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Urban pluvial floods are characterised by a number of features such as the high spatial and temporal resolution needed to capture their dynamics, the complexity of dual drainage systems and the lack of sewer data availability, which make them very different from other types of floods, like coastal or fluvial floods, and which increase the difficulty of modelling them. As a consequence, most flood management plans do not include a rigorous evaluation of urban pluvial flood risk. In this paper, we give a comprehensive view of the current state of urban pluvial flood modelling, not restricted to a mere description of the mathematical approaches, but also including the most relevant features that should be considered in their modelling, the validation studies that have been performed to date and our vision on the modelling challenges that should be addressed in the near future. [ABSTRACT FROM AUTHOR]

A common method for measuring sewer and drainage manholes with tape measure lacks precision in cases of sediment accumulation or deep manholes, impacting data accuracy. This paper proposed a method for measuring sewer and drainage manholes using terrestrial laser scanning. This method first utilizes a plane fitting equation and the RANSAC method to determine the ground and segmentation planes, enabling automatic trimming of the point cloud of the manhole. Subsequently, the pipe's inlet and outlet extraction is done using the point cloud combining Region Growing method. Finally, according to the feature of cylinder pipe and elliptical cylinder pipe, the inlet and outlet are reconstructed using the extracted point cloud. Experimental results show that the radius of pipe's inlet or outlet can be measured by the proposed method with an accuracy of 5.20 mm, the height difference of the manhole can be measured with an accuracy of 7.05 mm, meeting the requirement of a permissible deviation of 10 mm for measuring the lowest point of manhole specified in the " Code for construction and acceptance of water and sewerage pipeline works " (GB50268-2008). [ABSTRACT FROM AUTHOR]

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The ten Water and Sewerage Companies covering England and Wales were privatized in 1989, primarily due to the financial pressures they faced from historic underinvestment and the need to comply with EU environmental-related legislation. In the first decade, this worked well as inland and bathing water improved. More recently, environmental progress has been seen under a harsher light due to a number of factors, many of which reflect poorly on the way these companies are managed and regulated. A number of potential responses are put forward. [ABSTRACT FROM AUTHOR]

Municipal wastewater may contain toxic substances that have a negative impact on biological treatment processes and receiving waters. This paper presents the wastewater toxicity test results from the Lodz hybrid sewage system. Wastewater is discharged to surface waters through a treatment plant, but also during wet weather, partially without treatment by combined sewer overflows. The research was carried out using the ToxTrakTM method with the use of the microbial community of activated sludge from the wastewater treatment plant in Lodz. The median toxicity, expressed as the degree of inhibition, ranged from 16.0% to 30.7%, but sometimes exceeded 50%. Higher toxicity was observed in wet weather than in dry weather. Seasonal variability was found but typical daily variability was not observed. In the case of sewage samples with the degree of inhibition above 40%, a significant correlation was found with chromium concentration and non-ionic surfactants (Pearson's coefficient correlation above 0.7). [ABSTRACT FROM AUTHOR]

Traditional approaches devoted to upgrading the sewerage system functionality are highly costly and time demanding. Thus, the implementation of comprehensive modelling approaches can be intended as an effective and economically viable strategy to detect and outdo the critical issues of the networks. This paper presents an integrated procedure to monitor and simulate the network's performance, based on the coupling of Supervisory Control and Data Acquisition (SCADA) networks for data collecting and monitoring, with hydraulic simulations by the Storm Water Management Model 5.1 (EPA-SWMM) solver. The drawbacks of the network are then assessed by proposing several upgrades to improve the system. The proposed strategy was applied to the Nora-Noreña sewerage system, located in North Spain. Results show the potentiality of the methodology in reducing sewer network maximum filling degree requirements and overflows into the receiving water bodies. [ABSTRACT FROM AUTHOR]

The unplanned and rapid expansion of metropolitan areas reduces accessibility to existing and often outdated centralized water and wastewater systems. In this context, sanitation policies that focus exclusively on centralized systems become expensive and unfeasible. Using Q methodology, we identified three different social perspectives on onsite wastewater treatment systems (OWTS) in the metropolitan area of the Lerma Valley in northern Argentina. We focused our analysis on the legal, environmental, and technical aspects of onsite sanitation. The perspectives found were: 'OWTS have advantages', 'Hard path for sewerage', and 'Process before technology'. We describe the perspectives identified and we provide an analysis of their differences and similarities to discuss their possible policy implications for our study area and comparable regions in the country and beyond. [ABSTRACT FROM AUTHOR]

This study partially replaced the clay with sewer sludge (SS) and rice husk (RH-SS) to make fired bricks. The brick samples were examed in terms of shrinkage, water absorption, and compressive strength. Besides, they were analyzed via XRD and metal extraction to determine the heavy metal residuals in the products. The results showed that it was possible to fabricate fired bricks using sewer sludge or rice husk-blended sludge with up to 30% by weight. These brick samples complied with the technical standard for clay brick production, in which the compressive strength was more than 7.5 MPa, water absorption was from 11–16%, and the linear shrinkage was all less than 5%. The rice husk addition helped mitigate the heavy metal residuals in the bricks and leaching liquid, in which all the values were lower than the US-EPA maximum concentration of contaminants for toxicity characteristics. Implications: Previous studies have proved the possibility of mixing sewage sludge from different origins (sewage sludge, river sediment, canal sediment, sewer sediment, etc.) with clay and some wastes to make bricks. In which, mostof the studies used sewage sludge from wastewater treatment plants, very fewdealt with lake/river or sewer sediment. This study shall be the first to study the possibility of employing sewer sediments with the addition of rice husk powder to achieve two targets, including (1) the reuse of biowaste and sludge for brick fabrication and (2) the reduction of heavy metals in final calcined bricks. Different ratios of the rice-husk blended sewer sludge (RH-SS) – clay mixture shall be tested to find the optimized compositions. The results showed that it was possible to fabricate fired bricks using sewer sludge or rice husk-blended sludge with up to 30% by weight, which meant reduce 30% of clay in the brick production. The final products were proved to meet the quality standard in terms of compressive strength (more than 10 MPa), water absorption(from 11–16%), and the linear shrinkage (less than 5%). Larger scale of this study can be an evident to recommend for policy change in the waste reuse in construction field. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology for the optimal design of series of sewer pipes including pumping stations. It employs a Shortest Path Algorithm to select the optimal combination of pipe diameters and invert elevations, as well as the optimal pumping features such as the number of pumps, location, and pumping head. The methodology is intended to be applied to the design of any sewer series. Although these are uncommon in real infrastructure, the study allows an analysis of the effect of pipe roughness, inflows, and pipe length on the total cost of the system and pumping features. The methodology was tested in theoretical series of 10 and 20 pipes as well as in a real series that is part of the sewer system of Bogotá, Colombia. The resulting designs suggested that using smooth pipes and reducing the pumping flow rate would decrease the cost of sewer systems in flat terrain. [ABSTRACT FROM AUTHOR]

The Storm Water Management Model (SWMM) is a reliable software program for simulating stormwater runoff in combined drainage facilities. However, it faces challenges in efficiency, especially when executing real-time forecasting. This research explores an alternative machine learning (ML) approach to predict water levels in sewer and street drainage systems utilizing SWMM data for model training. The goal is to construct a hybrid ML model for urban flooding prediction, considering hydrological conditions, geomorphologic properties, and drainage facility features. A robust training method is introduced to deliberate complex flow conditions. The suggested approach achieves favourable performance in predictive accuracy and computational efficiency. Findings include: (1) similarity between ML and SWMM flooding depth on street nodes increases from 62.3% to 96.2% with the proposed training; (2) the proposed model is about 50 times faster than SWMM in urban flood simulations; (3) reliable predictions from the ML model are demonstrated through four accuracy metrics. [ABSTRACT FROM AUTHOR]

Optimization of the spatial distribution of green infrastructures (GIs) was performed for a combined sewer system located in the Province of Quebec, Canada, using a simulation-optimization tool with the aim of reducing seasonal combined sewer overflows (CSOs). The performance of four CSOs control alternatives involving the individual and integrated implementation of GIs with storage tanks and real time control (RTC) of the sewer was evaluated for a nine-year simulation period of historical rainfall data and for 20%-increased rainfall data (representative of potential climate change impact). The integration of GIs with RTC of the sewer (with or without storage tanks) lowered the total CSO volume by 95% to 99% under historical rainfall data and by 93% to 96% under increased rainfall intensities when compared to the reference scenario. Adapting GI's number and location for optimal CSO control rather than according to space availability criteria reduced CSO frequency but had only a slight impact on CSO volume reduction. [ABSTRACT FROM AUTHOR]

In many smart systems, such as cloud computing, networked control, manufacturing, and telecommunication, the effects of time delays are unavoidable. Saturation nonlinearity is common in many smart systems (e.g. electric systems with limited actuator power supplies, mechanical systems with position and speed constraints, fixed-point digital filters, etc.). Therefore, the study of stability of discrete-time systems (DTSs) with time delay and saturation is of high importance in practice. The global asymptotic stability (GAS) problem of such systems is investigated in this paper. The saturation nonlinearity is constrained by a convex hull with a free matrix whose infinity norm is smaller than or equal to unity. A new Lyapunov-based GAS criterion for DTSs with time-varying delay and state saturation is established. The GAS problem for DTSs with constant delay and saturation is also discussed. The obtained results can be used to ensure the absence of overflow oscillations in the considered system. In comparison to several existing criteria, the approach yields improved stability results. An example is provided to demonstrate the importance of the presented results. [ABSTRACT FROM AUTHOR]

The occurrence of combined sewer overflow (CSO) is a pressing environmental issue in many cities. This study aims to predict CSO occurrence using rainfall event characteristics, including rainfall depth, maximum intensity, and duration, and to determine which characteristic is the best predictor. Buffalo, New York, was selected as a case study. The results indicate that the prediction accuracy ranges from 80% to 100% for rainfall depth and maximum intensity, while rainfall duration is not a good predictor. Furthermore, rainfall depth is more likely to be the best predictor for sewersheds with a larger area. Additionally, combining the three rainfall event characteristics using the decision tree can only improve the average prediction accuracy slightly, from 93% (using a single characteristic) to 95% (using three characteristics). Using rainfall event characteristics and this simple method can be an effective alternative to complex urban hydrological models and/or expensive monitoring for predicting CSO occurrence. [ABSTRACT FROM AUTHOR]

This paper aims to develop a sediment deposits hydraulic deterioration model based on self-cleansing criteria to prioritize the inspection of sewer systems. The model was trained with benchmarking literature values from earlier experiments and validated with household connections complaints data from Bogotá, Colombia. Recursive Feature Elimination with Cross-Validation (RFECV) and Bayesian Optimization (BO) were used to construct a Random Forest (RF) model to predict, at pipe level, the likelihood for a pipe to present sediment deposits. To evaluate the model's prediction accuracy, two different performance indicators were used: (i) the Percentage of Effective Inspections, and (ii) Pipes per Inspection with sediments. The sediment deposits hydraulic deterioration model shows good overall performance with buffer zones radiuses of 250 m predicting which pipes tend to present sediment deposits over time. This model improves the understanding of sediment deposits in hydraulic deterioration models and can be used to prioritize inspection of sewer systems. [ABSTRACT FROM AUTHOR]

This study investigated the effect of environmental parameters on microbial-induced concrete corrosion during three corrosion stages. The corrosion effects and influencing factors in three corrosion stages were deeply analyzed and predicted, and the mechanism of microbial corrosion was summarized. When the H2S concentration was lower than about 15.0 mg/m3, the corrosion was maintained in stage II, which greatly delays the intensification of corrosion. In stage III, the H2S concentration has the significantly accelerate the corrosion rate. Additionally, incorporating min, max and mean values of input parameters greatly improved the accuracy of machine learning predictions of corrosion rates (R2 >0.99). Acidithiobacillus was found to be dominant in the microbial community at H2S concentrations of 12.0–37.5 mg/m3, and increased temperature promoted the reproduction of Acidithiobacillus. [ABSTRACT FROM AUTHOR]

Stormwater surcharge events are unavoidable above a certain rainfall intensity. Thus, for protection and damage mitigation, forecast systems are of outstanding importance. This study develops an ensemble forecast system (EFS) to predict the beginning and end of sewer surcharge events. It applies a nonlinear autoregressive with exogenous inputs (NARX) network to each member of the ensemble, making it suitable for real-time predictions. The fundamental idea is the forecast of water depth time series within manholes based on the given rainfall. The novelty lies in the consideration of uncertainty through the ensemble structure for which the numbers of neurons in the hidden layer, the weights, and biases are considered to be uncertain. The results are evaluated based on observed values captured within the uncertainty band (P f a c t o r ), and the width of the band (R f a c t o r ). The P f a c t o r varied between 74% and 94% and the R f a c t o r between 1.36 and 10.68. [ABSTRACT FROM AUTHOR]

This paper proposes a method to include drop manholes in the optimal design of sewer networks. These structures dissipate energy and reduce flow velocity, which is important in hilly regions where high slopes induce velocities that exceed the maximum allowable. The methodology proposed here introduces a new type of arc to represent drop manholes in a model that uses graph theory to achieve the minimum cost design of a sewer network. Also, for the estimation of drop manhole costs, a new cost function is developed based on pipe and manhole cost equations proposed in the literature. The methodology was tested in eight different series of pipe configurations, as well as a real sewer network located in Colombia, varying the pipe material and the land slope. The results demonstrated that the proposed methodology allows for the optimal design of sewer networks in hilly regions while satisfying all hydraulic and commercial constraints. [ABSTRACT FROM AUTHOR]

To investigate the sedimentation through urban wastewater pipelines a semicircular polyethylene pipeline of diameter 0.40 m and length 18 m in nearly horizontal orientation with a longitudinal slope of 0.01 for a discharge capacity of 0.0147 m3/s and a volumetric flow concentration of 30% has been used. The solid phase consists of three different particle sizes i.e. 0.25 × 10−3m, 0.35 × 10−3 m and 0.50 × 10−3m with the greatest frequency in the wastewater flow being a density of 2650 kg/m3. The flow has been simulated by Ansys-Fluent (2020) software. The effects of particle size on various slurry flow parameters such as pressure drop, solid phase velocity distribution, friction factor, granular pressure, turbulent viscosity, turbulent kinetic energy and its dissipation all have been analyzed. The location of maximum deposition is also determined and it occurred at x/R = 77.5. Finally, a relationship between the thickness of sedimentation and volume concentration has been proposed. [ABSTRACT FROM AUTHOR]

The modelling of complex free surface flows is challenging due to the mobility and deformability of the interface and air entrainment characteristics, which are highly affected by turbulence. With the framework of Reynolds averaged Navier–Stokes (RANS) models and the volume of fluid (VOF) method, turbulence quantities at the air–water interface tend to be over-estimated. In this study, interfacial turbulence treatment methods including the buoyancy modification model based on the simple gradient diffusion hypothesis (SGDH) and Egorov's turbulence damping model are investigated. Furthermore, due to the unconditionally unstable characteristics of the standard k-ε turbulence model, the stabilized k-ε turbulence model is applied as a comparison. The turbulence attenuation performance using different interfacial turbulence treatment methods in the vicinity of the interface is compared and discussed for stratified flows and free overflow weirs for aerated and non-aerated nappe scenarios. The turbulence quantities and free surface profile under different flow conditions are validated against experimental data and an analytical model. The results show that for free surface waves, both the SGDH model and the turbulence damping model give strong improvements in turbulence production compared with the standard k-ε model. The SGDH model augments the turbulence kinetic energy (TKE) in the unstable stratification, leading to unphysical behaviour for the partially dispersed and separated flow. [ABSTRACT FROM AUTHOR]

When designing a sewer system, the goal is to find the design with the lowest cost while complying with the hydraulic constraints. However, with the emergence of new concerns like climate change and high-density urbanization, those designs must also be reliable and resilient. This is the objective of the present research, to provide an approach for finding low-cost, sewer networks design while considering the reliability and the resilience as a criterion in the selection of the best design. For that purpose, a method is proposed for evaluating resilience and reliability in a variety of designs produced by modifying the objective function of the network's layout selection model. The methodology was tested in four scenarios using two cost equations and two sewer network benchmarks from the literature. In most of the scenarios, it was possible to find designs with lower cost and higher resilience and reliability than those previously published. [ABSTRACT FROM AUTHOR]

Predicting the structural condition of sewer pipes plays a vital role in the predictive maintenance of sewer pipes and renewal plans of many water utilities. This study explores the simultaneous utilization of physical and environmental features of sewer pipes in sewer structural condition prediction. Three (3) hybrid machine learning models which are the combination of Bagging (BG), Dagging (DG), and Rotation Forest (RotF) ensembles with a J48 Decision Tree (J48DT) based classifier were used to predict sewer pipe conditions in Ålesund city, Norway. The classification performance of the machine learning models was evaluated using the area under the receiver operating characteristic (AUC-ROC) and the area under the precision-recall (AUC-PRC) curves. The RotF-J48DT model had the highest (AUC-ROC = 0.857, AUC-PRC = 0.918) values, followed by the BG-J48DT, and the base classifier J48DT. The RotF-J48DT hybrid model should be considered when predicting the condition of sewer pipes in the study area. [ABSTRACT FROM AUTHOR]

Sewerage town communities often experience discrimination because of their association with sewerage, and yet they flourish on their abject margins. A recent study of sewerage town communities in Australia and the UK and specifically, the community that grew on Melbourne's Metropolitan Sewerage Farm, established on the Australian city's outskirts, highlighted that sewerage town communities are inclusive and highly connected. A poetics of creative writing research methodology supported many elements to come together to explore the abject through these sewerage town communities. The study highlighted the strength of the power vacuum that forms within the community living in a state of abjection, for a belonging existence. These powerful attributes remain once the community abandons the town, as a spirit or essence that continues to emanate as a haunting in the sewerage ghost town. The poetics methodology granted a rethinking of how sewerage towns survive and thrive in their abject margins and what happens once the community abandons the sewerage town, for a paradoxical aesthetic and haunting truth of the sewerage ghost town. Even the murk of mustarding waters, devoid of air but teeming in critters that thrive in the souring stench, and the poor blighter disappearing within those waters of olive and brown, can be beautiful. Insights can be applied to any marginalised or abject community and company town. [ABSTRACT FROM AUTHOR]

Visual inspection is currently the industry standard for assessing sewer and stormwater pipelines – a method prone to uncertainties as shown by previous studies. The data gathered from the visual inspection procedures is the main information base on which rehabilitation and replacement strategies are founded in current practice. Consequently, this study evaluates the quality of visual inspection data by quantifying the uncertainty and assessing its impact on the output of a deterioration model. The study was carried out by re-classifying pipe condition classes using the same video footage and transferring differences in the classifications into a distribution that was used as a measure of input data uncertainty. This quantified uncertainty was then propagated into a deterioration model using a Monte Carlo approach to assess its impact on the model behaviour. Results show that there is a considerable uncertainty in condition classes coded according to the Norwegian standard, and that it is comparable to uncertainties estimated in other studies using various European coding systems. The uncertainty assessment indicates that the uncertainties have a considerable impact on the model predictions, which in consequence demonstrates that the uncertainty in the visual inspection methodology can heavily influence the decisions for rehabilitation and replacement strategies. [ABSTRACT FROM AUTHOR]

A decentralized, and sustainable sewer inspection plan at the city scale demands multiple inspection methods with different areas of impact. While sewer deterioration models offer great areas of impact, spatial mapping can assess the vulnerability of the system without prior knowledge of the pipe's structural health condition. In this study, we assess and prioritize sewer deterioration factors such as pipe age, material, sewer type, node degree, flow velocity, and surface vegetation for vulnerability hotspot mapping of a sewer system in Dresden, Germany. The validation and sensitivity analyses revealed that flow velocity, pipe age, and surface vegetation are the most sensible factors to model, respectively. The linear model resulted in 76% efficiency and a mean squared error of 0.918 while it was improved with a random forest algorithm which points out vulnerability mapping potential as an early sewer inspection method at the city scale. [ABSTRACT FROM AUTHOR]

This note proposes a new formula for predicting the self-cleansing velocity of suspended particles in sewer pipes. Dimensional analysis is carried out to develop a new equation based on sediment and hydraulic characteristics. Model performance is tested using experimental data collected at laboratory scale and benchmarking data from the literature. The accuracy of the developed formula is evaluated with the Coefficient of Determination (R2), the Mean Absolute Percentage Error (MAPE) and the Root Mean Squared Error (RMSE). Results demonstrate that the proposed equation is able to predict the particle Froude number and hence the self-cleansing velocity for a wide range of variations of sediment concentration, particle diameter, and hydraulic characteristics. [ABSTRACT FROM AUTHOR]

This paper proposes a method for prioritizing sewer cleaning operations in the absence of historical data on failures. The method utilizes the Induced Ordered Weighted Averaging (IOWA) multi-criteria decision-making technique, incorporating experts' opinions to regulate subjective inferences and ascertain uncertainty. The study considers ten parameters categorized into three main focuses: structural, environmental, and operational to analyze sewer pipe conditions. As a case study, four small zones in Tehran city were prioritized using the proposed methodology. The findings reveal that (1) decision-makers' subjective priorities and evaluations do not significantly influence critical cleaning options, (2) pipe diameter is the most effective parameter for prioritizing since it allows pipes to be meaningfully categorized and compared, and (3) slope, age, depth, upstream manhole condition, and the number of connections and laterals are more important than other parameters. Overall, this study provides valuable insights into developing effective prioritization strategies for sewer cleaning operations. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyse the nationwide data on sick leaves (SL) due to work-related musculoskeletal disorders among Slovenian workers in section E "water supply; sewerage, waste management and remediation activities" from NACE Rev2 classification. We report both, SL frequency (ie, number of cases) and SL severity (ie, average SL duration), stratified by body region, gender, age and divisions within the section. In addition, trends in SL data (year 2015–2019 difference) were analyzed. Throughout the analysed years, ∼9,000 workers were employed in the section, with male to female ratio at ∼ 4:1. The major findings are as follows: (i) low back disorders were by far the most prevalent, however, the mean SL duration was the highest for lower limb disorders; (ii) older age was associated with increased SL frequency and duration, irrespective of gender; (iii) male gender was consistently associated with larger SL duration, while the data on SL frequency is inconclusive, as older females had more frequent SL than older males; (iv) the effect of division was relatively minor and the comparisons are limited due to large discrepancies regarding the number of workers across divisions; (v) a slight increasing trend for both SL frequency and duration was observed from 2015 to 2019. In conclusion, particular attention in terms of early diagnosis and treatment of musculoskeletal disorders should be given to male workers and older workers in general in section E. [ABSTRACT FROM AUTHOR]

The failure of sewage and drainage systems in SubSaharan African cities is frequent and can be considered as a critical issue, both from an environmental standpoint and in terms of associated maintenance costs. This study analyzes the state of the sanitation systems, the elements behind the failures, the environmental concepts used to classify the problems, and the tools and methodological alternatives for ranking the various management solutions. This research illustrates the causes that contribute to the dysfunctions in the sewage systems of Abidjan as a typical example of sewerage systems management challenges in SubSaharan Africa's large cities. Poor solid waste and wastewater management practices by residents, e.g., illegal dumping of solid waste into the sewers, unauthorized and defective connections to the network, structural dysfunctions related to the age of the network (cracked, denuded, or broken), urban agriculture in the vicinity of the channels, natural phenomena such as erosion, landslides in the undeveloped parts, and the high concentration of vegetation in the network, wholly contribute to the degradation of the network. A variety of decision support systems for the management of the assets of the urban sewage network were presented. The instruments have been categorized based on their capacity and functionality. The operating concept of each of these tools has been outlined, as well as their respective data needs. In addition, the study analyzes challenges related to the usage of existing decision support systems and provides an outlook on future research requirements in this area. This study offers a detailed analysis of the issues of sanitation management and could serve as a reference for other emerging nations in SubSaharan Africa. [ABSTRACT FROM AUTHOR]

Sewer pipe pressurization is a phenomenon that can cause structural damage in urban drainage systems and can result in a public health issue, especially in cities that have combined sewer systems. Studies have classified the phenomena of downstream to upstream pressurization in stages, proposing several mathematical models to predict pressure variations and the effect generated by air entrapment. This paper considers the opposite pressurization process, upstream to downstream, caused by a sudden increase in discharge. Using a physical model in which drainage time and flow rate magnitude are controlled, severe flood drainage events are simulated. Results show that the increases of water level are gradual, and when the depth reaches full pipe flow, pressure increases are also gradual without any transients. The contribution of this work relies on concluding that it is highly improbable that the pressurization process in this case could cause damage problems in the drainage infrastructure. The same results were obtained regardless of the rate of increase in flow and the maximum final pressure in the pipe, which differs from the downstream-upstream case. There are no pressure transients. [ABSTRACT FROM AUTHOR]

River water degradation arising from wastewater effluents is a major factor contributing to the deterioration of river ecosystems; yet direct evidence of the beneficial influence of long-term sewerage development on such ecosystems is scarce at a basin scale. The present study, over 12 years, examined changes in sewerage connection rate, water quality, and invertebrate assemblages at 10 study sites in the Shigenobu River, southwestern Japan, and investigated the relationships between them. Sewerage connection rates increased in the three main municipalities in the basin during the study period (range: 8.6%–31.4%). At the lowland sites, the concentration of total inorganic nitrogen (TIN) decreased by 38.9% on average and the richness metrics of invertebrate assemblages significantly increased at several sites. Furthermore, the richness metrics negatively related with TIN concentration, implying that invertebrate diversity recovery was the result of water quality improvement. Our findings strongly suggest that sewerage system improvement is an effective measure for restoring river ecosystems. [ABSTRACT FROM AUTHOR]

Urban flood resilience requires high-performance sewer systems, and multi-objective optimization methods are widely used to improve sewer system efficiency. A non-polynomial complete (NP complete) optimization problem may exist in urban sewer rehabilitation, which may cause low efficiency in optimizing large network systems. In this research, a sensitivity-based adaptive procedure (SAP) is proposed, which can be integrated with optimization algorithms. SAP was integrated with Non-dominated Sorting Genetic Algorithm II (NSGA-II) and Multiple Objective Particle Swarm Optimization (MOPSO) methods. We further used the Hydraulics and Risk Combined Model (HRCM), which is a risk-informed multi-objective optimization model designed for drainage system rehabilitation to validate the performance of SAP procedure. Results showed that SAP can improve the optimizing performance, and SAP-NSGA-II exhibited superior performance in solving the combined problems of pipe breakage and overflooding. [ABSTRACT FROM AUTHOR]

This research aimed to identify a tool to objectively analyse the performance and the environmental contextualisation of sewer systems (SwSs) and wastewater treatment plants (WWTPs). This procedure performs assessment by calculating performance indices which could be subsequently applied to SwSs and WWTPs with different characteristics. The proposed tool can be applied conveniently over the years by managers of integrated urban water management systems for the analysis of different realities also allowing the evaluation of the effects of upgrades carried out during the management phases. The proposed analysis allows the optimisation of SwSs and can profitably guide the choice and the priority among possible interventions for the sewerage infrastructure and WWTPs providing a verification and evaluation protocol as well as a financial planning tool. [ABSTRACT FROM AUTHOR]

Drop manholes are commonly employed to reduce slopes in sewer systems. Diverse particles can enter into these systems and gather in drop manholes where they can chain and clog the outflow. As their residence time in the manhole pool increases, the outlet blockage risk rises. The jet-breaker was used for improving the performance of drop manholes under Regime R2, in which the inlet jet collides with the manhole outlet. However, its effects on residence time were unknown, and its proper dimensions, in this regard, needed to be determined. Therefore, the effects of jet-breaker dimensions and the inlet pipe filling ratio on residence time were experimentally studied in this paper. Results showed residence time significantly reduces when the jet-breaker length and width are 2 and 1.4 times the inlet pipe diameter, respectively; jet-breaker sagitta is zero, jet-breaker angle is zero degrees, and the inlet pipe filling ratio is 80%. Under this optimum condition, residence time decreased 66% in comparison with the control test. [ABSTRACT FROM AUTHOR]

The earliest sewer networks of the city of Kolkata, or erstwhile Calcutta, covered a modest 19.1 km2 of the central district of the city and the first phase of the network-commenced operation in 1868. Calcutta, then, was the capital of imperial India under British rule and the combined sewer was only second in the empire after London. The conduits of this sewered catchment, and of the two others that followed subsequently, continue to be in operation despite heightened base flows due to population rise and increased stormwater runoff because of greater imperviousness arising from urbanisation. The recent lining of the sewer conduits or augmentation of the drainage pumping capacities has not, however, reduced street waterlogging during the monsoons by a great amount. One aim of this study is to investigate the reasons behind this failure of the system and evaluate the sustainability of these historic sewers with the help of mathematical models, verifying them as far as possible with the scant available data. The other objective is to make the reader aware of the engineering heritage of the country and document the available information about the Calcutta sewer networks for providing a base of reference for future researchers. [ABSTRACT FROM AUTHOR]

This article explores the career of Edward Bindon Marten, a civil and mechanical engineer based in the Black Country during the nineteenth and early twentieth centuries. It focuses on his role in sanitation engineering and industrial safety. In order to place him within the context of his time, the sanitary state of the nation and the Black Country is examined, as are steam boiler explosions including their consequences and prevention. Marten's work supplying clean water, building an effective sewerage system, inspecting steam boilers and undertaking accident analysis for coroners' inquests is explored. His non-technical abilities are also analysed, including his talent for communicating his knowledge and advice to a wide audience in an engaging manner. The article concludes that Marten made an important contribution to improving Black Country sanitary conditions, and to Black Country and nationwide industrial safety, and was a significant figure in the Black Country and beyond. [ABSTRACT FROM AUTHOR]

Scroll vortex intakes are commonly used in water supply, drainage and sewerage systems. Water flows into the intake via an eccentric approach channel, forming a swirling vortex flow with a stable air core along the dropshaft. Previous design theories have largely been based on unjustified assumptions on the velocity and pressure distributions of the vortex flow at the intake bellmouth. To clarify these assumptions, a validated three-dimensional computational fluid dynamics model has been developed. Model predictions compare well with independent measurements of flow profile, velocity and air core size. While the vortex flow in the scroll chamber can be described by a free vortex with constant circulation equal to that at the inlet, the tangential velocity and the pressure distribution at the bellmouth outlet have to be approximated by a forced vortex. A revised theory is proposed, providing significant improvement to the prediction of air core sizes and head–discharge relationship. [ABSTRACT FROM AUTHOR]

Wastewater materials change during transformation in sewer collection system. This study was conducted to evaluate the effects of temperature, mixed liquor suspended solids (MLSS) and velocity on the removal of organic pollutants and kinetic modelling in sewer systems. To evaluate the kinetics of organic pollutants, a pilot system was fabricated using a reactor in the laboratory scale. Chemical oxygen demand (COD) changes were assessed within 6 h of wastewater cycling in the reactor. The First order, Grau and Stover-Keane Canon models were used for predicting the removal of organic pollutants. The results showed that the pipeline removes COD during transformation. The results also showed that increased temperature, time and MLSS and decreased velocity significantly increased the removal of COD. Among the models used, the Grau and Stover-Keane Canon models efficiently predicted organic pollutants in real pipeline and the pilot system. It can be suggested that the Grau and Stover-Keane Canon models for predicting the removal of COD in sewer pipelines. The models can be used for more effective design and better real time control of wastewater treatment plants. [ABSTRACT FROM AUTHOR]

Separation in overflow spillways may occur when the hydraulic head is considerably greater than the design head. In this study, results obtained in a separation that occurred in a physical model were used for a numerical analysis of the phenomenon. A three-dimensional computational programme was used and the results using none or one of six different turbulence models were compared to the experiment. The results indicate that the renormalization group (RNG) model has a better capacity to simulate the separation zone; therefore, this turbulence model is recommended. Once separation still occurred when no turbulence model was used, the use of non-appropriate models may conceal the phenomenon. This is a computational indication that viscous effects have no major part in this separation condition, with the spillway profile being the most decisive aspect. When RNG was the applied model for several different hydraulic heads, good agreement in terms of discharge coefficient between numerical and physical model was obtained. [ABSTRACT FROM AUTHOR]

The main application of the mobile geo-electrical measurement is the detection of the presence and determining the location of leakage in sewer systems. To do so, this method relies on the increase in the measured electrical current between an electrode inside and an electrode outside the sewer system. To use this technique for the quantification of leakages further assumptions on the measured current are required. In this study, a model to simulate the geo-electrical measurement system is developed. Laboratory experiments are conducted to investigate the influence and contribution of the model components on the measured current and the validity of the assumptions. The experimental results demonstrate that multiple components significantly contribute to the measured current apart from the leakage in the pipe. As a consequence, the properties of the leakage in the pipe are likely to be significantly under- or overestimated in most measuring systems currently applied in practice. [ABSTRACT FROM AUTHOR]

Urban greenspace and green infrastructure are often cited for their many ecosystem services and benefits including stormwater management. However, the localized nature and limited range of effects of these benefits and the type of greenspace and green infrastructure, make planning and placement critical components to selecting for and maximizing desired benefits. Here, the authors test a framework to demonstrate a practical approach to simultaneously manage excess stormwater and maximize distribution of ecosystem services to underserved areas using spatial analysis. St. Louis was subdivided using census block polygons and polygons identified have combined sewer systems with high aggregate annual discharge. Additionally, indicators representing social, economic, and environmental characteristics, which have demonstrated effects from greenspace, were mapped to identify spatial distribution and overlap. The analysis identified one polygon that could promote multiple desired ecosystem services, while reducing annual discharge into combined sewers, and provide these services to an underserved demographic. [ABSTRACT FROM AUTHOR]

One of the most used 1D tools to model collection systems is the Storm Water Management Model (SWMM). Solving the full form of the Saint Venant equations, this model represents typical unsteady flow conditions in sewer systems. However, it may be insufficient to address fast transient flow conditions that can be present during extreme events or unscheduled operational conditions. SWMM version 5.1.013 was implemented the Preissmann slot as an alternative method to handle pressurization. To date, no studies were found analysing the applicability of SWMM to represent closed-pipe fast transient flows applying the Preissmann slot pressurization algorithm. Therefore, the present work investigates the ability to model different fast transients conditions in SWMM under various spatial and temporal discretizations along with variations in the Preissmann slot algorithm. Using an alternative implementation of the SLOT pressurization algorithm, along with artificial spatial discretization and routing time-steps estimated by the Courant stability condition, it is shown that SWMM is capable to perform satisfactory certain types of closed pipe transient simulations. [ABSTRACT FROM AUTHOR]

This study examines the efficiency and productivity of the Chilean water and sewerage industry over the period 2010–2017 using a stochastic cost frontier model. This methodological approach allowed us to evaluate the impact of water companies´ ownership on their productivity. This is very relevant for the Chilean water and sewerage industry which involves a public, full private and concessionary water companies. The results evidenced that the Chilean water and sewerage industry improved its productivity across years. However, the increase in the productivity of full private and concessionary water companies was larger than the one experienced by the public water company. [ABSTRACT FROM AUTHOR]

Certain sewer deterioration modeling approaches, represent the condition of a pipe as the sum of individual defect severities, leading to the loss of spatial information about defects in the pipe. This paper proposes a hybrid framework for incorporating spatial information of defects into the analysis of sewer pipe condition. The first component of the framework is called Defect Cluster Analysis (DCA) and it seeks to identify defect clusters (i.e. areas with multiple defects in proximity) and quantify their severity. The second component of the framework is called Defect Co-Occurrence Mining and it attempts to identify groups of defects, which occur simultaneously in pipes. The framework was evaluated on data from 7193 inspections of sewers in the US. Validation of the results by subject matter experts indicates that the proposed framework enables a fine-grained analysis of pipe condition and could be instrumental in rehabilitation decision-making. [ABSTRACT FROM AUTHOR]

This paper presents a novel model for predicting the sediment transport rate during flushing operation in sewers. The model was developed using the Evolutionary Polynomial Regression Multi-Objective Genetic Algorithm (EPR-MOGA) methodology applied to new experimental data collected. Using the new model, a series of design charts were developed to predict the sediment transport rate and the required flushing operation time for several pipe diameters. Accurate results (i.e. sediment transport rates) were obtained when applied to a case study in a combined sewer pipe in Marseille, as reported in the literature. The novelty of the model is the inclusion of the pipe slope, the inflow 'dam break' hydrograph, and the sediment properties as explanatory parameters. The new model can be used to predict flushing efficiency and design new flushing cleaning schedules in sewer systems. [ABSTRACT FROM AUTHOR]

The water and sewerage industry in England and Wales had undergone several reforms since its privatization. To evaluate to what extent they had impacted on the performance of water companies, an input distance function and its derived cost share equations was estimated. This allowed measuring technical efficiency, economies of scale and cost complementarities between water and sewerage services over the period 1991–2016. The results indicate that an average water and sewerage company (WaSC) reported a technical efficiency score of 0.731 which means that its inputs could be reduced by 26.9% over time. It is also shown that an average WaSC operated under decreasing economies of scale. Cost complementarities between water and sewerage connected properties were found. This implies that WaSCs could benefit from remaining integrated, i.e. providing both water and sewerage services. [ABSTRACT FROM AUTHOR]

The flow patterns in a street are investigated in the case of flow exchanges with the sewer. The experimental facility includes one street and one circular pipe located below eventually connected by one or two drains. Compared to the runs without drain or with drainage, overflow creates a strong (up to 50%) increase of the streamwise velocity in the street, particularly, near the bottom, and a high degree of turbulence close to the drains and downstream. For overflow from one drain, the rearrangement of the flow is marked by an asymmetrical pattern with a main secondary current moving across the street; this latter pattern disappears when two drains are present. In field conditions, such an increase is likely to permit entrainment of people and cars by the flow. The experimental data sets could help to validate detailed CFD models aiming at extending the latter results in various flooding conditions. [ABSTRACT FROM AUTHOR]

Pipe leakage from defect subsurface gravity sewer pipe networks potentially contaminates soil and groundwater. In recent times, an increasing number of numerical pipe leakage models incorporating pipe flow, saturated-unsaturated flow in the subsurface, and exchange fluxes from and to leaky pipes have been developed. Numerical benchmarks are required in order to demonstrate result accuracy of these models. The present technical note represents a novel numerical benchmark of the pipe leakage problem describing pipe water exfiltration into horizontal unsaturated-saturated soil. The present benchmark enables to test the accurate calculation of the spatial potential distribution in the soil, which is affected by the water level in the leaky pipe. The derivation of an analytical solution for stationary pipe water exfiltration into a horizontal aquifer and a conceptual model for the setup of a corresponding numerical model is shown. Results of the analytical model are reproduced using the numerical leakage model OGS-HE. [ABSTRACT FROM AUTHOR]

The optimal scheduling of water pumping systems has gained a lot of attention in the research community. Nevertheless, the advancements obtained in water distribution networks were not transferred to urban drainage sewer systems, due to the reduced storage volumes of the wet wells and the high flows variability. Moreover, the use of variable speed drives, which are required to face the flow variability, makes the problem more complex. In this paper, the authors present an optimization method for the regulation of a pump in a separate foul sewer system under variable inflow. A stochastic model has been calibrated on real data for the generation of the inflow patterns and several system conditions have been simulated. A mixed-integer optimizer was used to minimize the required energy. The results obtained were compared with the classic control rule showing that the use of variable speed drives can lead to large energy savings. [ABSTRACT FROM AUTHOR]

The toxic molecules evolved from sewer causes a threat to humans and animals. The prominent halogenated hydrocarbons, namely chlorobenzene, and 1,4-dichlorobenzene emitted from sewer are considered as target molecules. The adsorption features of chlorobenzene and 1,4-dichlorobenzene on theta arsenene sheets (θ-AsNS) are investigated based on the first-principles study. The adsorption of target molecules on θ-AsNS exhibits physisorption. The alteration in the electronic properties due to chlorobenzene and 1,4-dichlorobenzene on θ-AsNS are noticed with regard to band structure and projected density of states (PDOS) spectrum. The calculations suggest that θ-AsNS is appropriate material to detect the presence of chlorobenzene and 1,4-dichlorobenzene molecules. [ABSTRACT FROM AUTHOR]

Waste has been a generally overlooked material for historians of Cape Town. However, this article contends that it is through attendance to the material demands of waste with waste management infrastructure that the city landscape has been and continues to be produced. I examine this through four interconnected viewpoints, focussing on the years 1882 to 1913. First, in the late nineteenth century demands to manage waste justified the centralisation of planning power within the Cape Town City Council, increasing their ability to curate the city landscape. Second, through consistent reclamation, waste physically extended the shape of the city and allowed for its spatial and social reconfiguration. Third, in the attempts to isolate the city's black population after plague, the infrastructure set initially for waste management was instructive in the selection of the specific site for the newly prescribed 'Native Location'. Finally, as technological development in the twentieth century allowed the city's wealthier residents to distance themselves further from their detritus, waste came to greater effect the social and spatial scripts for the performances of race and class in relation to space. In all of this, I contend that as the city makes waste, the waste, in turn, makes the city. [ABSTRACT FROM AUTHOR]