Microplastic (MP, < 5 mm) and nanoplastic (NP, < 1 µm) pollution has become a growing environmental concern, as they are detected everywhere, including in surface waters used for drinking water (DW) production. Recently, NPs have been detected in finished DW, indicating incomplete removal by DW treatment plants (DWTPs). Coagulation-flocculation-sedimentation (CFS) is a promising treatment technique, but current research lacks connection to practice and/or mostly focuses on MPs. This thesis investigates the influence of coagulant type, dose, and NP size on NP removal during CFS. The research connects to practice by using coagulants and doses used in the Dutch DWTPs.

A survey with four Dutch DW companies provided insight into the CFS procedures. Jar tests simulated CFS in the lab, using ferric chloride (FeCl₃), aluminium chloride (AlCl₃) and polyaluminium chloride (PAC) to assess the impact of coagulant types. Theoretical optimum doses were compared to practical doses (obtained from survey) to determine the influence of the coagulant dose. Lastly, the effect of NP sizes on CFS removal efficiencies was studied using 200, 500, and 1000 nm NPs. All experiments were done with NPs spiked in tap water. CFS efficiency was evaluated through turbidity, pH, alkalinity, UV-VIS, residual coagulant and ζ-potential measurements.

PAC was identified as the most efficient coagulant considering all evaluated parameters. Theoretical doses, which were higher than practical doses for FeCl₃ and AlCl₃, achieved more effective NP removal than practical doses. Charge neutralisation was confirmed as the main mechanism for NP removal. Lastly, although particle size is generally thought to affect NP removal, this study’s results did not allow for confirmation or refutation of this statement. Overall, this research highlights that the type of coagulant and dose can influence NP removal in DWTPs. These findings can be a first step to help DWTPs optimise CFS for more NP removal.

Slow sand filters (SSFs) are essential for ensuring microbial quality and biological stability of drinking water in the Netherlands. However, gaps exist in understanding of removal processes of dissolved organic carbon (DOC) and ammonium and the effects of grain size, loading rate, and backwashing on removal in SSFs.
Four lab-scale SSF columns filled with fine (0.4-0.6 mm) and coarse (0.85-1.25 mm) sand were constructed and operated in two phases with a total of 165 days. In phase I, SSFs operated at a flow rate of 0.5 m/h to investigate the influence of grain size. After stabilization, higher loading rate of 2 m/h and backwashing procedure (20% expansion for 5 min) was applied during the phase II experiment. Various physicochemical and biological parameters, including DOC, ammnoium, phosphate, and ATP were analyzed in water along the filter depth. Additionally, biomass development on sand was quantified suing ATP measurement.
Results showed the stable SSF operation after 90-100 days, removing 100% of dosed 1.5 mg/L of DOC and 1.0 mg/L of ammonium. Compared with fine sand, coarse sand had similar removal performance but better backwashing effectiveness and lower clogging risk. Increased loading rate led to faster microbial growth, reducing operational lifespan, and poor removal performance. Backwashing showed minimal impact on DOC and ammonium removal capacity and microbial activity, which were recovered after backwashing within 7-14 days, indicating the potential for backwashing to prolong SSF’s operational lifespan.
This research investigated the DOC and ammnoium removal processes and the influence of grain size, loading rate, and backwashing on filter performance. Providing insights for optimized SSF design and operation. Future studies could delve into mechanisms using isotope analysis or metagenomics, along with more comprehensive sand sample analysis.

There is a rising concern on the sustainability of Zero Liquid Discharge (ZLD) desalination. In this study, Multi-criteria Decision-making (MCDM) is applied to compare the sustainability performance of various ZLD scenarios, which is part of a Strong Sustainability (SS) assessment of desalination. ZLD desalination systems are considered to be complex and have intricate interdependence among various factors, which were seldom recognized in previous research. The purpose of this study is to explore the impact of interdependence among criteria on the MCDM process, with a desalination case study from Water Mining project used for demonstration. A transparent MCDM methodology is proposed in this study, which consists of Best Worst Method – Decision Making Trial and Evaluation Laboratory (BWM-DEMATEL), hierarchical clustering, and Preference Ranking Organization Method for Enrichment Evaluations (PROMETHEE).
In the desalination case study, the use of hierarchical clustering allows for the identification and preservation of both majority and minority opinions, based on which, the same ranking of desalination scenarios is produced through PROMETHEE. Concerning the interdependence among criteria, the results reveal that it can help identify the crucial factors for improvement of sustainability performance of the alternatives. In addition, by considering it, the understanding of criteria is enhanced, which leads to more concentrated opinions of stakeholders in the desalination case. However, the findings indicate that the influence of incorporating the criteria independency on the final decisions is restricted in cases insensitive to weight variation.
The application of BWM-DEMATEL method is a complex and time-consuming activity. Considering the effectiveness and the cost of implementation, BWM-DEMATEL might be not as worthy of application in this case study. Inspired by this, it is meaningful to develop an approach to estimate the impact of the interdependence among criteria on the alternatives ranking in a certain decision problem in the future.

UV disinfection is an efficient way to inactivate chlorine resistant protozoan pathogens such as Cryptosporidium parvum and Giardia muris. In the United States, regulatory UV disinfection credit is typically granted when turbidity is <1 NTU. However, studies show turbidity does not correlate well with UV dose responses and partial inactivation when turbidity is > 1 NTU should be considered to avoid certain violations while still protecting public health. The objective of this study was to examine the impact of worst-case scenarios at drinking water treatment plants on UV disinfection. Indigenous spores from unfiltered source water and samples taken during the flocculation and softening steps at the Dublin Road Water Treatment Plant in Columbus, Ohio were exposed to Low-Pressure mercury UV254 disinfection from July 2019 to January 2020. Raw source water and softened water had similar dose responses despite significantly different water quality parameters. Flocculated water had the worst dose response: significantly lower maximum inactivation rate and higher residual population density than the other two water types despite having a lower turbidity than softened water. The modeled Geeraerd-tail maximum inactivation rates (k¬max) were 0.027, 0.021, and 0.030 cm²/mJ for raw source, flocculated, and softened water, respectively. The modeled Geeraerd-tail residual population density values (N¬res) were 1.168, 7.081, and 0.216 SFU/mL for raw source, flocculated, and softened water, respectively. Relationships between water quality parameters and modeled UV inactivation parameters were analyzed to determine and compare other potential indicators for UV disinfection to turbidity. Particle size and particle properties that govern the degree of particle-associated microorganisms best explained the differences in dose response between flocculated water and the other two water types. Larger particles are worse for UV disinfection. Microorganisms associated with particles are harder to disinfect with UV and lead to tailing. Climate change impacts on types, consistency, quantity, and quality of source waters for drinking water treatment make it especially important to understand UV disinfection kinetics under challenging scenarios. Informing regulatory changes to properly account for disinfection when turbidity is > 1 NTU could be especially useful for small or aged utilities that may not be as equipped to handle highly variable water qualities.

Throughout sub-Saharan Africa, agricultural activities in urban and peri-urban areas are threatened by urban sprawl. These activities are important not just for the livelihoods of those who take part in it, but also for the food security of the city. Historically, in Kumasi 40% of the crops in the city are sourced from urban and peri-urban agriculture. However, Kumasi is also a city that is growing rapidly both in population and in area: since the 1980’s population has more than quadrupled and the area has increased more than tenfold. Because of this, there is a need to find ways to maintain urban and peri-urban agriculture under the threat of urban sprawl and the climate change in the future and also work well in the Kumasi context.
We used the agro-hydrological model AquaCrop informed by 4.5 years of local weather data, soil data and crop data to model the effectiveness of adaptations in maintaining food security for three neighbourhoods in Kumasi. Local farmer management practices that were determined by a survey of 150 Kumasi farmers made a distinction in management practices between adaptations and crops. This model gave yields and irrigation water uses for five crop groups that are commonly cited as crucial for food security. Combined with population growth predictions and land use and land cover analysis this allowed us to make a statement about how well adaptations can meet current and future demand of crops and how much space is needed to meet demand. This model was supplemented with a survey of vendors and farmers to investigate barriers against- and preferences for adaptations.
Backyard gardening and sack gardening turned out to be the best options to maintain peri-urban agriculture. These adaptations use the least space, for the highest yields. From the survey of farmers and vendors, no strong objections were found against the implementation of these adaptations. Over 80% of surveyed farmers and vendors felt that backyard gardening was a good adaptation to maintain peri-urban agriculture in Kumasi. Backyard gardening and sack gardening are optimally suited for growing vegetables and legumes, which are the easily perishable crops and thus benefit from a short supply line, which many vendors cite as solutions for spoilage.
It is possible to ensure self-sufficiency for these crops with 5-9% of total land in the Feyiase neighbourhood, 11-20% in Ejisu and with 14-22% in the Kwadaso neighbourhood. It is therefore recommended to target at least a majority self sufficiency, by reserving a >50% fraction of this land for backyards and sack gardening spaces. At the same time, any available marginal lands should be allocated for the growth of cereals and tubers, to allow for the production of these subsistence crops, until the production of the remaining demand is fully met by rural import. With these adaptations and recommendations, it is possible for peri-urban agriculture in Kumasi to maintain its important role throughout the coming decades.
In order to determine if there are any deviations from these conclusions, future research should focus on including empirical crop data tailored to AquaCrop or use a model that is better suited to represent the chaotic nature of (peri-) urban agriculture. While the model results do not differ significantly from the crop yields as found in literature, a model informed by local crop data can be an even better representation of the situation in Kumasi. Furthermore, a study into the long-term effects of adaptation on nutrition can reinforce our conclusions on food security.
Finally, there is an opportunity to develop more high-tech agricultural methods like greenhouses and aquaponics. There is also an opportunity to incorporate wastewater reuse schemes, following examples from other countries, such a urine reuse, or low-tech treatment with sludge harvest. For this, it is recommended to set up educational programs and pilots.

This study explores the potential use of extracellular polymeric substances (EPS), commercially known as Kaumera Nereda Gum®, extracted from aerobic granular sludge (AGS), for foliar fertilization in agriculture. Koppert, a company specializing in sustainable agricultural products, is interested in using Kaumera Nereda Gum® for its biostimulating effects, water-absorbing capacity, biofilm formation, and adhesive properties. They are currently spraying leaves with a solution mixed with Kaumera Nereda Gum®, water, and other fertilizers.

Nonetheless, the utility of using Kaumera Nereda Gum® for foliar fertilization can be affected by several factors, such as seawater intrusion in AGS projects like Faro-Olhão in Portugal and the type of acid utilized for the precipitation of the polymer. In certain places like Utrecht, hydrochloric acid is used, whereas in Faro, sulfuric acid is employed. The latter acid is more favorable when considering agricultural applications.

Thus, the chemical composition of Kaumera samples from Faro and Utrecht was compared, and their suitability for foliar fertilization assessed. Parameters such as total solids, volatile solids, carbohydrate content, and protein content were quantified, and FTIR-ATR analysis was conducted to gain a better understanding of each polymer. Conductivity and pH levels were also measured and compared to expert recommendations against the ideal values for foliar fertilization. Additionally, nutrient levels were quantified and compared to regulatory guidelines and nutritional recommendations. An adhesion protocol was also designed to compare the adhesive properties between Kaumera Utrecht, Kaumera Faro, and Kaumera Zutphen (established benchmark).

Results indicated that Kaumera Faro has 0.114 ± 0.005 grams of carbohydrate per gram VS, whereas Kaumera Utrecht has 0.168 ± 0.002 grams of carbohydrate per gram VS (47% more). On the other hand, Kaumera Utrecht has 0.323 ± 0.009 grams of protein per gram VS, while Kaumera Faro has 0.456 ± 0.004 grams of protein per gram VS (41% more). High carbohydrate content could be positively correlated with strong adhesion properties, whereas a high protein content might demonstrate enhanced biostimulating effects. In addition, the pH and salinity adjustments required for applying the Kaumera solution to leaves are determined by its mixing ratios. When preparing the solution, it is essential to consider the low pH of Kaumera Nereda Gum® and evaluate whether washing the polymer to reduce salinity is necessary. Heavy metal concentrations in samples of Kaumera Utrecht and Kaumera Faro remained within permissible limits according to regulatory thresholds when considering the applied dosage of 35 liters per hectare per year (as suggested by Koppert). However, with such dosage, nutrient levels in the Kaumera samples were lower than recommended, confirming that additional fertilizers are to be mixed with Kaumera Nereda Gum®. Furthermore, the adhesion protocol proved to be a valuable screening tool, showing that Kaumera Utrecht has superior adhesive properties compared to the benchmark. In summary, this study confirms that Kaumera Utrecht and Kaumera Faro exhibit advantageous properties in foliar fertilization, but their effective use requires pH adjustment, salinity reduction, and nutrient supplementation.

Regulations and investments in new technologies for biofuel production as an alternative to fossil fuels have boosted in the last years due to concerns about climate change and anthropogenic CO2 emissions. A valuable supply chain of biomass for biofuel production is one the most significant factors, in order to support the market’s demand. A promising feedstock that is widely available and considered a residue can be Namibia’s encroacher bush (EB). Namibia is facing an environmental crisis with bush encroachment, where EB takes over grasslands, reducing biodiversity and groundwater availability. A thermochemical process that can take advantage of EB can be Hydrothermal Liquefaction (HTL). With HTL, biomass feedstocks are liquefied under hot compressed water, producing bio-oil (BO), biochar (BC), an aqueous phase (AP) and gases. Catalytic HTL is a more attractive pathway, due to the increased BO yield and quality. To this day, there has not been a study investigating the potential of catalytic HTL with EB, thus the present MSc Thesis will attempt to close that knowledge gap and provide state-of-theart insight.

To achieve that, Acacia Mellifera from Namibia was tested in sub-critical HTL conditions. In particular two campaigns were formulated with two different goals. The first one, focused on the selection of a suitable catalyst among 4 different categories of catalysts (zeolites, alkaline earth metals, lanthanides and transition metals). The catalysts performance was evaluated by comparing
the Energy Recovery (ER) under same operational conditions. Then, the catalyst with the highest ER was used in the second experimental campaign using a Desing of Experiments approach. This approach had the goal to optimize HTL reaction conditions -temperature, residence time and catalyst loading- for maximizing BO yield and energy content. Central Composite Design (CCD) of experiments was used, with the parameters ranges being 250-340oC, 5-60mins and 0-10wt%, respectively. Selected BO and BC samples from both campaigns were then characterized using various methods.

The HTL experiments with EB revealed that BO from EB could be produced. The highest ER obtained from the catalyst screening campaign was 41.1% . Main organic compounds found in all the BOs were phenolic derivatives, alicyclic ketones and fatty carboxylic acids. Using the best performing catalyst based one ER, the CCD model indicated that the optimum conditions for maximizing BO yield were 340oC, 60 minutes and 5wt%, which yielded 27.0wt% BO. However, the 330oC - 60 minutes - 7.5wt% point gave both the highest yield and highest ER, 28.5wt% and 46.2% respectively. The CCD also reduced the O content in the BO samples by 54%. Finally, BC samples showed fuel characteristics similar to lignite and low concentration of heavy metals, making them legitimate alternatives for solid fuels or soil amendment.

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.

Bromate is a possible human carcinogen that does not naturally exist in surface or groundwater bodies. Its formation mostly results from ozonating bromide-containing water during wastewater treatment or drinking water production. Bromate is difficult to remove from water due to its high solubility and low reactivity in the aqueous environment; however, some bacteria showed the ability to reduce bromate to bromide, but the mechanism is unknown. Previous studies postulated a cometabolic pathway of biological bromate reduction, a side reaction of denitrification using the same enzymes. This study investigates the biological bromate reduction mechanism with a focus on its relationship with the denitrification process.

Wastewater and biologically active granular activated carbon (BAC) from a methanolsupplemented pilot filter called O3 -STEP in the wastewater treatment plant (WWTP) Horstermeer, the Netherlands, were used for research. This study first measured the crucial water quality parameters at eight different heights in the filter to investigate the redox condition’s influence on biological bromate removal. After that, batch experiments were conducted to validate the findings. The filter showed the ability to remove bromate as it lowered the bromate concentration from 2.7 to 0.9 µg/L. Bromate reduction happened at all depths including the supernatant, although the redox conditions significantly changed. Decreasing nitrate and dissolved oxygen (DO) concentrations did not change the bromate reduction rate in the filter. The batch experiments confirmed that nitrate did not affect bromate reduction. However, a DO concentration of 8 mg/L led to a 50% reduced bromate reduction rate compared to anoxic conditions. Experiments with varying chemical oxygen demand (COD, in the form of methanol) concentrations showed an extensive accelerating effect on bromate reduction. This explained why the bromate reduction rate was not lower at high DO levels in the filter, as the high COD concentration promoted bromate reduction. Nitrate reduction was found to have a high positive correlation with bromate reduction in both filter and batch experiments, indicating similarities in their mechanisms. Nitrate reduction happened under highly oxic conditions. The intensive mixing of the granules in the filter may have provided alternating aeration and anoxic conditions for the enrichment of aerobic denitrifiers.

This study is the first study to observe simultaneous nitrate and bromate reduction under oxic conditions. Taken together, biological bromate reduction is likely to be a synergetic cometabolic process of aerobic denitrification. The robustness of the biological bromate reduction under high DO and nitrate conditions enables the O3 -STEP ® filter to steadily produce bromate-free effluents under more extreme influent conditions.

One-third of the global population relies on non-sewered sanitation. In urban areas of low-and-middle income countries, treatment of faecal sludge is often insufficient. On-site sanitation technologies can provide sustainable and more affordable sanitation solutions for urban areas, but only if functioning faecal sludge management is in place. As a first step for treatment, faecal sludge is dewatered, resulting in a solid stream and liquid stream. There are many existing technologies to treat the solid fraction. However, treatment technologies for the liquid are often insufficient and land-intensive. This liquid after dewatering of faecal sludge is called ‘supernatant’. The reason why treatment of this supernatant is difficult, is because the composition is prone to variability.

In conventional sewer-based wastewater treatment, attached growth processes have proven to be robust to influent variability. Those technologies do not take a lot of space, which is an advantage in urban areas. Attached growth processes are aerobic treatment processes in which the biomass responsible for treatment is attached to some type of medium. This research is a proof of concept whether an attached growth system, in this case an MBBR process, could be an alternative for existing supernatant treatment technologies in non-sewered sanitation. A 5000 people urban community-scale scenario is considered, covering variability in influent composition and intermittency in faecal sludge supply.

To prove this concept, there is looked whether COD and N removals can be achieved to certain discharge standards.
First there is assessed whether the MBBR is able to run on one type of supernatant. After this, the variability in influent composition regarding COD/N ratio, salt ratio, and pH is tested by spiking the baseline supernatant. Intermittency in influent supply to the reactor is also tested. After these separate experiments, a realistic scenario is tested with supernatants from different types of sources, and intermittent supply over the weekend.

As a conclusion, the concept of using an MBBR for treatment of supernatant after dewatering of faecal sludge is proven for a community-scale scenario of 5000 people, and further research has to determine new outcomes like the possibility of pathogen reduction and phosphorous removal. After this, field tests need to determine the actual feasibility full-scale in non-sewered sanitation setting.

With increasing pressure on natural water resources, wastewater is gradually being considered as a potential source for potable water. Current WWTPs are designed for the removal of parameters like solids, nutrients, organic matter, and pathogens. For achieving a high-quality effluent, that enables reuse, it is important to also address the removal of micropollutants, particularly antibiotics, from the wastewater. Due to these antibiotics, antibiotic resistance spreads among the microorganisms and increases through various mechanisms. Antibiotics of sulfamethoxazole (SMX), trimethoprim (TMP), ciprofloxacin (CIP), and ampicillin (AMP) are known to be found abundantly in natural waters all across the globe. The abilities of an anaerobic membrane bioreactor (AnMBR) of maintaining high SRTs with low biomass losses help in treating wastewater containing antibiotics. A recently developed technique of adding limited aeration to AnMBR has the potential of removing recalcitrant antibiotics by improving the performance of the reactor. Hence, this research aims to study the removal mechanisms of the antibiotics (SMX, TMP) and the persistence of corresponding antibiotic resistance in AnMBR, followed by the effect of the antibiotics on the performance of the AnMBR. In addition, antibiotics CIP and AMP were tested via anaerobic batch tests to investigate the effect of the limited aeration on their removal.
After adding the antibiotics SMX and TMP to the reactor, no significant difference in COD and nutrients removal was observed. The biogas production was reduced slightly after the addition of SMX 150 µg/L initially, however, it increased back to the original state after few days. Total removal of SMX and TMP was 86% and 97% respectively in the reactor. Results showed that 85% of SMX and 94% of TMP were removed through biodegradation/biotransformation and 14% of SMX and only 3% of TMP were discharged through the effluent. From the adsorption batch tests conducted, it was observed that the linear adsorption isotherm fits well for TMP. With the increase in temperature, the adsorption potential of TMP was reduced with a Kd value of 1.234 L/g at 10˚C and 0.513 L/g at 37˚C. The removal of SMX was low through adsorption and high due to degradation and follows the first-order rate kinetics with a half-life of 1.71 days. After two weeks of SMX addition to the reactor, almost all the bacteria present in the effluent gained resistance either to TMP or SMX or both. Of all the ARGs measured in this study, the genes responsible for the resistance development were sul1 and sul2. The addition of antibiotics increased the presence of ARGs in the system. The correlation between the presence of sul1 and TMP resistant bacteria, and sul1 and SMX resistant bacteria was 0.91-0.93, indicating that the gene sul1 might be involved in multidrug resistance. ARGs sul1, sul2, and dfrA1 were removed respectively by 3.2 log, 3.6 log, and 7.3 log units by the membrane. In addition, the class 1 integrons and 16s rRNA were removed by 3 log and 3.2 log units respectively. Removal of CIP and AMP was found to be high with values of 82% and 84% respectively in limited aeration assisted anaerobic batch tests. The removal efficiencies of all antibiotics were more than 80% and independent of their initial concentrations in the selected range. The increase in the removal of CIP and AMP in comparison to literature points to a relation with the added limited aeration. Nevertheless, more studies need to be performed to establish this.

In an aerobic granular sludge (AGS) reactor treating urban wastewater, nutrient removal depends on the availability of carbon source. Domestic wastewater consists of 40-60% of slowly biodegradable complex substrates, out of which proteins form a major fraction. Despite this, little is known about the mechanisms of protein degradation in AGS. This research assessed the anaerobic availability of protein substrates for enhanced biological phosphorous removal (EBPR) in an aerobic granular sludge reactor. Proteins have to be first hydrolyzed before being assimilated by the bacteria, and nutrient removal is often limited by the rate of hydrolysis. Therefore, a major part of this thesis attempted to look into the mechanisms of proteolysis in AGS. Next, the utilization of amino acids - the hydrolysis product of proteins - by PAO was explored, based on critical evaluation of available literature. Firstly, it is proposed that the important aspect likely to govern the hydrolysis of proteins in AGS is the substrate-granule interaction, taking into account the diffusion limitation of particulate substrates within the granules and the probable presence of hydrolytic enzymes on the granular surface. Further, it is seen that the amino acids may be utilized by the polyphosphate accumulating organisms (PAOs) either directly or after the anaerobic degradation of amino acids to simple VFAs (volatile fatty acids), which are then taken up by the PAOs. The anaerobic degradation or fermentation of amino acids may occur via two well-known pathways- Stickland pathway and the non-Stickland pathway. Non-Stickland reaction requires syntrophy with hydrogen consuming bacteria whose presence in AGS is questionable. The bacteria responsible for Stickland reaction are obligate anaerobes belonging to the genus Clostridium which has not been found in aerobic granular sludge. Thus, it seems more likely that the amino acids are directly taken up by the PAOs in an AGS reactor. However, the direct uptake of amino acids by the PAOs has been reported only for eleven amino acids in total. More research on the likely fate of the remaining amino acids is recommended, considering that very little is known about the fate of amino acids in AGS. Few laboratory experiments were also conducted to study the effect of substrate size and granule size on the rate of hydrolysis of proteins. From preliminary experiments, it was seen that aerobic granular sludge exhibited significant anaerobic phosphate-release activity when casein (protein) was the only available carbon source. In the lab experiment carried out with different sizes of protein substrates, the observed anaerobic phosphate-release activity was used to obtain the rate of hydrolysis of different sizes of casein. Based on the hydrolysis rate obtained, it is seen that in an AGS reactor with a typical sludge concentration of 8g/l, up to 90% of the proteins present in domestic wastewater influent could be potentially taken up by the PAOs, provided that the proteins are completely dissolved. It was also seen that 60-80% of the particulate casein COD (>0.45um) was hydrolyzed within 24 hours of the assay. In another lab experiment, fluorescent protease assay was performed to assess the effect of granule size on the rate of hydrolysis. A significant decrease (by at least 2 times) in the specific rate of protein hydrolysis was observed when the aerobic granule size was increased from 1-2mm to 3.15-4mm. This may be significant especially when the stratification of granules and plug-flow feeding in an AGS reactor is taken into account. Further research is recommended to analyze the relative effect of substrate size and granule size on the rate of hydrolysis of proteins in AGS.

Sludge management has gained importance over the years due to high sludge treatment and disposal cost, stringent disposal laws, and a need to move towards sustainable energy production. Anaerobic Digestion (AD) of waste activated sludge (WAS) is a favoured sludge stabilisation technique due to its low energy footprint. Hydrolysis – the first step in AD is often the rate-limiting step and thus pre-treatment such as Thermal Hydrolysis Process (THP) are implemented before AD to improve the biodegradability of WAS and biogas production. However, THP leads to the formation of recalcitrant compounds such as melanoidins which are presumed to have a similar effect as Humic substances on AD. Also, THP leads to the release of metals incorporated in sludge flocs by the degradation of extracellular polymeric substances (EPS) structures. Therefore, this study aimed to understand the effect of melanoidins and metals on the hydrolysis step in AD.
The interaction between melanoidins and cations Fe²⁺, Ca²⁺, Mg²⁺, Cu²⁺, K⁺, and NH₄⁺ was studied using ultra-filtration and ICP-MS. The effect of these melanoidins-metals interactions on enzymatic hydrolysis of cellulose and proteins was investigated using fluorescence essay and Response Surface Methodology (RSM) modeling. The mechanism of inhibition of hydrolysis by melanoidins and metal was investigated using SEC-HPLC.
The results showed that complexation of melanoidins with metals shows the trend - Fe²⁺ > Ca²⁺ > Mg²⁺ > Cu²⁺ > K⁺ ≥ NH₄⁺. The ions with higher charge and ionic radius interacted with melanoidins more effectively. The melanoidins-metal interaction increased with an increase in melanoidins concentration most likely due to more phenolic and carboxylic functional groups available for binding. Fe³⁺ leads to an increase in molecular weight (MW) of melanoidins due to inter-molecular interaction caused by complete charge neutralisation, while no MW changes are observed with Cu²⁺ and Ca²⁺. Individually, melanoidins decreased, Fe³⁺ increased, while Cu²⁺ decreased the rate of hydrolysis of cellulose. In the presence of melanoidins, the inhibiting effect of Cu²⁺ is decreased with increasing melanoidins concentration. Similarly, the positive effect of Fe³⁺ is decreased with increasing melanoidins concentration. Protein hydrolysis was completely inhibited with 3 mM metals concentration. Melanoidins and Fe³⁺ concentrations had no major impact on protein hydrolysis while Cu²⁺ inhibits hydrolysis even at 0.15 mM concentration.
Therefore, it was hypothesised that Cu²⁺ causes enzymatic inhibition, but in the presence of melanoidins, melanoidins-Cu²⁺ complexes formation mitigates the toxic effect of Cu²⁺ on hydrolysis thus improving the rate of hydrolysis. While, Fe³⁺ improved hydrolysis by facilitating substrate-enzyme interaction but in presence of melanoidins, melanoidins-Fe³⁺ complexation leads to the non-availability of Fe³⁺ to facilitate hydrolysis process thus having no major impact on the rate of hydrolysis.

The scarcity of water is a major global concern in the modern times. Hence, the judicial use of water must be coupled with water reuse to counteract the water depletion. To reuse water, we eye on available treatment technologies which can guide us to circular use and reuse of water and nutrients. Anaerobic digestion, is known for producing better quality effluent with a possibility of energy generation through biogas. It can also be coupled with post-treatment techniques to extract nutrients. Anaerobic membrane bioreactors have been used to treat high-strength wastewater to obtain higher particle and organic removal. Introducing limited aeration to such an anaerobic environments have been studied earlier to enhance the degradation process. Depending on the quantity of aeration added and the mechanism of aeration, studies have reported both positive and negative effects on the organic degradation. The existing studies only cover the effects of the applied aeration on the Anaerobic Digestion process. Little is talked about its effect on the sludge characteristics such as particle size and sludge rheology. This research focuses on studying the effect of applied aeration on the AnMBR performance, based on the effect of aeration on substrate degradation and on sludge characteristics. To study this, an AnMBR is operated with laboratory-made synthetic blackwater treating 5gCOD/l. A 2% increase in oxygen with respect to the sludge VSS is introduced through added air. The effect of this added aeration to the system is studied. The organic removal was enhanced by 11% when compared to the observed removal during the non-aerated phase. Ammonium concentration increased by 24% and sulphate concentration reduced by 12% in the effluent. The size of the coarser fraction of sludge, D90 increased by 13% and that of the finer fraction D10 increased by 15%. The viscosity profile of the sludge after aeration also increased. Inhibition caused to the Methanogenic activity of the sludge reduced as the sludge started adapting to the applied aeration. Activity changes to higher sets of aeration matching that of a Dissolved Aeration and Flotation system was studied. The feasibility of such a system is still a work in progress for the future. The obtained results are for an adapting sludge, and has to be continued for a better adapted sludge. Recommendations based on this study to future works on the same line, is given.

To cope up with the rapid industrialization, urbanization and population it is very important to make use of sustainable water treatment technologies to reuse the processed water. Now a days, with technological advancements in anaerobic digestion (AD) process it is possible to recover some of the resources. AD can be coupled with the membrane to provide the complete biomass retention ensuring the growth of slow growing bacteria. Considering these aspects an innovative configuration of Anaerobic Membrane Bioreactor (AnMBR) with limited aeration is developed aiming to improve the reactor performance. This AnMBR is tested, comparing its performance before and after aeration to assess the impact of subjected aeration especially on the activity of methanogens monitoring the biogas production and its composition. Results show that limited aeration helped in achieving significantly lower overall COD removal without adversely affecting the biogas production as well as composition. It also improved the biodegradability of less biodegradable ovalbumin (protein).Furthermore, limited aeration might improve the biotransformation of some of the recalcitrant micropollutants (MPs) possibly by activating mono-oxygenase enzymes of micro-organisms. They might convert the aromatic hydrocarbons into less recalcitrant phenolic intermediates, whose degradation process could occur anaerobically. From the group of available MPs, diclofenac (DCF), metoprolol (MPT), sulphamethoxazole (SMX), trimethorprim (TMP) are selected based on different characteristics. All the selected MPs are analysed for their removal through biodegradation and adsorption under anaerobic conditions. MPs are tested from liquid phase in dissolved form through liquid chromatography coupled with mass spectroscopy (LC-MS) technique while MPs sorbed onto the sludge surface are not analysed because of complex extraction process.Results shows that SMX and TMP are removed more than 99% through AD while DCF is removed with removal efficiency of more than 90%. Adsorption is found to be a major contributor for the removal of DCF, MPT and TMP while SMX is mainly removed through biodegradation. DCF and TMP are adsorbed well (>90%) compared to SMX and MPT (around 30%) onto the sludge contributing to overall removal. Octanol water coefficient (Kow) which defines the hydrophobicity of compound, is the key parameter deciding the extent of adsorption. Additionally, sludge retention time (SRT) and compound structure play major role in deciding the fate of MPs through biodegradation. Different aerations had not shown any significant impact on the removal of DCF, SMX and TMP. While in case of metoprolol effect of aeration was not completely understood. Considering the overall removal, DCF was found to be bio-degraded more with increased concentration. Granular activated carbon (GAC) used for adsorption removed all the four MPs with more than 90% efficiency. Further studies can be conducted on possibilities of adding GAC to the reactor so that they get adsorbed and later on degraded.

Pre-fermentation of influent has been proposed as a method to improve phosphorus removal capacity, granulation, and simultaneous nitrification denitrification for aerobic granular sludge plants. This thesis sought to determine the influence of increasing VFA concentrations on performance of aerobic granular sludge plants and key considerations for implementation of pre-fermentation. Two approaches were applied during this thesis: a modelling approach and an experimental approach. A mathematical model was built to show the influence of increasing VFA concentrations and to describe principles observed in practice at aerobic granular sludge plants. The experimental approach consisted of two measuring campaigns. First, experiments were performed to test the necessary operational conditions to ferment influent in a sequencing batch reactor fermenter. Second, a sampling campaign was conducted to determine the conditions which led to fermentation of organic matter in a sand trap on site in Utrecht. The model demonstrated the benefit of combining existing models to describe settling of aerobic granular sludge with size fractionations, plug flow feeding in a settled sludge bed, reactions in the bulk and in granules, and diffusion across granules and into bulk liquid. It was found that increasing acetate concentrations led to longer stability of phosphorus uptake capacity and that SRT control is necessary to maintain long term capacity. Increasing acetate concentrations also led to increases in phosphate release and simultaneous nitrification denitrification. These changes were attributable to differences observed across granules of different sizes: phosphate accumulating organisms dominated larger granules and nitrifiers were more dominant in smaller granules. Model calculations indicate that a maximum granule size exists because the most poly-phosphate storage was not performed by the largest granules. From the experimental work, fermentation was found to be occurring (at rates of 21 mg VFA-COD/L/h ± 15) in a hydraulically underloaded sand trap which led to significant VFA production and subsequent difficulties in fermenting in the controlled SBR reactor (which produced an average of 28 mg VFA-COD/l). More research is needed to determine the optimal operational conditions to ferment influent and to demonstrate the effect on aerobic granular sludge in practice.

Galdieria sulphuraria (G. sulphuraria ) is a eukaryotic, extremophilic, spherical and unicellular species of red algae. G. sulphuraria can grow at very low pH-values (pH 0.05 – 5.0) and high temperatures (35 – 56 °C). The growth conditions of G. sulphuraria make it suitable for axenic cultivation because the low pH and high temperature minimalize the risk of microbial contamination. Next to its ability to remove nutrients in wastewater treatment, G. sulphuraria is a prospective producer of a valuable product, Phycocyanin (PC), a thermostable blue pigment-protein complex, which is used as, among others food additive and food colorant.

These characteristics of G. sulphuraria lead its selection by Evides Industriewater for the uptake of the ammonium present in the reverse osmosis (RO) concentrate of New Energy and REsources from Urban Sanitation (NEREUS). NEREUS focuses on the re-use of nutrients present in wastewater, among others ammonium. One of the goals of NEREUS is to re-use the ammonium present in the RO concentrate with the use of algae. In order to recover ammonium from the RO concentrate of NEREUS, it is necessary to test whether G. sulphuraria is capable of growing on such medium. The possibility of cultivating of G. sulphuraria on the RO concentrate from water and resource recovery pilot plant of NEREUS was investigated in this thesis.

The objectives of this thesis were to find the optimal growing conditions and assess the biomass growth and nutrients consumption. Screening experiments with synthetic Allen medium, which is usually used for the cultivation of the G. sulphuraria, were conducted to obtain the best growing conditions of G. sulphuraria. In order to understand the best growing conditions for the cultivation of G. sulphuraria, the effects of several factors were investigated, which are: 1) different metabolism, 2) different nitrogen sources and concentrations (ammonium: 100 – 1000 mgNH4+-N/L and nitrate: 247 mgNO3--N/L), 3) different carbon sources (glucose, bicarbonate and CO2) and different glucose concentrations (C:N = 5:1 and 10:1), 4) different phosphate concentrations (N:P = 37:1 and 7.2:1), 5) culture densities. Ammonium with mixotrophic metabolism turned out to be the best nitrogen source. Biomass concentration on ammonium was four times higher than on nitrate. Increasing the ammonium concentration from 200 mgNH4+-N/L to 1000 mgNH4+-N/L resulted in around 25% more biomass and no firm conclusions could be drawn from the experiment performed with different phosphate concentrations. No significant increase in the growth of G. sulphuraria was observed between Carbon:Nitrogen (C:N) ratio = 5:1 and 10:1. Furthermore, culture densities higher than 0.7 g/L of biomass resulted to a slower growth of G. sulphuraria.

Experiment with synthetic RO concentrate shows that there was light limitation involved during the cultivation. Highest and fastest growth (µmax = 0.78 day-1) was observed in the mix of 40% real RO concentrate and 60% synthetic RO concentrate medium culture. Growth inhibition was observed in cultures containing RO concentrate of NEREUS. Still, G. sulphuraria did grow on RO concentrate of NEREUS. This work is contributing to the scientific and engineering community in the field of microalgae.

A pilot-scale PHA microbial enrichment reactor fed on OFMSW leachate was monitored in order to assess the influence of free ammonia nitrogen (FAN) on its performance. The enrichment reactor consisted of a SBR with a 12-hours cycle which included a feast phase, a settling phase and a famine phase with external nitrogen addition. Based on the microscope pictures and FISH analysis, at least two different PHA producing bacteria were identified: small (< 2.5 μm) and big PHA producing bacteria (< 5 μm). Big PHA bacteria appeared from FAN concentrations higher than 50 mg/L, but concentrations higher than 150 mg/L were highly toxic for the whole PHA microbial enrichment. Finally, it was found that a FAN concentration around 60-70 mg/L might produce a microbial enrichment with good settling properties (SVI30 < 80 mL/g and BLAS < 5%) and maximum PHA yields (around 0.50 g PHA/g sCOD), possibly due to the presence of big PHA producers which are assumed to be more efficient and heavier after feast. However, this FAN concentration may lead to a lower settleable biomass production yield (around 0.30 g VSS/g sCOD). Since these results are not conclusive, it is suggested to test the observations of this pilot study in lab-scale experiments to evaluate the potential of FAN as an additional selective pressure in a PHA microbial enrichment.

The ceramic Nanofiltration membranes are studied in TU Delft to treat the brine. It has abilities to concentrate NOM and separate it from salts, and chemical precipitation to recover a clean solution with regeneration salt (i.e., NaCl) from the membrane permeate.For achieving this, the first step should build up the Setup. Therefore, this additional thesis aims to upscale a previous ceramic nanofiltration setup, which should run overnight without supervision. This thesis is divided into two parts: (1) design and building, and (2) experiment. The results show that although the recirculation pump limits the potential of the setup, it can still provide high recovery and stable permeability.

Many rapidly expanding cities around the world including India’s capital New Delhi face increasing potable water quality and health risks due contaminated open drains carrying the cities untreated wastewater into the adjoining river, which is also the city’s water source. To tackle this problem in a practical and holistic way, innovative wastewater treatment solutions are needed. This is the goal of LOTUSHR project - to research and build a holistic and resource-oriented wastewater treatment plant (wwtp) to treat the Barapullah drain water in New Delhi, India. To achieve this goal, Dissolved air flotation (DAF), due to its ability to withstand fluctuating flows and low area requirements was identified as a possible technology in the LOTUS wwtp scheme. This research is focused on identifying and investigating critical operating parameters of a bench-scale DAF column set up with various influents for a comparative and deeper understanding. To achieve this, different influent at the site - Barapullah drain water and anaerobic sludge from a Delhi wwtp, and their counterparts in the laboratory - canal water and anaerobic sludge from a Delft wwtp were tested with the DAF. As there were potentially many critical factors that could have an impact on the DAF performance, experiments were conducted based on the Plackett-Burman experimental design. Furthermore, to understand the effect of particle characteristics and morphology on the DAF performance, microscopic images of the influent and clean effluent samples were analyzed using ImageJ-Fiji. Finally, Particle Image Velocimetry (PIV) analysis was done to gain insight into the characteristics and behavior of the particle-bubble agglomerate and its relation to the DAF performance. Additionally, pathogen (E-coli and C.Perfringens) removal potential of the DAF was studied with Barapullah drain water. The results obtained suggest that for canal water the critical parameters are Time of Coagulation prior to the DAF, Retention Time and Influent TSS Concentration. Whereas, for drain water, it was only the Influent TSS Concentration. For anaerobic sludge from the wwtp in Delft themost significant parameter was found to be Pressure and a similar trend with higher removal was observed for anaerobic sludge from Delhi. Image analysis with canal water, drain water and sludge samples showed that for higher TSS removal runs, a general trend of average influent particle sizes of 12 um,3-5 um and 80-100 um respectively was observed. And, clean effluent particle sizes were found to be 2-3 um for drain water and canal water. Furthermore, for drain water runs with high removal, the particle-bubble agglomerate rise velocities were found similar to the theoretically calculated values of 1.69E-03 m/s. Bubble to particle ratio for high TSS removal runs was calculated to be 34 bubbles/particle for drain water and 50 times more for sludge. In terms of pathogen removal, E-coli removal for drain was found as high as 1.65 log for higher influent TSS runs. No significant correlation was found between the TSS removal and E-coli removal by the DAF. It is recommended that for future research further optimization (with experimental designs such as CCDR) of the significant parameters identified should be done. More extensive research in addition to results found in this study is suggested to be done on the effect of different coagulants
and coagulation conditions on the DAF performance. To further understand the differences observed in the significant parameters of the influents, research on the influent properties such as hydrophobicity and density is recommended. More experiments with adequate site equipment are suggested to be done to understand the removal of Giardia and Cryptosporidium to further understand their relation to the TSS removal by the DAF.