Die Häufung der Befunde von Arzneimittelrückständen in Oberflächengewässern in Deutschland und weltweit, stellen eine aktuelle Gefährdung der stark belasteten städtischen Oberflächengewässer, als aquatisches Ökosystem und unentbehrliche Ressource zur Trinkwassergewinnung, dar. Als eine der bedeutendsten Eintragspfade in Oberflächengewässer gelten die Abläufe kommunaler Kläranlagen. Grund dafür ist, dass die oft persistenten und bioakkumulierenden Stoffe durch den konventionellen Klärprozess nicht aus dem Wasser entfernt werden können. Auch die verschärften Bestimmungen gegenüber den einzuhaltenden Wasserqualitätsparametern, wie Nährstoffgehalt oder Keimkonzentrationen, die sich aus der Umsetzung der EU-Wasserrahmenrichtlinie sowie der EU-Badegewässerrichtlinie ergeben, können voraussichtlich nur durch die Einführung einer 4. Reinigungsstufe eingehalten werden. Ein steigender Arzneimittelgebrauch, beschleunigt durch den demographischen Wandel, sowie eine geringere Verdünnung des gereinigten Abwassers aufgrund der erwarteten klimatischen Veränderungen, unterstreichen die Notwendigkeit einer 4. Reinigungsstufe mit dem Ziel einer weitergehenden Spurenstoffelimination. Die vorliegende Arbeit wurde in der Firma „Kompetenzzentrum Wasser Berlin gGmbH“ (KWB) im Zuge der Mitarbeit im EU-Forschungsprojekt „AquaNES“ am Versuchsstandort „Klärwerk Schönerlinde“ verfasst. Die auf dem Betriebsgelände der Berliner Wasserbetriebe (BWB) betriebene zweistufige Pilotanlage besteht aus einer Ozonung sowie einer nachgeschalteten biologischen Behandlung durch zwei parallel betriebene bepflanzte Bodenfilter (BF). Bodenfilter 1 (BF 1) wurde als klassischer Sandfilter konzipiert, das Filterbett von Bodenfilter 2 (BF 2) besteht aus einem kiesigen Lava-Biokohle-Gemisch. In der vorliegenden Arbeit wurde die Reinigungswirkung der vertikal durchströmten BF bestimmt, verglichen und bewertet. Diese wurde anhand der, zwischen Zu- und Ablauf, gemessenen Differenz verschiedener Wasserqualitätsparameter (WQPM), der Konzentration relevanter Abwasserkeime sowie ausgewählter Spurenstoffe untersucht. Im besonderen Fokus standen dabei die durch die BF erzielbare Spurenstoffelimination sowie der Rückschluss auf die jeweils verantwortlichen Prozesse im Filterbett. Als Grundlage der Analyse wurden die laboranalytischen Rohdaten von 60 Probenahmeterminen, die über einen 20-monatigen Beprobungszeitraum (Mai 2017 - Dez. 2018) bestimmt wurden, verwendet. Zusätzlich wurden eigene praktische Untersuchungen zur genaueren Bestimmung der gelösten Sauerstoffkonzentration im Filterbett der BF unternommen. Es konnte eine zusätzliche Reinigungsleistung der beiden BF gegenüber fast allen betrachteten Parametern, gezeigt werden. Für das Gesamtverfahren aus Ozonung und bepflanzten BF wurde eine Verbesserung für ausnahmslos alle untersuchten Parameter aus den Kategorien Wasserqualität, Mikrobiologie und Spurenstoffe erreicht. Für die untersuchten WQPM: CSB, BSB5, DOC, Nitrat, organischer Stickstoff, AFS und Trübung zeigte BF 2 eine höhere bzw. gleichstarke Reinigungsleistung. Auch die betrachteten Spurenstoffe CBZ, DCF, BTA, MTP und OXP wurden durch BF 2, aufgrund des adsorptiven Rückhalts an der Biokohle, effektiver eliminiert. Nur CLA wurde besser durch BF 1 reduziert. TCPP wurde durch beide BF etwa gleichgut zurückgehalten. BF 1 zeigte dagegen deutlich höhere Effektivität bei der Reduktion aller betrachteten Abwasserkeime (E. Coli-, Enterokokken-, C. Perfringens- und somatische Coliphagen). In den BF wurden biologischer Abbau, Adsorption in BF 2 sowie Filtration als hauptsächliche Eliminationsprozesse ausgemacht.

The focus of this study investigation was laid on the plant-specific applicability of a NaOH and thermal pretreatment of activated sludge AS with following mesophilic digestion and the influence on the biomethane potential BMP. Firstly, the hydrolysis of activated sludge from the granular sludge process of the Nereda technology, which differs from conventional activated sludge in terms of sludge formation, sludge stabilization, and sludge age, was investigated for the first time. A higher dose of NaOH (0.02 - 0.08 g NaOH per gVS, 70 °C) raised the COD and phosphate degree of digestion and the digester gas yield by 22 - 47 %. Different hydrolysis temperatures (50 - 90 °C, 0.05 g NaOH per gVS) also increased the sludge parameters. However, the BMP only enhanced by 12 % at temperatures higher than 70 °C. With increasing hydrolysis temperature, the digestion time was reduced by 2 - 5 days. Despite the process-related differences between conventional AS (from the Stahnsdorf wastewater treatment plant) and AS from the granular sludge processing, comparable results were obtained in the BMP test, with and without pretreatment. Due to a lack of time, the experiments could only be carried out once or twice. As there are currently no further experience and references on this subject, additional attempts for achieving significant results will follow. In the second part, sludges from the Waßmannsdorf sewage treatment plant were used. Laboratory tests have shown that primary sludge has no influence on the digestion process. The calculated BMP of 176.5 NmL/gCSB deviates by 3% from the value of 181.9 NmL/gCSB measured in the laboratory test. It is directly related to the ratio of the used sludges. Hydrolysis according to PONDUS (70 °C; 2 h; 2.5 mL NaOH 50 % per L AS) at laboratory revealed a comparable influence on the sludge parameters as with hydrolysis on a pilot scale. During the BMP test, the laboratory sample achieved a maximum gas yield of 143 NmL/gCSB, which is a 9 % higher BMP in comparison to the pilot sample with 132 NmL/gCSB. The laboratory results can, therefore, be transferred to the pilot scale, so that the effects of changes in operation can be reliably assessed by cost, time and effort saving laboratory tests. This thesis was written within the framework of the project “Evaluation of process options for the reduction of energy consumption and greenhouse gas emissions of Berlin sewage treatment plants" at the Berlin Centre of Competence for Water.

The objective of this work was to determine the effects of thermal-pressure hydrolysis (TPH) on dewatered secondary sludge (5-7 % DR) from the wastewater treatment plant Waßmannsdorf with regard to solubilisation properties, biogas production and the formation of refractory substances. In laboratory tests, the impact of the treatment temperature on the sludge due to the TPH was investigated by varying the treatment temperatures within the range of 130-170 °C with a constant hydrolysing time of 30 minutes. Furthermore, the effect of TPH (TTH: 140-170 °C; tTH: 30 min) on digested mixed sludge was studied to quantify the total biogas production of the “Degradation-Lysis-Degradation”-process (DLD). With increasing treatment temperatures (130-170 °C), the COD solubilisation of the hydrolysates was increased linearly up to 45 % which caused higher a biogas production and improved organic matter reduction rates during the anaerobic batch tests. An average methane yield of 212 L·(kg VSS)-1 was produced by the untreated secondary sludge. TPH caused an enhancement of the methane production of additional 17-27 % with the highest surplus observed at treatment temperatures of 170 °C. The organic matter degradation of 46.6 % in the untreated secondary sludge was 2.6 to 36.5 % higher in the hydrolysed sludges and increased with higher temperatures. TPH treatment of the secondary sludge caused formation of refractory COD, that has been measured in the digested sludge filtrate after 28 days of the aerobic degradation test. The organic matter of the untreated secondary sludge was found to be transformed to refractory COD up to 3 %. For the hydrolysed sludges (130-170 °C), the transformation of the organic compounds to refractory COD amounted, temperature-dependent, to 3.9-8.4 %. Raising the TPH treatment temperature from 160 to 170 °C, showed a sharp increase in refractory COD. In order to achieve high biogas yields with moderate loads of refractory compounds in the sludge water, a TPH-temperature of 150-160 °C is recommended. Applying the TPH to the DLD-configuration, hydrolysed sludges showed 20-30 % greater methane yields as well as 16-27 % higher biodegradation rates compared to the untreated digested sludge. At a treatment temperature of 170 °C of the digested sludge, 372 L·(kg VSS)-1 methane were produced with a organic matter reduction of 67.6 %. Comparing the test results of TDH at 170 °C and the Thermo-alkaline Hydrolysis (TaH) of secondary sludge, dosing 0,08 g NaOH·(g DR)-1 at a treatment temperature of 70 °C, the highest achievable methane yields were in the same range of approx. 270 L·(kg VSS)-1. TaH caused a 50 % lower refractory compound formation than TDH. However, the enhanced dewaterability of TDH treated sludge, compared to TaH treatment, provides cost-saving potential.

Insufficient public and municipal investment represent a major challenge for the long term management of urban drainage systems. Utilities are challenged to develop efficient rehabilitation strategies in order to maintain the level of service. Closed-circuit television (CCTV) inspection is used since the 1980’s as industry standard for sewer investigation system and structural performance evaluation. Due to budget restrictions, inspection rates are generally low and municipalities tend to inspect only a small part of their network (e.g. in France, less than 5% according to Ahmadi et al., 2014c). Since the definition of rehabilitation strategies is limited by the lack of information about sewer condition and remaining life, deterioration models have been developed to forecast the evolution of the system according to its current and past condition. One of the main factors hampering the uptake of deterioration modelling by utilities is the lack of real scale evidence of the tangible benefits provided. In particular, most utilities are concerned by the minimum amount of CCTV data required and the relevance of using such models on their networks with limited data availability. Finally, most utilities acknowledge the uncertainties in the procedure of sewer condition assessment, mainly due to the subjectivity of the coding operator. There is a strong need to quantify precisely the uncertainty of the sewer condition assessment procedure and its influence on the outcomes of deterioration modelling. The thesis aims at addressing these gaps by assessing the performance of sewer deterioration modelling using a case study with high CCTV data availability and by identifying the influence of CCTV data quality and availability on modelling performance. The study has been performed with a statistical (GompitZ) and a machine learning (Random Forest) deterioration models using the extensive CCTV database of the cities of Braunschweig and Berlin in Germany. Our results show, that at network level, both machine learning and statistical models can simulate with sufficient accuracy the condition distribution of the network, even in case of low data availability. At the pipe level, the machine learning model outperforms the statistical model. Regarding CCTV data uncertainty, our results highlight that the probability to inspect correctly a pipe in poor condition is close to 80-85% and thus the probability to overestimate the (good) condition of the pipe is close to 15-20% (False Negative). The impact of the uncertainties on the prediction of a deterioration model is not negligible. The analysis shows that the required replacement rate to maintain a constant proportion of segments in poor condition is underestimated if the uncertainties are not included in the analysis.

Wastewater treatment (WWT) is obligatory for the protection of ecosystems and human health but also produces the greenhouse gases (GHGs) nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2 ) along the process chain. According to the IPCC (2018) anthropogenic CO2 and carbon emissions must decline by 45% worldwide from 2010 levels by 2030 to keep temperatures from rising beyond 1.5 ° degrees. Currently the sector of WWT contributes about 0.11 % to the total carbon emissions in Germany and was responsible for about 5 % of global non-CO2 GHG emissions in 2005. N2O emissions in particular play the major role here. Aerobic granular sludge (AGS) for biological WWT has gained increasing interest mainly due to higher process efficiency compared to conventional activated sludge (CAS). Studies show a reduction potential of 20 – 25 % in operation costs, 23 – 40 % in electricity use and 50 –75 % in space requirements. AGS processes are implemented as sequencing batch reactor (SBR). SBRs with a small temporal and spatial variability for biological metabolism are likely to generate process conditions promoting N2O formation. A 1% increase in direct N2O emissions could already result in a 30 % increase of the carbon footprint of a WWTP. In this thesis direct GHG emissions from AGS treating domestic wastewater are studied. It was part of the project E-VENT where an AGS Nereda® pilot-plant has been operated at Stahnsdorf WWTP, Berlin (Germany). The reactor was fully-covered and GHG emissions have been monitored online over a 3 months period. A conservative approach for off-gas flow determination has been chosen to not over-estimate GHG loads. The plant was operated with domestic wastewater extracted after the primary clarifiers. At stable operating conditions maximum removal rates of 96 % chemical oxygen demand, 90 % nitrogen and 87 % phosphorous were achieved. Determined emission factors (EF) for N2O and CH4 over the complete measurement period were 2.86 % and 0.18 % respectively. Rising process temperatures from 13 – 20 °C showed a positive correlation with EFs and higher TN loads during the day lead to higher N2O complementing literature review on N2O EFs. The CO2 EFs showed that determined values for AGS are in accordance with 2.8 % ± 1.2 % found in a comparable study by Guimarães et al. (2017). Findings conclude that N2O contributes to about 95 % to total direct carbon emissions of the Nereda® plant and is a main factor for the climate impact of AGS.

The aim of this thesis is to investigate the effectiveness and economic feasibility of installing a biogas treatment plant and power-to-gas (PtG) technology at a wastewater treatment plant (WWTP) in Berlin. After extensive literary research, suitable technologies for the biogas treatment as well as the PtG technology were selected. The next step was to develop an energy tool to determine the best technological solution for the available biogas at the WWTP in question. Several scenarios were selected to be tested by the energy tool. In addition, the selected scenarios were analysed and evaluated from both economic and ecological standpoints. The results show that the use of a combined heat and power (CHP) plant along with a wind turbine or a biogas treatment plant is the best option for the selected WWTP. A biogas upgrading plant does not currently offer any environmental and economic benefits. However, the results of economic analysis also reveal that a biogas treatment plant is very cost-effective for digester gas. Compared to the current situation regarding the reference WWTP, the gas treatment technology requires approximately 75% less investment and approximately 85% lower operating costs. In addition, a biogas treatment can compete with a CHP plant if the 2017 CHP Act is considered and CHP subsidy is no longer granted. The results show that PtG technology is not an economically viable investment, since this technology is associated with very high investment costs and has no support scheme.

In order to reduce energy requirements of wastewater treatment plants, sludge disintegration in form of thermochemical hydrolysis is considered as an alternative method for sludge treat-ment. It is supposed to improve biogas yield by means of improved biodegradation, thus in-creasing energy production. However, accumulation of persistent organic matter has been re-ported as a result of thermochemical hydrolysis. To examine the effects, thermochemical hy-drolysis of excess sludge and thickened excess sludge has been carried out in the laboratory in the temperature range of 50 °C to 90 °C with a base addition of 0,02 gNaOH/gTS to 0,08 gNaOH/gTS. The treated sludge was then analysed in biomethane potential tests regard-ing its biogas yield and in Zahn-Wellens-Tests concerning the accumulation of persistent or-ganic matter. Due to complications in both experiments a methodology which solved these issues had to be developed first. Only the experiments done after the completion of this meth-odology were evaluated. The biomethane potential test resulted in an increase of biogas yield in nearly all tests. Optimal conditions were found at 70 °C and with 0,08 gNaOH/gTS with an increase of 26 % in biogas yield to 272 NmL/g oTR. Only one Zahn-Wellens-Test could be fully evaluated due to foaming problems. The treated sludge showed an increased formation of refractory COD from the initial VS of the samples. The conversion factor rose with an increased base addition. 3,15 % of VS of the untreated sample were converted into refractory COD, whereas it was 5,15 % for the sample treated at 70 °C and with 0,08 gNaOH/gTS. To obtain generalizable statements for wastewater treatment plants, foaming problems should be re-duced and further experiments carried out to verify the found results.