。实践表明，该法施工进度快，并避免了对高速公路路面的破坏，取得了良好的社会效益和经济效益。     

大比降高速水流排水管水力计算

大比降排水管水流通常为高速水流,其水力设计已经超过排水设计规范范畴。以实际工程为例,指出该类管道不宜按照有压管路或明渠均匀流计算公式进行水力计算,应按照掺气水流计算,这为实际工程设计提供了参考依据。     

Source apportionment of pollutants and flows of combined sewer wastewater

To reduce the combined sewer overflows (CSOs) and improve surface water quality in the Greater Milwaukee area, construction of a 19.5-mile (31.4 km) inline storage system (ISS) was completed in 1994 to capture and convey sanitary sewage and stormwater for treatment. However, one to six overflows per year still occur. Chemical mass balance (CMB) and positive matrix factorization (PMF) modeling was done in order to find origins of flows and pollutants in CSOs. Based on overflow events from 2000 to 2006 (CMB) and 2004 to 2006 (PMF), we found that between 27% and 56% of the total overflow is from sanitary sewage and most of the remaining from stormwater with possible minor contribution (< or = 8%) from groundwater. Most total suspended solids and metals (Cd, Cr, Cu, Pb, Ni, Hg, and Zn) are from stormwater, while sanitary sewage carries large contributions (> or = 28%) of BOD5, NH3, and total phosphorus. The fraction of NH3 is especially high, i.e., > or = 58%. Implications for a possible future sewer separation in combined sewer areas into separate sanitary and storm sewers are discussed.     

A Fuzzy Expert System for Prioritizing Rehabilitation of Sewer Networks

Abstract: Rehabilitation of sewer networks is a huge and very costly global problem that has often been treated on a crisis‐based approach. The development of a rehabilitation program requires models and tools for assessing the condition and performance of sewers. The original contribution of this study is the development of a ranking scheme for sewer rehabilitation priorities. A fuzzy expert system was applied with inputs from a combined assessment of hydraulic, structural performance and potential failure consequences. The fuzzy structural system computes the global structural performance index for each pipe using internal condition, surrounding condition, and site vulnerability (SV) as inputs. The fuzzy hydraulic system uses hydraulic performance index (HPI), hydraulic performance impact, and SV to compute the global HPI. Finally, the fuzzy global system uses all these factors to compute the global performance index for each pipe. This methodology was successfully applied to the sewer system of the City of Laval in Canada. The results show how the fuzzy inference system may be used to establish rehabilitation priorities for each pipe section. The fuzzy expert system provides more realistic results than the intuitive approaches that use structural and hydraulic performance maximum and mean.     

Predictive modeling of installation loads for directional drilled fusible PVC pipe

Today, trenchless technologies such as horizontal directional drilling (HDD) have increased significantly as an alternative installation method in the municipal sector. Installation of potable water, force mains, reclaimed water, and gravity sewer pipelines employing directional drilling have increased as demand for installations in difficult areas including under rivers or major highways and highly urbanized and congested utility corridors has increased. The nature of the HDD process necessitates the use of continuously joined pipe products capable of being pulled in, as opposed to being pushed, or “jacked” in as with segmental installations. Fusible polyvinylchloride pipe (FPVCP) is one such material for installation of water and wastewater, pressure and non-pressure infrastructure using HDD. This paper describes a model for predicting pull loads during HDD installations using FPVCP. Pull load data was captured using an in-line measuring device attached between the backreamer of the drill string and the product pipe to gauge exact loading transferred to the pipe. Detailed results from four field projects demonstrate excellent correlation between predicted and field data.     

基于管道沉积物控制的CSOs污染负荷削减分析

管道沉积物是合流制排水系统溢流(CSOs)污染的重要来源,因此控制沉积物对于削减CSOs污染具有重要意义。在合流制排水系统截流泵站的上游管道中安装穿孔管,给穿孔管提供高压水产生7.5 m/s以上的射流以冲洗管道,同时在截流泵站内设置旋流分离系统来去除冲洗水中的沉积物。对于水层较浅、管径为DN400、管长为40 m、沉积层厚度为3 cm的管道,可使管道流中的SS从冲洗前的75～170 mg/L增加到2 500～3 000 mg/L,且在2～3 min内冲洗干净。旋流分离器对冲洗水中SS的去除率达到55.6%。两周一次的管道例行清洗维护,可使CSOs中污染物降低25%左右,减轻了受纳水体的污染负荷。     

Influence of pipe material and surfaces on sulfide related odor and corrosion in sewers

Hydrogen sulfide oxidation on sewer pipe surfaces was investigated in a pilot scale experimental setup. The experiments were aimed at replicating conditions in a gravity sewer located immediately downstream of a force main where sulfide related concrete corrosion and odor is often observed. During the experiments, hydrogen sulfide gas was injected intermittently into the headspace of partially filled concrete and plastic (PVC and HDPE) sewer pipes in concentrations of approximately 1000 ppm_v. Between each injection, the hydrogen sulfide concentration was monitored while it decreased because of adsorption and subsequent oxidation on the pipe surfaces. The experiments showed that the rate of hydrogen sulfide oxidation was approximately two orders of magnitude faster on the concrete pipe surfaces than on the plastic pipe surfaces. Removal of the layer of reaction (corrosion) products from the concrete pipes was found to reduce the rate of hydrogen sulfide oxidation significantly. However, the rate of sulfide oxidation was restored to its background level within 10-20 days. A similar treatment had no observable effect on hydrogen sulfide removal in the plastic pipe reactors. The experimental results were used to model hydrogen sulfide oxidation under field conditions. This showed that the gas-phase hydrogen sulfide concentration in concrete sewers would typically amount to a few percent of the equilibrium concentration calculated from Henry's law. In the plastic pipe sewers, significantly higher concentrations were predicted because of the slower adsorption and oxidation kinetics on such surfaces.     

An evaluation of a sanitary sewer system using a computer model

The purpose of this study was to (1) provide the city of West Lafayette, Indiana, USA, with an analysis and evaluation of its sanitary sewer system and (2) make recomendations for improving the existing system and any modifications necessary for accomodating future growth within the service area. Using a computer model, virtually every sewer line within the city and Purdue University was modelled. The computer model was calibrated for dry weather flow using water use records, while wet weather flows were checked against field observations. The analysis included both the present condition and future growth projections. The unique aspects of this study include the use and enhancement of a comprehensive, user-friendly computer program that models the stormwater runoff component and provides easy calibration and verification.     

Illicit intrusion characterization in sewer systems

A very important aspect in sewer systems management is represented by the detection of illicit intrusions, which recently supported the development of online sensors for wastewater quality monitoring. The present paper proposes a new methodology for characterizing an illicit intrusion in a sanitary or combined sewer system, using on-line pollutant concentration measurements. The source identification is formulated as an optimization problem, solved combining the hydraulic and quality simulation tool storm water management model (SWMM) with the GALib code. The methodology, which includes a pre-screening procedure useful for complex and large systems, is applied to a literature scheme and a real test-case, showing promising results. An uncertainty analysis is also performed for checking its robustness with respect to inflow uncertainty and in the presence of measurement errors.     

A Simple Aid for Designing Sewers

A method for constructing design charts for the rapid selection of sewer diameter and gradient is described. A variety of design criteria for sewer capacity and minimum gradient can be incorporated in the chart, which may be adapted for different ranges of pipe diameter and material. The use of the chart should ensure that the most economical combination of pipe diameter and gradient can be chosen without the need for calculation.