Poly-hydroxy-alkanoate (PHA) is an intracellular polymer that can be used as an energy and carbon source by microorganisms. Measuring PHA is important for understanding the microbial metabolism of enhanced biological phosphorus removal (EBPR) and aerobic granular sludge (AGS) systems. There is a commonly used method to measure PHA, which is based on organic solvent extraction and gas chromatography (GC). However, there are different versions of the same method with different parameters, but the role of some of these parameters is unclear. When different types of biomass are analyzed, there is a requirement to understand the parameters and obtain an optimal protocol. In this study, the effect of various digestion times, different alcohols and organic solvents, and acid concentrations were tested to obtain the optimal protocol. The results showed that a minimum digestion time was required to get the maximum yield of PHA, and the time might differ when using different types of biomass. Methanol was shown to be better for GC separation than propanol. Using different organic solvents didn’t affect the final concentration, and an optimal acid concentration was required to determine by comparison. The GC temperature program optimization showed that lower oven temperature in GC is more beneficial for peak separation. From the analysis, it would be suggested to use methanol and chloroform for digestion and keep the digestion time for 24 hours.

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.

Lignocellulose is an abundant source of feedstock and consists of hemicellulose, cellulose, and lignin. Pre-treatment is done to fragment lignin and hydrolyse the hemicellulose and cellulose fractions into simple sugars which is then converted into bioplastics. The pre-treatment generates a mix of sugar solutions, lignin breakdown products and inorganic ions. However, the inorganic ions act an inhibitor for fermentation and needs to be removed. Electrodialysis is investigated as an alternative process to ion-exchange to desalt the sugar solutions for downstream processes. While the sugars are neutral compounds, the other organics are negatively charged and can cause fouling on the positively charged anion-exchange membrane.

The process waters are C5C6 and C5 sugar streams and the main ions present are sodium and sulphate. A desalting target of 60% is set for these two ions and the experiments are done using a lab-scale electrodialysis set-up. Tests are run to check the desalting rate, effect of filtration, powdered activated carbon (PAC) and acidification, persistence of fouling and the effect of cleaning-in-place. The increase in average resistance and run time is used as an indicator of membrane fouling.

The raw C5C6 sugar solution could not reach the desalting target but once the solution is filtered, a desalting of 75.5% (Na+) and 66.5% (SO42-) is achieved. The average resistance also drops significantly. The fouling is removed by a CIP and is deemed to be ‘reversible’ in nature. On the other hand, the C5 sugar solution did not improve in performance after filtration. Although the desalting target could be achieved after filtration, the average resistance rose to 130 ohms. A CIP did not have any effect and increased run-time and drop in desalting efficiency was observed. The main reason for fouling in both cases is attributed to the presence of lignin degradation compounds. Lignin is more concentrated in the C5 sugar as compared to the C5C6 sugar solution due to its production process. In C5 sugar, the irreversible fouling pattern is hypothesized to be due to adsorption whereas in case of C5C6 sugar the reversible fouling pattern is cake fouling. PAC was dosed to remove the organic foulants in C5 sugar and improved the average resistance to 48 ohms and significantly reduced the run time. Desalting of 61.4% (Na+) and 87.2% (SO42-) was reached. Acidification protonated the feed and reduced the charged interactions, thereby both reducing run time and the average resistance. Desalting of 65.79% (Na+) and 68.02% (SO42-) was reached after acidification.

To conclude, the studied ED system could desalt the organic C5C6 and C5 sugar streams after a treatment step. Lignin degradation products were found to heavily foul the AEM membranes as its increased presence in C5 sugar stream led to a more severe fouling which could not be restored even with a chemical CIP. However, mitigation of the degradation products in the pre-treatment step could ensure that the solution was desalted by the ED unit. Thus, quantifying the composition of organic streams is imperative to predict the propensity of fouling in an ED unit.

With the rapid population growth and industrialization, water bodies are being infiltrated by a rising number of contaminants like metals, pharmaceuticals, pesticides and detergents, which requires the need for novel treatment technologies. Electrocoagulation (EC) is a water treatment technology where the coagulant is dosed electrochemically from a pure metal electrode. The performance of Fe-EC in a full water column using a continuous flow setup has had little to no attention yet. The aim of this proof of principle study is to determine the feasibility and the practical potential of Fe-EC during a continuous flow implementation, and to give insight to the general performance of the system in terms of water quality improvement.

Experiments were conducted in a continuous flow Fe-EC unit with descending flow. Two pairs of electrodes were used, evenly distributed along the length of the unit, and at the bottom an air diffuser was used to provide aeration. Operational configuration of the unit was needed as no prior experiments had been performed with this unit and the exact behavior of the electrodes, flow and aeration within the continuous flow system were unknown. Furthermore, experiments were conducted to evaluate the removal efficiency of Fe-EC on nutrients, organic micropollutants (OMPs), microbes and (heavy) metals, operating at a pH of 8 and 7.

The operational parameters were set to deliver an Fe dosage of 50 mg/L, flow rate of 7.5 L/h, and a current density of 15 mA/cm2. It was found that the system was able to achieve high removal of phosphorus up to 99% during all experiment sets. Highest removal of E. coli and coliphages was found when operating at a pH of 7, reaching 1.56 and 0.65 log removal respectively. Removal of OMPs was found to vary greatly among the compounds and measurements. More stable results were found when using increased OMP concentrations (around 50 µg/L), reaching removals varying from 7% to 25% at a pH of 8, and slightly lower removals from 1% to 15% at a pH of 7. No correlation was found between the observed removal and the acid dissociation constant (pKa) or the η–octanol–water partition ratio (Kow) of measured OMPs. Lastly, various heavy metals show affinity for removal during Fe-EC, such as arsenic, copper, zinc, manganese, chromium and vanadium. Using increased influent concentrations of the heavy metals (around 80 µg/L) resulted in removals above 85% for arsenic, zinc, chromium and vanadium.

The system has shown to have high removal potential on secondary effluent, even when contaminant concentrations reach high levels. Nevertheless, uncertainties and were found for the practical implementation of Fe-EC, and design and operational parameters first have to be optimized in order to fully utilize the potential that Fe-EC has.

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.

Dunea’s drinking water treatment plants (DWTPs) want to reach the new arsenic (As) companytarget of < 1 µg/L, due to uncertainties on toxicity at the current WHO, European and Dutch guideline of 10 µg/L. The aim of this research was to lower the As concentration in Dunea’s effluent
to < 1 µg/L by improving our system understanding and exploring novel techniques for As(III) oxidation. Fieldwork was performed to assess whether each well section contributed to the elevated As concentrations. In order to enhance As(III) oxidation at Dunea’s DWTP, the use of electrochemical advanced oxidation processes (eAOPs) with a RuO2/IrO2-coated anode was examined during laboratory experiments. Fieldwork results showed that in each monitoring point the measured As concentration was > 1 µg/L, indicating that each well section contributed to the elevated As concentrations. The combination of strongly fluctuating groundwater tables, infiltration of oxygenated water, the observed pH decrease and synchronous mobilisation of several TEs, indicated that As was most probably mobilised by pyrite oxidation. It was observed that the As-bearing layer was present between -2.5 and -8.5 m NAP. With an average filter depth from -1.6 to -7.4 m, water was being extracted from the As-bearing layer. Laboratory results showed complete As(III) oxidation by eAOPs at a current density (i) of 7.5 A/m2, with a corresponding charge dosage (q) and hydraulic retention time (HRT) of 30 C/L and 1.4 min, respectively. At the aforementioned condition, the energy consumption of the eAOP cell was 0.066 kWh/m3 with operational costs of 0.04 e/m3. Free chlorine formation was minimized by reducing q, HRT and i. During the optimal anodic configuration of 7.5 A/m2, the estimated cathodic OH− production was sufficient to replace the dosed chemicals for pellet softening (PS). However, it was not sufficient to buffer for the anodic pH decrease. It was proposed to implement the eAOP cell at Dunea’s DWTP after PS and before aeration and rapid sand filtration.

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

Corrosion and fouling are considered major factors affecting the performance of water-steam cycles (WSC). Flow-accelerated corrosion (FAC), present in feed and condensate systems, is a well known corrosion mechanism, eroding and dissolving the protective magnetite layers. Fouling of the boiler, by suspended magnetite particles, is partly controlled by forces arising due to surface charging. Film forming amines (FFA) are gaining acceptance as means to control FAC. However, its performance in low pH regions is unknown. In addition, despite FFA being a surfactant, its effect on the colloidal magnetite surface charge and point of zero charge (pzc) are unknown. This research set out to determine the effect
of FFAs on the formation of a protective magnetite layer and its resistance against acidic FAC, and to determine the effect of FFAs on the surface charge of colloidal magnetite. This study focused on two FFAs, Octadecylamine (ODA) and Oleyl Propylenediamine (OLDA). In 48h 230-250 ºC immersion corrosion tests magnetite layers were formed on C1010 coupons, inside a high pressure high temperature autoclave under different treatments: untreated (blank), 2ppm ODA and 2ppm Ammonia, 2ppm OLDA and 2ppm Ammonia, and only 2ppm Ammonia. 48h 150 ºC re-immersion corrosion tests were performed to test the magnetite layer performance under acidic (acetate 0.08ppm) FAC. After the corrosion tests, the layers were verified using XRD, EDS + SEM and Weigh-loss measurements. Potentiometric titrations were employed to measure the proton induced surface charge of magnetite particles (10g/L) at an ionic strength of 0.01, and 0.1 mol/kg (KNO3) in the presence or absence of ODA, or OLDA (2ppm) over a wide pH range, at 25, and 150 ºC. This gave the magnetite surface charge density curves. The pzc was determined using the inflection point of titrations (pHinfl) and common intersection point (pHcip). XRD confirmed the presence of magnetite layers on all coupons after the immersion and re-immersion tests. The SEM measured magnetite layer decrease after the re-immersion tests was: 19.1%, 14.5%, 8.6%, and 23.3% for blank, ODA, OLDA, and ammonia treatment respectively. Weight loss determined corrosion rates taken over both immersion and re-immersion tests were: 0.070, 0.057, 0.060, and 0.073 mm/y for blank, ODA, OLDA, and ammonia treatment respectively. All magnetite surface charge density curves were unaffected by the presence of ODA, and OLDA, except for ODA at 0.1 mol/kg KNO3 and 25 ºC, which resulted in a raised/neutralized surface charge density curve in the alkaline pH region. Magnetite layers formed under ODA, and OLDA additions were smoother, thinner, and more uniform compared to layers formed under an ammonia only chemistry, and blank chemistry. Layers formed under the ODA, and OLDA chemistries were better resistant against acidic FAC and offered better protection, in terms of corrosion rate. At the applied concentration ratio, and ionic strength of 0.01M, ODA, and OLDA did not affect the magnetite colloid surface charge over pH. However, both caused magnetite particles to agglomerate. At higher ionic strengths of 0.1M, ODA neutralized the magnetite surface charge in the alkaline region.

There are more than 160,000 recreational crafts in the Netherlands with a toilet on board. It is forbidden to discharge blackwater into the environment from these crafts. Stricter enforcement of the law by the sealing of the valves of the external drain, leaves the owners of these crafts with a major problem. It is allowed, however, to treat the blackwater on board and then discharge it if the following two boundary conditions for fecal indicators are met: a maximum concentration of 330 cfu per100 ml of Intestinal enterococci and a maximum concentration of 900 cfu per 100 ml of E. coli. The overall objective of this research was to find and test a proof-of-concept (PoC) method to reach these boundary conditions. The method consisted of a series of conventional wastewater techniques: first a coagulation and flocculation step, then the filtration and subsequent dewatering of the TSS and lastly the filtrate was disinfected using UV-C irradiation. Bench scale experimental setups were used to get the data for this research. Results demonstrated that TSS was most efficiently removed by a combination of polyaluminnium chloride and a cationic polyacrylamide copolymer with a low charge density. Furthermore, polyaluminium chloride demonstrated to be highly effective at removing the fecal indicators. Dewatering experiments proved that increasing the polymer dosage did not affect the total dry solid content of the final sludge cake. Also, under the most ideal circumstances a dry solid content of the filter cake of 30% was achieved. Lastly, UV-C experiments were conducted on the filtrates of two different samples, with values for UV254 absorbance of 1.34 cm−1 and 11.85 cm−1 respectively. The first of which was sufficiently disinfected after a total irradiated UV-C dose of 180 mJ/cm2, of which the effective dose was 54.9 mJ/cm2. The fecal indicators in the second sample were not sufficiently removed after a total UV-C dose of 1100 mJ/cm2. The absorbance of UV254 of the filtrate was so large that the effective dose was only 40.0 mJ/cm2. The PoC method showed to have potential for implementation, but adjustments need to be made to make it more sufficient and viable for use of on board disinfection of black-water. Preliminary screening can extract most of the fecal material, which is already high in dry solid content, before homogenising with the liquid fraction. The quantity of conditioning agents need to be adapted to the specific blackwater, and if necessary the pH will need to be adjusted to ensure the right coagulation mechanism for efficient TSS removal. Finally, humic matter in the filtrate will have to be reduced for UV-disinfection to be an effective treatment method. This could possibly be achieved by mechanisms such as adsorptive coagulation or by implementing an intermediate ozonation step after filtration of the TSS, which would also help in the removal of fecal indicators.

Boron-doped diamond (BDD) is an electrode material applied in high end advanced oxidation processes and electrochemical sensing. BDD has a low background current, is robust and has a high affinity for the production of oxidizing radicals. BDD shows better degradation rates compared to competing electrode materials, and can also be used to detect trace amounts of compounds. The surface properties of BDD electrodes, such as the crystal sizes present on the electrode surface and the presence of non diamond content, influence their degradation and sensing performance. Electrochemical advanced oxidation processes using BDD electrodes are one of the methods investigated in literature to remove recalcitrant micro-pollutants from wastewater. Wastewater treatment at present faces a challenge to eliminate micro-pollutants of increasing complexity and toxicity. One of the compounds that could potentially benefit from the application of BDD electrodes in its removal from wastewater and detection in human blood and analogues is nevirapine. Nevirapine (NVP) is an antiretroviral on the World Health Organization’s list of essential medicines, used extensively in HIV treatment. NVP has been detected in wastewater in the continents where it is deployed as treatment, and has shown resistance to ordinary wastewater treatment. The removal of NVP from wastewater and the detection of NVP in human blood are current challenges considered in academic research. NVP has not been used in detection or degradation studies using BDD electrodes before. In this study, two types of electrodes were used to attempt to electrochemically degrade and detect NVP. The application of electrochemical activation in combination with micro-crystalline BDD electrodes for NVP sensing is a promising lead into new research to detect low concentrations of NVP using in-situ electrode cleaning. The results obtained indicate further research into the interaction between NVP and the surface of BDD electrodes as well as electrochemical activation could provide a stable detection method to asses NVP at levels competitive to those reported in literature. The research into degradation of NVP using BDD electrodes indicates the practical challenges the interaction between NVP and BDD surfaces poses, for the removal of NVP from wastewater using electrochemical advanced oxidation processes.

Studying the effects of different land uses on evaporation and stream flow is a hot and frontier topic in global hydrological research. The occurrence and development of flood disasters are restricted and affected by many factors such as meteorology, hydrology, underlying surfaces and human activities. In recent decades, the changes of evaporation and stream flow caused by land use in the river basin have been more and more important. By calculating the long-term average proportion of all land use types in each catchment during the study period, the effects of six main land use types are evaluated one by one, including forest, grassland, pasture land, cropland, shrub land and wetland.
This thesis mainly uses Budyko framework to analyze large-sample catchments with different land uses in the United States. Totally 200 small catchments (<1000 km2) located almost evenly in the continental United States are selected as the research samples. Budyko framework is established with long-term mean precipitation, potential evaporation and actual evaporation from 1981 to 2013. The difference between evaporation index estimated from data and theoretical evaporation index calculated from theoretical Budyko equation is regarded as the best indicator to evaluate the impacts of different land uses qualitatively. Then, the Budyko framework is divided into five bins according to the dryness index and these watersheds are studied in each bin. Besides, the effects of each land use are quantitatively evaluated by making multiple linear regressions. It also discusses two other methods, Fu's equation and Zhang's equation. The best-fit values of parameter w of the main land types are calculated by nonlinear regression. The best-fit w values in this thesis are compared with previous researches to find out some possible reasons causing the differences. 
From the results in this thesis, forest and shrub land coverage evaporate less and lead to more runoff. However, cropland, grassland and pasture land coverage evaporate more and lead to less runoff. It needs to be emphasized that the results show forest land evaporates more than grassland, which is contradictory with what others found. Some physical and hydrometeorological characteristics of the catchments are the possible reasons to explain the results, including mean slopes, precipitation, root systems and so on. Lastly, the evaluation of the impacts of land use in small watersheds on evaporation and stream flow also provides strategic guidance for future land use planning.

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

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

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

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

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.

The wide application of pesticides, pharmaceuticals and personal care products cause an increasing contamination of aquatic systems. Adsorption by zeolites is a promising process to remove target organic micro-pollutants (OMPs) selectively from water bodies. In order to have a sustainable adsorption process, restoring the adsorption capacity of the exhausted zeolites is necessary.
In this research, the gaseous O3 based process was applied to regenerate the column packed with acetaminophen (ACE) loaded zeolite granules. The aim of this study was to investigate the regeneration performance by using the gaseous O3 based process and the feasibility of its long-term operation. An initial concentration 200mgL^-1 of ACE was used for the zeolite granules adsorption process. After 120 hours of loading, the gaseous O3 based process was applied to regenerate the ACE loaded zeolite granules. It was found that an ideal ACE degradation rate of 80 -100% was obtained by drying the zeolite granules before the regeneration. While when the drained bed (without drying process) was applied, the ACE degradation rates were below 35% for both the gaseous O3 and the gaseous O3/H2O2 processes. The water content of zeolite granules was the main limiting factor that affected the regeneration performance. A higher ACE degradation rate was obtained with lower water content. It was also found that adding H2O2 to the process enhanced the ACE degradation rate for the zeolite granules with the same water content. Nevertheless, the highest ACE degradation rate was achieved when the water content was 0% without adding H2O2. Regarding the long-term regeneration, three cycles of regeneration were conducted to investigate the feasibility of long-term regeneration by using the gaseous O3 process in dried bed. The effect of ozone on zeolite surface characteristics and the accumulation of intermediates had minor influences on the adsorption capacity restoration. Compared to the fresh zeolite, owing to the incomplete regeneration of the adsorbed ACE in the inner part of zeolite, the used zeolite granules lost 25% of the adsorption capacity in the long-term operation. Therefore, it is feasible to use gaseous O3 process in dried bed to regenerate ACE-loaded zeolite granules from the long-term operation perspectives.

The presence of organic and inorganic contaminants in aquatic ecosystem has been threat to public health and environment. To produce drinking water, removal of natural organic matter has been of importance due to formation of DBPs. Of the many available treatments, ion exchange (IEX) has the potential to remove natural organic matter (NOM). However, IEX resins need to be regenerated upon saturation with NOM, which generates brine. Usually, NaCl is used to regenerate the resins, hence the desorbed NOM ends in the brine with sodium chloride and other ions like sulphate and nitrate which are present in surface or ground water. The disposal of high saline brine is complex due to aftereffects on the environment and the associated costs. Therefore, an interesting physical alternative is to separate the NOM from brine that can be further reprocessed as fertilisers for agriculture. Ceramic nanofiltration (NF) appears to be an alternative to treat the brine. This type of membrane is chemically and mechanically robust, can be operated at extreme pH conditions, withstands backwashing and chemical cleaning. Besides, ceramic nanofiltration membranes have the capability to separate multivalent ions which makes it suitable to treat the brine. However, NOM possess a complex matrix and relies on various factors for its high removal. In this research, it was interesting to recognize the NOM fractions and the behaviour alleviating NOM retention. Various IEX brines from water treatment plants were studied. For this, NOM was characterised using two different methods i.e., LC-OCD and NSM. The LC-OCD characterization done by Het Waterlaboratorium characterized NOM fraction based on the size of fractions into Humic substances, building blocks, Low molecular weight neutrals and low molecular weight acids. Characterisation of NSM was done by Udine University, Italy wherein the characterization of humics was done on the principle of the selective resin adsorption and precipitation. The characterisation of NOM by LC-OCD predicted the NOM rejection on membrane quite accurately. The effect of ionic strength was investigated to reflect NOM removal. NOM rejection for same NOM source and membrane pore size remained unaffected by the ionic strength of the brine. However, when different membrane pore sizes (600Da and 900Da) for different NOM source, NOM removal by ceramic nanofiltration was governed a combination of steric exclusion, electrostatic repulsion and hydrophobic nature of the humic content and. In longer duration, ceramic NF membranes may foul due to filtration process. To reflect the same, fouling test was conducted. Fouling test was conducted with the high ionic strength brine because during the filtration experiments, it showed highest permeability drop. The sudden drop in permeate flux was due to osmotic pressure difference. However, during NOM filtration period, the flux and permeability were quite steady which suggested no major fouling in that phase. Irreversible fouling did not affect the membrane pore size.

The presence of extracellular DNA (eDNA) containing antibiotic resistance genes in the treated wastewater effluents can contribute to the spread of antimicrobial resistance (AMR) among receiving waters. The removal of cell associated antibiotic resistance genes (ARGs) has been widely studied using advance treatments. However, these treatments were not evaluated for cell free or extracellular ARGs resulting from the cell lysis or secretion during metabolic activities. eDNA is known to well adsorb onto clay, suspended particles and other soil components. Thus, in this research the potential and the main mechanisms involved in the removal of eDNA by adsorption onto sewage-based biochar and iron-oxide-coated sands has been studied.

In the context of steering product formation in anaerobic digestion systems, the present thesis work elaborates on the potential role of elevated CO2 partial pressures as an environmental driver that may influence end-product selectivity from methane towards compounds from the carboxylic platform. As an emerging field of research, organic acid production via mixed culture fermentation is currently in an exploratory phase and the understanding of basic functional principles driving each of the biochemical conversions of interest is of vital importance.The present investigation forms part of a series of studies conjunctively aimed at elucidating the effect of elevated CO2 partial pressures on glucose fermentation, which consists of a complex network of several metabolic routes. Specifically, this thesis work focuses on the effects of CO2 partial pressure on the degradation of two key metabolites that are central and/or highly relevant to the glucose conversion pathways, namely pyruvate and butyrate.

Purple non-sulfur bacteria (PNSB) consist of wide genera of phototrophic bacteria found in various aquatic system. A high versatility in their mode of growth ranging from photoheterotrophic to dark fermentation gives them various potential applications. Their nature of being phototrophs require them to obtain light as energy source for growth and for that they require photopigments essential for light to ATP conversion. In contrast to pure culture of PNSB, the effect of different illumination on mixed culture PNSB is partly revealed. The response of altering light intensity on mixed culture of PNSB and the change of photopigments were to be answered in this study. Mixed culture of PNSB were grown in a sequencing batch reactor (SBR) operation of 8 h cycle. Four different light intensity settings were used to identify the effect of light on their growth and nutrient removal rate. Light distribution model was constructed to simulate the growth and nutrient removal of pure culture Rhodopseudomonas palustris in order to compare with mixed culture PNSB results. To track the growth and nutrient removal trend, biomass and nutrients (acetate, ammonium, and phosphate) concentrations at different points during reaction phase were measured. Bacteriochlorphyll content as major photopigment was analyzed with two different methods; micro well plate reader and reverse phased HPLC. It was shown that both growth rate and nutrient removal rate were significantly diminished as light intensity decreased. The decrease of growth rate with decreasing light intensity indicated that with the given conditions, light intensity was the growth rate-limiting
factor for the mixed culture PNSB studied. In comparison to simulation results, it was shown that the mixed culture PNSB was showing faster growth and higher removal rate. Bacteriochlorophyll content in the micro plate reader showed an increase to 75% intensity condition and then a decrease to 25% intensity conditions. Bacteriochlrophyll content analyzed by the two different methods showed relatively high deviation between each other as large error in both analyzing methods were present. The effect of changing light intensity on mixed culture PNSB with respect to its growth, nutrient removal and pigment content was studied. Further investigation on both higher and lower light intensity to identify the photo-inhibition level and saturation level is necessary. For a better approximation of the simulation to experimental data,
further works on precise measurement of light distribution in the photobioreactor is required. Photo-pigment analysis methods should be either replaced by a spectrophotometer using standardized cuvettes to minimize measurement error or be optimized to obtain reliable data.

Ammonia in aqueous environments leads to eutrophication and toxicity of the receiving water body (Metcalf & Eddy, 2003). In order to prevent environmental pollution, ammonia needs to be removed from residual water streams, before the water can be discharged to the aqueous environment (Song et al., 2012). Waste water treatment plants (WWTPs) reduce the ammonia-nitrogen concentration by applying biological treatment technologies. However, the oxidation of ammonia by bacteria requires high amounts of oxygen and consequently has a high energy consumption. The nitrification and denitrification of wastewater requires 15.83 kWh per kg-N (Magrí et al., 2013). Moreover, the reject water from the digested sludge contains high amounts of nitrogen, which is fed back to the biological treatment, and can contribute 15-20% of the nitrogen load (Fux et al., 2002). Concentrating ammonium fluxes lead to the production of a concentrated ammonium stream, used as potential energy source in the N2kWh project, and a sweet stream.

In a WWTP operating with full scale mesophilic digestion, a thermophilic digestion pilot and a digestate ammonia stripping pilot were installed. Benefits of the aforementioned sludge treatment processes, such as energy and nutrient recovery, are extensively recognized. However, drawbacks, such as deficient sludge dewatering, are amply disregarded despite their substantial influence on the treatment scheme and treatment cost. Consequently, the installations research resolved to determining the causality of the unsatisfactory dewaterability. The digester feed, mesophilic digestate, thermophilic digestate and ammonia stripped thermophilic digestate were compared. Harsher sludge treatments led to a severe deterioration in dewaterability. An increase in presence of colloids resulted in a worsening of dewaterability, to an extent originating from size and surface charge of colloids; unlike variations in presence and size of supracolloids, which were inconsequential. Moreover, inferior dewaterability was strongly associated with the increased concentrations of carbohydrates, proteins and humics in the bulk and loosely bound phases, and with the decreased presence of proteins in the tightly bound phase. Furthermore, the decreased calcium and increased iron presences in the bulk and tightly bound phases were correlated to a degradation in dewaterability; whilst sodium, potassium, ammonium and magnesium in all phases were found of no or insignificant influence. Recognizing the dewatering determinant factors enables the search for digestate specific conditioning and dewatering methods.