Organische Spurenstoffe, wie Pharmazeutikrückstände, werden durch die konventionellen Reinigungsschritte der kommunalen Kläranlagen nur unzureichend entfernt und können in die aquatische Umwelt sowie ins Trinkwasser gelangen. Ozon stellt eine Möglichkeit zur Elimination dieser Spurenstoffen aus Kläranlagenabläufen dar. Dabei werden Wasserinhaltsstoffe direkt durch Ozon und indirekt über °OH-Radikale oxidiert und transformiert. Für die Ausstattung einer Kläranlage mit einer Ozonanlage erfolgt oft eine aufwändige und langwierige Pilotierung. Daher ist eine Testmethode im Labormaßstab von Nöten, anhand derer Auslegungsparameter für die Dimensionierung einer Ozonanlage abgelesen werden können. Im Rahmen der vorliegenden Arbeit wurde ein einheitliches Testverfahren entwickelt und der Einfluss der Probenlagerung, der Wassertemperatur bei Versuchsdurchführung, der Wassermatrix und des Gehalts an DOC, Nitrit und abfiltrierbaren Stoffen untersucht. Des Weiteren wurden Methoden zur Vorhersage der Spurenstoffelimination mit Ozon überprüft und bewertet. Die Testmethode eines Semi-Batch-Verfahrens, bei der eine Wasserprobe mit einem Sauerstoff/ Ozon-Gemisch begast wird, wurde mit einem Batch-Verfahren, bei dem eine hochkonzentrierte Ozonlösung der Probe zugegeben wird, verglichen. Batchversuche können mit konstanten oder variablen Verdünnung durchgeführt werden. Dabei wird zu einer gleichbleibenden Menge an Probenlösung eine variierende Menge an Ozonstarkwasser gegeben und diese Lösung bei der konstanten Verdünnung auf einen festgelegten Wert mit voll entsalztem Wasser aufgefüllt, während bei der variablen Verdünnung keine Zugabe von voll entsalztem Wasser erfolgt, so dass variierende Gesamtvolumina entstehen. Zur Bewertung der Ozonung wurde der spektrale Absorptionskoeffizient bei 254nm benutzt, da er den Gehalt an Organik in einer Wasserprobe wiederspiegelt. Es wurde festgestellt, dass beide Versuchs- und Verdünnungsmethoden übereinstimmende Ergebnisse der SAK254-Reduktion und Spurenstoffelimination liefern, das Batchverfahren jedoch einen erheblich geringeren Proben- und Zeitaufwand benötigt. Durch eine zweiwöchige Probenlagerung bei 7 °C konnte ein Anstieg des pH-Wertes beobachtet werden, der jedoch nur eine geringe Erhöhung der Elimination mancher Spurenstoffe, wie Benzotriazol, bewirkte. Des Weiteren führte eine Variation der Wassertemperatur bei der Ozonung von 10 - 30 °C bei Batch-Versuchen zu keiner signifikanten Veränderung der SAK254-Reduktion und Spurenstoffelimination. Zwei Kläranlagenabläufe und Trinkwasser mit unterschiedlichen DOC- und Nitritkonzentrationen wurden verglichen. Dabei wurde festgestellt, dass die Korrektur des Ozoneintrags um die Ozonzehrung durch Nitrit und der Bezug auf den DOC ein gutes Instrument darstellt, um unterschiedliche Wassermatrizen vergleichbar zu machen. Während die Kläranlagenabläufe ähnliche Ergebnisse der Spurenstoffelimination liefern, wurde im Trinkwasser eine erhöhte Entfernung von Acesulfam, Benzotriazol, Candesartan, Gabapentin und Valsartansäure gemessen. Dies lässt sich durch die verschiedene Zusammensetzung des organischen Materials und der Menge an als Radikalfängern agierenden Stoffen im Kläranlagenablauf erklären. Zwischen der Spurenstoffelimination in filtriertem (0,45 µm, Cellulosenitrit) und unfiltrietem (AFS = 4 mg/L) Kläranlagenablauf wurde kein Unterschied festgestellt, während eine Zudosierung von suspendierten Stoffen (30 -75 mg/L) eine Verminderung der SAK254-Reduktion sowie der Spurenstoffelimination um bis zu 20% zur Folge hatte. Dies wird durch die Abreaktion des Ozons und der °OH-Radikale an den Partikeln erklärt. Zur Vorhersage der Spurenstoffelimination konnten Diclofenac, Benzotriazol, Valsartan und Iomperol als Indikatorsubstanzen im Kläranlagenablauf identifiziert werden, über die die Elimination weiterer Spurenstoffe genügend genau abgeschätzt werden kann. Darüber hinaus konnte ein linearer Zusammenhang zwischen delta SAK54 und der Elimination jedes Spurenstoffes aufgestellt werden, mit dem die zu erwartende Entfernung bei einem bestimmten Ozoneintrag berechnet werden kann.

The combined sewer overflow issue in the city of Berlin is becoming an increasing threat to the water quality of the surface water bodies, as the number and volumes of combined sewer overflow (CSO) events occurring per year may be on the rise due to climate variations among other aspects. For this reason, a case study was formulated to investigate the implementation of storage tanks in one of Berlin’s sub catchments, Wilmersdorf, in order to reduce the Occurrence of CSO to a once per year event on average. The investigation was made using InfoWorks Collection system (CS), one dimensional urban planning software used widely for sewer system modelling. The network of the Wilmersdorf catchment (majorly consisting of combined sewers, with small portions of separate rain and separate foul sewers) was modelled with the aid of InfoWorks. The implementation of tanks in the network was divided into two main parts: centralized and decentralized tanks. The centralized tanks addressed the issue of CSO, in order to reduce the CSO occurrence to once per year, firstly by using a short design storms representing a one year return period, to implement initial storage volumes, then this network was validated using rain series records for one year (1990) and for thirty years (1980-2010). The decentralized tanks were implemented at much smaller storage volumes compared to the centralized tanks, in localized locations to solve small surface floods in the separate rain sewer system, or to reduce the pollutant load Biological oxygen demand (BOD) of the CSO, by storing water from the separate foul system in the catchment. The results obtained for the centralized storage tanks show major reductions in CSO, with four centralized tanks implemented in central parts of the catchment. The target of once per year CSO event was achieved for the one year rain series (1990), but not for the thirty years rain series (1980-2010). Results for the decentralized storage tanks show reduction of surface flooding for the studied local areas in the catchment, with sometimes a reduction of surface floods also downstream of the targeted areas. On the other hand, the pollutant load (BOD) was reduced by negligible amounts with decentralized tanks at the studied separate foul system locations, with results showing that the overall BOD load reduction in the overflow volume is also accompanied with CSO overall volume reduction.

The paper presents semi-analytical mathematical model to estimate unsteady groundwater recharge resulting from variable depth of water in a large water body, influenced by time variant inflows and outflows. The model has been derived by integrating Hantush’s (1967) analytical expression for water table rise due to recharge from a rectangular spreading basin into the water balance equation of the water body. The model has been applied to a test study site in Raipur (India) for assessing viability of Managed Aquifer Recharge (MAR) from a lake located on an area dominated by the massive limestone formation. The components of the water balance equation have been carried out by the comprehensive analysis of the hydrological and hydrogeological aspects of the lake. The hydrological components include

Direct addition of powdered activated carbon (PAC) to the inlet of a deep bed filter represents an energy- and space-saving option to remove organic micropollutants (OMPs) during advanced wastewater treatment or drinking water purification. In this lab-scale study, continuous dosing, preconditioning a filter with PAC and combinations thereof were investigated as possible dosing modes with respect to OMP adsorption efficiency. Continuous dosing resulted in decreasing effluent concentrations with increasing filter runtime due to adsorption onto accumulating PAC in the filter bed. Approximately constant removal levels were achieved at longer filter runtimes, which were mainly determined by the dose of fresh PAC, rather than the total PAC amount embedded. The highest effluent concentrations were observed during the initial filtration stage. Meanwhile, preconditioning led to complete OMP adsorption at the beginning of filtration and subsequent gradual OMP breakthrough. PAC distribution in the pumice filter was determined by the loss on ignition of PAC and pumice and was shown to be relevant for adsorption efficiency. Preconditioning with turbulent upflow led to a homogenous PAC distribution and improved OMP adsorption significantly. Combining partial preconditioning and continuous dosing led to low initial effluent concentrations, but ultimately achieved concentrations similar to filter runs without preconditioning. Furthermore, a dosing stop prior to the end of filtration was suitable to increase PAC efficiency without affecting overall OMP removals.

Due to rapid economic development and population growth, China is facing severe water problems that include sea-level rise and increasing salinization, floods, water pollution, water shortage, soil erosion and ecosystem deterioration, as well as biodiversity loss. In recent decades, China is progressively more concerned with its water issues that are now at the center of social and political attention. Having to overcome similar challenges, Germany has taken a leading role in the field of water sciences and technology. In particular, China can benefit from the lessons learnt in Germany concerning the rehabilitation of water resources in areas heavily affected by chemical industry and mining after the reunification in 1989. German-Chinese cooperation in water sciences started over 25 years ago and dealt with increasing challenges in the 21st century. Following the open space workshop during the Water Research Horizon Conference in Berlin 2014, this article provides a view of some of the challenges and potential opportunities of German-Chinese cooperation in water science and technology.

To sustain good harvests, each year more than one million tonnes of mineral phosphorus have to be imported to the European Union (van Dijk et al., unpublished data), while the potential to recover and recycle this essential resource remains untapped or is just inefficiently used as in the case of sewage sludge, manure and food waste. In recent years various technical solutions have been developed to recover phosphorus providing mineral compounds suitable as raw material for fertiliser production or even as ready-to-use fertiliser. Regarding the implementation of these technologies, operational benefits for plant operators like the water utilities in the case of P recovery from wastewater and/or sewage sludge are the strongest argument for their market penetration. Without the provision of direct operational benefits, implementation needs to be motivated or even enforced by suitable and reliable policies. In order to realise a circular economy, it is important not just to focus on the recovery itself. The recovered materials need to match the requirements and needs of their intended users. Therefore, full value-chain solutions have to be promoted instead of isolated technology-focused approaches. Following our principles of sustainability and resource efficiency, the assessment of innovations must also include their environmental impact. This review provides an overview of recently developed and promising technologies for phosphorus recovery from wastewater and discusses aspects regarding their wide-spread application, along with their limitations. It will focus on recovery and recycling from sewage sludge. Not only the technologies themselves, also the recovered materials and their valorisation options are addressed. Results of the EU FP7 funded project P-REX entitled 'Sustainable sewage sludge management fostering phosphorus recovery and energy efficiency' and other recent initiatives will be included. Since innovation always needs an enabling environment for market penetration, barriers set by the existing legal framework and measures to resolve them will be reviewed. Finally, Goethe's words are true more than ever: 'Knowing is not enough, we must apply! Willing is not enough, we must do!'