The ongoing growth of the global population has led to increased resource consumption, particularly in the realm of water resources, resulting in potential shortages and environmental concerns. The surge in industrialization has intensified the demand for freshwater, consequently causing significant contamination of global water sources through the discharge of industrial wastewater. This wastewater contains harmful contaminants, such as heavy metals and organic compounds, which pose significant threats to both aquatic ecosystems and human health (Corcoran, 2010). To effectively address this issue, it is imperative to strengthen regulatory measures, promote industrialized initiatives for wastewater reduction and treatment, and foster technological
advancements in wastewater management.
Lipids within wastewater systems present both opportunities and challenges. Their high energy content holds promise for bioenergy conversion, yet they can also disrupt anaerobic wastewater treatment processes. Consequently, it is often advisable to extract lipids before commencing biological treatment processes (Alves et al., 2009). Lipids are commonly referred to as fats, oils, and grease (FOG) (Cavaleiro et al., 2008). At the core of FOG composition are triglycerides, formed through the esterification of glycerol with long-chain fatty acids (LCFA) (Alves et al., 2009). Within lipid-rich wastewaters, the prevailing LCFAs identified include palmitic acid (C16:0) and oleic acid (C18:1), as highlighted by Hwu et al. (1996). Anaerobic digestion (AD) plays a central role in advancing various sustainable development objectives by seamlessly integrating energy and resource recovery from organic residues and wastewater, all while effectively managing pollution. AD's ability to produce renewable gaseous energy, recycle essential nutrients, and minimize excess sludge production, combined with an enhanced understanding of microbiology and ecophysiology, has propelled AD technologies to the forefront. These technologies now serve as environmentally friendly treatment options for a wide range of wastes and wastewaters, as evidenced by their widespread adoption at the global level (van Lier et al., 2020). Sustainable and efficient conversion of these waste lipids into methane within anaerobic reactors is met with impediments including adsorption, sludge flotation, washout, and inhibition. However, these complications can be circumvented through feeding protocols, optimized mixing, and adept solid separation methods, underpinned by cutting-edge reactor designs and operational methodologies. More recently, developments such as the anaerobic membrane bioreactor (AnMBR) and flotation-based bioreactors have emerged as solutions tailored for lipid-intensive wastewater treatment (Cavaleiro et. al., 2008). AnMBR, a nexus of anaerobic digestion and membrane filtration, has proven particularly adept for dairy wastewater treatment. It alleviates the challenges tied to gravity-based separation, yielding effluents devoid of suspended solids and of superior quality (Judd, 201).
The central focus of this research centered on the assessment of solids retention time (SRT) and its critical role in the operational parameters of AnMBR. This was accomplished by studying sludge filterability and membrane filtration performance. Additionally, we investigated how the acclimatization of biomass impacted the transformation of longchain fatty acids (LCFA) in lipid-rich wastewater. Initial evaluations emphasized the role of SRT on AnMBR efficiency during the treatment of synthetic dairy wastewater laden with lipids. Employing two distinct AnMBR configurations with SRTs of 20 and 40 days, both systems manifested approximately 99%efficiency in waste removal at an organic loading rate of 4.7 g COD L-1 d-1. Significantly,lipid sedimentation was absent, facilitating their continued anaerobic degradation. LCFAaccumulation was minimal in both systems, with the 40-day SRT configuration showing slightly enhanced biological conversion and stability. Subsequently, the study delved into the effects of SRT on the filtration efficacy of AnMBR using lipid-rich synthetic dairy wastewater. When confronted with 40-day SRT, the system encountered elevated pressures and resistances, presumably due to escalated contaminant levels, including fats, oils, and LCFAs. While both systems showcased analogous filterability, the 20-day configuration exhibited superior membrane performance, suggesting potential membrane operational refinements for the 40-day SRT. Lastly, the influence of LCFA on anaerobic sludge processes was investigated. Trialing three distinct sludge samples—two lipid-acclimated and one non-acclimated—they were exposed to varying oleic and palmitic acid concentrations, ranging between 50 to 600 mg COD/L. Oleic acid showed superior degradation capabilities compared to palmitic acid across all samples, with heightened methane production. Lipid-acclimated sludges demonstrated augmented LCFA degradation potential. However, upon reaching LCFA concentrations beyond 400 mg/L, degradation of both acids into intermediate products was inhibited, albeit without affecting methane production. Intriguingly, specific bacterial taxonomies associated with LCFA degradation were identified in lipid-acclimated sludge samples, underscoring the potential of sludge adaptation strategies in enhancing anaerobic treatment of lipid-rich effluents.
In this doctoral research, we elucidated the prospects and challenges associated with the utilization of AnMBR for treating lipid-rich dairy wastewater. We highlighted the critical importance of Solid Retention Time (SRT), a key operational parameter that exerts a profound influence on both the biological and membrane aspects of the system.
Furthermore, our study underscored the paramount role played by the two most prevalent Long-Chain Fatty Acids (LCFAs), namely oleic and palmitic acid, within the domain of anaerobic digestion.

This thesis research investigated the dynamics of nutrient release and the formation of melanoidins during thermal hydrolysis processes (THP) of waste activated sludge (WAS) preceding mesophilic anaerobic digestion (AD). In Chapter 2, a fractionation of THP-sludge allowed for researching the distribution of nutrients and melanoidins over the liquid and solid fraction of the sludge matrix during AD. The soluble melanoidins formed during THP were found to be partially biodegradable during subsequent AD, particularly those with a molecular weight under 1.1 kDa, associated with protein-like substances. In addition, total ammoniacal nitrogen (TAN) concentrations exhibited a modest increase during THP, but a substantial increase was observed during AD, negatively impacting acetotrophic methanogenesis.

In Chapter 3, the influence of THP on PO43--P release and precipitation during AD is described. The dynamics in soluble PO43--P concentrations were most pronounced in WAS from enhanced biological phosphorus removal (EBPR) plants. The results indicated an increment in TAN and PO43--P release with THP temperature, while varying soluble concentrations were observed during AD. Full-scale samples provided insights into the precipitation of multivalent cations with PO43--P. The results showed that precipitation reactions during AD governed the concentration of soluble nutrients during THP-AD.

In this thesis, also the impact of THP on downstream processes was researched, particularly reject water treatment after AD. The research focused on the potential consequences of elevated concentrations of humic substances (HSs) and nutrients in the reject water from digestate dewatering. In Chapter 4, research is described on the effects of THP pre-treatment on the struvite precipitation efficiency, considering the chemical characteristics of HSs. Batch experiments revealed the influence of melanoidins and humic acids on struvite precipitation at different pH levels. The intrinsic characteristics of HSs emerged as critical factors affecting struvite yield, morphology, and colour of the formed precipitates.

In Chapter 5, six full-scale partial nitritation and anammox (PN/A) influents and effluents were sampled, with four wastewater treatment plants (WWTPs) using THP and two without. Characterization of the samples revealed that THP increased concentrations of TAN, and aromatic organics, which is an indication of melanoidins occurrence. Additionally, THP decreased stoichiometric NO3--N concentrations in effluents from the PN/A reactors. This study also emphasizes the importance of considering increased O2 consumption and possible limited trace element availability during PN/A process operation, when utilizing THP-AD to optimize overall system performance.

In summary, the results of this thesis provide an understanding of the interactions and consequences of THP in full-scale scenarios, focusing on the dynamics in nutrient release and the effects of melanoidins formation, in THP, AD, and downstream processes for nutrient removal (PN/A and struvite precipitation).

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

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

On the 14th of July 2013, a methane peak was observed in the Gale crater. This methane peak has been investigated in a non-biological context before. This study applies exoplanet research strategies and knowledge about biological methane production on Earth to investigate the biological context. Bayes formula is the foundation of the Bayesian framework approach as proposed by Walker et al. [53]. This Bayesian framework allows for separate investigation of biotic and abiotic methane production pathways to assess the likelihood that one of these pathways is responsible for the methane observation. Before probability is investigated, the viability of biotic methane production is gauged by Thermodynamic calculations. These calculations use the Gibbs free energy and show methanogenesis and sulfate reduction as viable catabolic reactions under Martian temperature and chemical soil and atmosphere compositions. Mars analogue Experiments were conducted into the kinetics of methane and hydrogen sulfide gas production under the influence of Martian Regolith analogue and Martian atmospheric analogue. The seed organisms were gathered from the Belgian Boom clay layer in the HADES lab because the Boom clay layer has strong mineralogical similarities to the Martian regolith. The experiments show that both methane and hydrogen sulfide gas production is not significantly affected by the introduction of modified Phylosilicate Martian Regolith Analog (P-MRA) and Martian Atmosphere Analog (MAA). Comparison with the ADM1 kinetic model shows that only methane gas production is comparable within one standard deviation between all experiments and the model. Biomass growth and sulfur gas production are inconsistent between experiments and the kinetic model. To quantify the probability of biotic methane production, a modified ADM1 model was used for Monte Carlo (MC) analysis of the correlation between the Martian observed methane peak and the kinetic model output for varying initial chemical conditions and virtual reactor volumes. Based on this, 78% of the simulations showed a significant correlation. Using Bayes formula, the posterior probability of the methane peak being biological in origin is higher than the prior probability of an anaerobic community being active around the Gale crater. However, this misses the crucial information on the chance of this methane peak occurring in abiotic conditions.

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.

Fine sieved fraction (FSF) is a solid waste generated from wastewater treatment plants (WWTPs). Cellulose fiber is the most important component of FSF, which can be fermented into volatile fatty acids (VFAs) and then be used as carbon sources in biological nutrient removal (BNR). This thesis measured and evaluated the aerobic & anaerobic biodegradability of solids in fermented FSF (fFSF) and the BNR performance of FSF-derived VFAs. In addition, this research tested the feasibility of using secondary sieving as a potential downstream processing technology. The products of secondary sieving (liquid: secondary filtrate, solid: secondary FSF) were compared with fFSF in terms of biodegradability and BNR performance. The aerobic biodegradability of raw FSF, fFSF and secondary
filtratewere 52.3 ± 1.4, 60.4 ± 4.7 and 72.1 ± 6.4 %, respectively. The anaerobic biodegradability of raw FSF, fFSF and secondary FSF are 56.8 ± 8.4, 68.2 ± 6.4, 51.5 ± 7.8 %, respectively. The results of biodegradability revealed that secondary sieving increased the proportion of readily biodegradable solids and reduced the overall organic load of activated sludge systems. The residual solids after secondary sieving could be converted into biogas or recovered as building materials. FSF-derived VFAs could substantially increase denitrification rates and phosphate release rates. fFSF and secondary filtrate could increase the denitrification rate by 40 - 50%and increase the phosphate release rate by around 200 % compared to blank. Theoretically, the effluent nitrogen load could be reduced by up to 53.7%if FSF-derived carbon sources are fully used for denitrification atWWTP Aarle-Rixtel. If used for phosphorus removal, the capacity provided by FSF-derived VFAs could nearly remove all phosphate from the effluent. To sum up, FSF-derived VFAs could effectively increase BNR rates
and significantly reduce the effluent nitrogen and phosphorus load. The main advantages of FSFderived VFAs over conventional carbon sources are sustainability and waste-reduction. Secondary sieving could reduce the solid load of activated sludge tank and achieve a combined recycling of VFAs and fibers, but the total COD available for BNR will be reduced as a compensation. The results in this thesis can facilitate the application of fFSF in WWTPs and the improvement of FSF-derived VFAs production.

Palm oil is a popular ingredient in domestic products. The palm oil industry has been growing rapidly over the past decades, so that the amount of palm oil mill effluent (POME) generated from the palm oil production has been increasing as well. The anaerobic membrane bioreactor (AnMBR) is a treatment solution that can remove organic pollutants from POME while generating methane as an energy source. In comparison to conventional anaerobic digestors, the AnMBR technology has an additional membrane unit that can produce effluent with higher water quality. More specifically, if ultrafiltration is applied, the AnMBR will be able to effectively remove bacteria from the effluent, making it suitable for direct fertigation (Uman et al., 2021; Bray et al., 2021). However, in cases where infectious viruses are also present, further disinfection method might be required. In this experiment, a lab-scale AnMBR system was used for POME treatment. In order to evaluate how well the system can perform in terms of pollutant removal and methane production, under the controlled experimental conditions, several criteria were monitored: (1) chemical oxygen demand (COD) removal, (2) biomass growth, (3) biogas production, (4) digestion efficiency, and (5) volatile fatty acids (VFA) accumulation. A Long chain fatty acids (LCFA) analysis method was developed using the liquid chromatography/mass spectrometry (LC/MS), to elaborate on underlying conversion mechanisms. A COD balance analysis was also conducted. Factors that would potentially contribute to the COD gaps in the COD balance analysis were quantified and discussed in this paper as well to validate the experimental results. The solid retention time (SRT) was controlled at 140 days, and the organic loading rate (OLR) at 3 gCOD·L-1·d-1 during the first phase of the experiment, when synthetic POME and VFAs were added to the bioreactor. During the second phase, the SRT and the OLR of POME remained the same, whereas the VFAs were replaced by starch and the OLR of starch was increased, in order to simulate the real POME composition, because in addition to lipid, carbohydrate and protein are also found in POME. During Phase I, the AnMBR system could remove 98%-99% of the incoming COD, and produce about 5 L of methane each day. During Phase II, the microbes did not have enough time to adapt to the new experimental condition, but the stability of the AnMBR system could be achieved overtime, when the mixing is improved and the buffer solution is adjusted properly according to the pH variation. Although, based on the positive biomass net growth and the increased methane production, it could be predicted that adding carbohydrates to the feed for a more representative POME composition would promote biomass growth and methane production, suggesting that the AnMBR system would have higher potential when the real POME is used for energy recovery.

The hydrolysis of sludge solids especially for difficultly degradable sludges such as WAS is not fully understood, yet. The first-order hydrolysis rate was shown to function well for most easily degradable sludges and soluble substrates. This description for substrate hydrolysis in the context of anaerobic digestion has the benefit of being very simple and therefore applicable for many engineering applications where little data is available. On the other hand, in the last decades many studies reported that the first-order hydrolysis would need a modification to better describe the degradation of difficulty degradable solids. Guo et al. (2021) developed a cascade system for anaerobic digestion of WAS that does not seem to follow first-order hydrolysis kinetics when lowering the applied SRTs from 22 to 15 and 12 days, respectively. Based on observations by Guo et al. (2021) and a statistical analysis of the cascade system performed in the study at hand it seems that the first order hydrolysis rate constant is in fact a coefficient and that the first-order hydrolysis rate is not solely dependent on sludge characteristics and substrate concentrations. This hypothesis is tested in the thesis at hand. In Guo et al.’s study the cascade system was always compared to a reference system. To test this hypothesis and understand the kinetics of the cascade system in more detail a statistical analysis was performed for both systems from which an empirical hydrolysis model was derived. This model was implemented in ADM1 to replace the existing hydrolysis rate expression and was tested for the mentioned cascade system and the reference system. The empirical model was compared to the results of the standard ADM1 which uses a first-order hydrolysis expression. The empirical model assumed a dependency of the hydrolysis rate based on load and residence time along the cascade system to achieve a change in hydrolysis rate coefficients along the cascade system. The models were compared based on visual inspection and quantitative analysis of the simulated results. Both models showed low R² values which is likely due to the high level of detail implemented in ADM1 that does not fit to the resolution of the experimental data. However, calculated RMSE values agreed with the standard deviations of the experimental results. Therefore, the overall predictive capability for both models is given. The ADM1 managed to model the reference system with reasonable agreement to the experimental data. The performance of the empirical model for the reference was comparable. For the cascade system however the ADM1 could not fully describe the experimental at the applied low SRTs of 15 and 12 days. The empirical model in this case showed better predictive capabilities. This is an indication that a hydrolysis rate which is made dependent on system characteristics such as load and residence time might indeed have its justification and be better applicable to anaerobic digestion systems that show a concentration profile along the reactor as it is in the case with plug-flow and cascade systems.

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

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

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

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

An increasing trend of urbanization, land shortages and frequent floodings have created unfavorable living circumstances for Philippine inhabitants. Finch Floating Homes aims to repurpose the permanently flooded ricefields in Hagonoy into flood-proof, typhoon-resilient, affordable housing. The floating neighborhood will serve as storm-resilient living and have an educational purpose on circular living and recovering resources. The pilot floating home is equipped according to current sanitation practices, a septic tank. The septic tanks are usually emptied in drainage fields or surface water. With the aim of circularity in mind, an alternative sanitation had to be designed.

The neighborhood aspects and social implications were analyzed after which a set of eight design criteria were drafted. With the design criteria a framework was set up for selecting a flexible sanitation system that fits a range of desired effluent qualities. The framework offered treatment compartments that can be combined depending upon the location and effluent requirements. Three different treatment scenarios were compared based on the effluent qualities and costs. Scenario 2 containing a UASB-septic tank as primary treatment and a polishing step with water hyacinths, was found to be the most cost-effective. A final effluent concentration of 3 g/L COD, 0,05 mg/L NH3 and between 53 and 134 mg/L P was reached. And based on the die-off of E.coli, a pathogen removal of 5 log units was achieved.

Next, the conceptualization was laid out. The platforms on which the houses float, were made up of standard modules that were prefabricated and assembled on-site. Rainbarrels in wooden frames provided floating ability. The UASB-septic tank had similar dimensions as the rainbarrels, meaning no specialized treatment platform had to be built since the reactor could take the place of a rainbarrel. The disinfection tubes are placed on top of the platform and could be added at any time if the effluent quality demands a low pathogen level.
The final polishing pond was constructed from locally sourced materials and can be built in any shape that suits the neighborhood as long as the surface area is 17 m2.

The treatment system also offered possibilities for resource recovery in the form of biogas, irrigation water, fertilizer and reuse of the plant mass (food, extra COD, fabric raw materials). The residents could benefit from the biogas in the form of a communal kitchen suitable for social gatherings. The fertilizer and irrigation water were applied in communal gardens. Communal areas aided in improving relations between neighbors which created a pleasant environment.

The final treatment design was a scalable, affordable and sustainable treatment system with a range of resource recovery possibilities.

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

The overall objective of the present study was to investigate the effects of thermal pre-treatment of waste activated sludge (WAS) at 70 °C with addition of H₂O₂ to enhance sludge hydrolysis and subsequent methane production during WAS anaerobic digestion. The research was divided into four parts: Firstly, a bibliographical part, in which literature research revealed that WAS can be considered a mixture of proteins, humic substances, cells (and others).
Subsequently, the effects of several pre-treatment techniques on these constituents and on biochemical and physicochemical properties of WAS, such as methane production and dewatering, were analyzed. This part reviews the response of WAS subjected to pre-treatments of different nature (e.g., thermal, acid-base, oxidative) at different energy intensities. It also compiles the role of pre-treatment techniques on sterilization, dewatering and methane production.
Ultimately, it was made clear that the mechanisms of most of the pre-treatments still remain unknown, hindering a fair comparison of their effects.
In the second part, the effects of low-temperature pre-treatment with the addition of H₂O₂ on WAS were analyzed in both lab- and pilot-scale scenarios to detect and quantify its effects. During lab-scale experiments, it was found that the application of low-temperature thermal pre-treatment combined with H₂O₂ at 70 °C; 30 minutes and 15 mgH₂O₂/g TS increased the methane production rate, which consisted of 2 differently recognizable parts. The high rate, k_{CH4 rapid}, increased from 0.44 ± 0.01 to 0.47 ± 0.01 d^-1 and the low rate, k_CH4slow, from 0.09 ± 0.00 to 0.11± 0.01 d^-1. There were inconclusive results regarding an increase in specific methane production. The lab-scale observations were reproduced during a pilot-scale experiment, although due to methodological restrictions, pre-treatment was applied together with two-staged compartmentalized digestion. It was observed that due to the adoption of pre-treatment and compartmentalized digestion, organic loading rates could be increased from 1.4 to 4.2 kg volatile solids VS/(m³d), which resulted in a solids retention time (SRT) decrease from 23 to 15 days without apparent process impairment. It was considered that most of the observed effects were caused by the pre-treatment, while the influence of compartmentalized digestion remained marginal in this study.
In the third part, further study at lab-scale was conducted to determine the individual contributions of the separate components of pre-treatments, i.e., thermal and oxidative. For instance, thermal pre-treatment solubilized most of the EPS; deactivated catalase and accelerated the reaction rate of H₂O₂, while H₂O₂ decreased the apparent viscosity of WAS by 12-30%, resulting in a synergistic effect on the WAS digestibility. As suggested by other rheological parameters, the addition of H₂O₂ improved the flowability of WAS at 70 °C. The cause of the decrease in viscosity was not determined. However, the presence of hydroxyl radicals via the Fenton’s reagent; the decrease in particle size of WAS, and the combination of H₂O₂ with conditioning agents were discarded. On the other hand, results suggested that the reason behind the decrease in viscosity was the molecular modification of the carbohydrates in WAS as a result of their reaction with of H₂O₂.
The above-described experiments were restricted to the grab samples taken at 3 wastewater treatment plants (WWTPs). However, WAS is a matrix of variable composition, depending on location and season. Therefore, in the fourth and last part, the applicability of the pre-treatment methods to WAS with a different composition was tested, using lab-grown sludge. Based on the results, it was inferred that the concentration of metals embedded in lab-grown sludge was relevant for the effectiveness of pre-treatment in terms of methane production, both rate and extent.
The evidence obtained in this study suggests that the lower viscosity of the pre-treated WAS was reflected in the viscosity of the digestate, which allowed a better mass-transfer during non-ideal mixing and therefore a higher methane production rate. Since full-scale digesters are very often poorly-mixed, the applied pre-treatment conditions might be a possible strategy to improve mixing and increasing the BMP without increasing the mixing energy.

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

Palm oil mill effluent (POME) is a high organic pollution produced during the palm oil mill process, with a brownish color and stingy odor at high temperatures. Given the popularity in palm oil output over the years, the massive amount of POME causes growing concern. The enforcement of wastewater discharge standards and laws, as well as energy recycling of sustainability goals have facilitated the development of POME treatment processes. Several lab-scale studies have looked into the treatment of industrial wastewater using anaerobic membrane bioreactor (AnMBR) which has received considerable research interest due to its demonstrated potential for POME treatment. In this study, the synthetic POME was treated by a lab-scale crossflow anaerobic membrane bioreactor system. This study tested the feasibility of thermophilic PVDF-AnMBR systems for synthetic POME treatment, and meanwhile evaluated the biological and filtration performance of AnMBR treating lipid-rich wastewater at different sludge retention times (SRTs = 60 days, 90 days, and 140 days). AnMBR showed an adequate biological performance during the stabilizing state. The synthetic POME could be treated with over 98% of COD removal efficiency in all operational conditions. Plus, better digestion efficiency could be achieved at higher SRT (140 days). However, this study stresses that even though the membrane ensures biomass retention, the AnMBR process is still dodged by long-chain fatty acid (LCFA) accumulation and inhibition problems, especially at short SRT (60 days). The continuous reduction of biomass concentration during the stabilizing process of SRT at 60 days eventually resulted in the decreased methane production and system instability. Under all operational conditions, sufficient filtration performance and net permeate fluxes between 8 and 11 LMH were achieved. The trans-membrane pressure (TMP) was under 200 mbar throughout operating process. No membrane cleaning was needed. The results showed that better sludge filterability could be achieved at SRT of 90 days. The sludge filterability was compared as per the standard methods, including specific resistance to filtration and capillary suction time, which did not show a linear relationship with SRTs. Meanwhile, the physical-chemical characteristics of the sludge during the operational phases, including TSS concentrations and SMP, have a close correlation with sludge filterability parameters, such as capillary suction time and supernatant filterability.

The presence of high levels of arsenic in groundwater, an otherwise preferred drinking water source, urges the need for innovative and highly efficient (in terms of chemical use and energy consumption) technologies to remove arsenic during drinking water treatment. This research focussed on embedding iron electrocoagulation (Fe-EC) within a biologically active rapid sand filter (RSF) by submerging horizontally perforated (Fe(0)) electrodes. These electrodes were designed in such a way that they could easily be submerged in the filter bed during backwashing. Based on As(V)/As(III) adsorption characteristics and iron removal mechanisms in a RSF it was hypothesized that the arsenic removal could be enhanced by placing the electrodes in the biologically active filter bed instead of in the supernatant. Iron to arsenic ratios (Fe:As) were reduced from 18.3 to 15.0 when the electrodes were placed in the filter bed instead of in the supernatant (for a charge dosage of 6.4 C/L and 150 µg/L As(III) in the influent), showing an improved arsenic removal efficiency. The arsenic oxidizing bacteria (AsOB) on top of the electrodes oxidized As(III) to As(V) (over 85 to 97% oxidation), which was subsequently removed by the iron that got released (by the embedded Fe-EC) and formed precipitates in the filter bed. The major drawback of embedding electrodes in the filter bed is the increase in energy consumption due to the increase in operating voltage. As(V) flowthrough experiments showed that the arsenic removal can be improved by lowering the pH from 8.0 to 7.0 and by increasing the charge dosage from 6.4 to 9.4 C/L. It was shown that besides arsenic removal efficiency, parameters as iron dosage, energy consumption, sludge production, and clogging have a significant relevance. Iron-As(V) experiments showed the flaws of the integrated system related to a partly homogeneous iron release and improper mixing, resulting in a decrease in the arsenic removal efficiency. Further, ways to potentially improve the design of the system are discussed and evaluated, pointing the way forward for future research.

The abundant presence of nitrogen in natural waters can be a threat to both humans and environment. Therefore, municipal and industrial wastewater streams need to be treated before their disposal in the environment. Currently used biological and physical-chemical treatment methods have drawbacks such as high greenhouse gas emissions, high energy use and high use of chemicals. This research used bipolar membrane electrodialysis (BPMED) as a technology for the removal of ammonium sulfate from industrial wastewaters with extreme characteristics. The industrial stripper/scrubber system removing nitrogen from industrial waters creates an ammonium sulfate rich water stream with a pH of 2, a temperature of 70 degrees Celsius and concentrations up to 250 g/L. The study investigated the influence of a low pH, high concentration and high temperature on the removal of ammonium and sulfate from wastewater and in situ generation of sulfuric acid and production of ammonium hydroxide. Key performance parameters to measure the influence of these extreme conditions were the efficiency of nitrogen removal in the form of ammonium current efficiency and ammonium removal efficiency}) and sulfate removal removal efficiency. Other key performance parameters of interest were the consumed energy for this removal in the form of electrochemical energy consumption, the purity of the generated acid and base and the final ammonium concentration in the base and the sulfate concentration in the acid. Model wastewater with a pH between 2 and 10, a concentration between 50 - 250 g/L ammonium sulfate and with a temperature between 20 degrees Celsius and 40 degrees Celsius was treated with BPMED. The influence of pH, concentration and temperature was researched independently in experiments of 180 minutes, after which the removal efficiency and the quality of the produced acid and base were assessed.

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.

Palm Oil Mill Effluent (POME) is an attractive medium for biogas production in an anaerobic membrane bioreactor (AnMBR) because of its high lipid content. Long-chain fatty acid (LCFA) accumulation is toxic and considered harmful for the biological performance within the reactor as they can be absorbed by biomass particles causing sludge flotation and biomass washout from the reactor. Membrane fouling can be caused by LCFA inhibition through adsorption on membrane walls. The biodegradation efficiency and filterability are affected by several factors such as solids retention time (SRT), and an organic loading rate (OLR). The objective of this research was to determine biological performance and LCFA inhibition while operating the AnMBR system at SRT of 90 days and an OLR of 3 g COD/ L/d under thermophilic condition (55 degrees Celcius).
It was observed that successful operation was achieved with high COD removal efficiencies over 98% and average biogas production of 5 NL/d. Acidification occur in the sludge causing signification drop in pH, biomass concentration and methane production. The reactor slowly recovered back normal after adding sodium bicarbonate in the VFA feed. In addition, acetic and propionic acid were the major VFA constituent presented in the sludge.

Anaerobic membrane bioreactor (AnMBR) is a promising technology to treat phenolic wastewater. Conductive materials such as magnetite and granular activated carbon have been reported to be capable of improving anaerobic digestion by facilitating direct interspecies electron transfer (DIET). This research first investigated the effect of magnetite on the treatment of synthetic p-cresol (a relative abundant compound in phenolic wastewater) wastewater in a lab-scale AnMBR. Magnetite increased the reactor stability, permitted higher p-cresol loading rate in the AnMBR, and reduced the fouling potential of supernatant of the mixed liquor. Activities of dehydrogenase and F420 were significantly increased and this may have contributed to the enhanced reactor performance. Magnetite supplement did not have a substantial influence on the soluble microbial products (SMPs) concentration compared to the stage without magnetite whereas extracellular polymeric substances (EPS) concentration significantly increased with magnetite supplement. Reduced fouling potential of the supernatant of the mixed liquor may be attributed to the decrease of protein content in SMPs in the stage with magnetite supplement. Second, the effect of magnetite on the methanogenic degradation pathway of p-cresol was studied, in which the rate limiting step was the conversion of intermediate compound benzoate. Moreover, magnetite increased the maximum substrate degradation rate of all the chosen intermediates as well as the accumulative methane production. Batch test using inoculum adapted to magnetite failed to yield faster substrate degradation rate in comparison with the batch test using non-adapted inoculum. This may be ascribed to the loss of biomass when magnetite was removed from the collected sludge because magnetite and DIET-based microorganisms were closely associated and shaking manually was not sufficient for microorganisms to detach from the magnetite. Since magnetite nanoparticles enhanced reactor performance and stability as well as reduced fouling potential of the supernatant of the mixed liquor, potential commercial application of magnetite nanoparticles in AnMBR may permit shorter hydraulic retention time (HRT) and higher flux, which can lead to higher treatment capacity and lower operational costs. Further research should investigate the effect of potential magnetite corrosion on the reactor performance, the effect of magnetite on fouling potential of the mixed liquor, and likely loss of biomass in case of magnetite removal and methods to remove magnetite with as little loss of biomass as possible.