Soil aquifer treatment (SAT) is one of the most promising water reclamation and storage techniques in water reuse. This document summarizes the experiences gained in two full scale sites (Shafdan and El Port de la Selva) focused on overcoming the barriers associated with this low-cost technology.

This report summarizes the results of Life Cycle Assessment, Water footprinting, and quantitative microbial and chemical risk assessment for selected demosites of water reuse in Europe, measuring the potential impacts of different types of water reuse on environment and human health. The case studies show that water reuse is often preferable from an environmental point of view in areas with water scarcity problems if compared to other alternatives such as water import or seawater desalination. Potential risks of water reuse for ecosystems or human health can be adequately managed if suitable processes for reclaimed water treatment are used and operated correctly. However, the study also shows the trade-offs between a higher level of reclaimed water treatment and increased environmental impacts from associated efforts in energy, chemicals and infrastructure. This inherent trade-off requires a site-specific assessment of reuse schemes to choose an adequate treatment scheme for risk management with reasonable global environmental impacts.

Objective of this synthesis report is to summarise the main achievements of the OPTIWELLS-2 project. Based on a preparatory phase OPTIWELLS-1 (2011-2012), the main project phase OPTIWELLS-2 (2012-2015) included the development of two different optimisation modelling methodologies (data-driven, process-driven) for minimising a well field’s specific energy demand whilst satisfying both, water demand and water quality constraints. Chapter 2 gives a short overview on the technical background on pipe hydraulics and the general methodology used within the project. The general workflow of the testing and application for the three case study well fields investigated within OPTIWELLS-2 is summarised in Chapter 3. For the first two case studies (Chapter Fehler! Verweisquelle konnte nicht gefunden werden. and Fehler! Verweisquelle konnte nicht gefunden werden.), a process-driven modelling approach was used, which enabled the assessment of three different management strategies (smart well field management, pump renewal or a combination of both) on the specific energy demand. This approach was more time and data-demanding (Chapter 2.5) compared to the data-driven approach used for the third case study (Chapter Fehler! Verweisquelle konnte nicht gefunden werden.). The cross-case analysis (Chapter 4) showed, that the energetic prediction accuracy of process-driven modelling (Chapter 4.1.3) was improved significantly by using pump characteristics derived from audits instead of relying on manufacturer data, whilst including steady-state well drawdown compared to assuming a static water level in the production well was much less important. This can be explained by the fact, that well drawdown contributed to less than 3% of the required pump head (Chapter 4.1.1), whilst the offset between audit and manufacturer pump characteristics is much more relevant because of pump ageing during long usage periods (up to 40 years). The data-based modelling approach used for Site C has yielded energy consumption forecasts with a similar accuracy, but is more robust as it relies on operational data, thus requiring no calibration.

This review covers state-of-the-art technologies for advanced anaerobic digestion of municipal sewage sludge. It is based on an extensive review of literature and available data, focussing on processes which have been realized in full-scale plants. The review includes information on single-stage mesophilic digestion, thermophilic digestion, temperature-phased digestion, high-load digestion and other process modifications, as well as mechanical, thermal, chemical, and biological disintegration methods. All processes are described with a set of key performance indicators such as degradation rate of volatile solids, biogas yield, return load, effects on dewatering, and capital costs.

Die Modellierung der biogeochemischen Prozesse im Sediment mittels QSim (2.3.1) sollte durch den Aufbau eines vereinfachten, prozessbasierten Modellansatzes optimiert werden. Konkret sollte die Weiterentwicklung des Sedimentmoduls SEDFLUX des Gewässergütemodells QSim unterstützt werden, indem die Abbildung des Stickstoffumsatzes im Sediment unter verschiedenen Intensitäten vertikaler Advektion untersucht wird. Diese Arbeiten stellen eine konzeptuelle Prüfung („proof-ofconcept“) der im Kapitel 2.3.1 abgeleiteten Hypothesen zum Austausch zwischen Wasser und Sediment dar, sowie ihrer Effekte auf den Stoffumsatz in diesem Kompartiment. Die Modellergebnisse werden mit Hilfe von Vertikalprofilmessungen plausibilisiert. Die Nutzung vereinfachter Modellansätze ermöglicht die Untersuchung einzelner Prozesse sowie eine schnelle Anwendung auf verschiedene Gewässer. Als Simulationsumgebung wird das frei verfügbare Softwarepaket R-ecosim genutzt (Reichert 2014).