Sewage systems hold a critical function within the fabric of urban infrastructure, primarily by ensuring efficient wastewater management. Within this network, sewage pumping stations emerge as important components. The performance of such stations is susceptible to being undermined by system failures and malfunctions, which can cause significant implications for both public health and occurrences of Combined Sewer Overflow (CSO) events. Consequently, discerning the patterns and root causes of these failures is of great importance.
The present study explores and seeks to understand the reliability of sewage pumping stations, particularly in the setting of the Department of Public Works in Rotterdam. The scope of this study is confined to data collected between 2016 and 2020. The research encompasses a diverse range of interconnected aspects, such as examining discrepancies in failure data, categorizing types of failures, tracking changes in failure patterns over time, and selecting a fitting statistical model to accurately represent the findings. The core focus of this study is to formulate an analysis framework to assess the reliability and failure patterns in wastewater pumping stations. In these patterns, various trends can be discerned through interarrival time - the period between two failures. For instance, an increasing trend indicates less frequent failures, suggesting improved reliability of the pumps. The devised framework combines both objective and subjective trend analyses, multiple trend tests, and employs a range of models such as the Homogeneous Poisson Process (HPP), Renewal Process (RP), and Non-Homogeneous Poisson Process (NHPP). This methodological approach is structured to facilitate a better understanding of the patterns of system behavior and shifts. Analyzing pump performance patterns over five years revealed various trends among 447 pumps studied. Of these, 254 had consistent failure patterns; 98 showed a stable trend, 146 improved over time with fewer failures, and 10 experienced more failures, indicating declining performance. The remainingpumps were divided into various trend groups or segments, demonstrating different patterns in their performance over the five years. The application of statistical methods elucidated these failure patterns, contributing to the evaluation of sewage pump station efficiency. Notwithstanding these progressions, my investigation has identified certain domains that could derive advantages from additional enhancements. The current methodology, which entailed manual configuration of kernel parameters and dependence on piecewise linear regression, was deemed insufficient for about 50% of the pumps. The study proposes the integration of sophisticated parameter estimation techniques, including Bayesian optimization or grid search, and alternative modeling methodologies to tackle this issue. It is recommended that forthcoming research expands its scope beyond Rotterdam and investigates a wider variety of pump mechanisms to validate the generalizability of the findings presented in this study. In conclusion, this thesis develops an analytical framework based on examination of failure patterns and system dynamics. It establishes a platform for future progress by outlining a distinct pathway for prospective investigations pertaining to the failures in sewage pumping stations.

This research analyses and evaluates the performance of the drainage system in Beira, Mozambique. It considers its formation, maintenance, failure modes and connections, to recommend improvements on its performance. The research identifies six primary failure modes - vegetation overgrowth, human interference, waste accumulation, sedimentation, underdimensioned structures and ’other’ - highlighting the disparities between technical design and real-world complexities. The study quantifies the presence of these failure modes by direct observations and transect walks, and uses hydraulic modeling software, D-FLOW FM 1D2D, to simulate their impact on inundation depths.

The results show that widespread flooding can be found even without failure modes. Additionally, it prioritises the risks of vegetation and human interference. Therefore, it recommends an increase of hydraulic capacity of a part of the system, proactive vegetation management, water level control, and community engagement in system management. It also underscores the importance of early land demarcation in urban planning, the implementation of flexible yet delineated canals, and the involvement of communities in flood adaptation.

This thesis provides knowledge on factors affecting the representativeness of wastewater-based epidemiology (WBE) for monitoring the SARS-CoV-2 virus. The application of WBE to monitor health parameters has become essential due to the COVID-19 outbreak in March 2020. WBE is a well-known method to track the SARS-CoV-2 virus in wastewater and is used as an early warning system for the spread of the virus. However, the accuracy of monitoring trends through WBE is affected by various methodological challenges. This thesis aims to identify and quantify factors that affect the representativeness of monitoring the SARS-CoV-2 virus through WBE as part of the National Sewage Surveillance (NRS).

Factors that possibly influence the representativeness of WBE for monitoring the SARS-CoV-2 virus from loo to lab are identified. To what extent these factors potentially affect the representativeness is discussed in a literature review. The results are presented in a dendrogram, showing the relationship between different factors. Based on the results of the literature review, the seven most important factors affecting the accuracy of monitoring SARS-CoV-2 through WBE were determined to investigate their effect in more detail. To create an overview of the effect of the various factors and to ensure comparison, the results of the different factors are synthesized based on four criteria.

The effect on the representativeness is quantified and synthesized for the following factors: location of shedding, temporary in-sewer storage, RNA decay, deviant flow values, loss of information by overflow events, automated samplers and flow rate measurements. The effect of each factor is quantified individually. Different methodologies were used for the quantification of the different factors. The results were based on data analysis and expert consultations.

It was observed that the effect on the load of SARS-CoV-2 monitored by temporary in-sewer storage is negligible, as well as the effect by the decay of SARS-CoV-2 RNA by temperature and residence time. For the following factors, the influence on representativeness may be significant: The location of shedding, deviant flow values, loss of information by overflow events, automated samplers and flow rate measurements. Based on the results of the synthesis an advice is given on which factors should be included in the methodology of monitoring the virus through WBE and which samples should be excluded.

In conclusion, WBE is a valuable method to use for pandemic preparedness and monitoring health indicators from wastewater. There are many factors that influence the representativeness of samples for the monitoring of the SARS-CoV-2 virus. This research adds knowledge to the understanding of factors influencing the accuracy of WBE. The results elaborated by this study hope to contribute to the early detection of, not only, the SARS-CoV-2 virus, but also for other epidemic viruses, as well as other health indicators.

This research explores the frequent urban flooding problems typically experienced in South-East Asian cities. Heavy rainfall during the monsoon period in combination with rapid urbanisation in the past decades causes an increasing amount of inundation events in the case study area Hanoi. The damage caused by these floods results in major economic losses that affect local citizens as well as governmental authorities. Flood waters are often heavily polluted with sewer water, threatening public health
and reducing the overall livability of Hanoi. In addition, inundated streets are difficult to navigate, and waves induced by vehicles can lead to dangerous situations for pedestrians and other road users. This research aims to have a better understanding of the failure mechanisms of Hanoi’s drainage system, and the risks associated with each mechanism. Since there is no standard methodology for probabilistic risk assessment of urban drainage systems, the methodology for levee assessment was adopted and adjusted to the field of urban drainage. This straight-forward method is transferable to other study areas and results in clear and comprehensive fault trees which are easily interpreted by drainage authorities.

A combination of expert judgement, qualitative fieldwork and analysis of newspapers was used to obtain an overview of all failure mechanisms and presented in the form of a fault tree. To investigate the potential damage that could be done by each failure mechanism, a probabilistic risk assessment was done using the urban drainage modelling software PCSWMM, and the potential risk of each mechanism was quantified. For the mechanisms with an unacceptably high risk, potential solutions were proposed. Four failure mechanisms were found that pose an unacceptably high risk on the drainage system: increased catchment size, pipeline blockage, inaccessible drains, and design inaccuracies. Potential solutions are to incorporate Low Impact Development (LID) in the urban area such as green and blue roofs, infiltration trenches and rain barrels. This type of infrastructure reduces the hydraulic load on the drainage system by reducing the runoff peak. In this way, urbanisation goes hand in hand
with preserving the natural flows. Other recommended solutions are to revise the cleaning schedule to make it more efficient, and raise awareness among local inhabitants to enlarge their role in the functioning of Hanoi’s drainage system.

From 2018 to 2020, the city of Breda (NL) faced drought, with significant economic losses and water scarcity problems. The water board within which the city is located began to consider new possible water management practices, due to the unsustainability of the current ones. This study aims to investigate how a change of the current paradigm can improve the current approach in water management, shifting from a linear to a water management circular approach, and from command-and-control to adaptive. Starting from the case scenario of Breda, the study considers how through the reuse of management wastewater treatment plant effluent and stormwater, and the application of sewer mining units, it may affect the circularity and adaptability of the system. Then, based on Breda's experience, an attempt is made to investigate the concepts of circularity and adaptability. \\To be able to understand the current water situation and approach in the city of Breda, a water balance for the year 2020 was drafted. The water balance for 2020 for the city of Breda shows a positive value of 50 mm/year. The definitions of circularity and adaptability for a water management system were determined, and for each of the concepts a framework has been developed, to assess the level of circularity and adaptability before and after the interventions. Then, a workshop with local experts in the field was organized. Different strategies of interventions were proposed to them, in order to evaluate their suitability. Then, a final strategy was formulated, where wastewater effluent is employed as irrigation water for agriculture in the south of the municipality, stormwater discharge into wetlands to recharge aquifers and three sewer mining units in the rural area of Breda. These interventions showed a positive effect on the water system, since the volume of water stored in the system has increased, giving an overall better performance of the circularity and adaptability indicators. Moreover, the final strategy shows a better water balance of 100 mm/year. This research aims at creating a better understanding of concepts like circularity and adaptability. The study shows that there is a potential for re-using water to enhance the overall performance of the water system under certain conditions.

Continuous functioning of sewer systems and water distribution networks is crucial for liveability, public health and economic prosperity in urban areas. Progressive deterioration of these underground water infrastructures leads to an increased probability of failure. Maintenance is needed to ensure a desired level of functioning. For municipalities and drinking water companies as asset owners, the trend is to develop risk-based asset management. A risk-based asset management strategy links the likelihood of failure with the consequences. Hence, knowledge is needed on the condition of the underground water infrastructure and the consequences in case of failure. Within this strategy, a risk assessment should be performed to prioritise the maintenance and renewal of underground water infrastructure. Based on their criticality, resources can be applied appropriately. The more critical a conduit segment, the more important it is to perform maintenance. To contribute to risk-based asset management, this study investigates the consequences of failure in sewer systems and water distribution networks. In this research, a methodology is developed for mapping consequences of underground water infrastructure failure to guide asset management. Including the consequences of underground water infrastructure failure in the risk determination may lead to a different prioritisation of maintenance activities. Three failure mechanisms are considered: structural sewer failure, hydraulic sewer failure and water distribution network failure. Structural sewer failure leads to partial or complete loss of the load-carrying capacity, whereas hydraulic sewer failure occurs when a system does not meet serviceability requirements for system performance. For water distribution networks, it is assumed that hydraulic failure (caused by overpressure) and structural failure occur simultaneously. Hence, no distinction is made between failure mechanisms in water distribution networks. Using a screening method, the consequences of underground water infrastructure failure are mapped. The consequences of failure are expressed as the affected area and the characteristics of the built environment. The affected area consists of the sinkhole area and the flood zone. The characteristics of the built environment are displayed by means of consequence categories. Within this study, five different consequence categories are taken into account, using hydraulic modelling and (open) classified data. The consequence categories are: 1) Damage to buildings 2) Traffic obstruction 3) Impact on human health 4) Costs of conduit reconstruction 5) Drinking water supply outage. A flat, typical Dutch study area in Tuindorp (Utrecht) is used to test the methodology. For these five consequence categories, findings are illustrated and compared with the results of the hydraulic network functioning according to the Graph Theory method (GTM). This GTM determines the effects of failure of individual conduits on the functioning of a system as a whole, based on a simplified network structure using links and nodes. Results of the analyses show a positive relation between the individual consequences in case of hydraulic sewer failure. For example, critical conduits in the category `damage to buildings', are critical for `impact on human health' as well. Besides, there is a positive relation between the consequence categories and the hydraulic network functioning. Conduits with large diameters are stated as critical for both methods, yet dead-end segments are only critical for hydraulic network functioning. Contradictory, individual consequences are uncorrelated for structural sewer failure and water distribution network failure. The consequences are independent and can not be linked. Besides, there is no relation between the hydraulic network functioning and the individual consequences of structural sewer failure and water distribution network failure.