Sewer Pipelines Research Articles

Multiattribute Utility Theory Deployment in Sewer Defects Assessment

AbstractAssessing the condition of sewer pipelines is a backbone process to plan for rehabilitation and maintenance work. The closed circuit-television (CCTV) method is the widely adopted method to...

A simple approach for characterising tunnel bore conditions based upon pipe-jacking data

There are several well-established jacking force models available for determining the jacking loads. However, their ability to characterise the tunnel bore conditions is limited. A simple approach to characterise the tunnel bore conditions is proposed and applied to a case study where four sewer pipelines of the Shulin district sewer network in Taipei County, Taiwan were constructed to verify its validity. In this paper, four jacking force models are reviewed. Based upon the given soil properties and pipe dimensions as well as the pipe buried depth, the normal contact pressure (σ′) in each jacking force model and the measured frictional stress (τ) in each baseline section are utilised for back-analysis of the frictional coefficient (μavg). The μavg values outside the range of 0.1–0.3 recommended for lubricated drives can be attributed to the increasing pipe friction resulting from excessive pipe deviation or ground closure or due to the gravel formation not being long enough to establish lower face resistance or total jacking load. JMTA (Japan Microtunnelling Association) has indicated a further potential use in assessment of the interface performance during pipe-jacking works.

Ecological risk assessment of heavy metals in salt-affected soils in the Natura 2000 area (Ciechocinek, north-central Poland)

This paper aimed to evaluate the ecological risk posed by the accumulation of heavy metals in the salt-affected soils of the habitat covered by the EU Natura 2000 program in relation to the activity of soil redox enzymes. The research was carried out in the halophyte reserve in Ciechocinek (north-central Poland) which is a very specific habitat as it undergoes a long-term human impact related to both the operation of the medical spa town and the agricultural use of soils in the adjacent areas. The obtained results showed that the content of Zn, Cu, Pb, and Cd in the studied soils exceeded the Polish standards. Based on the obtained data and statistical analysis, it was found that metals may come from two different sources: emission from household boiler rooms (Pb, Cd) and corroded brine sewage pipeline (Zn, Cu).They are characterized by limited mobility due to alkaline environment and strong sorption properties of the clay fraction and organic matter. The correlation analysis indicates that the dehydrogenase activities were negatively correlated with soil electrical conductivity (EC1:5) (r = − 0.665, P < 0.05). Taking into account the protective status of the area, it is difficult to indicate definitely the solution concerning the land management. However, according to the authors, one should pay special attention to a possibility of using halophytes which occur within the reserve for phytoremediation.

Determining Relative Weights of Sewer Pipelines’ Components and Defects

AbstractCondition assessment models for sewer network components can be considered a tool for key personnel to make informed decisions regarding the required interventions on the basis of the curre...

Defect based deterioration model for sewer pipelines using Bayesian belief networks

A defect based deterioration model to determine the condition ratings in a probabilistic manner for sewer pipelines is presented in this paper. Bayesian belief network (BBN) is used to develop a static model using probabilities of occurrences, and conditional probabilities from observations of existing sewage network. Time dimension is introduced to the developed BBN model by using logistic regression as temporal links required to construct a dynamic Bayesian belief network (DBN). The accuracy of the model’s prediction is examined using actual data where the mean absolute error and root mean square error for the BBN model resulted in values of 0.67, 1.06, 0.56 and 1.05, 1.60, 0.95 for structural, operational, and overall conditions, respectively. As for the DBN model, values achieved for the year at which a pipeline would reach a certain condition state were close to the actual values from the validation dataset.

Assessment on inflow and infiltration in sewerage systems of Kuantan, Pahang.

Inflow and infiltration are important aspects of sewerage systems that need to be considered during the design stage and constantly monitored once the sewerage system is in operation. The aim of this research is to analyse the relationship of rainfall as well as inflow infiltration with sewage flow patterns through data collected from fieldwork. Three sewer pipelines were selected at the residential areas of Taman Lepar Hilir Saujana, Bandar Putra and Kota Sas for data collection. Sewage flow data were collected in terms of flowrate, velocity and depth of flow using flowmeters with ultrasonic sensors that utilize the continuous Doppler effect in the sewer pipelines, while rainfall intensity data were collected using rain gauges installed at the study locations. Based on the result, the average infiltration rates of Qpeak and Qave for the locations were 17% and 21%, which exceeded the respective values of 5% and 10% stated in Hammer and Hammer. The flowrate of wastewater in the sewer pipelines was found to be directly proportional to rainfall. These findings indicate that the sewer pipelines in the study areas may have been affected by capacity reduction, whereas the sewerage treatment plants receiving the wastewater influent may have been overloaded.

OPTIMAL BUDGET ALLOCATION MODEL FOR REHABILITATION OF SEWER SYSTEM CONSIDERING SOCIAL AND ENVIRONMENTAL CHANGES

Municipalities face to challenges related to urban infrastructure, mainly related to aging infrastructure. The metropolitan area of Seoul, Korea, reported that more than half of the entire sewer systems are over 30 years old. The deteriorated sewer systems caused serious safety disaster such as sink hole and other social problems. Furthermore, these phenomena continue to accelerate because the sewer systems are seriously affected by variability of rainfall which results from the climate change and human migration from the social change. Therefore, it is necessary to do proactive rehabilitation instead of overdue maintenance considering the social and environmental change. This research presents the conceptual framework for deciding the priority for investment in the borough of Seoul which is based on the extensive evaluation for identifying the sewer pipelines which need rehabilitation work. To address the comprehensive evaluation of priority for investment, Genetic Algorithm (GA), is adopted to find optimal budget allocation for each borough which is derived from considering the technical, economic, environmental, and social aspects. The result can be used as reference to budget allocation to improve the sustainability of the sewer systems.

Law of Pollutant Erosion and Deposition in Urban Sewage Network

In order to investigate the scouring and deposition law of pollutants in urban sewer systems, the investigation of sewer systems was carried out in Xi'an. The results showed that the thickness of sediment in the branch pipe and the main pipe varied obviously. At the peak of the drainage, the velocity increased gradually, and the thickness of the pipeline sediment decreased. At the bottom of the drainage trough, the changes of the velocity and the thickness of the pipeline sediment were opposite, with variations of 0-24 mm and 0-12 mm, respectively. And the probability of granular contaminants sedimentation and scouring in sewer systems was high, while the thickness of sediment in sewage main pipe was less than the above mentioned pipes, the variation of which was 0-7 mm. In addition, the sedimentation and scouring in the main pipeline kept relatively balanced and the thickness of sediment remained stable. In order to clarify the relationship between the concentration of pollutants and the flow velocity, a pilot sewer system was established. The effects of different flow rates, which were 0.1, 0.3, 0.6, 0.9, 1.2 m·s-1, respectively, on the contents of carbon (organic), nitrogen and phosphorus in the pipeline were studied. The results showed that with the increase of the flow velocity, the scour intensity increased and the concentration of pollutants in the pipeline also increased sharply. As shown by the monitoring results of the static light scattering particle size analyzer, the carbon organic pollutants in the pipeline were easily adsorbed on the larger particles, while nitrogen and phosphorus pollutants were easily adsorbed on the particles with smaller size. Analysis on the change of the urban sewage pipeline showed, when the flow rate was less than 0.6 m·s-1, the sedimentation of granular pollutants in the sewage was greater than the scouring effect. When the flow velocity was higher than 0.6 m·s-1, the water scouring intensity increased and the scouring action was greater than the sedimentation, meanwhile, the sediments were carried by the water and the thickness of the sediments was reduced. The increase of the organic pollutants in the sewage was bigger than the nitrogen and phosphorus pollutants, so that the existing sewage carbon source was improved.

Design of a fuzzy differential evolution algorithm to predict non-deposition sediment transport

Since the flow entering a sewer contains solid matter, deposition at the bottom of the channel is inevitable. It is difficult to understand the complex, three-dimensional mechanism of sediment transport in sewer pipelines. Therefore, a method to estimate the limiting velocity is necessary for optimal designs. Due to the inability of gradient-based algorithms to train Adaptive Neuro-Fuzzy Inference Systems (ANFIS) for non-deposition sediment transport prediction, a new hybrid ANFIS method based on a differential evolutionary algorithm (ANFIS-DE) is developed. The training and testing performance of ANFIS-DE is evaluated using a wide range of dimensionless parameters gathered from the literature. The input combination used to estimate the densimetric Froude number (Fr) parameters includes the volumetric sediment concentration (CV), ratio of median particle diameter to hydraulic radius (d/R), ratio of median particle diameter to pipe diameter (d/D) and overall friction factor of sediment (λs). The testing results are compared with the ANFIS model and regression-based equation results. The ANFIS-DE technique predicted sediment transport at limit of deposition with lower root mean square error (RMSE = 0.323) and mean absolute percentage of error (MAPE = 0.065) and higher accuracy (R2 = 0.965) than the ANFIS model and regression-based equations.

Optimal crew routing for linear repetitive projects using graph theory

Abstract The line-of-balance (LOB) technique is considered as an effective tool for planning and scheduling linear repetitive construction projects. One of the main assumptions of the LOB technique is the uniformity and constancy of production rate for an activity. Moreover, some aspects of the LOB technique can be modified in order to suit the nature of construction projects. This paper proposes a hybrid approach for scheduling linear projects that optimizes resource allocation using the LOB scheduling technique. The paper presents an optimization model for resolving resource constraint dilemmas in linear scheduling projects. The proposed model utilizes a Matrix Laboratory (MATLAB) code using graph theory as a searching algorithm to automate the model formulation. The novelty of the model is that it supports decision makers in formulating the optimal crews routing among various activities and also considering the allocation of multitasking skilled crews. A case study for a repetitive 4-km sewage pipeline installation is used to test the capabilities of the proposed model. Results show that the model can feasibly reduce the number of crews employed in linear repetitive construction projects.

Estimation of greenhouse gas emissions from sewer pipeline system

The aim of this study was to estimate the total greenhouse gas (GHG) emissions generated from whole life cycle stages of a sewer pipeline system and suggest the strategies to mitigate GHG emissions from the system. The process-based life cycle assessment (LCA) with a city-scale inventory database of a sewer pipeline system was conducted. The GHG emissions (direct, indirect, and embodied) generated from a sewer pipeline system in Daejeon Metropolitan City (DMC), South Korea, were estimated for a case study. The potential improvement actions which can mitigate GHG emissions were evaluated through a scenario analysis based on a sensitivity analysis. The amount of GHG emissions varied with the size (150, 300, 450, 700, and 900 mm) and materials (polyvinyl chloride (PVC), polyethylene (PE), concrete, and cast iron) of the pipeline. Pipes with smaller diameter emitted less GHG, and the concrete pipe generated lower amount of GHG than pipes made from other materials. The case study demonstrated that the operation (OP) stage (3.67 × 104 t CO2eq year−1, 64.9%) is the most significant for total GHG emissions (5.65 × 104 t CO2eq year−1) because a huge amount of CH4 (3.51 × 104 t CO2eq year−1) can be generated at the stage due to biofilm reaction in the inner surface of pipeline. Mitigation of CH4 emissions by reducing hydraulic retention time (HRT), optimizing surface area-to-volume (A/V) ratio of pipes, and lowering biofilm reaction during the OP stage could be effective ways to reduce total GHG emissions from the sewer pipeline system. For the rehabilitation of sewer pipeline system in DMC, the use of small diameter pipe, combination of pipe materials, and periodic maintenance activities are suggested as suitable strategies that could mitigate GHG emissions. This study demonstrated the usability and appropriateness of the process-based LCA providing effective GHG mitigation strategies at a city-scale sewer pipeline system. The results obtained from this study could be applied to the development of comprehensive models which can precisely estimate all GHG emissions generated from sewer pipeline and other urban environmental systems.

Detection of cavities around concrete sewage pipelines using impact-echo method

Impact-echo method has been successfully used to detect flaws in concrete and to evaluate the state of grout bonding in tunnels. It has not yet been used to detect underground cavities formed by leakage of pipelines, which is becoming a major problem in many urban environments. We perform model and field tests to evaluate whether the impact-echo method can be used to detect cavities around concrete sewage pipelines. Fourier spectrum was used to determine the resonant frequency and the short time Fourier transform was used to determine the temporal variation of the resonant frequency component. Results show that the presence of cavity cannot be reliably predicted from the wave time history or Fourier spectrum. The spectrogram is demonstrated to be a better indicator for detecting the presence of a cavity. The cavity induces a longer tail in the spectrogram because of a higher impedance contrast and a lower attenuation. We propose a new quantitative index based on the resonant frequency and the spectrogram, denoted as the sustained duration. Both model and field tests demonstrate that the cavity in wet soils can be successfully detected using the proposed index.

Flow Design of Sewerage System – A Case Study in Taman Pandan Damai, Kuantan

Flow design parameters are important in the sewerage system design. The purpose of this research is to verify the design flow parameters in the sewerage systems within a residential area at Kuantan, Pahang. The residential area selected in this research was Taman Pandan Damai. The population equivalent was surveyed at 2244. This research is in collaboration with national sewage company Indah Water Konsortium Sdn. Bhd. ISCO 4250 Area Velocity Flow meter was installed in the Manhole (MH k) after calibration was done. Real time sewage depth, flow rate and velocity data in the sewer was collected using an ultrasonic sensor attached to the flow meter. The flow design parameters were focused on per capita flow as well as design criterion. Based on the results obtained the average per capita flow was 0.36 m3/day/person which is 60% higher than the 0.225 m3/day/person recommended in the Malaysian Sewerage Industry Guidelines. Conversely, the result of design criterion was 2.61, 44% lower than 4.7 which is also stated in the Malaysian Sewerage Industry Guidelines. This indicated that the design of the sewerage system in Taman Pandan Damai was more than capable of catering to the population equivalent serviced in that area. In other words, reduction of sewer pipeline diameters may be possible for future sewerage system design. More comprehensive studies are needed to initiate the review of revised flow design parameters taking into account the rising cost of materials around the world.

Cost benefit analysis for failure of sewer pipelines

Sewer pipelines failure in sewage networks can have adverse potential impacts on socio-economic aspects in any community. Due to the fact that it’s difficult to capture the relationship between the physical and economical aspects as a result of critical sewer pipelines failure, economic concepts are used to evaluate the economic loss as a result of these failures. In this paper an analysis for the costs resulting from sewer pipelines failure and the benefits achieved from avoiding failures are presented. The costs included in the cost benefit analysis are the direct costs used to reinstate failed pipelines and the indirect costs, borne by the society and economy. In the benefits analysis, only the tangible and measurable benefits limited to the health sector and preventing diseases are addressed in this paper. It is expected that the proposed approach could help in estimating the economic losses due to sewer pipelines failure especially for the intangible factors that are difficult to measure. In addition it could help decision makers in taking necessary measures to preserve critical assets that could have adverse potential impacts on valuable natural resources such as surface and groundwater and soil surrounding failed pipelines.

Effects of Bedding Types on the Behavior of Large Diameter GRP Flexible Sewer Pipes

Flexible pipes, such as GRP pipes, serve as effective underground infrastructure especially as sewer pipeline. This study is an attempt for understanding the effects of bedding types on the behavior of large diameter GRP flexible sewer pipes using three dimensional finite element approaches. Theoretical and numerical analyses were performed using both BS EN 1295-1 approach and finite element method (ABAQUS software). The effects of different parameters are studied such as, depth of backfill, bedding compaction, and backfill compaction. Due to compaction, an increase in the bedding compaction modulus (E’1) results in a reduction of both stresses and displacements of the pipe, especially, for well compacted backfill. An increase of (E’1) from 14MPa to 30MPa results in a reduction in stresses 40% and about 25% in displacements. Maximum reductions in stresses were found to be about 25% only while the reduction in displacement was found to be less than 10%. As backfill material compaction modulus (E’2) is increased from 14MPa to 40MPa, a maximum reduction in stresses within the pipe was found to be not less than 60% while the displacement reduces up to 65%.&#x0D;

Some aspects of calculation of joint operation of sewage sludge pumps and pipeline networks

Some aspects of calculation of joint operation of sewage sludge pumps and pipeline networks

Risk assessment model to prioritize sewer pipes inspection in wastewater collection networks

In wastewater systems as one of the most important urban infrastructures, the adverse consequences and effects of unsuitable performance and failure event can sometimes lead to disrupt part of a city functioning. By identifying high failure risk areas, inspections can be implemented based on the system status and thus can significantly increase the sewer network performance. In this study, a new risk assessment model is developed to prioritize sewer pipes inspection using Bayesian Networks (BNs) as a probabilistic approach for computing probability of failure and weighted average method to calculate the consequences of failure values. Finally to consider uncertainties, risk of a sewer pipe is obtained from integration of probability and consequences of failure values using a fuzzy inference system (FIS). As a case study, sewer pipes of a local wastewater collection network in Iran are prioritized to inspect based on their criticality. Results show that majority of sewers (about 62%) has moderate risk, but 12%of sewers are in a critical situation. Regarding the budgetary constraints, the proposed model and resultant risk values are expected to assist wastewater agencies to repair or replace risky sewer pipelines especially in dealing with incomplete and uncertain datasets.

Transformation and Sorption of Illicit Drug Biomarkers in Sewer Systems: Understanding the Role of Suspended Solids in Raw Wastewater.

Sewer pipelines, although primarily designed for sewage transport, can also be considered as bioreactors. In-sewer processes may lead to significant variations of chemical loadings from source release points to the treatment plant influent. In this study, we assessed in-sewer utilization of growth substrates (primary metabolic processes) and transformation of illicit drug biomarkers (secondary metabolic processes) by suspended biomass. Sixteen drug biomarkers were targeted, including mephedrone, methadone, cocaine, heroin, codeine, and tetrahydrocannabinol (THC) and their major human metabolites. Batch experiments were performed under aerobic and anaerobic conditions using raw wastewater. Abiotic biomarker transformation and partitioning to suspended solids and reactor wall were separately investigated under both redox conditions. A process model was identified by combining and extending the Wastewater Aerobic/anaerobic Transformations in Sewers (WATS) model and Activated Sludge Model for Xenobiotics (ASM-X). Kinetic and stoichiometric model parameters were estimated using experimental data via the Bayesian optimization method DREAM(ZS). Results suggest that biomarker transformation significantly differs from aerobic to anaerobic conditions, and abiotic conversion is the dominant mechanism for many of the selected substances. Notably, an explicit description of biomass growth during batch experiments was crucial to avoid significant overestimation (up to 385%) of aerobic biotransformation rate constants. Predictions of in-sewer transformation provided here can reduce the uncertainty in the estimation of drug consumption as part of wastewater-based epidemiological studies.

The interaction between road traffic safety and the condition of sewers laid under roads

The main objective of this paper is to show how the service condition of the underground pipeline infrastructure, especially sewage systems, may contribute to road surface failures such as subsidence, bulging and particularly collapse. The analysis was based on CCTV surveys conducted in Poland to investigate the causes of more than a hundred road surface collapse incidents.The method proposed in this paper enables us to determine the risk of road surface collapse as the product of the category of probability of road collapse caused by damaged sewer pipelines and the weighted arithmetic mean category of their consequences.The key conclusions highlight the causes of road collapse incidents, the scale of the hazards, and the benefits resulting from the application of the proposed method to prioritize roads according to the road collapse risk.

Material stock disparity and factors affecting stocked material use efficiency of sewer pipelines in Japan

Service is most often measured with a flow and monetary perspective using indicators such as gross domestic product (GDP) or the value added or income of a particular economic sector. However, infrastructures and therefore the associated material stocks also participate to the service delivery. Our study contributes to this emerging research field through a novel method of measuring stocked material use efficiency (SMUE) of sewerage pipelines in Japan, beyond monetary measures. We estimated the Japanese national and prefectural material stocks (MS) using statistical data and used direct service indicators such as the population with access to sewerage treatment services and the amount of treated wastewater to find the SMUE. Later, decomposition analysis was used to ascertain the main factors influencing SMUE. Results show an MS increase for all prefectures and a doubling of the national MS from 207 million tonnes (Mt) 520 Mt between 1984 and 2012. Material stocks are found mainly associated with population size, the highest populated prefectures Tokyo and Osaka also accounting for the highest material stocks. Concerning SMUE ranging from 4 to 48m3/ton for a national average of 27m3/ton, its main determinants are population density and pipeline size. This research promotes greater understanding of our stock use condition and thereby facilitates appropriate stock management.