In der Debatte um Strategien des Phosphorrecyclings zeichnet sich immer mehr ab, dass ein Ende der bodenbezogenen Verwertung von Klärschlamm nicht zielführend ist, wenn Schlämme für dieses Recyclingverfahren qualitativ geeignet sind.

Spree und Havel sind langsam fließende Gewässer, deren Wassermenge besonders durch die Reduzierung des Braunkohletagebaus am Oberlauf der Spree seit 1990 kontinuierlich zurückgeht. Die Berliner Wasserbetriebe leiten in diese Vorfluter das biologisch gereinigte Abwasser (Klarwasser) ein, das die Gewässersituation in Bezug auf Keime, NährstofFe und organisehe Spurenstoffe beeinflusst. Maßnahmen an der Quelle zur Vermeidung oder Verminderung des StofFeintrages in den Wasserkreislauf, eine Abwasserreinigung mit Ozonung, Pulverkohle sowie Membranfiltration könnten hier eine verbesserte Entfernung bewirken. Die Berliner Wasserbetriebe und das Kompetenzzentrum Berlin haben gemeinsam mit der TU Berlin zur Spurenstoff- und Keimentfernung das Verfahren der Ozonung von gereinigtem Abwasser durchgeführt. Das Ziel der Ozonung ist es, die Spurenstoffe möglichst weitreichend zu entfernen. Gleichzeitig lag der Fokus darauf, neben den Indikatororganismen für Fäkalverunreinigungen auch Krankheitserreger, besonders die Viren zu untersuchen, und zu bewerten. Es ist besteht das Interesse eine zukunftsweisende und kompakte Technologie, die alle Ziele umfasst, zu realisieren.

Ozone process control in secondary effluent used for elimination of trace organic compounds (TrOCs) requires the use of surrogates, such as the relative reduction of UV absorption at 254 nm (DUVA254) to adapt the ozone dose to a varying water quality. In the present study, a closed-loop process control based on two online UVA254 measurements was successfully implemented and tested under realistic conditions with ozone doses from 0.2 to 1.05 mg-O3/mg-DOC at a pilot scale ozonation system with subsequent coagulation filtration at a municipal wastewater treatment plant (DOC ~ 13 mg/L, UVA254 ~27m-1, and nitrite peaks of up to 1.6 mg-N/L). It could be shown that measuring the UVA254 at the ozonation effluent was superior to the measurement of UVA254 at the filter effluent in terms of response time due to changes in water quality, whereas online measurement at the filter effluent showed a better agreement with laboratory data and a reduced maintenance interval due to less particles. Additional online nitrite measurement is not necessary as the ozone consumption by nitrite directly impacts DUVA254.

To support decision makers in planning effective combined sewer overflow (CSO) management strategies an integrated modelling and impact assessment approach has been developed and applied for a large urban area in Berlin, Germany. It consists of an urban drainage model, a river water quality model and a tool for the quantification of adverse dissolved oxygen (DO) conditions in the river, one of the main stressors for urban lowland rivers. The coupled model was calibrated successfully with average Nash- Sutcliffe-efficiencies for DO in the river of 0.61 and 0.70 for two validation years. Moreover, the whole range of observed DO concentrations after CSO down to 0 mg L-1 is simulated by the model. A local sensitivity analysis revealed that in the absence of CSO dissolved oxygen principally depends on phytoplankton dynamics. Regarding CSO impacts, it was shown that 97% of the observed DO deficit can be explained by the three processes (i) mixing of river water with CSO spill water poor in DO, (ii) reduced phytoplankton activity due to CSO-induced turbidity and (iii) degradation of organic matter by heterotrophic bacteria. As expected, process (iii) turned out to be the most important one. However depending on the time lag after CSO the other processes can become dominant. Given the different involved processes, we found that different mitigation schemes tested in a scenario analysis can reduce the occurrence of critical DO deficits in the river by 30-70%. Overall, the study demonstrates that integrated sewer-river-models can be set up to represent CSO impacts under complex urban conditions. However, a significant effort in monitoring and modelling is a requisite for achieving reliable results.

Conventional sewer models such as SWMM or InfoWorks CS are widely used to analyse effects of relative runoff reduction or storage capacity increase on a global scale. However, the applied tools are usually insufficient for planning precise stormwater management strategies on city quarter scale. We propose a modelling approach that combines a 1D sewer model and a river water quality model with a detailed hydrological rainfall-runoff model that includes model components for a multitude of sustainable urban drainage systems (SUDS). The modelling approach is demonstrated to evaluate realistic measure combinations developed for a city quarter in Berlin, Germany. Results show that negative river impacts of combined sewer overflows (CSO), in our case fish-critical oxygen conditions, can be completely prevented with a set of adequate measures.

Powerstep wird auf der KA MS in zwei Etappen realisiert. Der erste Part umfasste die Generierung von maximalen Primärschlammmengen durch den Einsatz einer Flockung und anschließenden Filtration im Anschluss an die mechanische Reinigung. Zielstellung war es mit dem energiereichen Primärschlamm durch Faulung und Verstromung den Endenergiebedarf der KA MS decken zu können und durch die Überführung des wesentlichen Schmutzstoffanteils in den produzierten Schlamm die biologische Abwasserbehandlungsstufe, genauer die Belebung, zu entlasten. Die Reinigungsmethode wurde im Labormaßstab getestet und als erfolgreich bewertet. Allerdings konnte innerhalb der Laboruntersuchungen auf der Kläranlage nachgewiesen werden, dass bei dem neuen Verfahren keine Entfernung des Ammoniums realisiert wird. Da Ammonium einer der wesentlichen Parameter zur Bewertung der Reinigungsleistung einer Kläranlage ist und durch die Abwasserverordnung (AbwV) mit einem Ablaufgrenzwert belegt wurde, wird im zweiten Part von Powerstep eine Technik zur energieeffizienten Ammoniumelimination untersucht. Die Bearbeitung dieser Problematik ist Gegenstand der vorliegenden Arbeit. Das Ziel dieser Arbeit ist es, Methoden zur Ammoniumentfernung bei der Abwasserreinigung zu betrachten und tiefgreifend auf die Elimination durch den Einsatz von Wasserlinsen einzugehen. Dabei werden sowohl ökologische, als auch chemische und technische Belange beleuchtet.

UV/Vis spectrophotometers have been used for one decade to monitor water quality in various locations: sewers, rivers, wastewater treatment plants (WWTPs), tap water networks, etc. Resulting equivalent concentrations of interest can be estimated by three ways: i) by manufacturer global calibration; ii) by local calibration based on the provided global calibration and grab sampling; iii) by advanced calibration looking for relations between UV/Vis spectra and corresponding concentrations from grab sampling. However, no study has compared the applied methods so far. This collaborative work presents a comparison between five different methods. A Linear Regression (LR), Support Vector Machine (SVM), EVOlutionary algorithm method (EVO) and Partial Least Squares (PLS) have been applied on various data sets (sewers, rivers, WWTPs under dry, wet and all weather conditions) and for three water quality parameters: TSS, COD total and dissolved. Two criteria (r2 and Root Mean Square Error RMSE) have been calculated - on calibration and verification data subsets - to evaluate accuracy and robustness of the applied methods. Values of criteria have then been statistically analysed for all and separated data sets. Non-consistent outcomes come through this study. According to the Kruskal-Wallis test and RMSEs, PLS and SVM seem to be the best methods. According to uncertainties in laboratory analysis and ranking of methods, LR and EVO appear more robust and sustainable for concentration estimations. Conclusions are mostly independent of water matrices, weather conditions or concentrations investigated.

Deterioration modelling has been developed in the last decades to support operators and municipalities in defining mid-long term asset management strategies with limited availability of sewer condition data (CCTV). Modelling can help validating and showing the viability of current strategies or provide information to justify the relevance of additional investments and expenditures. Several modelling approaches are now available but not commonly used by sewer operators and municipalities to support strategies mainly because of the lack of real scale demonstration of the tangible benefits provided. Indeed, most of these models fail to show that they can adequately forecast future conditions (Ana and Bauwens, 2010; Scheidegger et al., 2011; WERF, 2012).

Deterioration modelling can be a powerful tool to support utilities in planning efficient sewer rehabilitation strategies. However, the benefits of using deterioration models are still to be demonstrated to increase the confidence of utilities toward simulation results. This study aims at assessing the performance of a statistical deterioration model to estimate the current condition and predict the future deterioration of the network. The quality of prediction of the deterioration model GompitZ has been assessed using the extensive dataset of 35,826 inspections of the city of Braunschweig in Germany. The performance of the statistical model has been compared with the performance of a simple model based only on the condition of observed sewers. Results show that the statistical model performs much better than the simple model for simulating the deterioration of the network. The findings highlight the relevance of using modelling tools to simulate sewer deterioration and support strategic asset management.