Organic micropollutants (OMPs) originate from organic chemicals such as drugs and pesticides that are widely used in human activities. OMPs are difficult to remove by conventional water treatment techniques, and hence continue to accumulate in natural water bodies. More effective methods need to be investigated for the removal of OMPs in drinking water treatment because of their toxicity and carcinogenicity, which may pose potential risks to human health. Previous studies have suggested that the use of activated peroxymonosulfate (PMS) catalyzed by Palladium (Pd) immobilized in ultrafiltration (UF) membranes can effectively degrade 1,4-dioxane and p-nitrophenol, while its removal efficiency for other OMPs, limiting factors and reaction mechanism still require for more research. In this study, PMS-Pd/UF system was established by coating Pd on the surface and 20 nm pores of the ultrafiltration membrane. The effectiveness of PMS-Pd/UF in the removal of OMPs from ultrapure water under various flux, pH, PMS dosages and ions presence was examined, as well as the performance in other water matrices including simulated brackish water, simulated brine water and river water. The results showed that PMS-Pd/UF achieved more than 95% of OMPs removal in 1 and 12-hour filtration tests at a flux of 30 LMH, while removal efficiency decreased with the increased flux due to the reduced contact time. The pH tests indicated that the system was more efficient under a neutral pH environment. The presence of 1 mM of various ions (Cl⁻, HCO3⁻, SO₄²⁻, and ClO⁻) had limited effects on the degradation of OMPs. However, the removal of OMPs was inhibited when OMPs coexisted with NOM in river water and, in combination with high salt concentrations simulated brine water (e.g., with 250mM of total anions). From specific scavenger dosing experiments, it was concluded that SO₄^•–, ^•OH, and O₂^•– were the main reactive species induced from Pd/UF-activated PMS for the removal of OMPs.

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.

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.

Membrane technology is widely used as an effective water treatment or pretreatment technology, especially in the filtration of oil-in-water (O/W) emulsions. Ceramic membranes have shown excellent performance in this regard. However, due to the complex composition of real wastewater, laboratory studies are limited to the filtration of simulated O/W emulsions, and there is little research on the favorable conditions for filtering real wastewater. Additionally, since actual devices operate as constant flux units, previous studies have been conducted under constant pressure conditions, thus further understanding of the effect of membrane pore size on constant flow membrane filtration is required to better understand the situation in real plant applications.

Water scarcity is a serious issue on many smaller islands, with population growth and the predicted impacts of climate change as driving factors. Bonaire is a small island located in the Caribbean Sea that has rural areas without grid connections to electricity and water. Agriculture, both livestock and hobby crop farming, in the Punta Blanku region used to rely on groundwater pumped from wells. Groundwater usage had to be discontinued due to salt intrusion causing the water to become brackish. Water for a large chicken farm that supplies almost all eggs for Bonaire now has water delivered by truck, but it is not reliable due to transportation issues and costs. Reverse osmosis (RO) is recommended as a reliable way to provide water to the Punta Blanku region. Water production can be powered by renewable energy and be more economically feasible with windmill power as the electrical energy source for the RO system. Surface seawater and brackish groundwater samples were tested to determine the best water source for the RO system. Total dissolved solids and electrical conductivity values determine the total power pumping need for the RO system. Using sample results and IMSDesigns, a reverse osmosis model designed by Hydranautics, it was determined that brackish water reverse osmosis (BWRO) was preferred over seawater reverse osmosis (SWRO). With Bonaire wind speeds, FreshWaterMill can easily power 200 cubic meters permeate production per day with BWRO. Additionally, less fouling is expected for BRWO than SWRO due to prefiltration by soil.

Constant flux MF/UF filtration is preferred in real-world applications because it
provides more consistent permeate flow rates than fixed transmembrane pressure studies. Particularly, little is understood about the fouling of ceramic membranes in constant flux filtration modes by nano-sized O/W emulsions. In this study, the effects of emulsion chemistry containing pH, different surfactants, as well as salinity on the alumina and SiC deposited ceramic UF membranes with various physicochemical surface properties in the constant flux mode were compared.

Ceramic ultrafiltration is a promising technology for water reclamation, but issues with membrane fouling and the removal of organic micro-pollutants have limited its development. Recent research has shown that catalysis-based ultrafiltration has the potential to address these problems. In this study, catalysis-modified (CuFe2O4 and Pd) ultrafiltration was investigated for fouling mitigation and organic micro-pollutant removal.

The membranes were successfully synthesized and it was found that using Fenton oxidation (a combination of CuFe2O4 membrane with H2O2 backwash) had a 93.9% higher cleaning efficiency than applying demi-water. Besides, it was found that the backwash flux and backwash time were crucial in determining the cleaning efficiency of Fenton oxidation, with a smaller backwash flux or longer backwash time resulting in better permeability recovery.

However, the application of Fenton oxidation was also found to be limited by the instability of the CuFe2O4 catalyst in acidic environment, and the problem of catalyst leaching led to a decrease in cleaning efficiency. Additionally, it was discovered that using PMS oxidation was more effective for OMPs removal compared to Fenton oxidation, with a removal efficiency of up to
90%. Overall, this work demonstrated the potential of catalyst-coated ultrafiltration for water treatment and highlighted the benefits of combining membrane filtration with advanced oxidation processes.

Large amounts of oily wastewater which included oil-in-water (O/W) emulsions, also known as produced water (PW), were produced in tandem with the enhanced oil recovery (EOR). Ultrafiltration (UF) was an effective and economic method to separate micron-sized O/W emulsions, while the membrane fouling limited its development. Understanding the fouling phenomena was essential to enhance the efficiency of membrane filtration for oil-water separation, hence this paper investigated the influence of different salinity (1 mM, 20 mM and 100 mM) and types of surfactants on the fouling of the alumina (Al2O3) membrane and the silicon carbide (SiC) deposited membrane filtrating 500 mg/L O/W emulsions with mean droplet sizes of approximately 4 ~ 7 μm, and the UF with the constant flux of 80 LMH and the crossflow velocity of 0.59 m/s was conducted. Sodium dodecyl sulfate (SDS, anionic), alkyl polyglycoside (APG, nonionic), and cetyltrimethylammonium bromide (CTAB, cationic) were chosen in this study due to the frequent use in EOR, and the N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DDAPS, zwitterionic) was selected because of its low tendency to foul at high salt concentrations.
Derjaguin-Landau-Verwey-Overbeek (DLVO) and the extended DLVO (XDLVO) models were used to quantify the membrane-oil droplet and deposited oil layer-oil droplet surface interaction. The results showed that the SiC-deposited membrane had less membrane fouling and irreversible fouling resistance compared with the Al2O3 membrane when filtrating O/W emulsions stabilized with SDS, APG or DDAPS. The DLVO model estimated emulsion fouling propensity to rise with increasing salinity when dealing with SDS, APG or DDAPS-stabilized O/W emulsions, while CTAB-stabilized emulsion fouling propensity for the SiC-deposited membrane would decrease with the higher salinity.

With the development of industry, there is an increasing focus on environmental issues, while organic micro-pollutants (OMPs) have garnered significant attention as emerging contaminants in water. Due to the low concentration and small size, OMPs pose a challenge to retain in traditional low-pressure membrane filtration systems. Prior researches found that membrane coupled advance oxidation processes (AOPs) could effectively degrade OMPs. However, membrane fouling caused by natural organic matter still remains an issue. In this study, the feasibility of simultaneous OMPs removal and fouling mitigation was validated in such a membrane coupled AOPs system, where the peroxymonosulfate (PMS) worked as the oxidants and palladium was immobilized on the ceramic ultrafiltration membrane surface to activate the PMS. In a continuous four-cycle experiment, the Pd-coated membrane maintained over 60% removal for 4 OMPs and improved the hydraulic clean efficiency significantly. Furthermore, the factors related to experimental conditions were also explored. The research
found that OMP removal rates were reduced by fouling due to the competitive effect of PMS. Take Trimethoprim as an example, its kinetics constant decreased from 22.491 to 0.916 s−1. PMS dosage also played an important role in both fouling alleviation and OMP removal. The improved performances were observed with increasing PMS dosage.

Water scarcity and uneven distribution of water resources pose a significant challenge globally. Searching for alternative water resources could alleviate this issue. Municipal sewage reclamation with ceramic NF membrane has gained momentum nowadays. However, the inevitable fouling, especially organic fouling during membrane filtration, is the major limitation of the application. To mitigate the fouling issues and protect the membrane from frequent sodium hypochlorite cleaning, a reaction-based CaCO3 pre-coating method, which could prevent the direct contact of foulant and ceramic NF surface was developed. Acid cleaning was applied to initiate the reaction between CaCO3, which was attached with foulants (sodium alginate) and acid. Lastly, forward flush was implemented to remove the loosened CaCO3 and sodium alginate layers.

The effectiveness of hydrochloric acid cleaning, formic acid cleaning and citric acid cleaning was studied in this paper. Citric acid was found to be the most effective way of cleaning because of the highest permeability recovery rate obtained and the lowest consumption rate of the pre-coating layer. This could be ascribed to the carboxyl groups chelation with calcium ions and the ‘peeled’ chelates adsorbed with more foulants were flushed away. Formic acid was less efficient showing moderate efficiency. Besides, HCl cleaning restored the lowest extent of membrane permeability. Additionally, experiments of increasing the pre-coated CaCO3 amount (7655 mg/m2) to apply for more filtration/acid cleaning cycles were executed. The effectiveness increases in the order of HCl, formic acid and citric acid. The pre-coated membrane cleaned with citric acid could last for the whole six cycles, while the membrane cleaned with HCl only worked in the first three cycles. Lastly, the effect of bubbles generated during the reaction was explored using CaHPO4 as a pre-coating layer. However, the hypothesized positive impact of bubbles was not verified.

Trials of surface modifications using low pressure chemical vapor deposition (LPCVD) has successfully decreased the high temperature needed for the fabrication of SiC membrane from 2000°C to below 900 °C. With this great success on the reduction of the energy con-sumption, however, further studies on the chemical stability and the fouling features of this kind of membrane were necessary. In this research, experiments were done on the SiC-Al2O3 UF membrane fabricated by LPCVD to study its chemical stability in a NaClO solution and its fouling features when filtrating sodium alginate and surface water under constant flux cross-flow mode. The backwash efficiency and the fouling resistance were analysed as well to further elucidate the fouling composition.
According to the results, the SiC-Al2O3 membrane coated under higher temperature (860°C) remained stable in the NaClO solution for 200 h, (1% for 100 h and then 5% for 100 h) while the membrane coated under lower temperature (750°C) showed a water permeability increase during chlorine treatment, indicating the dissolution of the SiC layer. The high temperature coated membrane (860°C) had a better antifouling ability than low temperature coated mem-brane (750°C) and the pristine membrane especially when filtrating the pure sodium alginate (SA) solution without Ca2+ under normal flux (170 LMH) or the surface water under lower flux (65 LMH). Cake filtration was observed in the fouling curves when the critical flux was not exceeded. The addition of Ca2+ into the pure SA solution resulted in the decrease of elec-trical repulsion and the increase of bridging between foulants and membrane surface. These led to the severe fouling of the high temperature coated membrane. The low temperature coated membrane had better antifouling ability than high temperature coated membrane and the pristine membrane when 2 mmol/L of Ca2+ was added. However, the backwash (back-wash flux of around 340 LMH for normal flux condition and around 195 LMH for lower flux condition) was not efficient for all the membranes and should be improved in the future ex-periments.

In this study simultaneous and continuous inline dosing of PAC and coagulant in UF was investigated. Surface water was directly treated with PAC-UF and performance of the system was assessed by looking at membrane fouling and organic micropollutants removal. Combining adsorption and membrane processes in one technique, hybrid membrane processes, enhances performance of OMP removal by membrane processes. Powdered activated carbon (PAC) combined with coagulation and ultrafiltration (UF) is a possible treatment technique for surface water.
Permeability in UF-membranes remains steady, when dosing coagulant. Only a small increase in irreversible fouling of 0.2-0.7*109 m-1h-1 is visible. However, absence of coagulant dosing causes irreversible fouling to increase to 8.7*1010 m-1h-1 and can not be easily reversed with a chemically enhanced backwash (CEB). Inline dosing of PAC alone causes an irreversible fouling of 11.4*1010 m-1h-1 and highest increase in reversible fouling of 11.7*1010 m-1h-1. Addition of coagulant (1.2 mg/l) lowers reversible fouling compared to no dosing, on the other hand addition of PAC to coagulant shows no clear increase or decrease in reversible fouling. Coagulation has a negative effect on capillary blocking, an increase of 4-8% compared to no coagulant or adsorbent. PAC and no dosing did not influence pore blocking.
Highest removal of low to good adsorbable OMP was 10-63% for continuous and simultaneous dosing of 12 mg PAC/l and 1.2 mg FeCl3/l. Increasing filtration time (30 to 60 min) showed highest removal efficiency of 75% of Sotalol and 5-Methyl-1H-Benzotriazole, both good adsorbable OMP. Removal of PFAS varies between a few percent and 37%. Continuous dosing of coagulant (1.2 mg/l) with PAC (10 mg/l) has a negative impact on OMP adsorption including PFAS. With a higher PAC dose (15 mg/l) removal efficiency was not affected.
Addition of coagulant with PAC-UF showed to be effective to prevent irreversible fouling, with direct surface water treatment. However, coagulation is responsible for blocking of capillaries even resulting in a small decrease of permeability. Removal of OMP including PFAS was much lower compared to other PAC-UF systems and therefore PAC-UF with simultaneous and continuous inline dosing of PAC is not a good set-up. Adjustments in set-up should be made in order to make this configuration work. Possible improvements are increase of filtration time between backwash and dosing sequence of PAC and coagulant.

Brine producing industries progressively become the centre of attentionas they carry greater environmental consequences. Despite the extensiveliterature that can be found on desalination, limited information is availableabout the practical comparison of the technologies with regards to the brineconcentration performance and associated energy consumption. This thesis studyaims to contribute to bridging this knowledge gap by comparing reverse osmosis(RO), electrodialysis (ED) and vacuum membrane distillation (VMD). RO wasstudied by simulations using WAVE software, while ED and VMD were studied byperforming lab-scale experiments. Feed NaCl concentrationsbetween 20 and 80 g/L were considered in this study. The achievedconcentration factor (CF) for RO was greatly influenced by the feedconcentration. It was found that applying higher netdriving pressures resulted in higher recoveries, but recoveries are limited by feed concentration. In the VMDstudy, the correlation between operating temperatures and permeate flux wasfound to be positive. A decrease in permeate flux wasobserved with increasing solute content, which is related to the vapourpressure lowering phenomena. It was found that the effect of operatingtemperature on permeate flux is greater than the effect of the feedconcentration. Condensation contributed to the highest energy consumption(81%), followed by the vacuum pump (18.9%). Efficient heating andcooling pumps result in a significant energy consumption decrease. In the ED study it was found that applying different current density (CD) did not influence the CF, so it ismore advantageous to apply lower CD to achieve the same desalination from anenergy saving point of view. Furthermore, the CF decreased with increasing feedconcentration and thistrend intensifies with larger volume ratios. The effectof absolute water transport became more significant at higher feedconcentrations and resulted in overall dilution of the concentrate stream. Thedistribution of mass transport was similar for different volume ratios, meaningthat higher CF can be achieved by larger volume ratios. Higher energy consumptionwas related to higher feed concentration and higher volume ratios resulted in higherenergy consumption due to smaller concentrate volume.RO, VMD and ED proved to be suitabletechnologies for concentrating different NaCl solutions. RO and ED showed verysimilar concentration performance and energy consumption. The concentration limit for RO was 118g/L, while for ED it was 140 g/L. RO was able to achieve higher CF with lowerenergy consumption at concentrations < 60 g/L, compared to ED. EDoutperforms RO at concentrations > 60 g/L. Theenergy consumption of ED and RO can be reduced by applying a multi-stageconfiguration. The VMD results showed that the energy consumptionto achieve a similar CF as RO and ED, increased by a factor of 61. VMD is moreadvantageous at higher feed concentrations and even more so with waste heat. VMD and RO are suitable for cases that require high qualitypermeate whereas ED is not. The technologies could also be applied togetherto minimize waste production, whilst prioritizing concentration.

Ultrafiltration (UF) is an efficient and effective method of filtrating oil-in-water (O/W) emulsions. However, the favorable conditions of filtrating nano-sized O/W emulsions have not been investigated. This study investigated the influence of four different parameters including membrane pore size, cross flow velocity, pH and salinity on membrane fouling as well as oil rejection. Alumina UF membranes were employed to filtrate nano-sized O/W emulsions. O/W emulsions were synthesized using soybean oil and stabilized by surfactants. The filtration experiments were conducted under constant flux for multi cycles. The results showed that 200nm was recommended to filtrate nano-sized O/W emulsions (average droplet size -100nm) based on the high oil rejection (95% ~ 99%) and low irreversible fouling resistance. Besides, alumina membranes were proved to be more effective in fouling mitigation at low salinity, high pH, and high cross flow velocities.

Natural organic matter is one of the key components to remove from source water during drinking water production. NOM not only negatively influences the colour, taste and smell of the water, it also decreases the effectiveness of common water treatment steps such as (membrane) filtration and UV desinfectation. A big fraction of natural organic matter is negatively charged and because of that it can be removed from water with ion exchange.

Suspended ion exchange is a relatively new type of ion exchange, invented and developed by drinking water company PWN in the Netherlands. The trademark aspect of this process is that ion exchange resin gets dosed directly into the influent in suspension, followed by a filtration and a regeneration step instead of fixed bed reactors. The big advantage of this way of operating is that it can operate raw surface water, it is not prone to clogging and can operate continuously. Therefore it is much easier to implement towards the beginning of the water treatment chain, allowing it to positively impact later treatment steps.

PHREEQC is a computer program developed to do geochemical calculations. It is designed to take into account different chemical processes happening simultaneously in complex ground or water matrices.

This report is about the research done to see if the removal of natural organic matter through SIX can be simulated with a modeling program such as PHREEQC. Therefore a series of jar tests and titrations have been done to determine the relevant chemical properties of four different NOM samples, the influence of pH on ion exchange and the influence of competition between different target anions.

The counter anion exchange equivalence of NOM has shown to be varying from around 1.8 to 8. This can explain why it is observed that the adsorption of natural organic matter is almost unaffected by the presence of competing anions such as sulfate, as this high counter anion exchange equivalence suggests that NOM sits high in the anion selectivity range. Additionally, the adsorption of NOM has been constantly high over a wide pH range. This is remarkable, especially at low pH values where titrations show that the charge of NOM decrease drastically. The release of chloride by the resin does get affected by pH a lot however, although this is minimally related to the changing charge of NOM and rather by the increasing amount of bicarbonate in the system adsorbing to the resin at neutral or high pH ranges.

Using the equilibrium constants calculated with results from the jar tests in PHREEQC give quite accurate results when a system of two anions is simulated. When a system with more than two anions is introduced however, the program values the equilibrium constants too much, resulting in vastly underestimating the adsorption of whichever anion has the lower selectivity in the system.
NOM is currently too complex to accurately represent in a computer model compared to other, more common anions such as chloride, nitrate and sulfate. On top of that PHREEQC needs more parameters beyond exchange equilibria to properly model the exchange reactions in a model.

This thesis constitutes a part of the "IMPRESS" project which is aiming at the production of bio-plastics by utilizing hemicellulosic hydrolysates. The hydrolysate stream, after following the steps of acid hydrolysis and neutralization, consists of monosaccharides (C5/C6 sugars), salt and sugar degradation products. The C5/C6 sugars need to be concentrated by a factor of 10 to be purified afterwards in downstream processes. Evaporation has been the most dominant technology in the sugar treatment sector, however the current study aimed to investigate tubular nanofiltration (NF) and vacuum membrane distillation (VMD) units for concentrating the C5/C6 sugars, as more sustainable alternatives. Synthetic solutions with C5/C6 sugars and salt were used to assess the performance of the NF and MD membranes in terms of sugar and salt rejection before the experiments with the real hydrolysate solution. Among the different NF and MD membranes, the one that met the C5/C6 sugar rejection requirements (>90 %) during the synthetic solution experiments was tested for concentrating the C5/C6 sugars. The most suitable technology for concentrating the C5/C6 sugars was also assessed for its energy consumption. Additionally, single filtration tests were conducted to characterize the NF membranes, while surface tension and contact angle measurements were performed to predict the membrane wetting phenomena during the VMD operation. Based on the C5/C6 sugar rejection values (range of 22-81 %) obtained with ceramic and polymeric NF membranes, it was deduced that the tubular NF membranes were not capable of meeting the C5/C6 sugar concentration goals. The polymeric membranes performed better than the ceramic ones in terms of C5/C6 sugar rejection, with a maximum sugar rejection of 81 %. However, the polymeric membranes were found to be more prone to fouling, showing a maximum decrease of 34 % in the water permeability after 4 hours of operation with the hydrolysate solution. Additionally, the characterization of the NF membranes based on the Donnan Steric Pore Model (DSPM) revealed membrane pore sizes larger than those provided by the manufacturer. On the contrary, the 0.2 μm MD membrane showed >99 % of C5/C6 sugar rejection and was used for the sugar concentration tests. The maximum C5/C6 sugar concentration factor (CF) achieved with the VMD was 8 with a negligible sugar loss (<1 %) in the permeate, indicating that concentrating the C5/C6 sugars by a factor of 10 is feasible with this technology. Surface tension and contact angle measurements disclosed inconsistencies in the hydrophobicity of the MD membrane, which can be linked to the membrane wetting phenomena occurred during the VMD operation. The fouling of the MD membrane (50 % of flux decrease after 39 hours of operation) was found to be reversible with complete flux recovery after chemical cleaning and drying of the membrane. The energy assessment of the VMD technology showed that the main energy consumer was the cooler, contributing to 96 % of the total consumed energy. Based on the cooler's efficiency, the energy consumption of the VMD unit was calculated to be in the range of 207-736 KWh/m³ of distillate. When compared with multi-effect evaporators with up to three effects, the VMD was found to be more energy efficient. Investigating less energy-intensive alternatives for concentrating the C5/C6 sugars, experiments with electrodialysis (ED) showed 90 % removal of both acid and salt from the raw and neutralized hydrolysate water, respectively, making it feasible for reverse osmosis (RO) membranes to be further tested for concentrating the C5/C6 sugars. Therefore, a treatment scheme of ED and tubular RO membranes is proposed for further research on concentrating the C5/C6 sugars. Overall, a pre-treatment step with the most permeable ceramic NF membrane is suggested, as evinced by the high color removal achieved (elimination of big foulants) and the high permeation of the C5/C6 sugars and salt.

Zeolites can be used for the adsorption of organic micropollutants (OMPs) from water. In this research, the potential applications of zeolite granules for OMP removal in wastewater treatment plants (WWTPs) were discovered. The adsorption of 18 target OMPs by zeolite granules was fully studied in batch and column experiments. The adsorption capacity and kinetics of OMPs in demineralised water (DW) and secondary effluent from WWTP (WW matrix) were investigated. A prediction model of OMP breakthrough curves in zeolite packed columns was established and evaluated.
It was found that the adsorption of OMPs by zeolite granules in batch and column experiments was influenced by OMP species, water matrices and operational parameters (e.g., superficial velocity and contact time). Positively charged OMPs were better adsorbed by zeolite granules than neutral and negatively charged OMPs. In most cases, the adsorption capacity and kinetics of OMPs were reduced in WW matrix, which led to an earlier breakthrough in columns. On the contrary, WW matrix enhanced the adsorption capacity and kinetics of a few negatively charged OMPs, such as diclofenac and clofibric acid.
Higher zeolite dosage resulted in faster OMP adsorption kinetics.
Column experiments showed that 12 of the 18 target OMPs could be effectively removed at the EBCT of 12 min, achieving removal efficiencies of 50% over 10 days. The mathematic model for the prediction of OMP breakthrough curves was optimized by applying larger kinetic constants obtained from the batch experiment. It was predicted an EBCT of 15 min is an alternative for a 7-day operation to remove OMPs sufficiently by zeolite packed columns.

Ceramic nanofiltration (NF) is a newly developed technology for municipal sewage reclamation for drinking water production, agricultural and industrial utilisation, but organic fouling limits it to pilot-scale application. Herein, Fenton-based cleaning catalysed by FeOCl pre-coat was performed on ceramic NF membrane to clean persistent gel-like fouling. FeOCl pre-coating on ceramic NF membrane was conducted by pressure-driven filtration. Gel-like fouling was simulated by Ca-alginate. The compact fouling layer was proposed to impede the diffusion of H2O2; therefore, NaCl was introduced to perform Na-Ca ion exchange to relax the fouling layer and improve the mass transfer in Fenton-based cleaning. The cleaning efficiency of Fenton cleaning and NaCl treatment were evaluated individually, and their synergistic effect was determined by a mixture of NaCl/H2O2. In pre-coating, the iron loading could be controlled by permeate flux. Moreover, the iron loading on the membrane had a linear relationship with FeOCl dosage. The pre-coated FeOCl layer slightly decreased membrane permeability (by 4%), presumably because the porous FeOCl pre-coat provided abundant channels for water permeation. NaCl pre-treatment displayed high efficiency in the removal of the reversible fouling layer, which contributed to 50% of flux decline. The FeOCl pre-coat catalysed Fenton-based cleaning, which achieved a complete flux recovery in 1 hour. The addition of tert-butanol (an ∙OH scavenger) in Fenton-based cleaning system decreased the cleaning efficiency, which confirmed the participation of ∙OH in Fenton-based cleaning. No remarkable synergistic effect was observed between NaCl induced fouling layer swelling and Fenton oxidation. It was likely due to the effect of turbulent flush on improving the diffusion of H2O2 in Fenton-based cleaning, which surpassed the effect of fouling layer swelling induced by NaCl treatment.

Reverse osmosis (RO) is considered the most reliable and cost-effective membrane desalination technologyworldwide. However, it suffers significant performance limitations due to mainly inorganic foulinggenerated in the highly concentrated brine. Especially, scaling caused by silica and silicates depositionsresults in irreversible damages with considerable economic implications. Recently, a different ROconfiguration, termed as closed-circuit reverse osmosis (CCRO), has been claimed to exhibit substantialbenefits over conventional RO in terms of both energy savings as well as higher scaling resilience.CCRO is operated in batches, during which the generated brine is continuously recycled inside theclosed loop until a desired recovery has been accomplished, after which the brine is released and replacedby fresh feed. Regarding CCRO scaling resistance superiority, an experimental-based proofis missing from the relevant literature. The current thesis was realized in collaboration with LenntechB.V., aiming at investigating the intrinsic propensity of CCRO to withstand and delay silica scaling. Tothat end, a campaign of filtration tests was carried out by means of a single-module CCRO pilot setup,during which two scaling indicators were periodically monitored. The used indicators were the masstransfer coefficient (MTC) and the applied feed pressure (Pfeed). Prior to the filtration trials, preliminarybatch tests, of 4-hour duration each, were carried out in order to simulate and more thoroughly examinethe circulated brine conditions. Various synthetic brines were prepared and silica polymerization wasmonitored. The effects of silica supersaturation level, pH and hardness ions were investigated. Of greatimportance was whether silica existed in its monomeric or polymeric form, since this greatly impactsthe scaling occurrence probability. Batch tests results revealed that at high pH conditions (pH>10)monomeric silica concentration remained unchanged in pure silica solutions (even at high supersaturationlevels), owing to the great silica solubility level. Nevertheless, when Mg2+ and/or Ca2+ werepresent in the solution, the quantity of silicic acid rapidly reduced. This was the result of the instantaneousformation of metal-silicate precipitates. Batch tests at pH 7 were also performed. In that case,monomeric silica concentration in pure silica solutions remained constant up to initial concentrations ofabout 450 mg/L SiO2 for the examined 4-hour duration. However, at higher SiO2 concentrations, suchas at 750 mg/L, rapid polymerization occurred. When hardness cations were included in the neutral pHsolutions, they showed an accelerating effect on silica polymerization process, but they did not reactwith either monomeric or polymeric silica. This effect relates to the suppression of the silica colloidsdiffuse double layer by the hardness cations, which subsequently facilitates colloids agglomeration.Regarding the CCRO filtration tests, they were conducted in sequences with duration of 20 or 40 min,which in its turn determined the achieved sequence recovery. For most of the carried out sequencesthe initial feed composition was: 120 mg/L SiO2 and 24 mg/L Mg2+. Only the final 5 out of the total40 sequences were realized in the absence of magnesium in the feed solution. All the filtration runswere performed at pH 7, at ambient temperature and at constant flux 15 L/m2h. The outcome was ascaling-free desalination process for a total cumulative operational period of approximately 11 hours,during which recoveries as high as 90.9% were reached, whereas severe scaling took place only afterabout 14 hours of total operation. The obtained results were contrasted with filtration tests results ofconventional RO received from literature resources and in that way the higher efficiency of CCRO towithstand and delay silica scaling was proved. Additionally, through silica mass balance calculations itwas shown that during all filtration tests significant silica polymerization took place. Also, cations analysisbe means of IC excluded the participation of Mg2+ ions in the formed scale layer. It was concludedthat the scale development was the result of an initial attachment of silica colloids to the membranesurface followed by monomeric units adsorption onto them. Finally, a simple customized method forthe prediction of silica scaling potential in CCRO operations based on batch tests was proposed.

Brine streams from industry is a burden to the environment if not disposed properly. “Zero liquid discharge” (ZLD) is an ideal way of converting saline streams from waste to resource through multiple membrane-based or thermal-based treatment technologies. The utilization of the recovered resource minimizes both costs and environmental impacts. Among the brine treatment technologies, the Eutectic Freeze Crystallization (EFC) is a promising thermal-based technology to obtain water and salt in high purity. EFC technology has higher energy benefit and simpler equipment than conventional evaporation technology. This technology is feasible for continuously recovering pure salt and ice in different stages, and separating them spontaneously. In this study, batch EFC experiment was conducted to determine the solubility curve of Na2SO4 under the different concentrations of NaCl. The effect of NaCl on the solubility of Na2SO4 at the low-temperature interval was investigated. It was found that with the increasing concentration of NaCl, the common ion effect between Na2SO4 and NaCl reduced the solubility of Na2SO4 and depressed the eutectic point (EP) of Na2SO4-H2O system. The decreasing EP showed a linear trend. A thermodynamic model in OLI Studio was used to evaluate the solubility of Na2SO4 as well. The modelling result was compared with the experimental data. The experimental result about the EP of Na2SO4-H2O system has a better agreement to the theoretical value than the eutectic concentration of Na2SO4. Besides, the effect of NaCl was compared with KCl in the OLI Studio, the salting- in effect of KCl promoted the solubility of Na2SO4. A scenario study was carried out to explore a proper process to treat reverse osmosis (RO) concentrate from a demineralised-water-producing (DWP) plant that was rich in Na+, SO42- and Cl-. The thermodynamic model was used to simulate the continuous EFC process and investigate how the different pre-treatment processes affect the recovery of Na2SO4. Four scenarios with different pre-treatment technologies were put forward based on the existing processing facilities: Scenario 1: RO – NF – EFC, Scenario 2: RO – TOC – NF – EFC, Scenario 3: RO – TOC – EFC, Scenario 4: RO – TOC – NF – RO – EFC. All the scenarios could reach more than 92% recovery of H2O. Among the four scenarios, Scenario 4 accomplished the highest recovery of Na2SO4 (98.4%) by -3℃. But the scaling tendency and poor permeate quality of the second RO unit made spontaneously. The gap between ice yield and Na2SO4·10H2O (Mirabilite) yield was significant in all the scenarios. It was suggested only to recover H2O rather than both H2O and Na2SO4, which can be achieved by means of Scenario 1 or 3. In Scenario 2, the close nucleation temperature of ice and mirabilite brought problem for separation work. To conclude, EFC is a newly emerging technology that can achieve a sequential removal of minerals from brine and is sustainable. There are barriers to overcome in impurity studies and those problems deserve attention. Further developments should be stimulated on recovering H2O and salt with an advance retrieving method, for example the design of multi-stage separation process, and the synergistic effect of different ion species and the combined effect of the organic compounds.