Enhancing sediment accumulation monitoring techniques in sewers will enable a better understanding of the build-up processes to develop improved cleaning strategies. Thermal sensors provide a solution to sediment depth estimation by passively monitoring temperature fluctuations in the wastewater and sediment beds, which allows evaluation of the heat-transfer processes in sewer pipes. This study analyses the influence of the flow conditions on heat-transfer processes at the water-sediment interface during dry weather flow conditions. For this purpose, an experimental campaign was performed by establishing different flow, temperature patterns, and sediment depth conditions in an annular flume, which ensured stable flow and room-temperature conditions. Numerical simulations were also performed to assess the impact of flow conditions on the relationships between sediment depth and harmonic parameters derived from wastewater and sediment-bed temperature patterns. Results show that heat transfer between water and sediment occurred instantaneously for velocities greater than 0.1 m/s, and that sediment depth estimations using temperature-based systems were barely sensitive to velocities between 0.1 and 0.4 m/s. A depth estimation accuracy of +/- 7 mm was achieved. This confirms the ability of using temperature sensors to monitor sediment build-up in sewers under dry weather conditions, without the need for flow monitoring.

Gully pots (GPs) are an integral urban drainage component, transferring surface runoff into piped systems and reducing sediment and contaminant load on downstream sewers and receiving waters. Sediment build-up in GPs impairs their hydraulic performance, necessitating maintenance for hydraulic function recovery. The variations in sediment accumulation rates between GPs suggested by earlier studies challenge the effectiveness of adopting a generalised maintenance frequency. This study addresses the knowledge gap regarding how various factors influence sediment contamination in GPs. The impacts of seasonal activities and traffic conditions on the contamination of sediments in 27 GPs in areas with varying traffic intensities and street features (roundabouts, intersections, and straight roads) were examined. Over one year, GPs were emptied twice, with sediments collected for winter-spring and summer-autumn accumulation periods. These sediments were analysed for 84 substances, including metal(loid)s, hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), alkylphenols, phthalates, per- and polyfluoroalkyl substances and organotins. Significant temporal changes were identified in key parameters such as electrical conductivity, total organic carbons, tungsten (W), heavy-molecular-weight PAHs (PAH-H) and diisodecyl phthalate (DIDP) in GP sediments, influenced by winter road safety measures and autumn leaf abscissions. Significantly higher concentrations of 4-tert-octylphenol, DIDP, diisononyl phthalate, antimony and W were identified in GP sediments from roundabouts compared to those at the other two street features, exclusively during the winter-spring period. This is attributed to the synergistic effect of winter road safety measures and stop-and-go traffic patterns at roundabouts. No consistent spatial and temporal patterns were identified for substance concentration and mass accumulation rates. Results underscore the potential to develop a prioritisation-based maintenance strategy as an opportunity to enhance the efficiency of GP maintenance operations, ensuring better resource allocation and reduced environmental impact.

With the global concerns on antibiotic resistance (AR) as a public health issue, it is pivotal to have data exchange platforms for studies on antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the environment. For this purpose, the NORMAN Association is hosting the NORMAN ARB&ARG database, which was developed within the European project ANSWER. The present article provides an overview on the database functionalities, the extraction and the contribution of data to the database. In this study, AR data from three studies from China and Nepal were extracted and imported into the NORMAN ARB&ARG in addition to the existing AR data from 11 studies (mainly European studies) on the database. This feasibility study demonstrates how the scientific community can share their data on AR to generate an international evidence base to inform AR mitigation strategies. The open and FAIR data are of high potential relevance for regulatory applications, including the development of emission limit values / environmental quality standards in relation to AR. The growth in sharing of data and analytical methods will foster collaboration on risk management of AR worldwide, and facilitate the harmonization in the effort for identification and surveillance of critical hotspots of AR. The NORMAN ARB&ARG database is publicly available at: https://www.norman-network.com/nds/bacteria/.

Stormwater runoff is a key pathway for diffuse pollutants to enter receiving waters. Mitigating measures include pollutant substitution, restricting their release into the urban technosphere and limiting the (re-)mobilisation of substances to minimise their negative impacts on receiving waters. Gully pots (GPs) are one of the most ubiquitous urban drainage infrastructure components, providing both a drainage function and limiting the onward transport of pollutants through in-pot sedimentation processes. In this study, sediments accumulated over a one-year period were collected from 26 GPs in catchments of four land-use types in Stockholm, Sweden. Sediments were analysed for 101 organic substances from eight substance groups (hydrocarbons, polycyclic aromatic hydrocarbons, alkylphenols, polychlorinated biphenyls, phthalates, organotins, per- and polyfluoroalkyl substances and brominated fire retardants) to inform an assessment of their occurrence and net accumulation rates over a typical unit operation period. A total of 63 substances were quantified in at least one GP, with aliphatic hydrocarbons, phthalates and organotins quantified in all GP sediments, highlighting their ubiquitous use. The identification of 14 and 21 organic substances in two pedestrian/bike path GPs emphasise the contribution of non-vehicular sources to diffuse pollutant loads. Significantly higher mass accumulation rates of 4-tert-octylphenol, 4-nonylphenols, formaldehyde, dioctyltin and dibutyltin are identified in commercial catchment GPs suggesting the need to enhance source-tracing and runoff quality-control measures within catchments of this land-use type. Sediments in 25 GPs were identified with at least one substance exceeding toxicology-based threshold values, highlighting the runoff quality-control function of GPs in reducing the potential ecotoxic impacts on recipients.

Urban stormwater typically enters sewer networks through gully pots, which allow a primary sedimentation of solids upstream of the piped network. The regular removal and disposal of retained sediment are necessary, costly and can involve environmental risks due to the contamination of sediments with substances from the urban environment such as metals. The concentrations and speciation of Cd, Cr, Cu, Ni, Pb and Zn were analysed in sediments from 26 gully pots located in different land use areas in Stockholm, Sweden. In addition, accumulation rates of both sediment and metal masses were evaluated, providing a basis for optimising maintenance practices and better understanding of impacts of characteristic urban land use types. Metal concentrations varied by at most a factor of eight between samples and were always below Swedish polluted site guidelines for less sensitive land use, with only eight samples exceeding the guideline values for Cu and Zn for sensitive land use. Sequential extraction showed Pb and Zn to be the most mobile metals. Sediment accumulation rates varied from 0.003 to 0.197 kg/m2 impermeable surface/year. Metal accumulation rates were much more variable than metal concentrations, with a factor of up to 172 between the highest and lowest rates and the highest metal accumulation rates corresponding to the lower range of mass loads in road runoff. Differences in metal concentrations, sediment or metal mass accumulations could not be solely attributed to either traffic or catchment land use. In contrast, traction grit used for winter road maintenance, which has low (but detectable) metal concentrations, is identified as a major component of gully pot sediments, with a combined effect of both moderating metal concentrations and contributing to total mass.

Current gully pot maintenance strategies lack a robust evidence base and clear aims against which performance can be benchmarked. To facilitate discussions, questions on their long-term in-situ performance in trapping sediments and associated contaminants - and how they are impacted by various factors - require robust interrogation. As a contribution, this paper presents sediments data from 27 gully pots located at sites with various street layouts (roundabout; straight road; road crossing) and traffic intensities (<1000-23666 vehicles/day), over two accumulation periods: winter-spring and summer-autumn 2020-2021. On an annual basis, gully pots retained 0.54–44.2 (median: 10.95) kg (dry mass) over 151–189 days, corresponding to a solids accumulation rate of 2.5–1140.6 (median: 69.4) g/m2/year. Of the 27 gully pots, 18 gully pots showed significant seasonal variations in solids accumulation rates though the dominant season was not consistent. For example, roundabouts exhibited a significantly higher solids accumulation rate over the summer-autumn period in comparison to road crossing and straight road gully pots where accumulation was typically higher in the winter-spring season. Further, in contrast to the latter street layouts, a significant negative correlation between traffic intensity and solids accumulation rate was identified at roundabout gully pots, with the turning action of vehicles generating higher levels of sediment resuspension suggested as a possible contributing factor.

Les stratégies actuelles d'entretien des avaloirs ne disposent pas de données robustes ni d'objectifs clairs permettant d'évaluer leurs performances. Pour faciliter les discussions, leurs capacités in situ àpiéger les sédiments sur le long terme en fonction de divers facteurs nécessitent un examen approfondi. Cet article présente des données sur les sédiments de 27 avaloirs situés dans différentes configurations de chaussée (giratoire, route droite, croisement) avec différentes intensités de trafic (<1000-23666 véhicules/jour), sur deux périodes d'accumulation : I’hiver-printemps et I’été-automne 2020-2021. Sur une base annuelle, les avaloirs ont retenu 0,54-44,2 (médiane : 10,95) kg (masse sèche) sur 151-189 jours soit un taux d'accumulation de solides de 2,5-1140,6 (médiane : 69,4) g/m2/an. 18 des avaloirs ont montré des variations saisonnières significatives de taux d'accumulation de solides, bien que la saison dominante ne soit pas constante. Par exemple, les ronds-points présentaient un taux d'accumulation de solides significativement plus élevé pendant l’été-automne, en comparaison avec les avaloirs des croisements de routes et des routes droites où l'accumulation était typiquement plus élevée pendant l’hiver-printemps. De plus, une corrélation négative significative entre l'intensité du trafic et le taux d'accumulation des solides a été identifiée dans les avaloirs situés à des giratoires. Une des explications envisagées est qu’en tournant, les véhicules remettent davantage en suspension les sédiments. 

The water quality implications of transferring stormwater through pipes composed of concrete (new and used), polyvinyl chloride (PVC), galvanized corrugated steel (GCS), high-density polyethylene (HDPE), and pipes subjected to cured in place pipe (CIPP) and spray in place pipe (SIPP) trenchless repair technologies on stormwater quality are reviewed. Studies involve either the use of flowing water or an immersion experimental design, with data showing contact with pipe materials can affect stormwater quality parameters including pH, electrical conductivity (EC), and concentrations of minerals, metals, and organic constituents, e.g. styrene. ‘In-transport’ changes in pH (1–3 units), EC (2–3-fold), bicarbonate (3–44-fold), and calcium (2–17-fold) in stormwaters were reported following exposure to concrete pipes. Differences between the use of synthetic and field-collected stormwater were identified, e.g. turbidity levels in field-collected stormwater reduced on passage through all pipe types, compared to synthetic water where levels of turbidity on exposure to concrete and cement-based SIPP increased slightly. Transfer through PVC and HDPE pipes had minimal effects on physicochemical parameters, whereas exposure to galvanized corrugated steel pipes led to increases in EC, Zn, and Pb. Though limited data was available, the use of CIPP repairs and associated waste condensate generated during thermal curing and/or incomplete curing of resins was identified to release organic contaminants of concerns (e.g. styrene, vinylic monomers, dibutyl phthalate (DBP), diethyl phthalate (DEP), and benzaldehyde). The implications of findings for both future research and stakeholders with responsibility for reducing diffuse pollution loads to receiving waters are considered.