Pharmaceuticals in wastewater are an urgent environmental concern. Many emerging technologies, such as advanced oxidation processes (AOPs), are being explored for their removal. One promising AOP is Photoelectrocatalysis (PEC), which combines photocatalysis with electrochemistry to enhance pollutant degradation by suppressing electron-hole recombination. Bismuth vanadate (BiVO₄) is a promising visible-light-responsive photoanode material due to its narrow bandgap and chemical stability. However, its overall performance is limited by poor charge mobility and rapid recombination of photogenerated electrons and holes. To overcome these limitations, surface modification strategies have been applied, including the use of surfactants to alter and enhance its surface properties. Quaternary ammonium compounds (QACs), widely used for their surfactant properties and structural flexibility, have shown potential in enhancing the photoelectrocatalytic performance of BiVO₄. This study evaluated the effect of six commonly used QACs on BiVO₄ photoanodes. The modified photoanodes were synthesized and comprehensively characterized using several techniques: X-ray Diffraction (XRD) to determine crystal structure, Scanning Electron Microscopy (SEM) to examine surface morphology, Energy Dispersive X-ray Spectroscopy (EDX) for elemental composition, X-ray Photoelectron Spectroscopy (XPS) to analyze surface chemical states, Ultraviolet-Visible (UV-Vis) spectroscopy to assess optical absorption, and Linear Sweep Voltammetry (LSV) to evaluate electrochemical behaviour.
Photoelectrocatalytic degradation experiments were performed using real secondary treated effluent collected from the Horstermeer Wastewater Treatment Plant (WWTP), which was spiked with 20 pharmaceutical compounds. The QAC-modified BiVO₄ photoanodes were tested under simulated solar irradiation. Characterization results confirmed that the monoclinic phase of BiVO₄ was preserved after QAC modification, with minor shifts indicating changes in surface properties. SEM images showed that the structural integrity of BiVO₄ was maintained, while EDX and XPS results revealed an increase in oxygen vacancies, suggesting improved charge transport characteristics. LSV confirmed that photocurrent generation occurred only under illumination, as expected in PEC systems. Among the modified electrodes, the BiVO₄ photoanode modified with DADMAC C18 exhibited the highest pharmaceutical degradation efficiency over a 120-minute PEC run, outperforming even the unmodified BiVO₄ electrode. The ATMAC C18 variant demonstrated rapid initial degradation within the first 15 minutes, while the BAC C18 variant showed relatively poor performance. Kinetic analysis indicated that sulfamethoxazole was the most persistent compound in the pharmaceutical mixture, with the longest half-life. To assess real-world application potential, full-scale PEC reactor designs were reviewed. A circular reactor configuration with annular electrodes was identified as the most suitable due to its balanced light distribution, effective photoelectrocatalytic surface area, and ease of operation. A conceptual full-scale design was proposed to replace the existing UV oxidation system at WWTP Horstermeer, targeting a treatment capacity of 25,000 cubic meters per day. Based on preliminary calculations, the estimated treatment cost was €0.24 per cubic meter, highlighting the potential economic feasibility of implementing PEC technology in municipal wastewater treatment.

In developing countries with increased industrialization, much research is carried out in order to recover the maximum ammonium from the environment. One of the methods to recover ammonium is Bipolar Membrane Electrodialysis (BPMED), a chemical-free technology that enables recovery and purification of the corresponding acid and base by the application of electrical energy. This thesis aims to evaluate five different BPMED cell configurations using the ammonium sulfate ((NH4)2SO4) salt. Experiments are based on evaluating operational parameters including flow rate, feed volume, base volume, and current density to achieve the maximum ammonium recovery using ammonium sulfate salt with efficient electrochemical energy consumption. Additionally, the optimum experiment was carried out with the best results of operational parameters to understand the overall impact on ammonium recovery and electrochemical energy consumption.

Nutrient recovery has lately been a concerning topic regarding the environmental friendliness of it and the high availability of technologies. Ammonia is one of the main compounds in reject water that could be recovered and utilized further in the agricultural sector. Several methods have been found, including conventional electrodialysis, in which anion and cation exchange membranes are being used and, with the application of electrical current, there is production of clean and desalinated water, creating at the same time a concentrated solution. As a further evolution of electrodialysis, bipolar membranes could be added in the configuration, leading to acid and base production. However, ammonium is not the only cation included in reject water, but also Na+, K+, Mg2+ and Ca2+ are present and affect the overall performance electrodialysis. Thus, the competition between the cations needs to be investigated further regarding the operational parameters of each configuration.
This study investigated the cation competition in electrodialysis and bipolar membrane configuration regarding the ammonia removal efficiency and the overall energy consumption. The research questions were focused on the effect of enriched solutions with cations on ED and BPC to the efficiency parameters, to the impact of cation composition in the feed solution when NH4+, Na+, K+, Mg2+ and Ca2+ are included in an ED and finally, the effect of municipal reject water cation molar ratios in a combined ED and BPC configuration. The experiments included batch mode systems, with several mass and molar ratios of NH4+ applied, the above-mentioned parameters were measured. More specifically, BPC and ED configurations were tested with mass ratios of other cations in an enriched NH4+ solution, while molar ratios were tested in case of an ED configuration with NH4+, Na+, K+, Mg2+ and Ca2+ be present in the feed solution. Finally, the two configurations were tested in a sequence batch, with ED to be the pretreatment step and BPC the final stage. The phenomena that were also investigated were proton production from bipolar membranes and EC pattern on the diluate solution in this case.
In ED removal efficiency was presented as a linear curve on time while in BPC the same value took a logarithmic trend, which is attributed to proton production and finally competition. During BPC operation, there was constant production of H+ through water dissociation that led to the acidic environment in the diluate solution but also to stabilization of EC when H+ presence was dominant. In addition, in molar ratio experiments with the application of ED, removal efficiency was higher for more challenging reject waters compositions such as molar ratios between 0.30 and 0.60. Considering 75% removal efficiency as an effective case, percent demineralization was also calculated. For removal efficiency below the effective case, percent demineralization presented a minimum for molar ratio of 0.60, while for higher removal efficiency the overall trend was slightly different, having a more exponential shape. Finally, energy consumption in molar ratio experiments, for removal efficiency of 75% presented a gradual decreasing linear trend with the increase of molar ratio.
Based on the results occurred in batch experiments, a sequence batch of ED to concentrate the feed solution was established, by applying the more challenging molar ratios of 0.30, 0.45 and 0.60 and the concentrate was then fed to a BPC to explore the proton effect in a concentrated solution. The percent demineralization and removal efficiency remained stable during the experimental phase while transport number had a notable increase with the increase of molar ratio, remaining approximately the same in every individual batch. Moreover, energy consumption had an important increase with the decrease of molar ratio due to the high membrane resistance and the observed scaling effect.

Reusing water is a crucial part of the solution for addressing the growing concern regarding the risk of water scarcity in industrialized and urbanized areas. This study introduces a tool for the design of water networks, focusing on water reuse in industrial parks. Utilizing a mixed-integer nonlinear programming (MINLP) model developed earlier, this tool is the first in water network design models that operates with open-source software, while considering water treatment systems and multiple constituents. A literature study is conducted to discover shortcomings in water network design models and to find a foundational model to use to develop the tool. The developed tool creates a water network based on the optimization of the costs of water obtained from water sources, the costs of treatment systems, and optionally the piping costs. The treatment systems are used to regenerate the water for reuse in industrial plants and to meet environmental discharge limits. The tool develops local optimal solutions as an output. Additionally, this study is the first to integrate a water treatment systems database into a water network design model. However, this database needs to be expanded before it is usable. This study demonstrates the tool through three case studies.

The excessive nitrogen in waterbodies, often caused by the discharge of ammonia-rich wastewaters, leads to eutrophication, disrupting aquatic ecosystems. Wastewater treatment plants play an important role in the removal and recovery of nitrogen from wastewater streams, thereby preventing pollution. Air stripping in combination with acid scrubbing has emerged as a promising technology not only for removing ammonia from wastewater, but also for recovering it as a valuable fertilizer, ensuring circularity. However, factors such as continuous consumption of chemicals and the hazardous use of strong acids need to be addressed. To reduce chemical consumption, a combination of air stripping and organic acid scrubbing with bipolar membrane electrodialysis (BPMED) has been proposed.
This study focused on optimizing BPMED for the recovery of ammonia and citric acid from ammonium citrate scrubber effluents. The impact of current density, membrane configuration, feed solution characteristics (pH and initial N concentration), and temperature on recovery efficiency, current efficiency, and energy consumption of a BPMED system was evaluated. The limiting current density (LCD), a key factor in the normal operating range of the system, was determined using the Cowan and Brown method, yielding a critical value of 1.01 A/m2.
Comparative experiments conducted on three BPMED configurations, including 3-chamber BPMED (BPCA), 2-chamber base BPMED (BPC), and 2-chamber acid BPMED (BPA), revealed the superior performance of the BPC in terms of current efficiency, energy consumption, and running time. The optimal operating time of BPC was determined to be 120 minutes, achieving a recovery efficiency of 55.9%, a current efficiency of 44.2%, and an energy consumption of 8.4 kWh/kg-N.
Moreover, regression models were established using Box-Behnken design (BBD) from response surface methodology (RSM) to optimize operating conditions (pH, initial N concentration, and temperature), maximize recovery efficiency, current efficiency, and minimize energy consumption. Verified by analysis of variance, normal probability plot, and residual analysis, the model showed high accuracy and significance.
Univariate analysis elucidated that pH and initial N concentration were found to be important variables, while temperature was not. Increasing pH (3–7) enhanced recovery and current efficiency while decreasing energy consumption. Higher initial N concentrations (2–10 g/L) improved current efficiency, decreased energy consumption, but reduced recovery efficiency, emphasizing the need for a careful balance. Temperature variations (20–40°C) had no significant impact on BPMED. Critical factors limiting ammonia recovery efficiency, current efficiency, and energy consumption were identified, including solution conductivity, H+ ion leakage, water migration, and NH3 diffusion.
Furthermore, the study revealed non-significant interactions between these variables through 3D response surface plots and 2D contour plots. Adjusting operational variables proved feasible for optimizing performance indicators. The optimized conditions (pH 6.05, initial N concentration 6.67 g/L, temperature 30°C) were experimentally verified, and the predicted values were in good agreement with the actual values, confirming the reliability of the optimization model. Specifically, the recovery efficiency was 52.9%, the current efficiency was 45.4%, and the energy consumption was 7.0 kWh/kg-N.
Energy evaluation of the BPMED system in BPC configuration under optimal conditions showed significant energy efficiency. Based on the comparison with the available literature, the integration of BPMED with air stripping and organic acid scrubbing could improve energy efficiencies and lower chemical consumption while offering a closed-loop system.
Future research should explore principles to inhibit ion leakage and water migration, analyze the combined effects of various operating variables using RSM, and validate the potential for lower energy consumption in full-scale BPMED. Developing continuous BPMED processes is crucial for full-scale application, and integrating BPMED with other processes such as air stripping and acid scrubbing may enhance ammonia recovery and production efficiency.
The insights gleaned from this study provided a solid foundation for enhancing ammonia recovery processes from ammonium citrate scrubber wastewater, thereby promoting sustainable and resource-saving industrial practices.

Removal of ammonium from simulated ammonium salt solutions was done using bipolar membrane electrodialysis (BPMED), without the use of chemicals. The effect of spacer thickness and open area on the overall energy consumption of BPMED to transport ammonium from the diluate was assessed in batch experiments. The electrochemical energy consumption decreased from 28 MJ/Kg-NH4+ to 16 MJ/Kg-NH4+ when the spacer thickness decreased from 750 μm to 140 μm.
The removal efficiencies of ammonium from the diluate increased from 77% to 85% when the spacer thickness decreased from 750 μm to 140 μm. These results show that with the increasing spacer thickness, the open area and porosity also increase, which accounts for higher resistance on the membrane stack. However, besides open area and porosity, it is the thickness of the spacer that plays a major role in higher energy consumption. This study demonstrated the energy-efficient application of BPMED for the removal of ammonium from simulated ammonium salt solutions.1

Driven by the increasing demand for waste reduction and green energy production, an integrated system which combines an anaerobic membrane bioreactor (AnMBR) and a solid oxide fuel cell (SOFC) was proposed in this research project for blackwater treatment and energy production. The potentials of using an AnMBR for wastewater treatment and biogas production, and the feasibilities of producing energy from biogas with a SOFC have been investigated by many researchers. Although, combining the two equipment might raise new challenges and opportunities. The AnMBR pH has direct impacts on the biogas composition, which would subsequently affect the SOFC operational strategy. Therefore, this research project focused on the influence of the AnMBR pH on the SOFC operational strategy, which would provide insights for connecting AnMBR and SOFC. The AnMBR pH was controlled around 8 initially, and then reduced to 7. The composition of the biogas produced under each pH condition was analyzed before the biogas was conditioned for the SOFC operation. Biochar adsorption and CO2 addition were applied for biogas conditioning. pH 8 was favorable for biochar adsorption, whereas pH 7 was favorable for CO2 addition. The aim of biochar adsorption was to ensure that the H2S concentration remaining in the biogas after adsorption was less than 0.5 ppm, so that sulfur poisoning could be avoided at the anode of SOFC. A biochar column (BC) was attached to the AnMBR for the adsorption of sulfur compounds in the biogas. The BC was packed with biochar made of cow manure. The adsorption capacity of the biochar was measured to determine the amount of biochar required in the BC. After biochar adsorption, the ratio between CH4 and CO2 was balanced by adding CO2 to the biogas, to reduce the risk of carbon deposition at the anode of SOFC. The exhaust gas discharged by the SOFC could also be recycled as an alternative to CO2 addition. The performance of the SOFC system using the conditioned biogas as the fuel was assessed based on electric power output and fuel utilization efficiency. Based on the results of biogas production, conditioning, and utilization, the influence of the AnMBR pH on the SOFC operational strategy was analyzed. Furthermore, the potentials and the limitations of connecting AnMBR and SOFC were discussed.

Producing green hydrogen can be done using alkaline water electrolysis. Recycling water might help to fulfil the large water demand of hydrogen production facilities. In fertiliser production, steam condensate could be a recyclable water source for hydrogen production. This condensate is relatively clean as its main contaminant is a small concentration of ammonia. This report researches the effect of adding ammonia to the electrolyte of an alkaline water electrolysis cell.

When steam condensate is used instead of ultra-pure water, it is important to find out what happens to the added ammonia and if it affects the production rate and the production efficiency, or if it degrades the equipment. The experiments in this report used three different ammonia concentrations and the electrolyte was made using potassium hydroxide. The electrolysis cell used nickel mesh electrodes and a Selemion™ anion exchange membrane. Each of the experiments were carried out at 2.15 Volts for a duration of 50 minutes.

It was found that adding 1 mmol/L ammonia to the electrolyte decreased the current density of the cell. Doubling the ammonia concentration led to an even larger decrease in current density of up to 19%. A significant effect on the Faraday efficiency was not measured. During the experiments, the ammonia was partially stripped from the electrolyte due to its high alkalinity. Another part was oxidised to produce nitrogen gas and nitrate. Some of the ammonia had not reacted after the 50-minute experiment and could be measured in the spent electrolyte. After all the experiments were carried out, the cell was disassembled. The cathode showed significant signs of degradation. However, the many starts and stops between experiments could be the primary reason for this degradation. The ammonia could have accelerated the degradation, but this was not proven.

Overall, the benefits of using steam condensate do not seem to outweigh the drawbacks. The ammonia caused a significant decrease in current density. On the long term, ammonia might cause electrode poisoning which would further lower the current density. The experiments also found nitrate in the spent electrolyte. Having additional pollutants in both the spent electrolyte and the produced gasses might introduce additional disadvantages to using an ammonia containing electrolyte. If steam condensate is used as a water source, a treatment step is advised. Aeration could be used to strip the ammonia from the electrolyte. To get a more accurate insight into the effects of ammonia on alkaline water electrolysis, additional research is necessary. In future research, the effects of ammonia should be measured more accurately, and the long-term effects should be researched.

Aromatic compounds have always been of concern regarding their toxicity to living organisms, including microorganisms. With more anthropogenic activities (e.g. coal gasification), the need for feasible treatment of industrial effluents is highly prioritised. With the anaerobic degradation process being a competitive solution, these compounds’ toxic impact on the biomass is still of concern. These implications influence the stability of the degradation process; thus, there was a search for mechanisms to make the anaerobic degradation process more resilient. One potential mechanism is enhancing syntrophic collaboration between different species and its corresponding electron transfer. Syntrophic collaboration in an anaerobic environment can be conducted using intermediates (e.g. hydrogen) or direct electron transfer. Direct interspecies electron transfer (DIET) is reported to be more energy efficient and more thermodynamically favoured over other mechanisms that include mediators (hydrogen/ formic acid). Conductive and semi-conductive materials have been investigated to simulate this direct interspecies electron transfer mechanism (DIET), with various materials being researched, such as iron oxides, zero-valent metals, and even carbon-based materials.
This study investigated the impact of magnetite addition (as a DIET-stimulator) on p-cresol degradation, methane production and sludge characteristics, with a further interest in membrane fouling mitigation. This investigation was conducted with continuous flow reactors and batch reactors. The continuous configuration was based on an anaerobic membrane bioreactor (AnMBR) fed with a synthetic-coal gasification-like solution of phenol and p-cresol to investigate mainly the conversion rate of p-cresol and monitor the influence on the methane production, sludge characteristics, and membrane fouling. At the same time, batch experiments were conducted to investigate the acetoclastic methanogenic pathway and p-cresol degradation as a sole carbon source. The continuous experiment lasted for 143 days but was divided into two separate phases with two different magnetite dosages, starting with 40 mmol/L in phase (I), then replacing the sludge with acclimatised one (from the control) with the addition of the second dosage (20 mmol/L) in phase (II).
A Magnetite dosage of 40 mmol/L showed signs of biomass-suppressed conversion capacity compared to the control, by which the reactor conversion rate deteriorated by reaching 212 mgCOD/ gVSS/d (under a feed of 900 mgPh/L & 900 mgPcr/L). Phase (I) showed no significant differences in the methane production rate between control and magnetite reactors. On the other hand, the batch experiments fed with 1 gCOD/L acetate showed that the magnetite reactor had a lower acetoclastic methane production rate than the control. It was suggested that the 40 mmol/L magnetite dosage was suppressing the acetoclastic methanogens, which was further contributing to the lower conversion capacity observed in the AnMBR by the end of the phase. With the same methane being produced in control and magnetite reactors, it was also possible that either hydrogenotrophic methanogenesis or the DIET pathways were enhanced; however the absence of intermediates (e.g. VFAs) and the similarity of the COD balance supported the possibility of the latter one. During phase (II), the conversion rate of both reactors (control and magnetite) reached 74 mgPcr/ gVSS/d, approaching the highest conversion rates reported in the literature. While the acetoclastic methanogens showed no significant difference in the batch experiment, the magnetite-AnMBR’s methane production rate was 10%-28% higher. Furthermore, the methane yield with magnetite supplementation showed an average enhancement of 15%. In addition, the batch experiment also showed that this magnetite dosage reduced the p-cresol conversion rate by 87% compared to the control.
Both magnetite dosages (20 mmol/L & 40 mmol/L) showed a reduction in the protein and carbohydrate content of the soluble microbial products (SMP) and the extracellular polymeric substances (EPS). Magnetite had adversely impacted the loosely-bounded EPS (regarding protein and carbohydrates), whereas it was shown to be significant compared to the control. The EPS-LB showed an inverse relation with the particle size distribution (PSD), verifying that the higher increase in the particle size could be correlated with the EPS-LB reduction by the magnetite. On the other hand, the fouling rate of the membranes showed an insignificant difference between both reactors. This was suggested to be related to the incomplete formation of a mature cake layer under the influence of low operational flux. However, with the reduction of the SMP/EPS, it was suggested that the formed cake layer would be more porous and permeable. This would mean that the cake-fouling and its corresponding resistance would be expected to be lower. As the cake layer acts as a protective barrier for the membrane, its reduction would lead to a higher risk of irreversible pore-blocking by fine particles from the magnetite and the sludge.

In the treatment of industrial wastewater, the biological removal of aniline & nitrogen often occurs simultaneously within the hyper-saline water matrix. This study focuses on pioneering the research
on combined aniline-nitrogen removal in a hyper-saline environment. The experimental approach assessed the cause of nitrite accumulation phenomena in this specific case study as well as the influence
of oxygen concentration and aniline as a carbon source on nitrification. The hypothesis of increasing aniline biodegradability by making it chemically react with nitrite was experimentally tested. In addition, data analysis of the full scale of this study was performed in order to create analytical models to represent its biological processes. It was found that the correlation between oxygen concentrations and nitrification was non-linear and differs from what is observed in the literature due to the significant influence of different boundary conditions. The unavailability of carbon sources during the nitratation process was the cause of nitrite accumulation, which crucially affects nitrification. The chemical reaction between aniline and nitrite (most likely polymerization) resulted in a compound that did not limit nitrification and had more biodegradable potential. Furthermore, an aerobic model was developed but the promising results were most likely caused by the mathematical optimization, which was done in order to bypass the lack of data. Nevertheless, respirometry was used to build an empirical model to detect nitrite accumulation in the effluent of the full scale, which showed promising results. This study can potentially pave the way for the application of Anammox technology in the combined treatment of aniline & nitrogen, which is discussed in the hypothetical design implementations.

This study evaluates the effectiveness of organic acids, specifically citric acid, lactic acid, and malic acid, as scrubbing agents for ammonia (NH3) recovery from waste air streams. The acid scrubbing process was modeled using Aspen Plus® and validated against sulfuric acid scrubbing process data available in the literature. The effects of various system variables, such as temperature, gas liquid ratio (G/L) pressure, acid and NH3 concentrations, on the scrubbing efficiency as well as outlet ammonium ion mass flow rate was investigated. Results showed that reducing temperature, acid reflux ratio, G/L ratio, and inlet NH3 concentration while increasing pressure and inlet acid concentration can improve scrubbing efficiency. Citric acid exhibited the highest ammonia removal rate, the lowest acid consumption, and the least change in scrubbing efficiency when changing inlet ammonia concentration, followed by malic acid and lactic acid. These findings suggest that citric acid is a promising alternative to sulfuric acid as a scrubbing agent for NH3 recovery in wastewater treatment plants. This study needs to further incorporate the dissociation reactions equations of organic acids to provide accurate results. Additionally, the simulation's simplification in the design of the scrubber system introduces uncertainties in the results.

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.

Currently, organic micropollutants (OMPs) are continuously and uncontrollably released into the water environment worldwide, as the reason for their special properties, OMPs removal has been a global challenge. This study focuses on acetaminophen degradation by photo-electrolysis (PEC) activities, which is one of the promising advanced oxidation processes (AOP) technologies. First, we report the fabrication methods of the BiVO4/BiOI heterojunction on FTO glass, then characterised the prepared photoanodes with XPS, XRD, SEM, EDS, UV-vis and IPCE. The results demonstrated the BiVO4/BiOI p-n heterojunction had been successfully electrodeposited on the FTO glass. Further, the LSV and EIS analysis in this study showed the BiVO4/BiOI photoanode had less photocurrent density than BiVO4 when carried out in the solution of acetaminophen. Even if the heterojunction did not improve the photocurrent, it significantly enhance the acetaminophen removal efficiency in the PEC degradation process. BiVO4/BiOI photoanode achieved 99% degradation efficiency in 3 hours and obtained 0.019 mi n−1 of the reaction rate constant. Overall, these results indicate that BiVO4/BiOI heterojunction has a great application potential for the degradation of OMPs in the wastewater treatment plants secondary effluent.

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.

This study aims to explore hydrogen production via alkaline water electrolysis using municipal effluent. The experiments were conducted in a flow cell electrolyzer using carbon fibre and Ni-foam as the anode, with another Ni-foam electrode employed as the cathode for all experiments. Synthetically prepared effluent and real municipal effluent obtained from the Harnaschpolder water treatment plant effluent was used with potassium hydroxide (KOH) as the supporting electrolyte. The composition of the synthetic effluent was prepared with 23.0 ± 2.1 mg O2/L humic acid (Sigma Aldrich) as the primary organic pollutant. Experiments were conducted to investigate the effect of electrolyte concentration ranging from 0.01M -1M KOH and the effect of applied current density ranging from 25 A/m2, 50 A/m2, 100 A/m2 and 150 A/m2. Further experiments were conducted to assess the effect of humic acid concentration ranging from 23.0 ± 2.1 mg O2/L to 90.0 ± 0.7 mg O2/L. This was subsequently investigated under potentiostatic conditions at an applied cell voltage of 1.5V using the carbon fibre anode and under galvanostatic conditions for the Ni-foam anode. Regarding the Ni-foam anode, the current density was calculated based on the concentration using the relationship for limiting current density of humic acid oxidation. The investigation focused on assessing the performance of the electrolyzer in terms of volumetric hydrogen production rate and energy efficiency of hydrogen production. The performance data was also compared with conventional alkaline water electrolysis using Ni-foam as the anode and cathode in 1M KOH solution. In addition, the extent of humic acid oxidation was also assessed in terms of COD removal efficiency, TOC removal efficiency and changes in the spectral scans obtained via UV-Vis spectrophotometry.
The performance data revealed that the energy efficiency of hydrogen production was lower for both synthetic and municipal effluent compared to alkaline water electrolysis; this was evident for both carbon fibre and Ni-foam anode. Further, the energy efficiency was also higher when the Ni-foam anode was used compared to the carbon fibre anode. For the electrolysis of municipal effluent, a maximum energy efficiency of 75 ± 2.7% was obtained for the carbon fibre electrode, whereas for the Ni-foam anode, the maximum energy efficiency obtained was 83 ± 3.0% at an applied current density of 12.55 A/m2 with 1M KOH as the electrolyte. Despite this observation, the volumetric hydrogen production rates were not significantly affected because the rates converged closely to their theoretical values; this was also evidenced by the coulombic efficiency of hydrogen evolution reaction (HER), which exceeded 90% in all the experiments.
Concerning the extent of humic acid degradation, the Ni-foam anode was able to oxidize some of the humic acid molecules during electrolysis, and a maximum COD removal of 24.6 ± 8 % was observed after electrolysis of synthetic effluent at an applied current density of 100 A/m2 with 1M KOH as the supporting electrolyte. In contrast, the carbon fibre anode was not able to do so. Instead, the humic acid molecules tended to adsorb on the surface of the carbon fibre anode, evidenced by the increase in COD and TOC after electrolysis. Similar behaviour was also observed for the carbon fibre anode when the effect of humic acid was investigated under potentiostatic conditions, whereas under galvanostatic conditions for the Ni-foam anode, oxidation of humic acid was evident. The extent of oxidation was dependent on the duration of electrolysis, i.e., humic acid concentrations of 49.8 ± 0.98 mg O2/L and 90.0 ± 0.7 mg O2/L required a duration of 6 hrs and 8 hrs to achieve a COD removal efficiency of 43.5 ± 5.0 % and 60.4 ± 4.2 %, respectively. Additionally, the possibility to integrate an electrolyzer with an aerobic treatment plant to supply high purity oxygen was investigated. The comparison was done using BioWin simulations with a standard aerobic bioreactor for a flow of 10,000 m3/day under two conditions: 1) with atmospheric O2(baseline) 2) with high purity O2(95% purity). The investigation revealed that combining a 1 MW electrolyzer with the aerobic wastewater treatment plant would provide sufficient amount of oxygen for the proper functioning of the high purity O2 plant. In addition, the flow requirement to produce the required amount of oxygen was only 0.03% of the discharged effluent (i.e., only 3.1 m3/day of the discharged 9708 m3/day).
Further, the use of high purity oxygen in the aerobic wastewater treatment plant was accompanied by energy savings of 1.2 kWh (4320 kJ) due to reduced load on the air pumps

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.

Industrial wastewaters generated in chemical industries are often characterized by extreme conditions, such as the presence of complex, recalcitrant, and toxic aromatic compounds, high temperature, and high salinity. The mentioned conditions predominantly occur when chemical industries reduce process water use or strive for closing water loops. For wastewaters with extreme characteristics, conventional wastewater technologies have limitations. However, granular sludge-based or membrane-assisted anaerobic bio-treatment offers many advantages such as in-reactor augmentation of the required microbial species and long sludge retention times, ensuring high metabolic conversion rates per unit of reactor volume, besides low investment costs and low or negligible energy use. Frequently, auto-immobilization or stable anaerobic sludge granulation cannot be guaranteed under extreme conditions. Thus, the application of anaerobic membrane bioreactor (AnMBR) technology for pre-treating industrial wastewaters could offer an alternative solution with several advantages, such as full retention of specific and slow-growing microbial communities, effluents free of suspended solids, and system compactness. The purpose of this thesis is to investigate the applicability of the AnMBR technology for the treatment of chemical wastewater under extreme conditions by studying the impact of high and fluctuating salinity, and high temperature on the conversion of phenol. Phenol was selected as a model aromatic compound because it is commonly found in chemical wastewaters, while it is also a known inhibitor for the anaerobic conversion process. Moreover, this thesis provides additional understanding of the AnMBR operation, including assessment of membrane resistance to filtration, microbial population dynamics under the different conditions. Three laboratory-scale AnMBRs and one upflow anaerobic sludge blanket (UASB) reactor were used to carry out the experiments at varied salinity, phenol concentration and temperature. Different operating conditions were tested to determine the limitations and robustness of the AnMBR and UASB reactor configurations. The high salinity, expressed as sodium concentration, varied between 6 gNa+.L-1 and 37 g Na+.L-1. Influent phenol concentrations from 0.1 gPh.L-1 up to 5 gPh.L-1 were applied. The AnMBR operational temperature was mainly set to the mesophilic range at 35°C, but experiments were also performed in the hypermesophilic (40-45 ºC) and thermophilic (50-55 ºC) range...

Anaerobic membrane bioreactor (AnMBR) technology is increasingly researched for wastewater treatment in a circular economy scenario to recover nutrients, water, and biogas. AnMBR couples the advantages of anaerobic digestion, such as low sludge production, no aeration requirement and biogas production, with the benefits of membrane technology, that is, complete solids removal and a high removal degree of pathogenic organisms. Nevertheless, membrane fouling remains the major operational challenge, limiting the economic feasibility and applicability of AnMBRs. Membrane fouling is responsible for lower flux, higher transmembrane pressure, the need for intensive biogas sparging or increased crossflow velocities for membrane scouring, and increased frequency of membrane cleaning and membrane replacement; consequently, increasing energy and operational costs. Researchers extensively studied the causes and mitigation of membrane fouling in both aerobic and anaerobic membrane bioreactors. Membrane fouling mitigation strategies have focused on optimisation of membrane operational variables, such as: gas sparging, crossflow velocity, filtration relaxation cycle, permeate flux and frequency and intensity of chemical cleaning. Although optimisation of operational variables might be suitable when the sludge has good or moderate filterability, it may not be adequate or sufficient when fouling is caused by a sludge with poor filterability. The application of flux enhancers for fouling control has been extensively investigated. Flux enhancers are adsorbents, coagulants and flocculants that decrease fouling by changing the sludge characteristics, thereby improving sludge filterability. Particularly, cationic polymers have been successfully applied as flux enhancers in short term tests on large scale aerobic membrane bioreactors (MBRs), whereas in AnMBRs research is scarce, and so far, only done at lab scale. Results from MBRs cannot be directly translated to AnMBRs because the extent and nature of membrane fouling under anaerobic and aerobic conditions are different. This thesis studies the feasibility of dosing cationic polymers into large scale AnMBRs for fouling mitigation, focusing on long term effects, possible side effects, optimal dosing strategy and variation of required dosage.

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.