Per- and polyfluoroalkyl substances (PFAS) have remained persistent environmental contaminants since the 1950s, despite ongoing efforts to curb their production and find alternatives. Most health studies have focused on Perfluorooctanoic acid (PFOA) and Perfluorooctane sulphonic acid (PFOS), leaving limited data on other PFAS compounds in water. The European Union, particularly the Netherlands, has implemented stringent measures to control PFAS in drinking water due to their uncertain health impacts on
humans. Recently, the Dutch Institute for Public Health and Environment (RIVM) proposed a new guideline of 4.4 ng PFOA equivalent (PEQ) per litre for PFAS in drinking water, a substantial reduction from the current European Drinking Water Directive standards of 100 ng/L for the sum of PFAS and 500 ng/L for total PFAS.

While improving drinking water quality is expected to have positive health outcomes, the advanced treatment technologies required to meet this new guideline can be harsh, potentially releasing emissions that may cause negative health effects. This research, centred on the Leiduin drinking water treatment plant operated by Waternet in the Netherlands, investigates whether the health benefits of the new guideline outweigh the potential harms caused by the treatment processes necessary to achieve it.

To explore this, the study first calculated the Disability-Adjusted Life Years (DALYs) lost due to PFAS exposure from drinking water at the current concentrations, exceeding the 4.4 ng PEQ/L guideline, using a literature review to link guidelines with PFAS health effects. The second step involved conducting a Life Cycle Assessment (LCA) of the treatment system at the Leiduin plant, focusing on the treatment steps necessary to meet the new guideline, and calculating the DALYs lost due to the environmental impact of achieving the 4.4 ng PEQ/L standard. These DALYs were then compared to assess whether adhering to the new guideline is justified in terms of health impacts.

The results indicate that the DALYs associated with the current and proposed guidelines fall within similar ranges, showing limited health benefits. Specifically, the health benefits (in DALYs) gained from implementing the new guideline range from 0.4 to 4 per year, while the DALYs lost due to the treatment technologies required at the Leiduin plant range from 1.55 to 3.25 per year for the population receiving drinking water from the Leiduin site, depending on the type of activated carbon used in the treatment process.

These findings suggest that the potential health benefits of stricter PFAS regulations in drinking water maybe counterbalanced by the negative health impacts of the treatment technologies required to achieve
these lower concentrations

UV disinfection is an efficient way to inactivate chlorine resistant protozoan pathogens such as Cryptosporidium parvum and Giardia muris. In the United States, regulatory UV disinfection credit is typically granted when turbidity is <1 NTU. However, studies show turbidity does not correlate well with UV dose responses and partial inactivation when turbidity is > 1 NTU should be considered to avoid certain violations while still protecting public health. The objective of this study was to examine the impact of worst-case scenarios at drinking water treatment plants on UV disinfection. Indigenous spores from unfiltered source water and samples taken during the flocculation and softening steps at the Dublin Road Water Treatment Plant in Columbus, Ohio were exposed to Low-Pressure mercury UV254 disinfection from July 2019 to January 2020. Raw source water and softened water had similar dose responses despite significantly different water quality parameters. Flocculated water had the worst dose response: significantly lower maximum inactivation rate and higher residual population density than the other two water types despite having a lower turbidity than softened water. The modeled Geeraerd-tail maximum inactivation rates (k¬max) were 0.027, 0.021, and 0.030 cm²/mJ for raw source, flocculated, and softened water, respectively. The modeled Geeraerd-tail residual population density values (N¬res) were 1.168, 7.081, and 0.216 SFU/mL for raw source, flocculated, and softened water, respectively. Relationships between water quality parameters and modeled UV inactivation parameters were analyzed to determine and compare other potential indicators for UV disinfection to turbidity. Particle size and particle properties that govern the degree of particle-associated microorganisms best explained the differences in dose response between flocculated water and the other two water types. Larger particles are worse for UV disinfection. Microorganisms associated with particles are harder to disinfect with UV and lead to tailing. Climate change impacts on types, consistency, quantity, and quality of source waters for drinking water treatment make it especially important to understand UV disinfection kinetics under challenging scenarios. Informing regulatory changes to properly account for disinfection when turbidity is > 1 NTU could be especially useful for small or aged utilities that may not be as equipped to handle highly variable water qualities.

In the recent decade, a wide range of emerging contaminants (ECs) has been regularly detected in the wastewater treatment plants (WWTPs) effluent, surface water and even groundwater. Among all these ECs, organic micropollutants (OMPs) are receiving increasing attention due to their characteristics of low concentration, difficulty in degradation and their harmful effects on humans and the environment. Nineteen OMPs have been included on the contaminant watch list of the European Union Water Framework Directive since 2015 and efficient and reliable methods to eliminate them are researched worldwide. Therefore, in this study, five of these 19 OMPs (benzotriazole (BTA), carbamazepine (CBZ), diclofenac (DIC), ketoprofen (KET) and caffeine (CAF)) were selected as target OMPs. And the research objective is to fabricate a ternary composite photoanode and to investigate its photoelectrocatalytic degradation performance for all five target OMPs.

BiVO₄/(TiO₂/graphene oxide (GO))_mix ternary composite thin films were successfully deposited on fluorine-doped tin oxide (FTO) glass substrates using ultrasonic spray paralysis (USP) method to form a ternary heterojunction structure and to improve the photoelectrocatalytic performance for degradation of the five target OMPs. The morphology, crystal phase, surface chemical composition, optical and electrochemical properties of this ternary composite photoanode were analyzed by scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, incident photon-to-electron conversion efficiency (IPCE), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS), respectively. The results of these analyses showed that TiO₂ P25 nanoparticles and GO sheets were distributed uniformly on the brain-shaped BiVO₄ structure which indicated that the ternary heterojunction structure was formed successfully. From the UV-vis analysis, it could be estimated that the band gap energy for BiVO₄/(TiO₂/GO)_mix ternary composite photoanodes is 2.43 eV. Further, the LSV and EIS analysis showed that the photocurrent of the ternary composite photoanodes is lower than pure BiVO₄ photoanodes.
The degradation experiments were divided into five stages. The optimal photoanode type was first determined in the pre-experiment stage using methylene blue (MB) as indicator organic pollutant and then the effect of initial concentrations of target OMPs and initial pH on the degradation efficiency were studied in stage II and III, respectively. The highest removal efficiency of the five target OMPs was obtained with initial OMPs concentration at 10 μg·L^-1 and initial pH range of 3.5-4.0. The degradation experiments were triplicated under this optimal condition in stage IV. It was noticed from the results that the degradation efficiency of different OMPs after 3 hours of reaction time varied from 31.1 % to 99.5 %. To further confirm that there is competition between the five target OMPs during the photoelectrocatalytic degradation process, experiments were carried out in which individual OMPs were degraded independently. The reusability and stability of the photoanodes were evaluated in stage V. Trapping experiments using scavengers were also included in this stage, which showed that superoxide anions was the most active species during the degradation process.

As industrialization advances rapidly in pursuit of refining the quality of human life, there has been a release of organic micropollutants (OMPs) such as pharmaceuticals into various water reserves. This has endangered the ecosystem and the possibilities of water recovery. Commonly used tertiary wastewater treatment technologies have proven to, not under all conditions, be less effective in OMP removal. Hence, Advanced Oxidation Processes (AOPs) have gained attention in the recent past due to their production of reactive oxidative species (ROS) that unselectively degrade OMPs. Photocatalysis (PC), an AOP that uses solar radiation to produce ROS, has been investigated earlier, but shows low efficiency due to fast electron-hole recombination. Photoelectrocatalysis (PEC) is a modified version that additionally uses electrical energy, thereby reducing the recombination and improving the OMP removal efficiency. Bismuth vanadate (BiVO4) photocatalyst has gained importance due to its narrow band gap of 2.4 eV and hence, efficient absorption in visible light spectrum. Thus, this research focused on investigating PEC using BiVO4 electrodes for the removal of OMPs in aqueous solutions. The BiVO4 electrodes were fabricated using dip-coating from 1 to 5 layers, and electrodeposition at -0.2 V and -0.4 V, each at durations of 2, 5, 7, 10 and 15 minutes. They were then characterized using analytical techniques to investigate their structural, optical and optoelectronic properties. Subsequently, all the BiVO4 electrodes were used for the photoelectrocatalytic degradation of Acetaminophen (ACT). The electrodes fabricated by dip-coating were shown to achieve superior degradation efficiencies of ACT of over 99% in 5 hours, due to optimum surface morphology and band gap. It was seen that their varied surface structures played an important role in improving OMP degradation, and compensated for their low average quantum efficiency at 7%, as compared to that of electrodeposition at 14%. Next, the photoelectrocatalytic degradation of multiple OMPs in a solution was studied, and it was determined that although the ROS unselectively targeted all the OMPs, some were degraded quicker than others due to their chemical structure. Scavenging experiments were also carried out that affirmed the role played by ROS in the photoelectrocatalytic degradation of the OMPs. Eventually, the degradation of OMPs in secondary wastewater treatment effluent was conducted to test its usage in purification applications. Overall, PEC using BiVO4 electrodes was found to be feasible and successful in OMP degradation, and has the potential to be developed for usage in environmental remediation strategies like water treatment and recovery.

Bromate is a possible human carcinogen that does not naturally exist in surface or groundwater bodies. Its formation mostly results from ozonating bromide-containing water during wastewater treatment or drinking water production. Bromate is difficult to remove from water due to its high solubility and low reactivity in the aqueous environment; however, some bacteria showed the ability to reduce bromate to bromide, but the mechanism is unknown. Previous studies postulated a cometabolic pathway of biological bromate reduction, a side reaction of denitrification using the same enzymes. This study investigates the biological bromate reduction mechanism with a focus on its relationship with the denitrification process.

Wastewater and biologically active granular activated carbon (BAC) from a methanolsupplemented pilot filter called O3 -STEP in the wastewater treatment plant (WWTP) Horstermeer, the Netherlands, were used for research. This study first measured the crucial water quality parameters at eight different heights in the filter to investigate the redox condition’s influence on biological bromate removal. After that, batch experiments were conducted to validate the findings. The filter showed the ability to remove bromate as it lowered the bromate concentration from 2.7 to 0.9 µg/L. Bromate reduction happened at all depths including the supernatant, although the redox conditions significantly changed. Decreasing nitrate and dissolved oxygen (DO) concentrations did not change the bromate reduction rate in the filter. The batch experiments confirmed that nitrate did not affect bromate reduction. However, a DO concentration of 8 mg/L led to a 50% reduced bromate reduction rate compared to anoxic conditions. Experiments with varying chemical oxygen demand (COD, in the form of methanol) concentrations showed an extensive accelerating effect on bromate reduction. This explained why the bromate reduction rate was not lower at high DO levels in the filter, as the high COD concentration promoted bromate reduction. Nitrate reduction was found to have a high positive correlation with bromate reduction in both filter and batch experiments, indicating similarities in their mechanisms. Nitrate reduction happened under highly oxic conditions. The intensive mixing of the granules in the filter may have provided alternating aeration and anoxic conditions for the enrichment of aerobic denitrifiers.

This study is the first study to observe simultaneous nitrate and bromate reduction under oxic conditions. Taken together, biological bromate reduction is likely to be a synergetic cometabolic process of aerobic denitrification. The robustness of the biological bromate reduction under high DO and nitrate conditions enables the O3 -STEP ® filter to steadily produce bromate-free effluents under more extreme influent conditions.

In the context of climate change and urbanization, sustainable urban drainage systems (SUDS) are widely adopted measures to manage stormwater in the city on-site. However, their performance in practice often differs from modelled and laboratory-scale predictions due to the variability in properties of real sediments (in terms of size, shape, density and coagulation) compared to the silicate standard Millisil®W4. Clogging is a common source of failure. 
The SediSubstrator L is a decentralized stormwater treatment device installed as a pre-treatment step to mitigate clogging in a storage and infiltration system on the Rooseveltlaan in Amsterdam. It consists of a sedimentation pipe with a flow-separating grate, the SediPipe, and a filter-adsorbent, the SediSorp+. It is purported to remove 80 % of TSS by DiBT (the technical authority in the German construction sector) test principles that use Millisil®W4 to simulate real sediments. The full-scale unit was monitored in the city throughout May-September 2022 to assess its performance. 
The stormwater runoff discharged from the catchment had high concentrations of lead (54 μg/L) and zinc (790 μg/L), likely due to contact with gutters and old roofing material, amplified by the relative contribution of these roofs to the total catchment discharge (accounting for 50 % of the area contributing to runoff). The sediment (TSS) concentration was low, equivalent to 20 mg/L on average. The sediments were also light and fine—with an organic fraction of 66 % and with 78 % of diameter smaller than 63 μm.
In the SediSubstrator L, the TSS removal efficiency was 34 % on average. This corresponds to an estimated caught load of 2.7 kg for this period. The removal efficiency was shown to increase with an increasing stormwater TSS concentration, with longer antecedent dry periods and with lower TSS organic fractions. Turbidity dynamics in the system suggest that while a net sequestration of solids occurs in the SediPipe, there is a resuspension of fine solids. This was observed in a camera inspection to occur from solids which settle on or near the grate. In an extreme rainfall event on September 28th 2022, water collected on the section of the street connected to the SediSubstrator, the cause of which is still subject to speculation. The observed SediSorp+ filter resistance across the summer was not indicative of gradual clogging, but an inspection showed signs of decayed organic matter throughout the full length of the filter bedas well as traces of cement in two of the four cartridges. It is possible that these two effects together with turbulent inflows prompted the acute clogging behavior.

There is interest in using the SediSubstrator beyond the city of Amsterdam to reduce phosphorus loadings in the road runoff discharged to sensitive nature areas. On the Rooseveltlaan, the average total phosphorus removal efficiency was 18 % (50 % for dissolved, readily bioavailable ortho-phosphate). Interactions with settled sediments generated ortho-phosphate in the SediPipe, and fine particulate and colloidal organic phosphorus was shown remobilized in both the SediPipe and SediSorp+. The removal of ortho-phosphate in theSediSorp+ in natural rainfall was good (on average 50 %) and was shown to be consistent at different contact times (approximately 10-30 minutes). 
The installed unit should be monitored over a longer time period of two years for statistical significance and to capture seasonal variation in loads. Nevertheless, the removal efficiency observed on site is consistent with the results of a sedimentation model developed according to Ferguson & Church (2004), using a stormwater sediment particle density as measured at another location in the city. Design adaptations are recommended to improve the SediSubstrator L to the conditions observed in Amsterdam: namely, better site selection, a longer SediPipe section (24 m) and a second filter stage to better capture the fine suspended solids.

Magnesium is one of the most critical natural resources and 96% of magnesium used in Europe is imported. The present study investigated possible ways of implementing circularity in the magnesium cycle within the borders of Waternet, a water utility in the Netherlands. The wastewater treatment plant at Amsterdam-West produces struvite from anaerobic digestate. The production of struvite requires 4400 tons of 32% MgCl2 annually. At the same time, a reverse osmosis (R.O.) process treating brackish groundwater for drinking water production produces a concentrate rich in magnesium ions. This R.O. concentrate, after being treated by aeration and filtration to remove iron and ammonium, is considered for use in the wastewater struvite recovery process. Technologies for recovering magnesium from this R.O. concentrate were investigated in this study. After analyzing the constraints of the magnesium dosing system, the struvite reactor, and the R.O. concentrate composition, two technologies were selected for the study of Mg2+ recovery: Nano-filtration (N.F.) and Ion exchange. The present study investigated both these processes via software simulations and laboratory experiments. The study revealed that while the N.F. process is not viable, the cation exchange using a weak chelating resin AmberLite IRC747 in Na+ form (regeneration with H2SO4 and NaOH) is possible when the resin is saturated with divalent cations. The regenerant stream (produced via acid regeneration) is a sodium-free stream having gypsum precipitates. After gypsum separation, the process created an Mg2+ dose with a concentration of 4.45 g/l. This study developed a 1 step process for extracting Mg2+ from RO concentrate.

The presence of organic micro-pollutants (OMPs) in water bodies has become a major hindrance to protecting water quality in recent years. One of the main sources of OMPs is wastewater treatment plant (WWTP) effluents. One of the most recent Advanced Oxidation Processes (AOPs) technology is photo-electrocatalysis (PEC), which can produce radicals to oxide OMPs in an aqueous medium driven by solar energy and an external bias potential. In this study, ultrasonic spray pyrolysis was determined as a proper method to fabricate the ZnO/BiVO4 heterojunction. Then, the prepared photoanodes were characterised by X-ray Photoelectron spectroscopy (XPS), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV-vis and Incident Photo-to-electron Conversion Efficiency (IPCE). The results demonstrated the ZnO/BiVO4 heterojunction was successfully fabricated on the Fluorine-Tin-Oxide (FTO) glass. Moreover, the LSV and EIS analysis were carried out in this study to analyse its photo-electrochemical properties. The PEC degradation experiments were carried out in 10 μg/L of 11 OMPs spiked in MiliQ and in real WWTP effluent under simulated solar illumination at 1 V potential bias for three hours. Nine and four of 11 OMPs had achieved more than 70 % degradation efficiency when ZnO/BiVO4 photoanode was conducted to degrade spiked MiliQ and spiked real WWTP effluent. Except for diclofenac and sotalol, the real effluent showed inhibition to the degradation efficiencies and kinetic coefficient of the other nine OMPs. The concentrations of TOC, COD and NO3-N increased after the PEC process. The increase was found to be related to the disintegration of the carbon stick cathode. To further enhance the PEC process, the ZnO@GD/BiVO4 photoanode and adding persulfate were conducted the PEC degradation experiments separately in spiked real WWTPs effluent. Both two approaches showed an enhancement of the PEC process and improved degradation efficiencies. The results obtained in the present work reveal that the PEC process has excellent potential for the removal of OMPs from WWTPs effluent.

As antibiotics now save millions of human and animal lives annually, the World Health Organisation (WHO, 2019) declared Antibiotic Resistance (AR) as the number five most dangerous risk to global health. Several researchers mention WWTPs to be an important source for AR as the growth of bacteria is stimulated in an environment with a selective pressure facilitated by a relatively high concentration of antibiotics.

Tertiary treatment steps are implemented primary to polish the effluent and reduce the OMP load of the effluent. The O3-STEP filter is an innovative example of such a tertiary treatment combining the oxidative effects of ozone with the adsorption effects of a Granular Activated Carbon (GAC) filter. In addition to these effects, a coagulant is dosed for the removal of Phosphorus (P). The implications for AR are still unknown. In literature varying results are found on the disinfecting effects of ozone, GAC and coagulation and nothing is found on the combination of these treatment steps yet. The purpose of this document is to present how effective the treatment with ozone and coagulation is in the removal of antibiotic resistant bacteria (ARB) in comparison with antibiotic sensitive bacteria (ASB).

Agar growth media are used to test four different microorganisms: two faecal indicators (E. coli and Enterococci) and a resistant strain of each of these bacteria (ESBL E. coli and Vancomycin Resistant Enterococci (VRE)). Several experiments are conducted in the laboratory to test disinfection of ozone and coagulation on these microorganisms.

In confirmation of the hypothesis, ozonation and coagulation disinfect ARB as well as ASB. However, as both treatment steps are not aiming at the removal of microorganisms but at the removal of OMPs and phosphorus respectively, the microorganism removal is limited (with 0.7 log on average). Increasing the coagulant and ozone dosage showed promising results in the laboratory. Dosing the coagulant above the optimum sweep coagulation dosage is not favourable because the increase in removal stagnated above this concentration whilst the residual coagulant concentration in the supernatant water increased.
In the GAC of the O3-STEP filter and its backwash water, an increase of VRE is found relative to Enterococci in comparison with the ozonated water but not over the complete O3-STEP filter. This was different for the 1-STEP filter which showed the worrying result that VRE increased in the same amounts as Enterococci decreased. As the 1-STEP filter is a filter with a matured biology, where O3-STEP was recently started, the O3-STEP filter might increase the absolute and relative amount of ARB in long term as well.

In case the aim for the O3-STEP filter is to remove AR as well, several suggestions are made. As ozone and coagulation both potentially remove ARB, an increase in these concentrations is a no-regret possibility. Furthermore, ultrafiltration (UF) and the combination of ultraviolet (UV) and O3 are proposed as possible alternatives. Using a multicriteria analysis (MCA), increasing the ozone dosage with the existing bypass is recommended.

Research towards aquathermal energy solutions is still in a pioneering phase. Especially in urban environments, these solutions could potentially form the missing connection between heating supply and demand. This study focuses on the application of these solutions in the city canal waters in the largest city of the Netherlands, Amsterdam . Currently, these so-called Surface Water Heat (SWH) systems have not been implemented at all in the inner city canals of Amsterdam. One of the reasons for this can be found in a lack of knowledge about natural water temperature variations in these types of waters and the unknown thermal effects related to SWH systems. This study is an answer to this knowledge gap and an attempt is made to provide insight in the thermal effects of SWH on a city canal. The Amsterdam city canals form a unique water system in open connection with larger waterways and they are part of a hydrodynamically complex interaction between sea and the river Rhine. Until date, such a study towards SWH system effects, not being restricted to the boundaries of the respective water body, is scarce or even non-existent.\\ The case study location is situated at the Jacob van Lennepkanaal in Amsterdam, where a collective of civilians has recently started the exploratory phase for installation of the first SWH city canal system for heating of their own district. To respond to this societal development, this specific case study location was chosen. To be able to model the SWH system for this neighborhood, the first part of this thesis focuses on system layout and related system characteristics. It was found that open-loop SWH systems are often applied at district level. Secondly, a reference surface water temperature model without SWH systems was built and validated upon meteorological forcing with local water temperature measurements. The third part of the followed method was to apply the modelled SWH system to this validated three-dimensional thermodynamic model. For this purpose, the Delft3D model was chosen, which computes the RANS equations under the hydrostatic assumption. Several scenarios were calculated with varying temperature difference through the SWH heat exchanger and varying distance between system intake and outfall. The modelling results for the Jacob van Lennepkanaal case show that SWH systems used for heating purposes, thereby cooling the surface water, produce a negatively buoyant flow, causing the discharged cold water plume to sink to the bottom. Existing thermal stratification in the city canals is enhanced and hydrodynamic mixing processes are not strong enough to disturb this stratification built-up. Further away along the plume, in the far-field, a combination of buoyant spreading and the process of passive diffusion mix the water column and the temperature decrease, induced by the SWH system, becomes uniformly spread over the entire water column. Currently, steady state one-dimensional models are often used for assessment of SWH thermal effects. It was demonstrated that these models are useful and accurate, provided that the right heat exchange coefficient is used and near-field mixing at the outfall is represented correctly. These models can be used to study for example the time-averaged extent of the cold water plume, but fail to provide insight in time-varying and spatial characteristics of the canal. Local changes in bed level height, attraction of ambient water by the intake and intersections with lateral canals also influence the thermal profile. For a study towards these effects in greater detail, three-dimensional modelling or 2DV-modelling are preferred. Also, in case of a study towards application of multiple systems, these are the models of choice.

Urban water management is faced with upcoming challenges due to climate change, the deterioration of existing infrastructures and the depletion of water sources. Climate change brings about more intense rainfall events and longer periods of drought. On top of that, the deterioration of the piped network urges for investments in the existing system, to ensure that the provision of water services can be maintained. Furthermore, the depletion of water sources is raising awareness regarding the value of freshwater which gives rise to the re­use of water flows that have up to now often been considered as nuisance rather than viable resource. Examples of these flows are the wastewater and the stormwater flow.

The existing centralised infrastructure consists of three reliable systems. The first system supplies high­quality water, the second drains out stormwater and the third one discharges wastewater. These three systems operate separately from each other and follow a linear approach to
water management. In recent years, circular water management has become more prevalent. Instead of following a linear approach in the three separate systems, the re­use of water flows as viable sources are applied more often. New, often local, solutions can be designed to effectively complement existing systems in maintaining the high provision of water services that societies have consistently been using over the past decade. This circular approach can ensure that current water requirement levels can be met sustainably by the improved urban water systems.

By dealing with the upcoming challenges of high­intensity rainfall and long periods of drought– which both have a high spatial variability – local solutions are able to support the centralised infrastructure. This is done by both mitigating the pluvial flood risk, as well as by providing a high ­quality water source. An arguably ideal solution which addresses both the pluvial flood risk and also provides a high­quality water source, is the Bluebloqs system. The Bluebloqs system can help mitigate pluvial flood risk by the attenuation of flow, the result of implementing an attenuation tank in the stormwater drainage system. Also, the Bluebloqs system is able to filter and store this stormwater to provide a high­quality water source during water­scarce seasons.

Whether the Bluebloqs system is a viable solution which addresses both the mitigation of the pluvial flood risk as well as the provision of water challenge, is investigated in this research. The Bluebloqs system is a circular water solution that makes use of an attenuation tank, a bio­filter and an aquifer storage and recovery (ASR) system. The attenuation tank is physically connected to the drainage system and it consequently decreases the risk of surcharged pipes in the drainage network. From the attenuation tank, the water is pumped towards the bio­filter, where pollutants from the water are removed and the water is filtered to such an extent that it can be infiltrated into the aquifer. In the aquifer, the water is stored to overcome seasonal variations in
water availability. The Bluebloqs system has the objective to supply water in the dry season, even though its source is stormwater, which enters the system during the wet season. This research has analysed the performance of the Bluebloqs system for different dimensions and operations.

Within this thesis, a framework has been built that presents the performance of the Bluebloqssystem. This framework consists of three groups; the interactions with centralised infrastructure, the water quality indicators and the impact of the Bluebloqs system on its environment. These three have their own distinct performance indicators, which characterise the effectiveness of the Bluebloqs system in providing a specific water service. The group of the framework dealing with the interactions with the centralised infrastructure uses performance indicators for the volume of water lost in overflow events, and volume of water supplied through the Bluebloqs system as high­ quality water source to the end­user. The indicators for the other groups characterise the Bluebloqs system differently. Each group within the framework projects the performance of the Bluebloqs system for other interest groups. For example, the indicators regarding the impact of the Bluebloqs system on its environment are of interest to municipalities thinking about implementing the system.

The behaviour of the Bluebloqs system has been modelled. This model presents the physical processes taking place within the Bluebloqs system. The output of the model are the performance indicators of the framework. By running the model under different input parameters, the performance of the modelled Bluebloqs system is tested on the three groups of the framework.

The outcome of testing the model on the framework has shown that the Bluebloqs system can be improved. One of the suggested improvements is to work with feed cycles for the bio­filter. These feed cycles consist of the periodic saturation of the bio­filter. Once the bio­filter is saturated, the flow from the attenuation tank towards the bio­filter is interrupted, to let the water gradually filter through the bio­filter.
By applying feed cycles, the bio­filter is better capable of removing pollutants from the water. However, periodically interrupting the water flow from the attenuation tank towards the bio­filter negatively impacts the effective storage capacity of the attenuation tank. When having more feed cycles in a day, these interruptions last for a shorter period of time. Depending on the desired performance of the system, which is based on the performance indicators, these feed cycles should be aligned with the capacity of the attenuation tank and the discharge of the pump for the flow between the attenuation tank and the bio­filter.
Fitting the feed cycles to the seasonality of rainfall patterns can further increase the performance of the system in mitigating flood risks. Applying predictive control when overflow events occur is an additional control option that minimises the environmental impact of the system. Finally, the performance of the Bluebloqs system can be presented based on all the performance indicators included in the framework, and the model can be used to adjust the system dimensioning and operations to present the consequences of adjustments to the desired performance of the Bluebloqs system.

The frameworks’ performance indicators can be used to understand the Bluebloqs ideal configuration to deliver a specific desired performance. The desired performance of the system determines the dimensions and operations of the system. Co­designing the Bluebloqs system is thus crucial to its delivered performance.

In conclusion, the framework and model can be used to present the Bluebloqs system for different scenarios. The framework can generate a comprehensive overview of what can be expected of the Bluebloqs system when implementing it in a specific project site, in comparison to other solutions that may be considered, such as green roofs or storage tanks. Also, its use as circular solution being complementary to existing urban water infrastructure can be presented by the framework and model output. This will help in the transition of urban water systems in dealing with the upcoming challenges related to climate change, the deterioration of the piped infrastructure and the depletion of water sources.

This thesis proposes a novel design approach for a monitoring system that can detect hidden leaks in intermittent water supply (IWS) systems. Cities with IWS conditions in their drinking water network, such as Nairobi and Harare, often have a high percentage of non-revenue water (NRW) in their system. Estimations of the amount of NRW in these cities range from 40% to 50%, of which a large part is due to a leaky infrastructure. Intermittency of water supply is usually caused by a shortage of available supply, making it extra poignant to notice that these areas lose significant volumes of water. The leaks are also important locations for contaminant intrusion, which deteriorate the quality of drinking water. Additionally, intermittency of supply results in people using storage to fulfill themselves with their weekly water demand, which provides new challenges when constructing hydraulic models. Hidden leaks, which are leaks that do not appear at the surface, can be noticed in continuously supplied areas through reports of pressure deficiencies or the absence of supply. As these are regular circumstances in IWS areas, these hidden leaks are seldom noticed. Therefore, methods that are applicable in IWS systems need to be developed to detect these hidden leaks. This thesis proposes a new approach to detect hidden leaks in IWS areas with a smart hydraulic monitoring system. The approach optimizes the design of such a system in a district metered area (DMA) with IWS conditions in sub-Saharan Africa, by balancing information density and investment costs. By using as little equipment as possible, this optimization study aims to be not only scientifically and practically relevant, but also cost-effective. The methodology that was used to design the monitoring system makes use of a similar concept as the Dynamical Bandwidth Monitor (DBM), which is a smart hydraulic monitoring system that has been applied regularly in networks with continuous supply. The monitoring system consists of sensors that continuously measure flow or pressure and it compares these measurements to a range of expected values, attributing deviations from these expected values to a potential leak. A case study of Ashdown Park, a DMA with IWS conditions in Harare, was used to assess the performance of the design. The flow into this DMA and the pressure at its inlet had been monitored for one year. Two designs of the monitoring system were made, one which mainly consisted of flow sensors and one with mostly pressure sensors, to showcase which type of sensor could best be used in Ashdown Park. A hydraulic model was constructed for the DMA using pressure dependent outflow modelling. Daily demand patterns were constructed from analyzing the inflow measurements and used to calibrate the hydraulic model. The proposed calibration method assumes linear relationships between the demands and inlet pressure on one side and the pressure at a specific node and flow at a specific pipe on the other side. The range of expected flows and pressures within the DMA was calculated by Monte Carlo analyses, during which demand realizations were modelled by using a novel method which made use of a random weighted choice of demand, based on the outflow from a single tap. The ability of the monitoring system to detect leaks during different demand realizations was stored in a three-dimensional Boolean matrix, which was then used to determine the optimal sensor placement. A social and financial analysis, summarized in a business model canvas, shows more practical challenges and opportunities that could arise from implementing the monitoring system. The lessons learnt from this thesis were used to showcase whether the monitoring system could be applicable for IWS systems around the globe. Several conclusions can be drawn from the results of this thesis. The daily demand patterns in Ashdown Park showed a different pattern than in continuously supplied systems, showing less strong peaks. This could be due to a constant water demand for filling storage, leaks in the system or different consumer behaviour. The calibration method made it possible to model flows and pressures at the DMA inlet which were comparable to the measurements. The novel method to model demand realizations with a random weighted choice and a single tap capacity, showed promising results since the spread of the modelled inflow was well comparable to the spread of the inflow measurements. This standard tap capacity is especially suitable for IWS areas, since most people in IWS areas usually only have one tap directly connected to the water supply system and water end-use devices are not directly connected to the network. Furthermore, it was found that the water use behaviour of inhabitants of Ashdown Park had been more constant than the supply behaviour of the water utility. This irregular supply behaviour of the utility increased the difficulty of designing a pressure monitoring system. Using a flow monitoring system to detect leaks showed a better performance (leaks could be found on a daily basis in 25% of the pipes in the DMA) than using a monitoring system with pressure sensors (leaks could be found in 1% of the pipes). Making the monitoring system with pressure sensors dependent on the inlet pressure increased its performance (from 1% to 8.3%). Branched parts of the system were more favorable locations to place sensors and sensors at the DMA inlet were crucial for calibrating the hydraulic model. Practical barriers that were identified during this thesis were irregular operational schemes, unknown demand patterns and incomplete GIS data. Furthermore, costs can be saved as soon as leaks are detected, making the financial profitability very dependent on the performance of the system and the occurrence of leaks. The applicability of the monitoring system in IWS areas around the globe is determined by the priorities of a local water utility, its network characteristics and the ability of the local utility to overcome implementation barriers. The main limitations in this research are due to making some simplified assumptions, such as assuming a constant flow-rate from the tap in all households in Ashdown Park, and due to a lack of understanding of the local situation, since this research was performed in the Netherlands. To validate assumptions and get better understanding of the local situation, it is advised to conduct follow-up research at the location of interest. Especially a pilot project of the proposed monitoring system would likely find more practical barriers and limitations than could be thought off in this thesis and therefore bring more valuable information for the implementation of a smart hydraulic monitoring system. If prioritized, properly installed and operated, the proposed smart hydraulic monitoring system could generate substantial water savings and provide many social benefits, such as an increased access to clean drinking water and employment opportunities. Above all, it can assist a local utility with fulfilling their responsibility: supplying people with the basic need of drinking water.

Though slow sand filtration is one of the oldest and effective means of drinking water treatment, the mechanisms contributing to bacteria and viruses removal are not well understood. The lack of understanding of actual removal potential and different mechanisms occurring in the filter bed has limited the development of new filter design and operation. This research aims at assessing the bacteria and viruses removal capability of filter material in different depths from the top 40 cm of full-scale slow sand filter (SSF) operated for 436 days. In addition, the focus is to identify the key removal mechanisms that aid bacteria and viruses removal in the schmutzdecke.
The results show that three depths: 0-5, 5-20 and 20-35 cm contribute to E. coli removal of 0.55, 1.3 and 1.04 logs, PhiX174 removal of 0, 0.30 and 0.14 logs. The log reduction value of E. coli and PhiX174 is rather similar in different layers, even though the schmutzdecke is considered to be the critical component for E. coli removal. It indicated that the deeper layers are also important in a well-established SSF. No removal of PhiX174 was observed in 0-5 cm with a thick biofilm, which indicates that the thickness of a certain level would impact the performance of virus removal.
To determine mechanisms, filter material from 0-5 cm was operated under three conditions: active, inactive, and ignited condition. The results show E. coli removal of 0.68, 0.74, and 0.43 logs, PhiX174 removal of 0, 0, and 0.28 logs for active, inhibited, and ignited sand, respectively. Contrary to previous studies, no function of microbial mechanisms is observed for E. coli removal. That key mechanism might change with the different maturity levels of SSFs might be a possible reason. In addition, this may ascribe to incomplete microbial active inhibition. On the other hand, despite evidence that virus removal enhances with filter maturation, schmutzdecke did not improve PhiX174 removal. Poor virus removal may be attributed to higher interstitial velocity along with higher shearing forces caused by abundant biofilm within the schmutzdecke.

Intensive urbanisation enhances warming of cities’ ambient and subsoil environment. The local drinking water distribution system (DWDS) is likewise affected. Hotspots of anthropogenic heating were perceived to influence drinking water temperature and pose a threat for microbial drinking water quality. Information on temporal and spatial relation between drinking water temperature and microbial indicating parameters was however scarce. This is especially the case for a full scale unchlorinated DWDS in a metropolitan area. Therefore, this research aimed to explore the spatial and temporal relation between drinking water temperature and microbial indicating parameters Aeromonas and Heterotrophic Plate count (HPC). 11 Years of sample data from the DWDS in the metropole of Amsterdam was explored, with the objective to possibly draw conclusions beyond this DWDS. This DWDS consists of two interconnected subsystems. Each subsystem is fed by its own treatment facility. Areas with repetitive exceedance of threshold temperature (14 oC) for accelerating Aeromonas growth, were not inextricably tied to repetitive exceedance of the Aeromonas standard for safe drinking water. Areas with repetitive exceedance of the Aeromonas standard were often linked to prolonged residence time. For regions on the outskirt of observed DWDS it was suggested that the influence of residence time was more important than the absolute water temperature to explain Aeromonas concentrations.

The removal of organic micropollutants (OMPs) in the aquatic environment is crucial to avoid health hazards. Zeolites have been confirmed as a selective adsorbent and can effectively remove target OMPs. To achieve sustainable application of adsorbents, regeneration of zeolites is required.
The objective of this study was to investigate the regeneration performance of dried OMP-loaded granular zeolites through gaseous ozonation process, and the regeneration feasibility in long-term adsorption-regeneration processes. Three types of zeolites (MOR, MFI and BEA) were applied for target OMP (benzotriazole, methyl-benzotriazole, carbamazepine, diclofenac hydrochlorothiazide, sulfamethoxazole, metoprolol, sotalol, trimethoprim, propranolol, and clarithromycin) removal. A sequential process coupling zeolite adsorption and oxidation by gaseous ozone was established in batch mode. To assess the ozone effect on OMP degradation and zeolite itself, ozone bubbling tests and adsorption isotherm experiments were executed as pre-experiments. The relative adsorption capacity obtained through regeneration was used to demonstrate regeneration performance. Operating conditions, adsorption duration and regeneration duration were determined and applied. Ultimately the regeneration performance in long-term adsorption-regeneration processes was investigated.
Experimental results showed that all target OMPs were not resistant to ozonation in the water phase. Gaseous ozone was showed no influence on the adsorption capacities of zeolite granules. 120 hours and 500 mgL-1 zeolite granules were applied in OMP-loading adsorption experiments. Zeolites always showed high adsorption capacities of metoprolol, trimethoprim and sotalol, which regeneration effect was not evidenced. 60 minutes of ozonation was effective and sufficient for regenerating low and medium adsorption OMPs, except for carbamazepine. The regeneration of carbamazepine probably required a longer regeneration duration. In four cycles of adsorption-regeneration experiments, regeneration of sulfamethoxazole could be achieved after four rounds of ozonation. Regarding carbamazepine, diclofenac, benzotriazole, and methyl-benzotriazole, the regeneration performance were significantly reduced after the first cycle of regeneration. The ozonation duration is supposed to be extended above 60 min in long-term regeneration experiments. Intermediates were potentially responsible for the reduction of regeneration performance in ozonation and adsorption processes. Particularly, the effect of intermediates accumulation might be the main factor that hampered the regeneration performance of low and medium adsorption OMPs in long-term operation.

In this thesis, I develop and evaluate a demand-side approach to transition from an intermittent to a continuous water supply using a district metered areas approach in Accra, Ghana, an urban metroplex of 4.0 million persons in western Africa. Intermittent water supply (IWS) is inherently inefficient. These systems foment health hazards and are expensive with an inherent low return on investment. Various causes and effects with positive feedback loops exacerbate intermittency. And building more robust IWS systems does not help because of rapid system degradation and high socio-economic costs render them unsustainable. Continuous water supply (CWS) systems are superior in every respect. Therefore, I view transitioning from IWS to CWS as the optimal choice for urban water districts. The general strategy to make this transition is to increase production and sharply improve the transmission capacity and efficiency of the drinking water system, the so-called supply-side approach. But because the supply side approach does not factor the underlying causes of IWS-- leakage and variable pressure levels, I used a demand-side approach for this study and designed a novel method, based on leakage theory with the application of district metered areas (DMAs). We tested this method on a case study performed in Accra, Ghana. The method is essentially a set of requirements and boundary conditions used to facilitate the transition from IWS to CWS from a demand-side perspective. A decision tree gives insight into the causes of IWS per DMA and the interventions required to reduce intermittency. Based on the foregoing, water engineers can build strategies to roll out a demand-side CWS systems in DMAs for an entire region. In our Accra study, we tested three DMAs using this approach with a focus on supply security. Data from those DMAs was collected and a top down NRW assessment was performed. We selected one DMA to collect and analyse flow and pressure data (minimum night flow, non-revenue water, billing, intermittency level, average zonal pressure). Furthermore, the supply conditions and proposed intervention (pressure adjustments) were hydraulically modelled for the district. Based on the DMA data, a transition strategy was developed for the Greater Accra Metropolitan Area. We also assessed the applicability of the demand-side approach to other areas through a survey among water supply specialists. The study shows that gains in water savings at the DMA level to more than justify the costs of transitioning to CWS. In cases of high pressure and high real loss volumes, pressure management improves supply conditions for customers. And, after attaining CWS, water recovered from loss reductions can be redistributed into neighboring districts, increasing their water availability. Because hydraulic pressure dependent demand (PDD) modelling cannot model leakage accurately, it was not possible to evaluate leakage reduction interventions. And it was not possible to create a working hydraulic model to assess the effect of this DMA approach for the entire Accra metroplex because of limited data availability at a district level, leakage parameters that were difficult to verify with field measurements, and the lack of a proven hydraulic PDD software able to distinguish between domestic demand and real losses. In conclusion, the developed method looks promising. But two factors limited fully exploring its real-world application: (1) the absence of mature modelling software; (2) detailed water district data. Developing a working hydraulic modelling software was beyond the scope of an MSc. thesis. But such hydraulic modelling software should be developed to help water utilities with limited technical and human resources improve services. Further research is required into leakage component modelling and validation from field measurements, after which interventions can be more properly and easily applied.

The transition towards sustainable and resource efficient urban water systems is a major challenge nowadays. To meet the high demands of urban life resources need to be efficiently used and resource recovery from generated “waste” streams should become a “new normal”. Water and wastewater can provide an alternative and environmentally viable source of resources supporting the resilience of natural systems under water stress. There are many resources that can be recovered via the water path, such as water itself, energy and components such as nutrients and metals. However, the urban water system is an assembly of complex and interconnected processes which have to be taken into account in order to create an overall sustainable value. Managing the entire water-energy-nutrient nexus for the built environment requires a full system analysis of the life cycle energy consumption, water consumption, global warming potential and freshwater eutrophication potential of the municipal water and sanitation services. This work is an assessment of the environmental impacts of various urban water systems which aim to the water conservation and resource recovery. Each alternative system was assessed under four main planning scenarios applied at a dwelling level$\colon$ greywater treatment and reuse, rainwater harvesting and use, usage of water-efficient appliances, food waste valorisation via the sewer system. The scenarios were investigated from two different perspectives (eight scenarios in total), all based on the principles of water fit-for-purpose and resource recovery. In the first perspective the four scenarios limited the interventions at a dwelling level, while in the second one additional techniques for phosphorus and nitrogen recovery were applied at a centralised wastewater and sludge management level. The comparative results revealed that the usage of water efficient devices (low-flush toilets, water efficient shower heads, waterless washing machines, waterless dishwashers) at a household level, coupled with centralised wastewater treatment with simultaneous recovery of struvite and biogas, and sludge waste drying to produce biofuels promotes a robust and resource efficient urban water system. This strategy was estimated to offset 79% of the overall embodied energy consumption, 72% of life cycle carbon footprint, 22% of life cycle freshwater eutrophication potential and 56% of embodied water consumption. A sensitivity analysis revealed that the energy requirements for water heating in showers, dishwashers and washing machines and the carbon intensity of the national electricity mix were the most important parameters for determining the comparative life cycle global warming potential results.

Wastewater discharged from the domestic household has proven to be a potential source for resource recovery. Apart from wastewater, kitchen organic waste contains an enormous amount of energy in terms of organic content and nutrients such as TKN and TPH. Now that the disposal of waste into landfills is prohibited in most parts of Europe, one of the options is to divert the organic waste to wastewater treatment plants using kitchen waste grinders (KWG). Since KWG is a water-consuming appliance, the installation of KWG with water conservation technologies may be a viable option in the future. This can aid efficient recovery of resources and reduce the drinking water demand. The evolution towards sustainable urban sanitation will lead to several positive and negative effects. Some of the positive effects, apart from resource recovery, are the possibility to postpone the enlargement of existing sewer systems, to construct new sewers of smaller pipe diameter and to lower energy consumption for sewage pumping. While the negative effects are blockage of sewer due to reduced flow rates, increased sedimentation and release of malodour in the contemporary sewerage system and increased treatment costs due to increase in COD oxidation and nitrogen or phosphorus removal. Eventually the low flow-high load wastewater needs to be transported through sewers and treated locally (decentralised treatment). In this study, an attempt was made to investigate the effect of coupling the effluent from KWG at various penetration rates such as 100%, 75%, 50% and 25% with water conservation scenarios on hydraulic and quality parameters in the sewerage system. Water conservation scenarios were onsite greywater and rainwater reuse and application of ultra-low water demand appliances. SIMDEUM was upgraded with the addition of an extra appliance in the form of KWG to generate stochastic discharge patterns with appliance specific wastewater flows and quality. The data generated was incorporated into the sewer network model, InfoWorks ICM to analyze the impact of the addition of KWG with water conservation strategies on the contemporary sewer network. The results obtained showed that there is an increase in the mass load of COD, TKN and TPH of 118%, 84% and 90% respectively and reduction in flow, velocity and shear stress of up to 54%, 49% and 74% respectively for the application of water conservation strategies with KWG. This substantiated the fact that the contemporary sewer system is not efficient in transporting the wastewater generated due to the addition of KWG along with water conservation strategies at the household level. A new sewer design with smaller diameters and steep slopes was used to study if the low flow-high load wastewater can be safely transported, in terms of adequate self-cleansing velocity and shear stress. The results from the investigation of new sewer design showed that 100% and 75% implementation of KWG with water conservation technologies will achieve self-cleansing capacity which will help prevent clogging and sedimentation for a piping network of 110mm diameter at a slope of 1:160. KWG market penetration rates of lower than 50% along with water conservation strategies might face issues of sedimentation and clogging. In conclusion, the up-gradation of SIMDUEM with KWG was successful to generate stochastic discharge patterns. This research has demonstrated that the application of KWG along with water conservation strategies may aid in resource recovery and reducing freshwater demand in the urban water cycle. The accomplishment of implementation of KWG with water conservation strategies is not realistic in the contemporary sanitary system however, this transition can be adopted in new urban developments with efficient design of wastewater transport and decentralized treatment system. Further research is required into the feasibility of a decentralised resource recovery system for the implementation of KWG with water conservation strategies.

The city of Amsterdam aims to supply buildings in the historic centre of Amsterdam with sustainable, reliable, and affordable heat for space heating. However, currently only hight temperature heat from biomass and waste incinerators can generate sufficient heat to supply this area. This solution does not lead to reducing the carbon emission reduction goals of 2050. Current alternatives such as aqua thermal energy or a hybrid solution contribute to a reduction in CO2 emission but cannot supply sufficient heat to meet the high demand of historic buildings.