Search Results (152)

In fecal sludges (FSs) from non-sewered sanitation systems, bound moisture constituted 46–67% of total moisture across all sanitation types investigated, yet the energetic basis for its resistance to removal has not previously been characterized. Existing classifications of moisture fractions lack quantitative binding energy data, leaving the thermodynamic limits of solid–liquid separation undefined for FS. This study investigates the distribution and binding energies of bound moisture fractions in FS obtained from ventilated pit latrines, urine-diverting dehydrating toilets, and septic tank systems. Bound moisture fractions were determined using moisture sorption isotherms, low-temperature convective drying, nuclear magnetic resonance, and thermogravimetric–differential scanning calorimetry analyses. Results show that interstitial moisture constituted 37–50% of total moisture, followed by vicinal (6–14%) and intracellular (3–9%) fractions, with net isosteric heat rising sharply below 20–30% moisture content (w.b.). Evaporation enthalpy exceeded that of bulk water at moisture contents below ~30% (w.b.), consistent with EPS-mediated adsorption and capillary confinement contributing to increased energy requirements for moisture removal and indicating a transition from capillary-controlled to structure-influenced retention. These findings provide a thermodynamic basis for interpreting why conventional mechanical dewatering stalls at a residual moisture content that differs systematically between VIP, UDDT, and septic tank sludges. These insights are relevant for improving FS treatment strategies, particularly in selecting appropriate combinations of dewatering, drying, and pre-treatment processes. Full article

Predictive Maintenance (PdM) approach in Combined Sewer Systems (CSS) is gaining momentum due to advances in sensor technology, affordability and availability of data, and the rise of machine learning and data analytics. This study aims to characterize the general behavior of CSS under Dry and Wet weather conditions. To achieve this, 10 min resolution precipitation and water level data were collected from nearby SIAS stations and AMAP radar water level sensors, installed at the outlet chamber of the CSS, respectively. Precipitation data was used to segment continuous time series data into Dry Weather Flow (DWF) and Wet Weather Flow (WWF). DWF analysis exhibited unique flow patterns that strongly correlated with water consumption behaviors of households. For wet weather, a comparison was made between key rainfall parameters (depth, intensity) and peak water level data, and nonlinear relationships were observed that highlight the complex rainfall–runoff process. These findings underscore the need for separate predictive models tailored to DWF and WWF characteristics. Integrating high-resolution sensor data with machine learning models such as Long Short-Term Memory (LSTM) networks and anomaly detection, Autoencoders can enhance PdM, improving CSS management and reducing risks of blockage events and infrastructure failures. Full article

Pharmaceuticals and personal care products (PPCPs) are widely recognized as persistent contaminants in urban aquatic systems, yet their behavior is typically interpreted under steady-state assumptions driven by continuous discharge of treated wastewater. This paradigm overlooks the dominant role of episodic pollution pulses associated with combined sewer overflow (CSO) events. This review advances a new conceptual framework in which PPCP contamination is understood as a manifestation of complex phenomenon, arising from the interaction of intense precipitation, hydraulic exceedance of sewer systems, and mobilization of accumulated contaminants. We critically synthesize current knowledge on the occurrence, transport, transformation, and removal of PPCPs across wastewater effluents and CSO discharges, integrating insights from degradation kinetics, environmental monitoring, and treatment technologies. Comparative analysis reveals strong matrix-dependent variability in PPCP attenuation, with enhanced degradation in estuarine and marine systems driven by complex photochemical and biogeochemical interactions. However, under CSO-driven pulse conditions, these processes become transient and non-linear, challenging conventional assumptions of steady-state degradation and risk assessment. The findings highlight that CSO events can generate short-duration but high-intensity contamination peaks, often exceeding baseline concentrations and potentially amplifying ecological risks and antimicrobial resistance selection. We propose a matrix-reactivity and pulse-driven framework to better capture the dynamic fate of PPCPs under real-world conditions. Future research should prioritize event-based monitoring, real-time sensing, and time-resolved risk assessment models to address the limitations of current approaches. This work redefines PPCP pollution as a dynamic, episodic, extreme-event-driven process, with important implications for urban water management under increasing climatic variability. Full article

The revised EU Urban Wastewater Treatment Directive (UWWTD, EU 2024/3019) expands the scope of the previous directive (Council Directive 91/271/EEC, 1991) by explicitly including combined sewer systems, stormwater discharges, and overflow events while promoting energy neutrality and reducing greenhouse gas (GHG) emissions across urban wastewater systems. Although the Directive establishes energy accountability at the system level, it does not define how energy performance in wastewater collection networks should be structured, assessed, or benchmarked, resulting in a significant implementation gap. This paper presents a novel, regulatory-aligned, data-driven framework to organise, analyse, and interpret energy-relevant information in support of UWWTD requirements, with specific focus on wastewater collection networks. Using Portuguese regulator datasets, supplemented with published sources, existing metrics are reorganised into energy-significant dimensions that differentiate structural, excess-driven, operational, and renewable-related components of energy use. The preliminary findings show that available datasets already support a screening-level diagnosis of specific energy intensity, pumping-related energy shares, inflow-driven excess volumes, and associated GHG emissions. However, important gaps remain regarding subsystem disaggregation, hydraulic normalisation, and measurement granularity. The study restructures existing information into a novel audit-compatible framework, proposes additional metrics and measurement requirements, and identifies measures to facilitate UWWTD implementation. Although developed for the Portuguese context, the framework offers a scalable pathway for integrating wastewater collection networks into energy neutrality governance across European Member States. Full article

Methane (CH₄) emissions in urban areas remain a major source of uncertainty in greenhouse gas inventories, particularly in Eastern European cities, where observational studies are limited. This study presents a comprehensive, system-based assessment of CH₄ sources in Cluj-Napoca, Romania, based on high-resolution in situ measurements across five representative urban systems: aquatic environments (AQs), natural gas distribution end-use points (NG), sewer infrastructure (SE), building basements (BSs), and traffic emissions (TEs). Elevated CH₄ concentrations were consistently detected across all investigated systems, confirming the coexistence of both diffuse and point sources within the urban environment. Dissolved methane (dCH₄) in aquatic systems showed strong and persistent oversaturation relative to atmospheric equilibrium, reaching up to 3 × 10⁵% of air–water equilibrium, indicating active microbial methanogenesis enhanced by urban inputs of organic matter and nutrients. Measurements at natural gas end-use points revealed highly localized leaks with concentrations up to 482 ppmv. Sewer infrastructure exhibited extreme variability (up to 1222 ppmv), likely controlled by a combination of microbial production, hydraulic conditions, and potential interactions with adjacent gas distribution networks. Basement environments showed CH₄ accumulation up to 12 ppmv, reflecting the combined effects of gas leakage and limited ventilation. Measurements at vehicle exhausts identified transient CH₄ peaks reaching 162 ppmv during vehicle engine acceleration, with distinct ethane-to-methane ratios, indicative of pyrogenic sources. Overall, these results demonstrate that urban CH₄ emissions are spatially heterogeneous, temporally variable, and derived from multiple coexisting sources. The urban area should, therefore, be understood as a hybrid environment, with natural and anthropogenic CH₄ contributions. Full article

Sewerage systems are among the most fundamental and indispensable components of urban infrastructure. However, inadequate management can result in malfunctions and subsequent rehabilitation processes, leading to various negative consequences. Identifying areas at high risk of failure and conducting system-based inspections can significantly improve the performance of sewer networks. This study identified and categorized 33 criteria that could cause sewer system failures: structural, operational, hydraulic and environmental defects. A Bayesian network (BN) model was developed to determine dependencies between the criteria, quantify uncertainty, investigate new information about the structural condition of assets and calculate the effects and sensitivities of the criteria on the probability of failure. A probability-based risk assessment model was then created using a fuzzy inference system (FIS) to predict risk levels in sewerage systems under different combinations of physical and operational conditions and hydraulic and environmental effects. A case study was performed on a sewer network in Malatya, Turkey, determining its failure probability to be 76.6%, placing it in the high-risk category. When the probability of pipe failure was set to 100% in the Bayesian network model to evaluate the relative influence of different criteria, the most influential factors were identified as flow velocity (74.8%), clogging (71.4%), and failure rate (71.1%). Thanks to the flexible structure of BNs, the proposed model is expected to be useful for performing risk analyses in systems involving uncertainty or missing data. It can also be used to prioritize rehabilitation, inspection and maintenance programs, improve infrastructure service quality and ensure system reliability in urban sewerage systems. Full article

This dataset compiles continuous hydraulic and water quality observations from the combined sewer overflow structure at the outlet of the Graz-West R05 catchment in Austria, covering the period from 2008 to 2011. It integrates high-resolution in-sewer measurements of flow rate, water level, flow velocity and water quality parametres (COD, TSS, temperature), complemented by laboratory analyses of discrete grab samples. Water quality parametres were monitored using an in situ UV/VIS spectrometer installed on a floating pontoon. Additional locally calibrated COD values derived from laboratory measurements are included. The in-sewer data were acquired at 1 or 3 min intervals depending on flow conditions. Flow rates, water levels and overflow discharges were monitored using radar and ultrasonic sensors. Three nearby tipping-bucket rain gauges provided time-stamped precipitation increments, enabling the detailed reconstruction of wet-weather dynamics. A hydrodynamic SWMM model of the catchment, including geospatial information and dry-weather calibration, is included to support modelling applications. This combination of long-term measurements and a calibrated hydrodynamic model supports the development, testing and validation of process-based, statistical or data-driven approaches for simulating combined sewer system behaviour and pollutant dynamics. Full article

Wastewater-Based Epidemiology (WBE) has emerged as a critical tool for monitoring SARS-CoV-2 circulation at the community level. This study assessed spatiotemporal viral dynamics in Las Heras, Mendoza, Argentina, by comparing wastewater samples from six sewer maintenance holes and three wastewater treatment plants (WWTPs) between January and June 2021, and by conducting long-term surveillance at Campo Espejo WWTP during epidemic (2020–2021) and endemic (2024–2025) phases of COVID-19. Viral particles from sewer manholes and WWTPs samples were concentrated by polyethylene glycol precipitation or aluminum polychloride adsorption–precipitation methods, and then SARS-CoV-2 RNA was quantified by reverse transcription quantitative polymerase chain reaction targeting N1 and N2 nucleocapsid viral markers. Results showed consistent detection of viral RNA across all sites, with peaks in wastewater preceding diagnosed COVID-19 cases increases, confirming WBE as an early-warning system. Localized sewer sampling identified urban hotspots, while WWTPs monitoring captured broader epidemiological trends. Recently, COVID-19 surveillance showed lower and intermittent viral loads, decoupled from diagnosed cases, compared to epidemic phase, indicating a transition to endemic circulation. Overall, combining upstream and downstream WBE enhanced spatial and temporal resolution, demonstrating its utility for public health monitoring during both epidemic and endemic phases. Full article

The performance of a building drainage system, “BDS”, is determined by the complexity of internal airflow and pressure dynamics, governed by unsteady wastewater flows from randomly discharging appliances such as WCs, sinks, and baths. Designers attempt to optimise system safety by equalising pressure and incorporating ventilation pipes and active devices such as AAVs and positive pressure reduction devices (PPRDs). However, failures within these systems can lead to foul gases and potentially hazardous microbes entering habitable spaces and posing a risk to public health. This study, for the first time, develops a novel model that simulates the effect of air from the sewer on BDS performance, which describes the correlation between system airflow and air pressure under the influence of air from the sewer. A combination of full-scale laboratory experiments representing a 3-storey building and real-world data from a 32-storey test rig configured as a building demonstrated that sewer air significantly modifies airflow and air pressure within a BDS. These findings are crucial for modern urban environments, where the prevalence of tall buildings amplifies the risks associated with air pressure transients. This work paves the way for updating codes to more effectively address real-world challenges. Full article

This paper examines the tensions between existing infrastructure and the need for transitional change in Dutch municipal wastewater collection and treatment. In the Netherlands, sanitation is primarily managed by public actors, with local government playing a major role. The paper demonstrates how local governments navigate these tensions and are both restricted and enabled by the current infrastructure and governance arrangements. Based on interviews, literature reviews, and analyses of statistical trends, it describes five attempts at reform in Dutch sanitation from 1980 to 2020: phosphorus removal; separating stormwater from combined sewers; water cycle companies; energy factories; and decentralized sanitation. The multi-level governance system, with decentralized infrastructure and financing, allows local governments to experiment with alternative practices, develop knowledge, and employ various interactions to mainstream innovations. However, the division of tasks in Dutch sanitation governance tends to optimize sub-systems rather than the entire system. For nationwide implementation, legislation and strong central coordination are essential. Additionally, New Public Management reinforces existing infrastructure lock-in. The paper enhances our understanding of the local government’s role in transitional change and offers insights into how the challenges of existing infrastructure can be mitigated in pursuit of sustainable wastewater solutions. Full article

Building drainage systems are essential for protecting occupant health and indoor air quality. While recent studies have focused on high-rise drainage dynamics and riser offset mitigation, ventilation components—particularly appliance vent pipes—remain underexplored. This study employed a full-scale proportional drainage experimental tower to assess appliance vent pipes on horizontal branches as a strategy for water seal protection in dual-riser systems. Maximum drainage capacities were quantified under varying pipe positions and diameters (DN50, DN75, DN100), alongside analyses of pressure transients and water seal losses. Results indicate that appliance vent pipes increase maximum drainage capacity from 6.5 L/s (baseline cast iron dual-riser) to 7.5 L/s, a 1.0 L/s gain, though improvements are modest. Position does not affect capacity (uniformly 7.5 L/s across configurations) but profoundly influences water seal losses: P-type trap placement yields the lowest losses on most floors, combined P-type trap/floor drain placement achieves intermediate values, and floor drain placement the highest. Thus, the P-type trap is optimal. Diameter similarly has no impact on capacity but shows nuanced effects on seals; DN75 minimizes losses on most floors, outperforming DN50 and DN100, indicating that appliance vent pipe design should adopt a height-zoned approach tailored to anticipated drainage loads and pressure characteristics. Appliance vent pipes effectively dampen positive/negative pressure fluctuations, reducing seal depletion and sewer gas risks. These findings guide engineering designs for healthier indoor environments in high-rise buildings. Full article

The water quality characteristics of urban stormwater in a small town (La Almunia, 8000 inhabitants) in Northeast Spain with a combined sewer system have been studied. A specific device was designed to collect stormwater just before it enters the drainage network at five different points in the urban area, thus obtaining an approximate calculation of the mean event concentration values for the surface runoff generated during eight rainfall episodes. The results obtained demonstrated a high variability in the average concentrations of the events. The highest measured values corresponded mainly to the periods of the greatest road traffic from agricultural machinery within the town (harvest and manure seasons), resulting in peaks mainly in electrical conductivity and dissolved oxygen demand. This finding has been confirmed by the spatial study of the results, since the maximum values of these parameters were located in those areas of preferential transit of agricultural machinery; in addition, a possible relationship has also been observed between the maximum values of nitrogen and phosphorus in stormwater and older urban areas, due to the washing of bird droppings accumulated on the roofs. In general, all obtained results indicate that the stormwater samples generated in La Almunia present a low contaminant load, with the mean concentration event values calculated for half of the events falling within the discharge limit values established by the European Union. This fact, combined with the spatial and temporal location of the highest levels of stormwater pollution, helps evaluate urban cleanup operations and the operational capacity of both the urban drainage network and the wastewater treatment plant. Full article

Combined sewer overflow (CSO) pollution threatens urban water environments, yet optimizing integrated green–grey infrastructure solutions remains computationally intensive, often making robust, large-scale multi-algorithm comparisons impractical. This study’s primary contribution is the development of an innovative physics-guided optimization framework that overcomes this computational barrier. By coupling a deep learning surrogate (trained on 60,000 scenarios generated in 7.7 h) with evolutionary algorithms, this framework provides a 6.2- to 7.7-fold acceleration in total project time (approximately 13 h vs. 80–100 h) compared to direct SWMM optimization. This significant speedup enabled a comprehensive comparative analysis of four multi-objective evolutionary algorithms (MOEAs), which established NSGA-II’s superiority in discovering a larger and more diverse set of optimal trade-off solutions. The physics-guided surrogate achieved an R² of 0.9965 and a Mean Absolute Error (MAE) corresponding to 0.5% of the baseline overflow volume. The validated framework successfully identified Permeable Pavement as the dominant control variable and a critical knee-point scenario. This solution, requiring a 426 million CNY investment, achieved a 67.0% overflow volume reduction and a 74.4% COD load reduction under the 5-year design storm. Furthermore, the optimized system demonstrated high resilience to extreme events, contrasting sharply with the failure of a cost-minimized approach, which underscores the importance of designing for resilience. This framework provides urban planners with a validated, efficient, and reliable methodology for designing resilient, cost-effective CSO control systems. Full article

Rapid urbanization in China has overwhelmed traditional drainage systems, resulting in frequent flooding and water pollution in densely populated urban areas. This study focuses on the East Lake core area of Wuhan, proposing a deep tunnel drainage system to improve sewage storage and conveyance capacity. A pilot-scale pipe model was employed to determine the critical non-silting velocity for full-pipe sewage flow. Based on projected dry-season inflows and intercepted combined sewer discharges, the design capacities for pumping stations and pretreatment facilities were defined. A three-dimensional gas–liquid two-phase numerical model was used to simulate inflow shaft hydraulics at Erlangmiao, Luobuzui, and Wudong pretreatment stations. Simulation results confirm that all shafts meet energy dissipation and ventilation requirements, with uniform flow and velocity distributions that could be obtained by a vortex-type shaft. The system not only mitigates regional environmental challenges but also shows significant social, environmental, and economic benefits. Overall project design, applied methodology, simulation study, and outcomes could provide a valuable reference to deep tunnel drainage design and research. Full article

One of the limiting factors in the implementation of water resource management is the absence of tools that help water programs evaluate processes and progress. This is because, until now, the indicators that have been developed have not addressed specific local characteristics and issues. Therefore, in this research, a set of indicators has been proposed, with the purpose of developing a management index for urban public water supply, which will consider the Drinking Water and Sewer System of León (SAPAL), in the Mexican state of Guanajuato, as case study. This index will be useful to measure progress toward sustainable development, monitor the impact of public policies, and foster citizen participation. In order to propose a methodology that aligns with the changing environments, where proper decision-making is key to the current water management requirements, the combination of the Analytic Hierarchy Process (AHP) and Fuzzy Logic (FL) methodologies will be helpful for proper decision-making. All this will foster a paradigm shift towards appropriate water management actions that allow for the conditions and availability of human and natural resources, which the municipality has control of, for a long-term improvement that guarantees the well-being of the population. Full article