The main research question of this project was:
"How effective is the integration of a foam fractionation system in an activated sludge water treatment plant, on the removal of Per- and Polyfluoroalkyl Substances?"
To determine how foam and activated sludge can have an influence on PFAS removal, a controlled environment was created by building a bench-scale reactor that tries to mimics the full scale activated sludge WWTP of landfill Zeeasterweg. By doing this the effect on the biological performance was tried to be determined. Furthermore, a representative sample of the landfill leachate from the landfill, was used as the influent for the bench scale reactor. This leachate predominant PFAS compounds were: MeFBSAA (13.5 μg/L) and PFBS (8.8 μg/L) accounting for 70 % of total PFAS levels. To answer the main research question, two mass balances for a selected group of target PFAS compounds were develop for two experiments. The fist experiment was focusing on the PFAS removal efficiency without any foam production at all. To achieve this, antifoam was dosed on top of the nitrification zone so that no foam could be produced. The second experiment was called the "Foam Fractionation". In this experiment anfoam fractionation system was added to the nitrification zone of the bench scale reactor. This was done to determine the effect of collecting and removing the foam that was being produced inside the reactor.

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.

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.

Pulp and paper industries are water-intensive industries and composed of complex production processes. Untreated pulping wastewater is very toxic and lethal to aquatic life if discharged untreated. Anaerobic treatment technology has gained interest in treating these types of wastewater by reducing organic compounds. This thesis research aimed to evaluate the potential toxicity which might present in chemithermomechanical pulp (CTMP) wastewater, through the biological performance of a lab-scale expanded granular sludge bed (EGSB) reactor.
In the theoretical part CTMP process, characteristics of wastewater, toxicants, the functionality of an EGSB reactor, and any limiting factor that influences the treatment were investigated. In the experimental part, CTMP wastewaters from a mill in Sweden were analyzed using a lab-scale EGSB reactor for 182 days. Anaerobic biodegradability and toxicity test were done to measure the extent of anaerobic digestion in this wastewater. Different parameters such as chemical oxygen demand (COD) removal efficiency, volatile fatty acids (VFA), alkalinity, pH, and nutrient uptake were measured to access the biological performance of the EGSB reactor starting from unacclimated anaerobic granular biomass. Data analyzing tools including Excel and PHREEQC modeling were used in this research study. Excel tool was used to plot the graph and curve fitting whereas the PHREEQC model was done to understand the corrosivity of the biogas and calcite precipitation in the effluent discharge pipe.
The results showed that about 60% of the organic compounds in the wastewater were biodegradable, and no significant toxicity was found. Also, the performance of the EGSB was good with COD removal of roughly 50% at the stable phase. The presence of wood cellulose fiber in the wastewater had a negative impact on the performance of the reactor more specifically blockage in the recirculation and reduce methane production. However, based on the experimental results, EGSB alone would not be enough to remove most of the organic pollutants, which require additional post treatment such as aerobic system and membrane filtration to meet the discharge limit.

Excess nitrogen disposal into the environment increased with the discovery of an artificial way of nitrogen gas conversion to ammonia, and its implementation to industrial scale. The excess wasted fixed nitrogen ended up in rivers, lakes, oceans which resulted in degrading air, water and soil due to exceedance of the amount of nitrogen that can be absorbed by soil and plants. Currently, the global wastewater treatment objective has been adapting sustainable solutions by shifting from contaminant removal to resource recovery. Nutrients that were once considered as waste are now being considered as resources. Bipolar membrane electrodialysis (BPM-ED) in combination with stripper/scrubber is one of the combined technologies that aim at contaminant removal and resource recovery.

This study looks into energy efficiency and treatment performance from ammonium sulphate and ammonium citrate scrubber effluents by BPM-ED technology. A three-compartment BPM-ED was used to investigate the use of salt mixture in the feed solution and factors affecting ammonium yield.

Salt mixture of ammonium sulphate and tri-ammonium citrate were used. It was found that use of a salt mixture of ammonium sulphate and tri-ammonium citrate decreased the energy consumption and increased the current efficiency for both of the salts. Use of a mixture of ammonium sulphate and tri-ammonium citrate resulted in better energy performance than either of the salts when they were used alone. Ammonium recovery performance was higher when tri-ammonium citrate concentration was higher in the initial feed solution. This was due to increase in buffer capacity and basic pH in feed solution due to OH- leakages from base compartment. Sulphate ions were favored over citrate ions in their transfer through anion exchange membranes due to higher mobility of sulphate ions. As a further investigation a BPM-ED stack with different combinations, perhaps a two-compartment stack, can be tested to get a deeper understanding to optimize the operation.

Factors affecting ammonium yield that were investigated were H+ leakages and ammonia diffusion. It was found that H+ leakages were same for ammonium sulphate and potassium sulphate feed solutions and H+ leakages were not affected by ammonia diffusion. Ammonia diffusion resulted in higher energy consumption and loss of ammonium recovery potential. Ammonia diffusion increased even with experimental time of 60 minutes. Ammonia diffusion rates also increased through experimental time of 60 minutes. Ammonium and potassium transfer rates from diluate compartment did not follow a specific trend within the first 30 minutes. Clear reasoning behind this was unknown and the results were not completely satisfactory. In current study, it was assumed that ion cross-over and back diffusion were identical for ammonium and potassium. Investigating ion cross-over and back diffusion of the ions in BPM-ED could bring a deeper understanding to the energy efficiency and treatment performance.

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

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.

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

Aniline, a toxic aromatic amine present in certain wastewaters from the petroleum-, pharmaceutical- , and textile industry is regarded recalcitrant under strict anaerobic conditions. This study assessed the feasibility of methanogenic aniline biodegradation under saline (8 gNa+/L) conditions (1) by performing biodegradability batch assays using biomass from three different origins, and (2) by treating aniline-containing synthetic wastewater in a continuous anaerobic membrane bioreactor (AnMBR), seeded with granular sludge coming from an up-flow anaerobic sludge blanket (UASB) reactor treating petrochemical wastewater. In addition, the inhibitory effect of aniline and phenol on the aceticlastic methanogenesis, as well as the toxic effect on the integrity of cell membranes of the anaerobic biomass were assessed. Methanogenic biodegradation of aniline was not observed in the AnMBR, nor in the biodegradability assays. However, the results from the AnMBR operation fed with synthetic wastewater (20-200 mg aniline/L) demonstrated a 10-20% aniline removal, which was mainly attributed to volatilisation of aniline. Results from specific methanogenic activity (SMA)-inhibition tests demonstrated a half maximal inhibitory concentration (IC50) of aniline for the aceticlastic methanogenesis of 2.5 g aniline/L. The IC50 of phenol for the aceticlastic methanogenesis was 1.0 g phenol/L. The cell membrane integrity (CMI) of the anaerobic biomass was not significantly affected after 72 hours of exposure to 4 g aniline/L or 2 g phenol/L. This research constituted the first report demonstrating the application of an AnMBR with the aim to biodegrade aniline-containing synthetic wastewater under methanogenic saline conditions. The results of this research demonstrated that, after 200 days of AnMBR operation, the methanogenic enrichment culture was not able to biodegrade aniline.

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

Besides wastewater and rainwater, the sewers in the Netherlands also transport a lot of water that is not supposed to be in the sewer. This water is called extraneous water and is the result of unwanted discharges in the sewer system. This could be groundwater infiltrating leaky sewer pipes, or pumped from construction sites directly into the sewer. Or it could be surface water flowing in from wrong illicit connections. In the Netherlands, all this extra water account for a quarter of all the influent that enters the treatment plants.

This thesis studies the effect of a reduction of extraneous water in the influent on the workings of the treatment plant. For this two cases are studied: the treatment plant of Dokhaven in Rotterdam and Willem Annapolder in Kapelle. Dokhaven is a high loaded treatment plant with an A-B configuration that treats the wastewater from the center of Rotterdam in which it is located. Willem Annapolder is a low loaded treatment plant with biological phosphor removal and pre-denitrification and treats the wastewater from different cities and municipalities in its surroundings connected by long pressure mains. Both cases are known to receive a lot of extraneous water in their influent.

Two models were made for each case study: one that simulates the dynamics of the influent concentrations and another that describes the water treatment processes in the treatment plant. After calibration, the models of the treatment plant were run with a different influent in which the extraneous water was reduced.

Previous studies have indicated that a reduction in extraneous water leads only to small changes in the effluent concentration, but due to the reduced flow leads to significant reduction in the effluent load. In the case of Dokhaven the models show similar results. In the case of Willem Annapolder, the effects of the pressure mains was also taken into account. This caused the resulting effluent ammonia concentration to increase when extraneous water was reduced. The reduction in clean extraneous water increases the dry weather concentration of the pollutants in the pressure mains. When a rain event occurs, this water with high concentration is pushed towards the treatment plant with increased flow, which causes increased peak loads at the start of every heavy rain event.
Although the overall nitrogen load on the effluent was also decreased at Willem Annapolder when the extraneous water was reduced, the pressure mains resulted in a much lower decrease than in the case of Dokhaven. This thesis thus shows that it is important to take into account the sewer system when evaluating the effects of reducing extraneous water.

This study is part of a project titled: “Phenolic compounds degradation in AnMBR under mesophilic and thermophilic operation: BioXtreme-following up”.
Phenol is a toxic contaminant found widely in industrial effluents. It is toxic to humans and animals even at very low concentrations. Anaerobic digestion uses phenol as a carbon source and then to degrade it to non-toxic products for lower costs. Industrial effluents are also likely to have high concentrations of salinity which causes inhibition at high concentrations. Anaerobic membrane bioreactors are an attractive method as it enables biomass retention for biomass. The aim of this study is to understand the effect of Na+ concentration in a batch phenol degradation by phenol adapted mesophilic AnMBR biomass. NaCl concentration ranging from 0-90 g/L were tested on adapted AnMBR biomass. COD, phenol degradation, particle size distribution and methane production of adapted AnMBR biomass were analysed. The results from the batch test were used to model kinetic parameters. The biomass was acclimatized to 30 g/L of NaCl in AnMBR. Phenol removal of 98% was observed at 30 g/LNaCl and it decreased further with elevated salinity. Similarly, biogas production was also highest for 30g/L NaCl and decreased further with higher NaCl concentration. The highest value for SMA of 0.10 ± 0 gCOD-CH4.gVSS-1 d -1 was observed for 30g/L. However, the data did not indicate a specific trend with increasing salinity and showed high variability. The data showed poor fit to both Haldane and Monod growth model as these models were used for substrate inhibition. Modelling with modified Gompertz equation also failed to yield any conclusive results.

In this thesis, direct application of hollow fiber nanofiltration on surface water is suggested as an efficacious method for surface water treatment. This thesis was carried out as a collaborative effort between Lenntech B.V. and TU Delft. The current research aims to assess the performance of these membranes as a potential solution for surface water treatment and to gain a meaningful understanding of rejection performance and fouling tendencies of these modules through lab-scale experimentation of a low MWCO hollow fiber membrane. Direct application of nanofiltration on surface water was carried out on a lab-scale using the dNF-40 hollow fiber nanofiltration membrane supplied by NXFiltration B.V. Enschede. This membrane is fabricated using a technique called Layer-by-Layer (LbL) polyelectrolyte deposition which consists of an assembly of alternatingly deposited polycationic and polyanionic nanolayers on a polyethersulfone (PES) ultrafiltration support. The dNF-40 membrane is negatively charged at neutral pH. The main objective of the research was to determine the effectiveness of the dNF40 membrane for surface water treatment in terms of three key performance parameters viz. rejection, membrane fouling and concentration polarization. Membrane characterization was carried out by measuring the pure water permeability, Molecular Weight Cut Off (MWCO) of the membrane and rejection of single salt solutions. The pure water permeability of a pristine membrane was 1.53×10^{-14} m. The MWCO was measured using PEG filtration method and was found to be 200 Da. The membrane performance is limited in terms of the flux due to concentration polarization. CP factor was measured experimentally and compared with Sherwood analytical model. Since the flow through the fibers in laminar, high cross-flow velocities are required to reduce CP are high (< 0.5 m/s) due to which hydraulic pressure losses along the feed channel are high. A pressure drop of 0.2 bar was measured for a pristine membrane at a cross-flow velocity of 0.5 m/s. Filtration experiments were carried out with two kinds of surface waters: Delft Schie water and Biesbosch reservoir water. The influence of flux and cross-flow velocity on the rejection of ions were investigated. The removal of Natural Organic Matter (NOM)in both surface waters was between 80 and 85%. The rejection of divalent cations viz. Ca2+and Mg2+was higher at low system recoveries (upto 30%) but a severe drop in rejection was observed at higher recoveries (80%). The final permeate collected at 80% recovery contained 37 mg/L of Ca2+and less than 1 mg/L of NOM. 98%rejection of SO42- was observed irrespective of the feed composition and operating conditions. The dNF-40 membrane exhibited high fouling-resistance during surface water filtration showing no mass transfer coefficient(MTC) decline during 6-hour experimental cycles with surface water. To test for fouling fractions of surface water,additional tests were carried out with model foulant solutions including sodium alginate, humic acid and bovine serum albumin with varying foulant concentrations and ionic strengths; of the three, alginate fouling was most severe in terms of flux decline. Irreversible fouling was observed during the alginate filtration tests. Fiber-blocking was also observed during alginate filtration due to aggregation of alginate and Ca2+. Chemical cleaning with 200 ppm NaOCl solution at pH 12 completely re-stored the permeability. The results presented in this thesis demonstrate that the dNF-40 hollow fiber membrane with the LbL structure can treat surface water with-out pre-treatment. These membranes are ideal for applications such as production of drinking water where partial removal of hardness and complete removal of organic matter is required.

Nitrogen (N) removal is one of the key tasks for every wastewater treatment plant under the growing pressure of environmental protection. Prevailing applied N treatment technologies are mostly energy-intensive. This dilemma triggers a rethinking of the way to approach N management. “N2kWh-From pollutant to power” is a project that aims at creating an energy-positive 푁 treatment system by exploiting the energy potential stored in reduced N compounds. Both thermal and electrical energy needed in this scheme will be provided by Solid Oxide Fuel Cell (SOFC) using the ammonia recovered from wastewater. To guarantee a proper function of the SOFC a minimum of 5 wt% of ammonia in the gas mixture is a prerequisite, whereas, the reject water of anaerobic digester only typically contains 0.15 wt%. Therefore, selectively stripping NH₃ in waste streams is the main technical bottleneck of this project.This study aims at contributing to the understanding of selective transport of NH₃ by pervaporation. A comprehensive literature study indicates silica-based ceramic membrane is able to perform this selective transport. Therefore, the task of this research was to test the feasibility of selective transport of NH₃ by commercially available silica-based pervaporation membranes (hydrophobic PDMS and hydrophilic Hybrid Si AR). The objective was to find the optimum operating condition for maximizing the selective transport of NH₃ by silica-based ceramic pervaporation membrane. To this end, the impact of flow regime (laminar and turbulent flow), temperature (35 ^oC and 45 ^oC), presence of additional salt (NaCl and Na₂CO₃) and TAN concentrations (total ammonium nitrogen; 1.5, 12.0 and 20.0 g TAN·L^-1, respectively) was assessed through a series of systematic experiments.It was found that the PDMS membrane was unable to selectively transport NH₃ from liquid solution because both H₂O and NH₃ are polar molecules while the hydrophobic PDMS was nonpolar. Besides, the PDMS membrane tested was not stable under solutions used in this study.The results of Hybrid Si pervaporation membrane showed that the optimum operating conditions for selective transport of NH₃ was 35 ^oC, Re=2,400, 20.0 g TAN·L^-1 ammonium bicarbonate solution (pH adjusted to 10). For these conditions, the highest perm-selectivity (ratio of mass transfer coefficients of NH₃ and H₂O) was 0.5 indicting NH₃ was less selectively transported than H₂O.The impact of flow regime on selective transport of NH₃ was related to polarization effects and depended on TAN concentration in feed solution. In the tested temperature and TAN concentration range, perm-selectivity was independent on both parameters. In addition, the effect of both temperature and TAN concentration on the ammonia was mainly due to the driving force, so their influence on the perm-selectivity was limited. Presence of salt seemed to have a positive impact on the perm-selectivity. Although salt has little impact on the mass transfer coefficient of NH₃, it decreased the mass transfer of H₂O resulting in a better selective transport of NH₃.As for energy consumption, it was inversely related to TAN content. At the optimum operating condition 7 MJ·kg^-1 - N was consumed by pervaporation in this study. Compared with the energy consumption of air stripping, pervaporation is a promising technology for NH₃ recovery.

With the growing population and industrial development, there is more stress on natural water resources. Additionally, environmental laws make the disposal of waste streams from industries difficult. In this scenario, it is crucial to treat waste streams to recover water and possibly minerals, for reuse in the industry, reducing the dependency on new resources. Reverse osmosis (RO) is a membrane-filtration technology that has been in use for decades. RO systems can waste up to 30% of the feed water through the production of brine, containing the rejected minerals. This rejection is high when dealing with saline waters. Treatment of this brine stream for reclamation of water would increase the overall efficiency of RO systems. In this research, the treatment of RO brine by a closed-circuit configuration of RO – closed-circuit desalination (CCD) - is investigated. In CCD, filtration is done in batches, with the recirculation of the concentrate stream back into the feed stream. The high cross-flow velocity and short filtration batches result in prevention of scaling in these systems.
This research focused on proving the resilience of the CCD system to silica scaling despite supersaturations of silica. Lab-scale experiments were performed on a single-element CCD system, specially built with relevant measurement instruments. Silica scaling was monitored by mass transfer coefficient (MTC) calculations, silica mass balance calculations, and membrane autopsies. Synthetic feed water was used, containing only NaCl (10 mg/L) and varying concentrations of silica (70 – 120 mg/L as SiO2). No anti-scalants were used. Longer experiments were performed, i.e. 20 consecutive cycles of 1 hour each with 120 mg/L of silica in the feed. The cycle duration was increased, 2 cycles of 3-hour each were performed, with 120 mg/L of silica in the feed.
The MTC curves in all the experiments had a gradual decline with the progression of each cycle, but always recovered at the beginning of the next cycle. This decline was probably due to the increasing osmotic pressure in the recirculation loop. There was no permanent decline in the MTC, leading to the observation that there was no scaling in the system. This was supported by the silica in the mass balance calculations, that showed there was no loss of silica from the brine. The reactive silica concentration in the brine was as high as 1800 mg/L in the 3-hour cycle, attaining a recovery of 93%, without signs of scaling. The membrane autopsy showed that the membranes used for the experiments with 120mg/l silica in the feed had higher silicon content compared to the blanks. However, there were too few samples to compare against and make strong conclusions whether there was scaling.
Thus, the designed CCD system was resistant to silica scaling in these conditions, of high pH and in the absence of other components such as iron, aluminium, calcium and magnesium. The results of this study proved that, despite high concentrations of silica in the feed, CCD can improve the total efficiency of RO systems (with regard to the water wastage) by recovering water from the brine produced by RO installations. The extremely high recoveries attained by the system would result in small volumes of very concentrated brine, making the extraction of minerals more cost-effective, because lesser volumes must be treated to obtain the same amount of minerals.

Control of wastewater treatment plants has received more attention as a method to improve nutrient removal processes. Improved nutrient removal, results in an increased effluent quality, whilst minimising the energy consumption. Aeration control of oxidation ditches often focuses on adjusting the aeration intensity based on the nitrogen removal process, using ammonium measurements. The control systems do not incorporate biological phosphorus removal. Biological phosphorus removal, on the one hand, needs sufficient aeration and on the other hand, can deteriorate when subjected to excessive aeration. The complex relation to aeration, makes control of biological phosphorus removal difficult.

This research investigates the control of biological phosphorus removal in an oxidation ditch using simple sensors. Control systems often require expensive instrumentation. To limit the costs, cheap sensors using alternative monitoring variables for biological phosphorus removal are desired. Literature research was done to investigate the principles of biological phosphorus removal, possible alternative monitoring variables, current control systems and existing mathematical models and benchmarks that could contribute to a renewed control strategy. Some important variables found in literature were potassium, pH, ORP, ortho-P, nitrate, ammonium, conductivity, and DO. A measurement campaign was set up and executed to measure the trend of these variables throughout the oxidation ditch and to obtain more information on the state of the variables in the (un)aerated zones. A full-scale operating wastewater treatment plant in Hattem was made available to execute the measurement campaign.

The results obtained from the measuring campaign did not point towards alternative monitoring variables for biological phosphorus removal. Relationships between the variables and phosphorus found in literature, could not be directly derived from the measurement results. However, nitrate and ammonium measurements can give an insight into the biological phosphorus removal process. A change in ammonium and nitrate indicates an anaerobic, anoxic or anaerobic environment. Nitrate can in addition contribute to a control system by making sure that the zone before withdrawal from the oxidation ditch is anoxic, to inhibit P-release. However, it cannot on its own monitor the biological phosphorus removal fully as it cannot indicate the effect of the aeration intensity on biological phosphorus removal directly. The results from the measurements indicated a low biological phosphorus removal activity. From literature, it is known that several factors can influence the biological phosphorus removal, such as insufficient anaerobic zone and aeration settings.

To investigate the response of the WWTP to these factors, a BioWin model was constructed. This model simulates the performance of the treatment plant and investigates the impact of several adjustments, such as altered aeration and an extended anaerobic zone.

The simulation results showed that the DO setpoints of the aerators influenced the process in several ways. Increasing the aeration improved the results to a certain extent, after which the biological phosphorus removal deteriorated due to over-aeration. An extended anaerobic tank improved the biological phosphorus removal.
Unfortunately, a control system for biological phosphorus removal, using alternative monitoring variables, was not obtained. A benchmark of an oxidation ditch is suggested for further research and the implementation of biological phosphorus removal in a benchmark of an oxidation ditch was started.