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 steady 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.

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Les réseaux d’assainissement séparatifs sont de plus en plus préférés aux réseaux unitaires mais ils sont sensibles aux erreurs (in)volontaires de branchements entre les bâtiments et le réseau. Il existe quelques techniques d’inspections spécifiques à ce type de recherche : les tests à la fumée et aux colorants sont les plus utilisés. Ces techniques restent chères et chronophages. Cette étude présente une nouvelle méthode, simple et bon marché, basée sur des pilules imprimées en 3d. Ces pilules, numérotées (avec un code unique) et colorées (bleu ou rouge), sont envoyées par courrier aux habitants, jetées à différents points (toilettes, gouttières, etc.) puis collectées dans les réseaux. Après une analyse automatique des pilules récupérées, une comparaison entre les bases de données des pilules jetées et collectées permet l’identification et la localisation des erreurs de branchements (à l ‘intérieur même des bâtiments). Les conceptions de pilules et de l’analyseur, les méthodes d’analyses et les outils en ligne sont décrits dans ce résumé. L’acceptabilité sociale de la méthode est brièvement discutée. Des tests in situ sont prévus aux Pays-Bas et en France d’ici la conférence. Separate sewers are more and more preferred than combined ones but are sensitive to (in)voluntary mistakes in the connections between buildings and the network. There are only a few inspection techniques specifically devoted to such investigations: smoking test and dye tracing are the most popular. Those techniques are time consuming and expensive. This paper presents a new, low-cost and easy method based on 3D printed pills. Numbered (with a unique code) and coloured (blue or red) pills are sent by mail to inhabitants, thrown in different locations (toilets, downpipes, etc.) and then collected in sewers. After an automatic treatment of the collected pills, the comparison between the sent and collected pill databases allows the identification and the location (inside the building itself) of the misconnections. Pill and pill analyser designs, analysis methods and on-line tools are described on this paper. Social acceptability is briefly discussed. Some in situ tests will take place in France and in the Netherlands before the conference. @en

Separate sewers are more and more preferred over combined ones but are sensitive to misconnections. Several inspection techniques (time consuming and expensive) are specifically devoted to detecting such misconnections: smoking test and dye tracing are the most popular. This paper presents a new, low-cost and easy to apply method based on 3D printed pills. Numbered (with a unique code) and coloured (blue or red) pills are thrown in toilets, washbowls etc. and then collected in sewers. After an automatic treatment of the collected pills in both the wastewater and the storm water system, the comparison between the sent and collected pill databases allows the identification and the location (inside the building itself) of the misconnections present. Pill and pill analyser designs, analysis methods and on-line tools are described on this paper. Social acceptability and legal issues are briefly discussed.@en

A greater understanding of the erosion behaviour of sewer sediments is necessary in order to reliably estimate the amount and nature of the sewer sediments released from deposits in sewers and transported either to waste water treatment plants or discharged into the environment. Research has indicated that microbial activity in sediment can influence the physical release of sediment from in-pipe deposits. This paper reports on a series of erosion tests in which sewer sediments from different sewer networks are kept under different environmental conditions and their resistance to erosion is examined. The erosion tests are carried out under aerobic and anaerobic conditions and two temperatures, one representing ambient sewer temperatures and a lower temperature that significantly suppresses bacterial activity.@en