Jul 2026· AQUA — Water Infrastructure, Ecosystems and Society· Vol 75, pp. 628-639· 0 citations· 17 references
Abstract
Service reservoirs (SRs) are critical assets within drinking water distribution systems, yet water service providers (WSPs) lack methods for in-service performance assessment. Using data from 17 SRs and 2 WSP, a novel framework assessing SR integrity and mixing characteristics is developed and validated. While single-parameter analysis yields limited insights, combining level and flow data enabled mass balance calculations to detect integrity issues such as leaks and ingress up to 3 months before the scheduled inspections. Hydraulic residence time calculations, based on flow and level data, identified SRs operating beyond their recommended range with water age, sedimentation, and disinfectant residual consequences. By comparing hydraulic to cross-correlation residence times, calculated using inlet and outlet conductivity data, SRs exhibiting short-circuiting were identified. These were linked to poor mixing behaviour, creating zones of reduced disinfectant residual and higher bacteriological risk. An operational trial was subsequently conducted that demonstrated that by enhancing the SR level cycling, an approach highlighted by self-organising map analysis of data from 329 SRs, a 33% improvement in mixing was obtained. This new framework, using standard network data, facilitates WSPs to transition from reactive and periodic assessment of SRs to proactive and effective real-time smart water infrastructure management.
The increasing contribution of non-dispatchable renewable energy sources has changed the operating patterns of hydropower plants, especially in run-of-river schemes with limited storage capacity. Under intermittent dispatch, turbine shutdowns may occur while environmental-flow requirements must still be maintained. In these situations, spillway releases become more frequent, creating hydraulic conditions that can lead to total dissolved gas (TDG) supersaturation downstream. This study evaluates TDG supersaturation as an operational constraint in an Amazonian run-of-river hydropower plant. This assessment combines field measurements with controlled laboratory exposure tests using representative native fish species. Total gas pressure (TGP) was measured in both field and laboratory settings and converted into TDG saturation percentages. A laboratory-scale TDG generation system was developed to reproduce supersaturation conditions associated with spillway operation. Field measurements recorded TDG levels above 130% during spillway-activation events associated with dispatch decisions. In the laboratory, exposure tests showed rapid loss of viability in native Amazonian fish at TDG levels of 115% and above. These results indicate operational warning ranges for sustained spillway use. The findings suggest that TDG supersaturation should not be treated solely as an environmental issue. Rather, it represents a technical constraint on hydropower dispatch in systems with increasing renewable penetration. Incorporating TDG-related limits into operational planning and spillway management may help preserve hydropower flexibility while supporting environmental compliance.
G. Ferraz, C. Martinez, D. Ribeiro et al.· Water· 1 citation
Landfill leachate circuits that operate without discharge, by recirculating aerated leachate onto the waste mass, are widespread in South-East Europe, yet their long-term behaviour is rarely documented with sample-level data. This study reports a six-year (2020–2025) seasonal monitoring campaign at a sanitary landfill in northern Serbia (alluvial aquifer of the Sava River, transboundary Danube basin) and re-examines it with a transparent multivariate protocol. Seventy-two leachate samples (collection well, aeration lagoon, sedimentation lagoon; n = 24 each, 30 parameters), 28 realised surface-water campaigns, and six years of groundwater summaries were evaluated by principal component analysis/factor analysis (PCA/FA, Varimax normalized), hierarchical cluster analysis, PERMANOVA, non-parametric paired tests and, for benchmarking, supervised machine learning. The pooled leachate model (n = 72; 21 variables; KMO = 0.700; Bartlett χ2 = 956, p < 0.001) retained four factors by parallel analysis, explaining 61.6% of total variance; after rotation the factors accounted for 27.7%, 14.3%, 10.4%, and 9.3%. Factor 1 grouped organic load with particle-reactive metals (COD, BOD5, Fe, Ni, Cr, As, Zn), Factor 2 a reduced sulfur–fluoride–BTEX signature, Factor 3 temperature-driven nitritation, and Factor 4 a nitrate–manganese redox contrast. Crucially, paired campaign-by-campaign comparison showed no removal of the dominant pollutants along the circuit. Median COD, BOD5 and NH4-N were not lower in the sedimentation lagoon than in the collection well, while pH rose from 8.08 to 8.75 (p < 0.001); only Cu, Pb, NO3-N, and NO2-N decreased significantly. The circuit therefore homogenises and concentrates dissolved load rather than removing it. Downstream surface water was significantly enriched in electrical conductivity (+110 µS/cm), total dissolved solids, NH4-N, and NO2-N relative to upstream (Wilcoxon, p < 0.05), and groundwater showed episodic conductivity up to 12,760 µS/cm and NH4-N up to 102 mg/L. Cytotoxicity (MTT) confirmed biological relevance, with MRC-5 viability falling to 37% after 24 h exposure to 50 vol.% groundwater (Pw3) versus 60% in A549 cells. A random-forest classifier separated circuit units far better than PCA-based discrimination (76.4% versus 54.2% cross-validated accuracy) and distinguished the 2020–2021 pandemic period from 2022–2025 with 94.2% accuracy, a period effect also confirmed by PERMANOVA (R2 = 7.2%, p < 0.001). The results indicate that closed-loop recirculation without an engineered discharge barrier transfers, rather than eliminates, contaminant load, and that after-care of such systems requires mass-balance monitoring and polishing treatment.
N. Grba, V. Mihajlović, Goran Benedeković et al.· Processes· 0 citations
Urban combined sewer systems are increasingly challenged by climate-intensified rainfall, combined sewer overflows, and receiving-water degradation. This study presents a retrospective evaluation of a hybrid green-gray retrofit program implemented in the Zhenjiang Sponge City pilot watershed, China, where green stormwater infrastructure, drainage network upgrades, and a centralized deep tunnel system were integrated within a densely developed watershed constrained by limited space, low native-soil permeability, shallow groundwater, and aging infrastructure. System performance was evaluated using long-term operational observations, representative hydraulic and water-quality monitoring, municipal operational records, and supporting engineering analyses at both facility and watershed scales. The results demonstrated sustained hydraulic functionality after 7–10 years of operation, with approximately 90% of the monitored bioretention systems maintaining effective infiltration rates greater than 80 mm h−1. Event-based monitoring indicated substantial reductions in runoff volume and pollutant loads, including TSS, COD, NH3–N, and TP. Following implementation, annual combined sewer overflow occurrence at major outfalls decreased from 318 to 24 events, representing a 92.5% reduction. Supporting engineering analyses indicated that green stormwater infrastructure retrofits alone reduced overflow frequency by approximately 41.8% and overflow volume by approximately 61.1%, while integration with deep tunnels increased reductions to approximately 58.8% and 85.3%, respectively. Official receiving-water monitoring records further indicated that Class III or better water-quality conditions were maintained during approximately 74.7% of the monitored days between 2021 and 2026. These findings provide long-term watershed-scale evidence that hybrid green-gray retrofit strategies can integrate green stormwater infrastructure with centralized overflow regulation to achieve sustained overflow reduction and receiving-water improvement in highly constrained urban watersheds.
Zhentao Xie, Nian She, K. Zhou et al.· Water· 0 citations
Access to safe and reliable drinking water remains a persistent challenge across rural sub-Saharan Africa, especially in Tanzania where most rural water supply systems exhibit unbalanced pressure regimes, low flow velocities, and high non-revenue water losses largely due to the absence of systematic hydraulic analysis and evidence-based network management. Consequently, the objective of this paper was to evaluate hydraulic performance and evidence-based network management of Nyakanazi water distribution network in Kagera, Tanzania by using a calibrated EPANET 2.0 model. The model performance was evaluated using the Coefficient of determination (R²) and Nash-Sutcliffe Efficient (NSE). The model performance results indicated R2 = 0.838 and NSE =0.814 during calibration and R2 = 0.84 and NSE =0.85 during validation. The baseline simulation results revealed that only 62.1% of nodes operated within the design pressure range of 20–54 m, 14% exceeded 60 m, 1.4% fell below 15 m, 55.58% of pipes operated below the 0.5 m/s self-cleaning threshold, while 3.49% exceeded 2 m/s velocity. The pipe diameter optimization for nodes raised the pressure from 62.1% to 78.2%, excessive-pressure nodes decreased from 14% to 4%, sub-threshold velocity pipes decreased from 55.58% to 25.4%, and all over-velocities were eliminated. It is recommended that undersized pipe mains be increased and pressure-reducing valves be installed in high-pressure zones to improve the hydraulic performance of the Nyakanazi water distribution network.
L. M. Jackson, S. Livingstone, E. Mutayoba· Journal of Applied Sciences...· 0 citations
The expansion and reconfiguration of water resource infrastructure within the United Kingdom, particularly through Raw Water Transfer (RWT) has resulted in increased connectivity of previously isolated aquatic systems. While crucial to enhancing resilience in national water supply, this increased connectivity may lead to a greater risk of invasive non-native species (INNS) spread. Despite RWT being recognised by the UK’s environmental regulator and the water industry as an important invasion pathway, risk assessment and risk analysis approaches remain fragmented. There is currently a need for a consistent framework for evaluating INNS risks associated with RWT schemes, and mechanisms for determining and monitoring the scale of biosecurity mitigation needed.
The Strategic Resource Option Aquatic Invasive Non-Native Species Risk Assessment Tool (SAI-RAT) provides a structured approach to assessing the risk of INNS spread, establishment, and impact associated, primarily, with RWT, but also operational assets, and large-scale water resource schemes. The tool allows the technical parameters of the RWT to be incorporated, which influence organism survival and therefore risk. The tool builds on previous industry work and was developed by APEM ltd. on behalf of the UK’s Environmental regulator.
By providing a consistent assessment structure, SAI-RAT supports more coherent and defensible prioritisation of INNS risks, improves comparability between schemes and enables better integration and performance monitoring of biosecurity options within long-term water resource options. Crucially, the developed approach moves beyond, while still integrating, species‑specific impact assessments to adopt a future‑proofed, system‑ and pathway‑focused framework that bridges ecological theory and operational decision‑making.
This presentation outlines the conceptual rationale, scope, and theoretical underpinnings of INNS RWT risk assessment, illustrated through SAI-RAT, highlighting risk assessment's role in advancing integrated, scalable, and proportional approaches to managing aquatic biosecurity in increasingly managed and connected water resource systems.
Tom Hill, Paul Stebbing· ARPHA Conference Abstracts· 0 citations
Biofilm development in drinking water distribution systems (DWDS) affects water quality, hydraulic performance, and microbial risk, yet its spatial distribution and structural properties remain poorly characterized. Existing assessment methods rely on microbiological or bulk water indicators that are difficult to interpret at the system scale and do not directly reflect biomass accumulation on pipe walls. This study presents the first model to predict the mean biofilm thickness in drinking water pipes using routinely measurable operational variables under controlled laboratory conditions. Biofilms were grown in a controlled pipe facility over ten months, and thickness was quantified using a hydraulic residence time method. A random forest model using seven variables describing hydraulic, thermal, and limited chemical conditions achieved high prediction accuracy (R2 = 0.91 on unseen data) and identified flow rate, water temperature, and environmental stability as dominant factors. Feature importance and SHAP analyses highlighted the influence of conditioning shear stress and recovery time, while meta-analysis showed how operational conditions govern the formation of a stable biofilm base and a more easily removable outer layer. By linking operational conditions to biofilm thickness, this work provides a foundation for assessing and managing biofilm accumulation in drinking water systems subject to further validation.
Konstantinos Glynis, M. Blokker, Z. Kapelan et al.· ACS ES&T Water· 0 citations