Der vorliegende Abschlussbericht fasst die Ergebnisse des Forschungsvorhabens IST4R (Integration der Spurenstoffentfernung in Technologieansätze der 4. Reinigungsstufe) zusammen, in dem verschiedene Verfahrenskombination von Aktivkohle und Ozonung zur Entfernung von anthropogenen Spurenstoffen als weitergehende Abwasserreinigung untersucht wurden. Dabei stand insbesondere die Integration dieser Verfahren in die Flockungsfiltration zur weitestgehenden Entfernung von Phosphor und abfiltrierbaren Stoffen im Fokus, die eine Planungsvariante zum zukünftigen Ausbau der Berliner Klärwerke darstellt. Ein wesentliches Ziel war die Bewertung der Verfahrensalternativen (1) Direktdosierung von Pulveraktivkohle, (2) Festbettadsorption an granulierte Aktivkohle und (3) Ozonung zur Spurenstoffentfernung, um zukünftige Anforderungen an Oberflächengewässer zu erfüllen. Die mittels Pilotversuchen gewonnenen Ergebnisse verdeutlichen, dass sowohl Ozonung als auch Aktivkohle sinnvoll mit der Flockungsfiltration kombiniert werden können. Alle untersuchten Verfahrensvarianten sind geeignet, den Spurenstoffeintrag kommunaler Kläranlagen signifikant zu verringern und gleichzeitig die Zielwerte für die suspendierten Stoffe (TSS < 1 mg/L) und Gesamtphosphor (TP < 0,1 mg/L) sicher einzuhalten. Es erfolgt eine zusätzliche Entfernung von CSB und DOC. Die Entfernung der einzelnen Spurenstoffe ist stoffspezifisch. Sie ist außerdem abhängig von der Konzentration des im Wasser vorliegenden gelösten organischen Kohlenstoffs (DOC) und der Dosis von Aktivkohle bzw. Ozon, aber unabhängig von der Ausgangskonzentration der Spurenstoffe. Für ausgewählte Indikatorsubstanzen wurden Dosis-Wirkungsbeziehungen für die Adsorption an Aktivkohle und die Reaktion mit Ozon ermittelt und an den Pilotanlagen überprüft. Der spezifische Absorptionskoeffizient bei 254 nm (SAK254) ist eine geeignete Größe zur Steuerung und Überwachung der Spurenstoffentfernung und sowohl für die Ozonung als auch die Adsorption an Aktivkohle aussagekräftig. Eine Regelung der Ozonung mittels SAK254 wurde im Pilotmaßstab getestet. Die Pilotuntersuchungen wurden darüber hinaus durch ein toxikologisches Monitoring begleitet, bei dem unterschiedliche, etablierte Untersuchungsmethoden eingesetzt, aber keine Hinweise auf humantoxikologische bzw. ökotoxikologische Risiken aufgezeigt wurden, auch nicht durch Oxidationsprodukte der Ozonung. Um eine vollständige ökotoxikologische Bewertung zu ermöglichen, müssen die Methoden weiter entwickelt werden. Neben den verfahrenstechnischen Untersuchungen wurden für die Verfahrensvarianten auch eine Kostenschätzung und Ökobilanz erstellt. Sowohl die Gesamtkosten als auch die Umweltwirkungen einer weitergehenden Phosphorentfernung mit Flockungsfiltern erhöhen sich deutlich, wenn mittels Ozon oder Aktivkohle zusätzlich auch Spurenstoffe entfernt werden sollen.

Changes in rainfall patterns or land use require flexible adaptation strategies for urban drainage systems. However, finding effective measures to reduce combined sewer overflows (CSO) and flooding is not straight-forward. The presented study proposes a holistic assessment approach that combines CSO quantity and quality criteria with indicators for the spatial extent and severity of flood events. The approach is tested for three selected adaptation measures with a detailed calibrated model of Berlin’s largest combined sewer catchment in the software Infoworks CS. The results indicate that a detailed assessment based on multiple performance criteria is necessary to fully understand measure effects. The presented work is embedded in an integrated modelling study involving different elements of the drainage and the wastewater treatment system.

In this study, a method is proposed to activate the maximal in-sewer storage volume of a combined sewer system (CSS) with a limited number of flow regulators to reduce negative impacts of combined sewer overflows (CSO). Based on a detailed analysis of the CSS structure, it indicates suitable locations to install flow regulators. The method has been developed in the programming language R and tested on the Berlin’s biggest CSS. Flow regulators have been implemented in the CSS Infoworks model at the five most suitable locations found and tested for different rainfall conditions. It was found that significant additional in-sewer storage capacity can be activated (~50% of the already existing capacity) leading to CSO volume and pollutant load reductions up to 62% for a three-monthly rain event of 60 minutes duration.

To cope with the occurrence of organic micropollutants (OMPs) in the urban water cycle, different technologies have been tested to upgrade wastewater treatment plants for OMP removal. Measures are either based on adsorption onto activated carbon or ozonation. To ensure an economic and effective operation of the OMP removal, an automatic control system, which adapts the dosage to the varying water quality of the secondary effluent, is necessary. An online OMP measurement is not possible because of the high analytical afford, thus other surrogates have to be used for control purposes instead. One promising surrogate is the reduction of the ultraviolet absorption at 254 nm (delta UVA254) at the ozonation stage, which correlates very well with the OMP removal. In this study, the results of the successful application of the delta UVA254 for a closed-loop control at an ozonation pilot plant for OMP removal are presented with a focus on implementation issues like coping with delay time and the choice of measurement points. OMP removal was assessed for three different delta UVA254 setpoints, of which two of them also were performed as an advanced ozone process. It could be shown that changes of the ozone demand, e.g. by a varying concentration of the dissolved organic carbon (DOC) or nitrite, can be detected and countered by an adaption of the applied ozone dose.

To cope with occurring traces of organic contaminants in the effluent of waste water treatment plants, ozonation is a suitable technical treatment method. However, there is an ongoing discussion about the necessity of a posttreatment of ozonation effluents to remove possible toxic ozonation by-products. This study compares a dual media filter (DMF) and a biological activated carbon filter (BAC), which were used for ozonation post-treatment, and were also designed as coagulation filters for tertiary phosphor removal. The results of this study demonstrate that both rapid filters performed similarly in respect to DOC reduction and oxygen demand, and could also be used for tertiary phosphorus removal without any impairments. A comparison of a serial mode of the DMF and the BAC with a slow sand filter, which was used as a surrogate for an infiltration pond, showed that this two-stage process could increase the degradation of the DOC, but was not able to remove the entire biodegradable DOC.

To cope with occurring traces of organic contaminants in the effluent of waste water treatment plants, ozonation is a suitable technical treatment method. However, there is an ongoing discussion about the necessity of a posttreatment of ozonation effluents to remove possible toxic ozonation by-products. This study compares a dual media filter (DMF) and a biological activated carbon filter (BAC), which were used for ozonation post-treatment, and were also designed as coagulation filters for tertiary phosphor removal. The results of this study demonstrate that both rapid filters performed similarly in respect to DOC reduction and oxygen demand, and could also be used for tertiary phosphorus removal without any impairments. A comparison of a serial mode of the DMF and the BAC with a slow sand filter, which was used as a surrogate for an infiltration pond, showed that this two-stage process could increase the degradation of the DOC, but was not able to remove the entire biodegradable DOC.

To cope with occurring traces of organic contaminants in the effluent of waste water treatment plants, ozonation is a suitable technical treatment method. However, there is an ongoing discussion about the necessity of a posttreatment of ozonation effluents to remove possible toxic ozonation by-products. This study compares a dual media filter (DMF) and a biological activated carbon filter (BAC), which were used for ozonation post-treatment, and were also designed as coagulation filters for tertiary phosphor removal. The results of this study demonstrate that both rapid filters performed similarly in respect to DOC reduction and oxygen demand, and could also be used for tertiary phosphorus removal without any impairments. A comparison of a serial mode of the DMF and the BAC with a slow sand filter, which was used as a surrogate for an infiltration pond, showed that this two-stage process could increase the degradation of the DOC, but was not able to remove the entire biodegradable DOC.

Managed Aquifer Recharge (MAR) is a means to replenish aquifers in case of over-abstraction and store water, especially in regions with semi-arid or arid climate. For water re-use schemes MAR can offer additional treatment in the subsurface so the CO2-footprint can be reduced. Pre-treatment via ozonation and dual media filtration before infiltration of treated wastewater was studied to compare the obtained water quality to guidelines for water reuse. While the removal of bulk parameters such suspended solids or chemical oxygen demand were easily reduced by ozonation and filtration, the disinfection turned out to be the limiting process.