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Wastewater Generation Model to Predict Impacts of Urine Separation on Wastewater Treatment Plants
(2023)
Wastewater treatment plants are under increasing pressure to enhance resource efficiency and reduce emissions into water bodies. Separation of urine within the catchment area may be an alternative to mitigate the need for costly expansions of central wastewater treatment plant. While previous investigations assumed a spatially uniform implementation of urine separation across the catchment area, the present study introduces a modelling framework which allows to determine the influence of targeted urine separation on the operation and emissions of central wastewater treatment plants. The framework includes an adapted stochastic wastewater generation model, the Stormwater Management Model, and Activated Sludge Model No. 3 with Bio-P module (SIMBA#). The entire application is embedded in the R programming language. The model is validated by an extensive sampling and measurement campaign. Preliminary results based on observed and simulated wastewater generation and transport for a catchment area of 436 residents indicate the suitability of the model for wastewater generation and transport modelling, but also show further need for calibration.
Im Zuge des Klimawandels wird der landwirtschaftliche Bewässerungsbedarf auch in Deutschland zukünftig steigen. Die EU-Verordnung 2020/741 stellt Mindestanforderungen an die Wiederverwendung weitergehend aufbereiteten kommunalen Abwassers zur landwirtschaftlichen Bewässerung, um die Nutzung natürlicher Wasserressourcen hierfür zu begrenzen. Die EU-Verordnung wird am 26. Juni 2023 Gültigkeit erlangen und soll in Deutschland in das Wasserhaushaltsgesetz eingebettet und um eine neue Bundesverordnung ergänzt werden. Zentrales Element der Wasserwiederverwendung wird der für jeden Einzelfall zu erstellende Risikomanagementplan sein, der der Minimierung möglicher hiermit verbundener Risiken dient. Als Hilfestellung für die praktische Umsetzung von Wasserwiederverwendung wird die DWA die Merkblattreihe M-1200 veröffentlichen.
Due to high bedload sediment transport, many sediment bypass tunnels (SBT) are prone to severe invert abrasion. However, there is little information about the flow characteristics in SBTs after invert abrasion initiated and progresses with time. In the present study, laboratory flume experiments were performed to investigate how the hydraulic conditions change after abrasion patterns developed on the invert. A typical invert abrasion pattern was produced using 3D-printing technique and implemented in the laboratory flume. Flow depths were measured to compare the initial with the abraded state.
Furthermore, turbulence measurements using 2D-laser Doppler anemometry technique were performed to obtain the mean and turbulence flow characteristics. This paper describes results of these measurements focusing on the streamwise and vertical flow velocities, turbulence intensities and Reynolds shear stress.
Reservoir sedimentation is increasingly affecting the majority of reservoirs all over the world. As many dams are more than 50 years of age, this problem is becoming more and more seriou403s nowadays. Reservoir sedimentation leads to various severe problems such as a decisive decrease of the active reservoir volume leading to both loss of energy production and water available for water supply and irrigation. These problems will intensify in the very next future, because sediment supply tends to increase due to climate change. Therefore coun-termeasures have to be developed. They can be divided into the three main categories sediment yield reduction, sediment routing and sediment removal. This paper focuses on sediment routing by means of sediment bypass tunnels. Sediment bypass tunnels are an effective measure to stop or at least decrease the reservoir sedimentation process. By routing the sediments around the reservoir into the tailwater in case of flood events sediment accumulation of both bed load and suspended load is reduced significantly. However, the number of sediment bypass tunnels in the world is limited primarily due to high investment and above all maintenance costs. The state-of-the-art design criteria of constructing bypass tunnels are summarized herein; major problems such as tunnel invert abrasion are discussed. The need for further research regarding sediment transport in bypass tunnels and invert abrasion is highlighted.
Entlandung des Stausees Solis mit Hilfe eines Geschiebeumleitstollens – hydraulische Modellversuche
(2009)
Das Reservoir der Talsperre Solis in Graubünden wurde 1986 vom Elektrizitätswerk der Stadt Zürich (ewz) in Betrieb genommen. Bei Hochwasserereignissen werden grosse Sedimentmengen in den Stausee transportiert. Über 25 % des ursprünglichen Reservoirvolumens sind bereits verlandet. Aus diesem Grund plant ewz den Bau eines Geschiebeumleitstollens, der das bei Hochwasser ankommende Sediment um die Talsperre herum in Richtung Unterwasser leitet. Die Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie (VAW) der ETH Zürich untersucht und optimiert in einem hydraulischen Modell den projektierten Umleitstollen. Bei Hochwasser wird der Stausee auf den minimalen Betriebswasserspiegel abgesenkt, der Verlandungskörper liegt grösstenteils frei, das Sediment erodiert. Mit Hilfe einer Leitkonstruktion wird die Strömung in Richtung Einlaufbauwerk des Stollens gelenkt und der Abfluss sowie das Geschiebe durch diesen geleitet. Bei Abflüssen, die die Ausbaukapazität des Stollens (HQ5) überschreiten, wird die überschüssige Strömung in den vorderen Bereich des Sees in Richtung Grundablass abgeführt. Das Geschiebe wird dennoch nahezu vollständig in den Stollen eingeleitet. Bei Hochwasser mit Schwemmholzaufkommen wird mit Hilfe einer Tauchwand sowie einer Teilablleitung des Hochwasserabflusses in den vorderen Seebereich verhindert, dass Schwemmholz in den Umleitstollen
eingezogen wird.
The Solis reservoir is located in the Alps in Grisons, Switzerland and is operated by the electric power company of Zurich (ewz). Since its construction in 1986, high sediment input during flood events has led to major aggradations in the reservoir. Up to date, nearly half of the original reservoir volume has been filled with sediments from upstream mountain torrents. The deltaic deposition starts extending into the active water volume. Therefore, ewz plans a sediment bypass tunnel to flush the incoming bedload around the dam to the downstream reach. In a first step the reservoir level during flood events is lowered to the minimum operation level. The delta is subjected to free surface flow and the bedload is transported over the delta and deposited further downstream. This sediment relocation decreases the delta volume within the active storage. During further flood events, the incoming sediment is led to the bypass tunnel intake using a guiding structure and flushed through the tunnel. If the flood exceeds the capacity of the bypass tunnel, the surplus flow passes the tunnel intake towards the bottom outlets with the bedload still being flushed through the tunnel. A skimming wall located upstream from the tunnel intake prevents driftwood blocking by leading it to the reservoir front where it can be safely removed. Both the sediment relocation due to water level drawdown and the flushing through the bypass tunnel are investigated and optimized in a hydraulic model at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) of ETH Zurich. Additionally, the sediment relocation process in the model is compared with a relocation test in the prototype.