Search Results (36)

This study addresses the microbial corrosion of cement-based materials in coastal urban sewer networks, systematically investigating the kinetic mechanisms of sulfur biogeochemical cycling under seawater infiltration conditions. Through dynamic monitoring of sulfide concentrations and environmental parameter variations in anaerobic pipelines, a multiphase coupled kinetic model integrating liquid-phase, gas-phase, and biofilm metabolic processes was developed. The results demonstrate that moderate salinity enhances the activity of sulfate-reducing bacteria (SRB) and accelerates sulfate reduction rates, whereas excessive sulfide accumulation inhibits SRB activity. At 35 °C, the mathematical model coefficient “a” for sulfate reduction in the reactor with 3 g/L salinity was significantly higher than those in reactors with 19 g/L and 35 g/L salinities, with no significant difference observed between the latter two. Overall, high sulfate concentrations do not act as limiting factors for sulfide oxidation under anaerobic conditions; instead, they enhance the reaction within specific concentration ranges. The refined kinetic model enables prediction of sulfur speciation in tropical coastal urban sewer pipelines, providing a scientific basis for corrosion risk assessment. Full article

Consecutive oscillatory eruptions of a mixture of gas and liquid in urban stormwater systems, commonly referred to as sewer geysers, are investigated using transient three-dimensional (3D) computational fluid dynamics (CFD) models. This study provides a detailed mechanistic understanding of geyser formation under partially filled dropshaft conditions, an area not previously explored in depth. The maximum geyser eruption velocities were observed to reach 14.58 m/s under fully filled initial conditions ($h_w/h_d$ = 1) and reduced to 5.17 m/s and 3.02 m/s for partially filled conditions ($h_w/h_d$ = 0.5 and 0.23, respectively). The pressure gradients along the horizontal pipe drove slug formation and correlated directly with the air ingress rates and dropshaft configurations. The influence of the dropshaft diameter was also assessed, showing a 116% increase in eruption velocity when the dropshaft to horizontal pipe diameter ratio ($D_d/D_t$) was reduced from 1.0 to 0.5. It was found that the strength of the geyser (as represented by the eruption velocity from the top of the dropshaft) increased with an increase in the initial water depth in the dropshaft and a reduction in the dropshaft diameter. Additionally, the Kelvin–Helmholtz instability criteria were satisfied during transitions from stratified to slug flow, and they were responsible for the jump and transition of the flow during the initial rise and fallback of the water in the dropshaft. The present study shows that, under an initially lower water depth in the dropshaft, immediate spillage is not guaranteed. However, the subsequent mixing of air from the horizontal pipe generated a less dense mixture, causing a change in pressure distribution along the tunnel, which drove the entire geyser mechanism. This study underscores the critical role of the initial conditions and geometric parameters in influencing geyser dynamics, offering practical guidelines for urban drainage infrastructure. Full article

This study introduces an innovative energy harvesting system designed for industrial applications such as fluid pipelines, air conditioning ducts, sewer systems, and subsea oil pipelines. The system integrates magneto-electric flow coupling and utilizes a dynamic vibration absorber (DVA) to mitigate the vibrations induced by fluid flow while simultaneously harvesting energy through magnetic dipole–dipole interactions in a vibration energy harvester (VEH). The theoretical models, based on Hamilton’s Principle and the Biot–Savart Law, were validated through comprehensive experiments. The results indicate the superior performance of the small-magnet system over the large-magnet system in both damping and power generation. The study analyzed the frequency response and energy conversion efficiency across different parameters, including the DVA mass, spring constant, and placement location. The experimental findings demonstrated significant vibration reduction and increased voltage output, validating the theoretical model. This research offers new avenues for energy harvesting systems in pipeline infrastructures, potentially enhancing energy efficiency and structural integrity. Full article

This paper presents a Fault-Tolerant Model Predictive Control (FTMPC) algorithm applied to a simulation model for sewer networks. The aim of this work is to preserve the operation of the predictive controller as much as possible, in accordance with its operational objectives, when there may be anomalies affecting the elements of the control system, mainly sensors and actuators. For this purpose, a fault detection and diagnosis system (FDD) based on a moving window principal component analysis technique (MWPCA) will be developed to provide an online fault monitoring solution for large-scale complex processes (e.g., sewer systems) with dynamically changing characteristics, and a reconfiguration algorithm for the MPC controller taking advantage of its own features such as constraint handling. Comparing the results obtained considering various types of faults, with situations of normal controlled operation and with the behavior of the sewer network when no control is applied, will allow some conclusions to be drawn at the end. Full article

Wastewater pipelines are largely buried underground, and techniques for assessing and visualizing their condition are critical for planning and rehabilitation. This paper introduces a framework for integrating Geographic Information System (GIS), 3D-creation platform, augmented reality (AR) techniques, and machine learning algorithms for the dynamic visualization of the condition of sewer networks. A sewer network in Ålesund City, Norway, was used as a case study, and the developed framework was implemented on an Android OS and Microsoft HoloLens. The results show the potential applications of the integrated framework of GIS, AR, and 3D models for sewer condition visualization. The positioning accuracy of the application for 2D objects is equivalent to that of well-designed GPS receivers (approximately 1–3 m), depending on the handheld device used. Loading and locating 3D objects will be limited by the performance of the devices used. Full article

The loss coefficient is one of the most critical parameters in computing the hydraulic grade line of sewer systems. The head loss coefficient of a manhole is dependent on various hydraulic and structural characteristics, such as manhole mold, connection angle, and the ratio of manhole diameter to pipe diameter. Three different manhole molds, flat, half-bench, and full-bench, and connection angles of 180°, 90°, and 135° are investigated, where the manhole diameter to pipe diameter ratio is 5.3. This paper presents the results of experimental and numerical investigations focused on determining the loss coefficient for two-way straight-through and angled manholes. The flow structure inside the chimney is the significant parameter for the magnitude of the energy loss coefficient. The head loss coefficient is almost constant under the surcharged flow conditions for all kinds of manholes. In terms of head loss coefficients, half-channel manholes do not have a significant advantage over flat-bottomed manholes in the cases of 135° and 90° flow inputs. The full-bench bottom manhole head loss coefficient is the smallest. The computational fluid dynamic modeling results agree with the experimental studies. Full article

Combined sewage overflows (CSOs) are a common consequence of heavy rainfall events and can have significant implications for water quality in receiving waterbodies. With climate change, these events are becoming more frequent and intense, placing greater pressure on aquatic ecosystems. To prevent water pollution, it is essential to utilize numerical tools to investigate, forecast, and establish control measures for CSOs. Typically, these tools involve a dynamic model for flow simulation combined with either a detailed model for pollutants or a simplified event mean concentration (EMC) calculation. However, both approaches have drawbacks: a detailed model requires extensive calibration time, while the EMC does not account for system dynamics. To overcome these issues, a novel system was developed that integrates the dynamic nature of the detailed model with the rapid calibration of the EMC. This model employs two distinct concepts for pollution modeling: one for soluble compounds and one for suspended solids. The resulting model was evaluated at multiple locations with varying hydraulic dynamics, demonstrating its potential utility at any location where a dynamic model of the sewer system is available. Full article

This article presents a distributed model predictive control algorithm including fuzzy negotiation among subsystems and a dynamic setpoint generation method, applied to a simulated sewerage network. The methodology considers WWTP as an additional objective of control. To improve the performance of a DMPC using a hydraulic model for prediction, a more detailed model has been considered including suspended solids concentration (TSS). The results obtained with the proposed methodology have been validated on a benchmark simulation model for sewer systems developed to test and compare methodologies, showing good performance. Full article

Urban pluvial floods (UPFs) are a threat that is expected to increase with economic development, climate change, and the proliferation of urban cover worldwide. Methods to assess the spatiotemporal magnitude of UPFS and their impacts are needed to research and explore mitigation measures. This study presents a method for the assessment of UPFs and their impacts by combining a hydrodynamic sewer system model with a GIS-based overland diffusive flow algorithm. The algorithm is implemented in the software GIS-based Agent-based Modeling Architecture (GAMA) along with the depth-damage functions and land use data to estimate financial impacts. The result is a dynamic and interactive model that allows the user to monitor the events in real-time. Functionality is demonstrated in a case study in Dresden, Germany and with ten to 100-year design storms. The majority of flood extents and damages occur in the early stages of the event. Sewer surcharge emerges from few of the manholes, suggesting early action vitally reduces flood risks and interventions at a few hot spots, largely reducing impacts. Flood protection barriers were interactively implemented as a potential response measure in the hot spot areas reducing the damage by up to 90%. The user can compare different parameters in a visually compelling way that can lead to a better understanding of the system and more efficient knowledge transfer. Full article

Identifying the location and estimating the magnitude of urban pluvial flooding events is essential to assess their impacts, particularly in areas where data are unavailable. The present work focused on developing and exemplifying a tool to evaluate urban pluvial flooding based on open-access information. The tool has three separate submodules: (1) sewer network generation and design; (2) hydrodynamic model development; (3) urban pluvial flood evaluation. Application of the first two modules in two catchments and comparison of these results with real data indicated that the tool was able to generate systems with realistic layouts and hydraulic properties. Hydrodynamic models derived from this data were able to simulate realistic flow dynamics. The third module was evaluated for one of the study cases. The results of this indicated that the current approach could be used to identify flood areas and associated flood depths during different rainfall scenarios. The outcomes of this study could be used in a wide variety of contexts. For example, it could provide information in areas with data scarcity or uncertainty or serve as a tool for prospective planning, design, and decision making. Full article

The conventional top-down scope of relying only on centralised sewerage has proven insufficient to reach the entire global population with safely managed sanitation and meet Sustainable Development Goals 6.2. and 6.3 by 2030. Citywide Inclusive Sanitation (CWIS) has emerged as an approach to accelerate progress by considering different technologies and service provision models within the same city to expand sanitation access equitably and sustainably. However, to generate an enabling environment for CWIS to be implemented successfully, regulatory frameworks must be adapted, as they are often unsuited for non-sewered sanitation solutions. By analysing the Colombian case study through a mixed qualitative methodology comprised of a policy review, semi-structured interviews, and workshops with key stakeholders in the urban sanitation sector, the country’s regulatory framework was evaluated to determine if it is adequate to implement CWIS. Regulations were identified to pose barriers for CWIS and produced a disabling environment for its application. This research proposes recommendations to adapt the regulatory framework to allow CWIS application in Colombia based on the encountered barriers. This is the first comprehensive study on regulations for CWIS in the Latin American context and therefore provides the basis for further research to understand the dynamics related to effective regulations for CWIS globally. Full article

Elevated phosphorus loads play an important role in the deterioration of water quality and can subsequently pose a threat to the aquatic organisms in a river or a standing water body. The accurate assessment of total phosphorus (TP) fluxes from a catchment is of high importance to the well-being of the entire river ecosystem. In this study, we assessed the yearly input of TP from the urban areas of the Passaúna catchment in southern Brazil. The catchment drains into the eponymous reservoir, which provides drinking water for more than 800,000 inhabitants of the Curitiba Metropolitan region. The protection of the water quality in the river as well as in the reservoir is of paramount importance, yet high phosphorous inputs have been detected. For adequate protection, the catchment emissions need to be accurately assessed. Initially, the TP concentration in the river sediment was determined in order to assess the relationship between the TP export of the urban areas and the TP stock of the river. It was found that in areas with a higher share of urban land cover and especially in areas with a lack of sewage treatment, the TP concentration in the sediment reached up to 6700 mg/kg. The assessment of the overall TP input from urban areas was based on a regionalized emission-modeling approach, combined with data from long-term water quality monitoring of the river. The monitoring station established upstream of the Passaúna Reservoir inflow provided an initial assessment and the necessary output for the validation and calibration of the model. From the drainage basin of the monitoring station, an overall TP input of 2501 kg/a (0.31 kg/(ha a)) was measured between 1 May 2018 and 1 May 2019 (3508 kg TP/a or 0.23 kg/(ha a) when extrapolating the overall catchment of the Passaúna Reservoir). The monitoring data indicated that the TP input increases during the wet months of the year. The sediment stock of the river also plays an important role in the interannual budget of TP. During the timespan of one year, many deposition–resuspension events happen. The resuspended material is included in the baseflow and hinders the differentiation between urban and nonurban input. After calibration, the model was able to predict the yearly input of TP from the urban areas of the Passaúna catchment. In addition, the share of inhabitants who are not connected to the sewer system was assessed. Overall, the combination of monitoring and modeling in this study offers a valuable overview of the TP dynamics of the system, while the model ensures reproducibility with high accuracy at the same time. Full article

A sewer dynamic model (SDM), an innovative use of combined models, was established to describe the reactions of compounds in a pilot sewer pipe. The set of ordinary differential equations in the SDM was solved simultaneously using the fourth-order Runge–Kutta algorithm. The SDM was validated by calculating the consistency between the simulation and observation values. After the SDM was validated, the reaction rate was analyzed. For heterotrophs in the water phase and biofilm, their growth rates were greater than the organism decay rate. For ammonia, the supply rate was greater than the consumption rate at the initial time, but the supply rate was smaller than the consumption rate from the 3rd hour. The supply rate was smaller than the consumption rate for the other six compounds. The supply rate of oxygen was smaller than the consumption rate before the 4th hour because of the microorganism activities, and, subsequently, the supply rate was greater than the consumption rate after the 4th hour because of reaeration. The results of this study provide an insight into the reaction rates of different compounds in urban sewer pipes and an urban water network modeling reference for policymaking and regulation. Full article

The aim of this study is to develop a relocatable modelling system able to describe the microbial contamination that affects the quality of coastal bathing waters. Pollution events are mainly triggered by urban sewer outflows during massive rainy events, with relevant negative consequences on the marine environment and tourism and related activities of coastal towns. A finite element hydrodynamic model was applied to five study areas in the Adriatic Sea, which differ for urban, oceanographic and morphological conditions. With the help of transport-diffusion and microbial decay modules, the distribution of Escherichia coli was investigated during significant events. The numerical investigation was supported by detailed in situ observational datasets. The model results were evaluated against water level, sea temperature, salinity and E. coli concentrations acquired in situ, demonstrating the capacity of the modelling suite in simulating the circulation in the coastal areas of the Adriatic Sea, as well as several main transport and diffusion dynamics, such as riverine and polluted waters dispersion. Moreover, the results of the simulations were used to perform a comparative analysis among the different study sites, demonstrating that dilution and mixing, mostly induced by the tidal action, had a stronger effect on bacteria reduction with respect to microbial decay. Stratification and estuarine dynamics also play an important role in governing microbial concentration. The modelling suite can be used as a beach management tool for improving protection of public health, as required by the EU Bathing Water Directive. Full article

In this work, a Distributed Model Predictive Control (MPC) methodology with fuzzy negotiation among subsystems has been developed and applied to a simulated sewer network. The wastewater treatment plant (WWTP) receiving this wastewater has also been considered in the methodology by means of an additional objective for the problem. In order to decompose the system into interconnected local subsystems, sectorization techniques have been applied based on structural analysis. In addition, a dynamic setpoint generation method has been added to improve system performance. The results obtained with the proposed methodology are compared to those obtained with standard centralized and decentralized model predictive controllers. Full article