Elevated levels of ammonia in discharged water leads to eutrophication and potential toxicity in water bodies. To combat nitrogen pollution, strict ammonium discharge limits of 1 mgNH₄-N/L standard is set by the water framework directory. In many cases, current wastewater treatment facilities struggle to consistently meet this standard, particularly during peak concentration periods. For years now, the influent's peak pattern has been mirrored in the biologically treated water and currently, there lacks an effective solution to address this issue. This study explores use of zeolite in a biological filter, a potential technology to remove ammonia peaks from effluent wastewater. The fundamental concept of this technology involves combining zeolite with a nitrifying biofilm. In this process, the zeolite dampens the ammonia peak by adsorption, while the nitrifying biofilm regenerates the zeolite. Clinoptilolite, a natural zeolite of 1mm particle size and synthetic wastewater were chosen in this study. The impact of competing cations was investigated due to clinoptilolite's affinity for cations. It was found that the presence of other cations decreases ammonium removal capacity by 6.2 times of which potassium is the main competitor. But, percentage of potassium removed is much less than ammonium though it's concentration is 5 times higher. 44.2% of the total potassium was removed in 60 minutes compared to 70.9% ammonium removal. In the experiments with the nitrifying biofilm, it was found, that it does
not affect rate of adsorption by zeolite, but enhances ammonium removal. Experimental results indicate that zeolite can be bio-regenerated effectively, and rate of conversion is faster than rate of desorption of adsorbed ammonium. The system of zeolite and biofilm has some buffer capacity, but cannot compensate for the bicarbonate anions needed for H⁺ released. A BioWin model
was designed to simulate the survival of biomass during extended periods of low concentration, and the results indicated that conversion capacity of the system reduces after 7 days of DWF concentrations. But the biomass can sustain longer periods of DWF concentrations, but it takes some time and exposure to higher substrate concentrations to revive it's capacity. In conclusion this study
confirms the potential in this technology and confirms effective bio-regeneration capabilities. The results from this research can built upon to answer questions regarding knowledge gaps with reactor operation and design. This paves the way for future studies to make it an industrially viable technology. 

Globally, drinking water sources are polluted with poly- and perfluoroalkyl substances (PFAS). The toxicity and persistent properties of these industrial chemicals raised concerns about environmental and public health. As a result, drinking water companies are removing PFAS from drinking water using separation technologies. Anion exchange and nanofiltration membranes have been proven to be effective drinking water treatment methods for the removal of PFAS. However, these drinking water technologies produce large volumes of PFAS-containing waste streams, which poses new challenges for the drinking water industry. To prevent toxic PFAS from re-entering the environment, these waste streams must be treated. This can be done by PFAS destruction, however, due to the large volumes of the waste streams, this is very expensive and energy-intensive. Therefore, concentrating the drinking water waste streams before destruction is desired. This research examined existing PFAS-concentration technologies and compared their PFAS removal efficiency, volume reduction, and cost-effectiveness in concentrating the PFAS waste streams produced during drinking water treatment. These waste streams include the concentrate of nanofiltration and the brine from anion exchange. The analysed concentration technologies are foam fractionation, adsorption of PFAS onto DEXSORB+ and all-silica BEA zeolites, and nanofiltration.
Foam fractionation removes PFAS from the waste stream by injecting air bubbles. Two laboratory setups were made for the injection mechanism of the air bubbles. First, by passing pressurized air through an air stone, and second, by adding pressurized water (i.e. white water) to the waste stream. The adsorbents were tested in the laboratory by conducting equilibrium batch experiments with different adsorbent dosages. The laboratory experiments were performed on both drinking water waste streams. The performance of concentrating the anion exchange brine solution with nanofiltration membranes was evaluated with the use of IMS Design models.

The aim of this research was to evaluate the feasibility of direct hollow fiber nanofiltration membranes for drinking water purposes. The experiments were performed on the dNF40 pilot provided by NXF. The fouling potential and the ion retention of the dNF40 pilot were determined by continuous filtration experiments using raw IJssellake water under different operational conditions. The performances (ion retention and fouling potential) of the dNF40 on raw IJssellake water were compared with the dNF40 performances on pre-treated water from Waterwinstation Prinses Juliana (WPJ) (previously done at PWNT). The WPJ pre-treated water has undergone extensive pre-treatment consisting of drum screens, flocculation, sedimentation, rapid sand filtration (RSF) and granular activated carbon (GAC). The OMP retention of the dNF40 pilot was determined by full recirculation experiments using WPJ pre-treated water under two different operational conditions with elevated concentrations 'spiked solution'.
Limited to no fouling impact was observed on the membrane performance when feeding the pilot with raw IJssellake water. The membrane performance parameters (mass transfer coefficient (MTC), trans membrane pressure (TMP) and normalized pressure drop (NPD)) were stable over time. In addition, limited to no fouling impact was observed on the membrane when feeding the pilot with WPJ pre-treated water. However, membrane performance (i.e. MTC) was better for raw IJssellake water (1 year old membrane) compared to WPJ pre-treated water (virgin membrane). This implies that the active outer layer of the membrane has undergone a change in properties leading to these higher MTC values.
An increase in recovery, flux and crossflow velocity resulted in a decrease in ion retention. However, a decrease in ion retention with elevated crossflow velocity is unusual. Higher crossflow velocities should actually lead to an increase in ion retention due to reduced ion build-up next to the membrane surface (i.e. lower concentration polarization effect). However, the lower ion retention can be attributed to the elevated MTC during experiments. The removal of natural organic matter (NOM) was consistently above 90% and was not influenced by a change in operational condition. Ion retention was higher for WPJ pre-treated water (virgin membrane) compared to raw IJssellake water (1 year old membrane). This can be attributed to the increase in MTC of 1.5 LMH/bar in raw IJssellake water (compared to WPJ pre-treated water) potentially caused by a change in the properties of the active outer layer.
For determining the OMP retention of the dNF40 membrane, a spiked solution containing per- and polyfluoroalkyl substances (PFAS) and pharmaceutical compounds was analyzed. The PFAS compounds of the spiked solution were retained very well (above 80%). As expected, the retention increased with increasing MW. The adsorption percentage of PFAS was between 40%-90%. The pharmaceutical retention was around 30%, although all pharmaceuticals analyzed had a MW below the MWCO of the membrane.
A 5-stage full-scale dNF40 plant was designed based on a permeate flow of 15 M m3/year, a total hardness concentration in the permeate stream below 1.4 mmol/L and a recovery percentage of 85%. Based on the 5-stage full-scale dNF40 plant an economical analysis was performed and compared to the full-scale UF-RO in Heemskerk. The total cost (OPEX and CAPEX) were cheapest for the full-scale dNF40 plant fed with raw IJssellake water (12 ct/m3), followed by the dNF40 plant fed with WPJ pre-treated water (32 ct/m3) and most expensive for the UF-RO plant (35 ct/m3). The major factors in the OPEX was the membrane replacement cost for the dNF40 plant and the energy and chemical cost for the UF-RO plant.

In this research, a few initiatives were completed with practical industrial information and water samples from Heineken®. A Python model was built for an imaginary bottle washer, and tested with difference operational variables under the four testing scenarios. Based on the operational information fromthe Spanish brewery, a second Python model was built for the real-life case study, which was then optimised with several operational variables to reduce either WFP or CFP as caustic soda in five optimisation scenarios. With three water samples from three caustic baths from another bottle washer operated in a Belgian brewery, a composition analysis on significant water parameters was carried out in the Water Lab in TU Delft. This lab analysis gave a basic insight of the compositions of caustic wastewater from bottle washers, and provided possibility to discuss the treatment methods.

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 brine generated from desalination is a threat to the environment, and its disposal has been a great challenge. A new concept Zero liquid discharge (ZLD) can minimize the environmental impact of brine. However, the high costs for construction and running of a ZLD plant limits its growth in desalination market. Therefore, a new strategy integrating brine mining with desalination is proposed to improve its economic performance due to the valuable minerals in brine. A cost-effectiveness analysis (CEA) is carried out to assess its economic performance and compare this strategy with other ZLD strategies. The results present that the cost-effectiveness of the studied strategy is lower than ZLD systems which only maximize water recovery. The cost-effectiveness ratio of the studied strategy is 0.056€/kg of freshwater, higher than ZLD maximizing water recovery (0.032€/kg of freshwater). However, its profitability is higher than other ZLD schemes. This study shows that the integrated desalination and brine mining strategy has a great economic potential. Its cost-benefit of is 1.12, far lower than that of ZLD only maximizing water recovery (26.08). In addition, it can be indicated that CEA is not comprehensive enough to assess the economic performance of a multi-product desalination system. It doesn’t include the revenues from by-products, which are an important part of the studied strategy. For further research, a more integrated approach of economic analysis is needed to make a decision on the different alternatives of desalination.

Colloidal fouling has attracted increasing interest in the membrane field. Oil and water (O/W) emulsion droplet and Extracellular polymeric substance (EPS) are significant colloids in produced water and surface water, respectively. Oily wastewater is produced in many industrial processes such as oil and gas extraction processes, and can take a product, a by-product or a waste stream. In this study, silicon carbide (SiC) membranes were employed to separate oil droplets from O/W emulsion. The effect of ionic strength, pH, surfactant concentration on threshold flux of commercially SiC MF using O/W emulsion stabilized by the sodium dodecyl sulfonate (SDS) were investigated. The results indicated that the threshold fluxes, determined by both the TMPavg method and fouling rate method, increased with an increase of SDS concentration, but decreased with the salinity when using commercial SiC MF membrane filtering 400 mg/L O/W emulsions. Besides, a higher threshold flux was observed for emulsions with a higher pH. Moreover, the high absolute value of zeta potential of O/W emulsion could alleviate fouling. In the end, we produced SiC UF membrane by depositing SiC layer on the alumina supports by low pressure vapor deposition (LPCVD) due to its low fabrication cost. We investigated the anti-fouling abilities of pristine Al2O3 UF membrane and SiC-UF membrane by using sodium alginate as foulant (SA) solution in multi-stage experiments. When fouling experiments operated with pure SA solution or SA solution with a low calcium ion concentration, SiC UF membrane has a better anti-fouling ability compared with pristine Al2O3 UF membrane due to a lower reversible and irreversible fouling resistance and a slower increase of TMP.

A reverse osmosis (RO) membrane followed by a packed tower aerator and rapid sand filter are used by an agricultural company in Emmen to treat brackish groundwater to supply water for growing crops and cleaning purposes. The iron removal by the treatment plant is sufficient most of the time throughout the year. However, the farmer periodically (once per year) reported yellowish treated water, indicating insufficient iron removal. Nevertheless, it is still not clear what is the cause of the insufficiency of the iron removal. This thesis aimed to investigate the iron removal in the water treatment plant in Emmen and propose a solution to improve the iron removal. The iron removal of the treatment plant was investigated through a set of batch iron oxidation, flocculation, and filtration experiments. The pH of the water was the main parameter that influenced the oxidation of Fe(II). It was found that within the retention time that was available in the treatment plant’s tower aerator and the rapid sand filter (20 minutes), the Fe(II) was not fully oxidized and flocculated. At pH of the permeate in the range of 6 – 7, only <11.5% of the initial Fe(II) was oxidized in 20 minutes. Increasing the pH to 8 accelerated the oxidation of Fe(II), and the Fe(II) was completely oxidized within 30 minutes.Although removal of iron that is dominated by floc filtration was not achieved, the treatment plant also removed the iron through adsorption on iron hydroxide deposit in the packed tower aerator and sand particle. However, the Fe(II) adsorption capacity of adsorbents was low at low pH. The regeneration of the adsorption capacity was achieved through oxidation of the adsorbed Fe(II) which is also influenced by pH. COMSOL model showed that without regeneration, the adsorption capacity of new sand and iron oxide-coated sand was exhausted after 24 hours and 230 hours, respectively.When the concentration of CO2 in the permeate is in equilibrium with air, the pH of the permeate should be in the range of 7.9 – 8. However, the maximum pH of the permeate was 7 after aeration because the contact time of the tower aerator was not sufficient to completely strip the CO2. The tower aerator was also clogged by iron deposits that reduces the airflow and causes short-circuiting that decrease the CO2 stripping efficiency over time.Installation of a bubble column reactor was proposed to improve the CO2 stripping and increase the pH of the permeate. The Phreeqc model showed that the CO2 could be stripped until approx. 1 mg/L within 4 minutes, and the pH also increased to approx. 7.9. Moreover, the bubble column reactor will provide additional retention time for Fe(II) oxidation, and approx. 20 – 30% of the initial Fe(II) concentration can be oxidized within 4 minutes. The bubble column was considered preferable compared to the packed tower aerator because it was not susceptible to clogging by iron deposits and requires lower maintenance.

The presence of organic micro-pollutants (OMPs) has caused increasing contamination of aquatic systems. In recent years, the selective adsorption of target OMPs by zeolites have been proved efficient for OMP removal. For the potential application of zeolites in the wastewater treatment plants, zeolite granules are preferably used in order to avoid the post-filtration for zeolite powders. Therefore, the knowledge on the performance of zeolite granules for the removal of OMPs should be fully understood. In this research, BEA and MOR zeolite granules were used as adsorbents for the removal of 11 OMPs from water, which were carbamazepine, diclofenac, 1H-benzotriazole, methyl-benzotriazole, hydrochlorothiazide, sulfamethoxazole, clarithromycin, propranolol, trimethoprim, metoprolol and sotalol. The aims of this study were: (1) to investigate the adsorption capacity and kinetics of the 11 OMPs by zeolite granules in both demineralized water and wastewater (WW), in batch experiments; (2) to predict the breakthrough curve of columns packed with zeolite granules by using a mathematical model combining the parameters determined by batch experiments. It was found that the charge and hydrophobicity of OMPs were the two main factors that affected the adsorption capacity of OMPs by zeolites, while the effect of OMP size on the adsorption capacity was negligible. The OMP adsorption capacities by zeolite granules were less than OMP adsorption capacities by zeolite powders. The fittings of the IPD model to the adsorption kinetic data showed that film diffusion and intra-particle diffusion were both the rate-limiting steps in the adsorption of OMPs by zeolite granules. Furthermore, the adsorption capacity and rate of OMPs in WW were lower in comparison with OMP adsorption in demineralized water, which could be caused by the higher pH in WW and the pore-blocking effect by background organic matters. In the column experiments, it was found that OMP breakthrough percentage in the column was determined by both the adsorption capacity and kinetics of OMPs by zeolite granules. In the breakthrough model, the kinetic and isotherm constants from batch experiments overestimated the adsorption rate and capacity of zeolite granules in the columns, and the overestimated isotherm constant was the main factor that caused the deviation of the model prediction. With a lower isotherm constant, the model was able to provide good resemblance between modelled and measured breakthrough curves. Furthermore, with a known breakthrough curve at a certain EBCT, the model was able to determine a proper isotherm constant, which can be used to predict the breakthrough curve at a different EBCT.

Current climate change characterized by increasing temperature has led to an increase in the intensity and frequency of extreme droughts that have more prolonged and profound ecohydrological and social impacts. By paying attention to the hydrological change before and after extreme drought and the patterns of drought recovery of ecohydrological system, it is possible to better understand the consequences of extreme drought on ecohydrological system. Both climate change and landscape change have an influence on catchment hydrological condition. The drought-related hydrological change is, therefore, the combination of changes induced by these two drivers. To further explore extreme drought impacts and the root causes of hydrological change under extreme drought events, it is necessary to separate the impact of drought-related climate change from the impact of landscape change. This study aims to characterize the variations in hydroclimatic conditions before and after extreme drought by studying the hydroclimatic movements in Budyko space, explore post-drought ecohydrological system recovery, and further separate and investigate the effects of climate and landscape change on catchment hydrological conditions. Monthly SPEI at a 12-month timescale was used to characterize and define the extreme drought events. The Budyko framework was applied to study the hydroclimatic changes of 63 basins in the United States induced by extreme drought events from 1990 to 2013 by quantifying the hydroclimatic movements in Budyko space. The climate effect on precipitation partitioning was distinguished from the landscape effect that is mainly related to vegetation response to extreme drought events. The contributions of precipitation and potential evaporation were quantified to further understand the effect of climate change which is caused by alterations of these climatic variables. To understand the effect of drought-related vegetation change on catchment precipitation partitioning, NDVI was applied to examine the response of vegetation to drought in terms of alteration in vegetation greenness and patterns of vegetation recovery. There were significant hydroclimatic changes in the basins before and after extreme drought. In post-drought period, more precipitation tended to be partitioned into evaporation in most basins. Change in streamflow was larger than the change in evaporation. 63.5% of all the basins experienced wetter conditions and more precipitation after drought. All basins gradually recovered in post-drought period, but not fully restored to their pre-drought states. The hydrological change under extreme drought was not explained by climate change alone in these basins, suggesting the existence of landscape drivers. The climate and landscape effects on precipitation partitioning could either enhance or counteract each other. The landscape drivers contributed more to change in catchment precipitation partitioning. In terms of the climatic effect that associated with the change in aridity index, climate change affects catchment precipitation partitioning by changing the precipitation and potential evaporation, among which precipitation is a more crucial climatic driver. From a vegetation-related landscape perspective, vegetation greenness reverted to pre-drought level within three years in most basins. The rapid or slow recovery, regrowth and even degradation of vegetation in post-drought period cause landscape-driven changes in catchment precipitation partitioning through directly changing vegetation transpiration and streamflow.

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.

This thesis aimed to elucidate the effects of dissolved organic matter on the applicability of electrocoagulation (EC) with iron electrodes for per- and polyfluorinated alkyl substances (PFAS) removal from landfill leachate. The research methodology consisted of an experimental and a computational part. Galvanostatic EC experiments were conducted in an aerated beaker with 500 mL working volume, using iron electrodes with a surface area of 8 cm2. The pH, voltage and current were measured continuously for 50 minutes. Blank measurements were conducted in a 2 g/L NaCl solution. PFAS removal was tested from 0.25 mmol/L perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) solutions at current densities of 12.5 and 25 mA/cm2, as well as from solutions with a commercial humic acid (HA) source added at 25 mA/cm2. The removal of HA was also tested separately. Eventually, the removal from real leachate samples was examined. A computer model was constructed in PHREEQC (pH Redox Equilibrium Calculation), a program for modelling chemical processes in water. The model simulates the removal of all tested pollutants based on electrostatic adsorption to a continuously forming surface, associated with the precipitating ferrihydrite. Model rate constants for O2 and CO2 dissolution and Fe(II) oxidation were determined from the results of the blank experiments. Good model fits were obtained for these datasets. HA could be removed completely within 50 minutes at all tested current densities and initial concentrations. PFOA removal was unsuccessful with and without HA as co-solute, with a maximum removal of 17 %. PFOS removal reached 81 % at 25 mA/cm2, but the removal essentially stagnated after 5 minutes treatment time. The presence of HA did not significantly affect the PFOS removal. Instead, HA removal was retarded by the presence of PFOS. For the real leachate samples, no significant removal of PFAS occurred. Conversely, approximately 20 % PFAS removal was observed after 5 minutes treatment of a leachate sample spiked with 0.15 mmol/L PFOA, perfluorobutane sulfonic acid (PFBS) and perfluorobutanoic acid (PFBA). However, this removal reversed during the remaining treatment time. The adsorption equilibrium constants were the most important model parameters. These parameters were determined for HA, PFOA and PFOS based on the experimental data. The model fits were good for HA and PFOA removal, indicating that these were indeed mainly removed by electrostatic adsorption. Contrarily, PFOS removal could not be represented accurately by the current model. Instead of stagnating after five minutes, the simulated removal continued to completion. The poor model fit may indicate that the mechanism of PFOS removal extends beyond strict electrostatic adsorption. Instead, charge neutralization of PFOS molecules causing their aggregation or mass transfer limitations in the vicinity of the electrodes could be involved. Further research is needed to explore these possibilities and determine improved equilibrium constants for the relevant adsorption reactions. In conclusion, this research did not confirm the high PFAS removal efficiency as observed in previous studies. Instead, significant removal of PFOA did not occur and removal of PFOS did not exceed 81 %. Competition effects were not observed in the simultaneous treatment of PFOA and HA. The presence of PFOS impeded the removal of HA, indicating that PFOS was removed preferentially under the current experimental conditions. The established model could simulate most experimental results accurately.

Dissolved air flotation (DAF) is a water treatment technology meant for the separation of suspended particles from the water. Since the fifties of the XIX century, it has gained an important role in many sectors of water treatment applications. In general, the flux variability, the small space requirement, and the limited energy consumption excel as some of the most relevant advantages of the DAF system. However, because of its not always excellent removal efficiency, DAF applications are usually considered as pre-treatment technologies to reduce the particles' load from more effective technologies as sand or membrane filtration technologies. Briefly, the amelioration of the suspended solids' separation is of particular interest because it decreases the maintenance cost of the next filtration units and, in some cases, it might substitute them. Coagulation and flocculation processes prove to be of extreme importance for the DAF performance as it is characterized by particles cut-off around 1-10 μm. The purpose of this research was the application of extra-polymeric substances (EPS) as a flocculant to enlarge the floc dimension of an anaerobic digested sludge and improve DAF efficiency. In the literature the flocculation ability of EPS is not completely acknowledged, but there are some succesfully results with microalgae and activated sludge. Specifically, the feasibility of producing EPS directly on-site, is interesting because it makes the treatment plant possibly independent from the flocculant purchase. Moreover, an extra amount of EPS might be sold (1$/kg) or used for the production of other valuable products (e.g. biodiesel production).
In collaboration with the Water Lab at the faculty of Civil Engineering in Delft and Royal Haskoning (DHV), it was possible to perform some experiments to understand the flocculation properties of EPS in the dissolved air flotation technologies. More specifically, the effects of the EPS were studied with two experiments: a jar test and a flotation column experiment. The sludge used for the experiment was collected from Harnashpolder facility after being digested for at least 25 days. With the jar test experiments, it was examined the effects of sludge settleability (5 gTSS/L): increasing EPS doses (200-1200 mgEPS/L), increment by 20% the original SVI value, on average. Furthermore, it was performed a small scale flotation experiment with two Alka seltzer pills. After a certain EPS dose (400 mgEPS/L), TSS in the formed foam resulted 1.78 times more concentrated. Finally, it was also analysed the particle size distribution (PSD) variation, but the measurements were characterized by a high standard deviation which reduced the reliability of the results. The scope of these first experiments was the individuation of a certain EPS dose to apply in the flotation column experiment simulating the DAF performance (800 mgEPS/L). The EPS addition did not improve the quality of the effluent (65%), and was slightly inferior to the blank series (69%). However, the obtained foam was almost 1.75 times more concentrated when compared to the blank solution. Towards the end of the experiment, a better removal efficiency was notated within the EPS series and it was correlated to the foam concentration (R2= 0.989). Despite the errors, PSD of the EPS series were characterized by a higher frequency of small particles, between 1-10 μm. In the discussion chapter two explanations are proposed considering the effect of zeta potential variations after the EPS addition. In conclusion, the use of EPS to enhance the solid-liquid separation of the sludge was not successful. However, further research with different doses of EPS and different types of sludge should be studied to assess the potential use of EPS to improve the efficiency of a DAF system.

Fouling is the main limitation to the application of membrane bioreactors (MBRs). Understanding the complexity of fouling has led to better decision making for design and operation of MBRs. However, studies have shown contradictory results of the impact of sludge characteristics on membrane filtration performance and fouling propensity. The purpose of this study was to characterize the sludge under different operating conditions of an anaerobic membrane bioreactor (AnMBR) treating dairy wastewater, to assess the impact on the filtration. The real flux method was used to determine the flux, while the characteristics of the sludge varied in time. The real flux method is when the feed, retentate and transmembrane pressures are controlled to induce similar hydrostatic conditions applied in full-scale anMBR in crossflow configuration. Total solids (TS), volatile solids (VS), total suspended solids (TSS), volatile suspended solids (VSS), viscosity, and different fractions of the chemical oxygen demand (COD) were performed for sludge characterization. The specific resistance to filtration (SRF), capillary suction time (CST), and supernatant filterability were used as parameters for filterability of the sludge and supernatant. Principal component analysis (PCA) was used to determine the correlation between the sludge characterization and the filterability methods. Five principal components (PC) attributing to 91% of the variance were extracted, based on an eigenvalue greater than 1. The principal components showed the correlation between the different variables studied. PC1 consisted of fraction of solids (total dissolved solids, VSS/TSS, and fixed suspended solids), the CST, and the normalized versions of the CST (CST/TSS, CST/Viscosity, CST/TSS/Viscosity). Five of the variables in PC1 are derived from the TSS concentration most likely indicating why they were grouped under this principal component. PC2 consisted of the particle size distribution of particles ranging from 0 to 10 micrometer. PC3 consisted mainly of a different fraction of solids (VSS, VS, TS, and TSS) and SRF. SRF is a function of TSS, this can explain why these variables were grouped together in PC3. PC4 consisted of the soluble and colloid particles. PC5 consisted of the hydrostatic conditions of the membrane. A multiple linear regression of the PC revealed statistically significance (ANOVA, p-value <0.05) to estimate the flux. A stepwise multiple linear regression was done to determine what variables can be used to estimate the flux based on the data obtained. The selection of the best model from the multilinear regression was based on the highest R squared value, statistical significance from ANOVA, and the variance inflation factor to take into consideration collinearity. Based on the criteria from the PCA and the multiple linear regression, the independent variables for predicting the flux were the CST/TSS, crossflow velocity, the SRF, and the VS/TS.

In drinking water production, natural organic matter (NOM) is sometimes removed using ion exchange (IEX) resin. This treatment method has a limitation based on the exchanging capacity on the resin. Therefore, the resin needs to be regenerated when it is saturated with adsorbed NOM which leads to the production of brine. In general, NaCl is used to regenerate the resin, hence, the brine will contain NOM, high sodium and chloride concentrations. Moreover, some other anions are also found in the IEX brine, such as sulphate that is usually present in surface water and ground water. Because of its salinity, the disposal of IEX brine is not possible to be done conventionally due to its impact on the environment and high cost. Therefore, separating chloride from the brine is an interesting alternative that can be reused for the regeneration of the IEX in the later process.

Ceramic nanofiltration (NF) emerges to be an interesting alternative for water treatment. Compared to polymeric membranes, this type of membrane offers great mechanical robustness and can be operated under extreme conditions, and tolerates high-pressure backwash, chemical cleaning, and high-temperature sterilization, which leads to longer periods of reliable performance. Moreover, ceramic NF membranes are potentially capable to separate multivalent ions from monovalent ions. Hence, this method could be applicable to treat IEX brine. Alternatively, chemical precipitation using barium and calcium is widely used to remove sulphate from water which is more straight forward than membrane filtration. The precipitates can be mechanically separated from the supernatant for further treatment or use.

Combination of chemical precipitation and ceramic NF membrane (later called as integrated sulphate removal) was investigated to remove sulphate from IEX brine. Along with that, investigation using synthetic brines consisting of Na2SO4 and NaCl for a binary salt solution and only Na2SO4 for a single salt solution was also conducted to build the understanding in treating the IEX brine. Barium salt was proved to efficiently remove sulphate due to its very low solubility. However, calcium salt was not as effective as barium salt. The treatment was followed by NF using a ceramic membrane with MWCO of 900 Da. In the end, the integrated approach was able to remove 86% of the sulphate and 85% of NOM from IEX brine. Furthermore, the precipitation stage was also modelled in PhreeqC by using Pitzer database.

Barium salt (BaCl2.2H2O) was preferred in this research for precipitating the sulphate. However, due to its toxicity, alternative precipitation was desired. Ettringite (calcium sulfoaluminate) precipitation was considered since the involving salts were not toxic. The efficacy of this method was predicted through modelling in PhreeqC to give some insight to alternatively removing sulphate from IEX brine. Eventually, a comparison using cost estimation and Life Cycle Assessment (LCA) were performed to obtain some considerations to implement the treatment alternative in a full-scale application.

UV/chlorine, as an emerging advanced oxidation process, is able to degrade organic micropollutants in water via the generation of reactive oxidant species and direct reaction with HOCl/OCl- as well. In this study, light-emitting diodes (LEDs) were applied as the UV sources to investigate the efficacy of UV/chlorine process for the degradation of trimethoprim (TMP, a frequently detected antibiotic in waters), at slightly alkaline pH.

As freshwater resources are predicted to become more scarce in the future, desalination will become a more prevalent treatment method. Microbial desalination, defined as the use of microbial processes to remove ions from a saline solution, may have potential as a new desalination method to produce water for domestic, agricultural or industrial purposes. This research explored the theory, performance, application and feasibility of microbial desalination. It consists of three research lines. Firstly, the performance and optimal conditions for microbial desalination were examined in batch experiments. In the second research line, the use of microbial ion transport proteins in a biomimetic membrane was proposed and the microbial light powered transport protein SyHr was genetically designed and expressed for this purpose. Finally, two models weremade which evaluate the feasibility ofmicrobial desalination at full scale; one which compares the costs of microbial desalination in sequencing batch reactors to seawater reverse osmosis and one to calculate the recovery and required size of a biomimetic membrane as described in the second
research line. Based on the results of all research lines, it was concluded that microbial desalination is be a promising new technology for desalination, which should be further developed.

Water is the most dominant substance on the planet and has always been a synonym for life. On this planet, water has always been plentiful. Therefore, the conclusion of the United Nations in 2015 was even more shocking. The United Nations estimated that in 2030 a water gap would exist of 40%. The withdrawal of fresh water would be 40% larger than the amount that is replenished every year. We are living on borrowed time, and we need to close this gap. Since most water on the earth is saline, desalination could be a possible solution. Unfortunately, desalination is an energy-intensive process, and it will always be. There are different methods. However, energy consumption would always be rather large. Much of our energy is still created by fossil fuels in most areas in the world. Our increasing demand for fresh water can lead to a further large fossil footprint and therefore more climate change. Climate change negatively impacts our water supplies. A negative spiral could be the result.
The world is consuming a large amount of energy. Unfortunately, this is not done efficiently. It is estimated that 72% of worldwide energy consumption is lost after conversion. Waste heat is an unwanted product as a result of this inefficient conversion. It is estimated that 63% of this waste heat has a temperature of 100 degrees Celcius or lower. A temperature that is not even sufficient to boil an egg, but it is energy nonetheless. If this energy could be harvested, the water gap could be closed by desalination without increasing the carbon footprint. However, how to do this? A solution could be found in Japan and your dry cleaner. In the seventies, when the oil crisis was at its peak, Japan had a problem. It has a high need for air conditioning which has a high need for energy. A device was created that could use waste heat to create cooling with silica gel. The general public knows silica gel as moist eaters that are included in your dry cleaning. By placing silica gel in a closed environment, liquid water could be evaporated. Evaporation needs energy, and this could create cooling. In early 2000, some folks in Singapore realised that this technology could also be used to desalinate. Adsorption Desalination was born. Adsorption desalination (also known as AD) is a boiling point elevation and vapour pressure lowering desalination technique. Silica gel has a high affinity to adsorb water vapour. Since this is done in a closed environment, the pressure is lowered till boiling. When an energy source is placed inside the liquid, an equilibrium can be found without lowering the pressure further. Once the silica gel is saturated, it is heated till a certain temperature that it starts to desorb the vapour again. This vapour is collected and condensed into a clean product. The mass transport takes place by a pressure difference. Since the evaporation takes place in vacuum conditions, it is around room temperature. Therefore it can have a low sensitivity for erosion. Since it is an evaporation technique, it also has a low sensitivity for fouling. On paper, it can be a desalination technology with low operational costs compared to others. In reality, a couple of barriers have to be conquered. One of the barriers is the characteristics of the core element of this technology, the silica gel. The reason that silica gel can adsorb water vapour so well is due to two main elements. First, it is an incompletely dehydrated polymeric structure of colloidal silica acids. Therefore it can create hydrogen bonds, polar bonds and weak electron bonds with other molecules. Water is a bipolar molecule, and therefore silica gel can adsorb water exceptionally well. It can create hydron bonds efficiently, and due to the bipolar nature of water, multiplayer on top of each other can be formed. The second element is the high specific surface of silica gel. It has many pores, and therefore a specific surface equal to human lungs can be formed. In the end, the best qualities can adsorb until 40% of their body weight.
These two elements determine the maximum amount of vapour silica gel can adsorb. However, two parameters determine if silica gel can adsorb. These two parameters are the temperature and vapour pressure. If the temperature is high, the vapour pressure has also to be high to ensure adsorption and the other way around. The same account for the opposite effect. Therefore energy transfer is vital for smooth operation. Unfortunately, the thermal conductivity of silica gel is extremely low. Besides energy transfer to change the temperature of silica gel to go from adsorping to desorbing and reverse, much energy has to be transported during the adsorption and desorption phase. During adsorption, water vapour transforms from a gas phase to a semi-solid phase. In this phase, the energy level is lower. Since energy cannot be destroyed, this energy has to be removed. The same applies to the opposite. If the heat exchanger is not well designed, the adsorption and desorption phase are prolonged, and the daily water production diminished. Even if the whole set-up is well designed, there is still one element of silica gel that can also diminish the water production of the set-up: the degradation of silica gel. Multiple mechanisms can degrade silica gel, but the two most important are fragmentation and pore pollutions by metal ions. Fragmentation (the breaking up into smaller parts) occurs by the high thermal stress the silica gel endures and the pollutions by the feed. A part of the sorption ability is destroyed or temporarily inhibited. The use of acid water can remove the pollution, so maintenance on the silica gel is necessary. Replacing the silica gel by other sorbents like zeolite is possible. Unfortunately, it has a lower adsorption capacity which leads to a less compact device and is, therefore, more expensive. Another unfortunate fact is that zeolite desorbs at a higher temperature. When using zeolite, adsorption desalination can no longer use waste heat of low quality to desalinate. The last problem with using silica gel, but also other sorbents, are the instabilities with the sorption characteristics in vacuum conditions. The sorption characters depend as said before on the temperature and the vapour pressure. Inside vacuum conditions, a disturbance of the vapour pressure can negatively influence the sorption characteristics and can lead to desorption at the wrong moment. Since it is done in a closed environment, it can lead to condensation which lowers the vapour pressure further. A complete breakdown of performance can be the result. Disturbances can happen through air leakage, which is are a common problem in industries. There are some solutions, but in the end, the permanent one is a high-quality vacuum system and intensive maintenance. Even with these barriers, adsorption desalination is still an attractive technology due to its relationship with its own energy consumption pattern. The energy consumption is high but stable and barely sensitive to change in conditions like feed salinity and recovery. Its energy consumption stays around the 40 $kWh/m^3$ in most cases. Only a small part, around 1.38 $kWh/m^3$ or even less has to be mechanical energy. All others can come from waste heat. If the other operating costs are kept low, it is an exciting technology to use, especially for brine treatment since waste heat is an inexpensive energy source. Some researcher claim it is a free energy source, but that statement cannot be valid. To use waste heat, infrastructure is necessary to collect it and transport it. It is not the same as putting a plug in the wall. There is probably enough waste heat in the world to close the water gap. As an example, the Netherlands is the second biggest producers of waste heat in Europe and creates enough to produce probably more 850 $km^3$ potable water. Unfortunately, there are some uncertainties. Waste heat is only classified in three rough categories, low, medium or high. Low is everything below 100 degrees Celcius. It could be that most energy is trapped in waste heat with a temperature of 30 degrees. More validation is necessary since the future of adsorption desalination is intertwined with waste heat. Without waste heat, it cannot be an inexpensive desalination technique. Since it is still an experimental technology, not a lot of data is available to create a solid picture of the costs involved with adsorption desalination. Only two studies exist today, and both estimate that the cost for seawater desalination using adsorption desalination is between 50% and 70 % of the cost while using reverse osmosis. Only one study gives insight into the different sectors of cost. What is notable is that the other costs, replacement cost for parts and chemical cost for adsorption desalination are kept at zero. A strange conclusion since silica gel can degrade and replacement can be necessary, chemicals are necessary for the heating and cooling water AD uses. No conclusion can be made about the final costs of AD, but it the conclusion of these studies seems unlikely. For seawater desalination, the costs are probably in the same range as reverse osmosis. Furthermore, there is a strong case that AD can remove biological pollutants since it is an evaporation technique where temperatures are reached until 80 degrees Celcius. There are a few remarks and only solid empirical data can prove these claims. The original intent of this research was to research these claims. Unfortunately, the set-up was not functioning properly due to practical problems like air leakages. Even with this result, much knowledge was gained, and a few remarks and conclusions can be made. To conclude, adsorption desalination is a newly emerging technology with many interesting aspects. It can provide an alternative for standard desalination techniques while being sustainable. There are a few barriers to overcome, but it deserves attention. Further developments should be stimulated since the water should be close in an environmentally friendly matter. Adsorption desalination is a sustainable solution that should always be considered.

This work investigated which NOM fraction from secondary wastewater effluent were causing competition with metoprolol and clarithromycin for adsorption site on high silica zeolites (HSZ). This thesis works with five commercially available HSZ frameworks (FAU, MOR, BEA, MFI and FER). Adsorption batch test were performed with demi water, wastewater and nano filtrated wastewater with molecular weight cutoff around 400 Da. The competition between two organic micro pollutant (OMP) metoprolol and clarithromycin in demi water were not obvious for FAU type high silica zeolite. Metoprolol is adsorbed much better than clarithromycin regardless of the water type or high silica zeolite framework. Adsorption of clarithromycin was the best with MOR and BEA in demi water, but the removal deteriorated severely in secondary wastewater effluent. Clarithromycin adsorption on BEA and MOR in micro filtrated wastewater and nano filtrated wastewater seems to be comparably impaired. Metoprolol on the other hand showed counter intuitive results. It adsorbs worse in nano filtrated wastewater compared to micro filtrated wastewater for MOR and BEA.