Industrial wastewaters often have unique properties and contain impurities that pose a significant challenge to their treatment. Lab-scale experiments were performed to provide answers on the feasibility of aerobic granular sludge (AGS) technology for the treatment of organically polluted industrial wastewater.
Glycerol is found in a variety of industrial effluents such as biodiesel and epoxy resin production facilities. However, little is known about the conversion and the impact of glycerol on AGS processes. Chapter 2 describes glycerol conversion in AGS capable of enhanced biological phosphorus removal (EBPR). Robust granules with good phosphorus removal capabilities were formed in an AGS sequencing batch reactor fed with glycerol as the sole carbon source. The interaction between the fermentative conversion of glycerol and product uptake by polyphosphate accumulating organisms (PAO) was studied using stoichiometric and microbial community analysis. The analysis of the biomass identified a community dominated by Actinobacteria (Tessaracoccus and Micropruina) and a typical PAO known as Ca. Accumulibacter. Glycerol uptake facilitator (glpF) and glycerol kinase (glpK), two proteins involved in the transport of glycerol into the cellular metabolism, were only observed in the genome of the Actinobacteria. The anaerobic conversion appeared to be a combination of substrate fermentation and product uptake-type reaction. Initially, glycerol fermentation led mainly to the production of 1,3-propanediol (1,3-PDO) which was not taken up under anaerobic conditions. Despite the aerobic conversion of 1,3-PDO, stable granulation was observed. Over time, 1,3-PDO production decreased and complete anaerobic COD uptake was observed. Overall, the results demonstrate that glycerol-containing effluents can effectively be treated by the AGS process via a collaboration between fermentative and polyphosphate accumulating organisms.
The sugar production industries generate a significant amount of wastewater rich in sugars such as glucose. In Chapter 3, glucose conversion by AGS and its impact on phosphate removal is studied. Long-term stable phosphate removal and successful granulation were observed. Glucose was rapidly taken up with a rate of 273 mg/gVSS/h at the start of the anaerobic phase, while phosphate was released during the full anaerobic phase. Lactate was produced as the main product during glucose consumption, which was anaerobically consumed once glucose was depleted. Other products such as propionate, acetate, and formate were also detected in minor quantities. The phosphate release appeared to be directly proportional to the uptake of lactate. The ratio of phosphorus released to glucose carbon taken up over the full anaerobic phase was 0.25 Pmol/Cmol. Along with glucose and lactate uptake in the anaerobic phase, polyhydroxyalkanoates and glycogen storage were observed. Quantitative fluorescence in-situ hybridization (qFISH) revealed that PAOs accounted for the majority of the total biovolume. Anaerobic conversions were evaluated based on theoretical ATP balances to provide the substrate distribution among the dominant genera. In conclusion, this research shows that AGS can be applied for the treatment of glucose-containing effluents and it is a suitable substrate for achieving phosphate removal.
Industrial wastewaters often have high levels of salt, either due to seawater or e.g. sodium chloride (NaCl) usage in the processing. In Chapter 4, the impact of NaCl concentration gradient and seawater on the granulation and conversion processes of AGS was investigated. Glycerol was used as the carbon source since it is regularly present in industrial wastewaters, and to allow the evaluation of microbial interactions that reflect industrial effluents. Smooth and stable granules as well as EBPR were achieved up to 20 g/L NaCl or when using seawater. However, at NaCl levels comparable to seawater strength (30 g/L) incomplete anaerobic glycerol uptake and aerobic phosphate uptake were observed, the effluent turbidity increased, and filamentous granules began to appear. The latter was likely due to the direct aerobic growth on the leftover substrate after the anaerobic feeding period. In all reactor conditions, except the reactor with 30 g/L NaCl, Ca. Accumulibacter was the dominant microorganism. In the reactor with 30 g/L NaCl, an increase in the genus Zoogloea was observed. Throughout all reactor conditions, Tessaracoccus and Micropruina, both actinobacteria, were present which were likely responsible for the anaerobic conversion of glycerol into volatile fatty acids. None of the glycerol metabolizing proteins were detected in Ca. Accumulibacter which supports previous findings that glycerol can not be directly utilized by Ca. Accumulibacter. The exposure of salt-adapted biomass to hypo-osmotic conditions led to significant trehalose and PO43--P release which can be related to the osmoregulation of the cells. The findings provide insights into the effect of salt on the operation and stability of the AGS processes and suggest that maintaining a balanced cation ratio is likely to be more important for the operational stability of the system than absolute salt concentrations.
Extracellular polymeric substances (EPS) are important constituents of biofilms with promising application potential. The properties of EPS vary depending on environmental conditions and microbial communities which also entails inconsistencies in the material. In Chapter 5, we investigated the EPS of AGS grown under varying salinities induced by NaCl concentration gradient and seawater conditions. Fourier transform infrared (FTIR) spectroscopy revealed the likely presence of polysaccharides, phosphates, proteins, carboxylic esters, and lipids in all extracted EPS. Further analysis with 2-D correlation spectroscopy identified notable differences in various regions corresponding particularly to phosphate and glycan functional groups. Sugar monomer analysis of acid-hydrolysed EPS identified eight monosaccharides, with glucose dominant in saltwater conditions and glucosamine in freshwater. We further evaluated the potential of the extracted EPS as a bio-based flame retardant, via burning tests on EPS-coated cellulose fibres. The tests indicated a linear correlation between increased residual mass and the condensed phosphate content in the EPS, suggesting that higher condensed phosphate levels enhance the flame-retardant properties of the EPS. The EPS from saline conditions had higher condensed phosphate content in contrast to the freshwater EPS with higher orthophosphate fraction. In conclusion, the findings highlighted the potential of wastewater-derived EPS as a bio-based flame retardant and the impact of salt on EPS properties.
Finally, the thesis is concluded with Chapter 6 providing an outlook on the future research, economics, and application of AGS technology. Overall, the findings suggest that AGS technology can be applied for the treatment of industrial wastewater containing salts (pure NaCl or sea salt crystals) as well as glycerol and glucose as organic pollutants, with the added benefit of recovering valuable resources.@en

The industrial sector is one of the most energy consuming and CO2-emitting end-use sectors. To reach climate goals, decarbonization of these industrial sectors is imminent, however, not so apparent. Especially the hard-to-abate industry sectors, such as the chemical, mineral processing, iron, and steel sectors, are difficult to decarbonize as they require either high temperature heat or use fossil fuels as feedstock.

Hydrogen has the potential to reduce carbon emissions in industries such as chemicals, glass, iron and steel, as well as to serve as a cleaner heat source. To reach net-zero emissions by 2050, sectors that currently use fossil fuels for high-temperature processes and as feedstock will likely need to shift towards blue or green hydrogen. Currently, some industrial hydrogen use relies on gray hydrogen, produced from fossil fuels and contributing to emissions. In contrast, blue hydrogen captures and stores CO2 produced from fossil sources, while green hydrogen is entirely emissions-free, generated from renewable energy. In other words, some processes need to change from gray to green/blue but most of them need to change from other fossil fuel based processes to hydrogen processes.

Hydrogen offers a way to cut carbon emissions in industries like chemicals, glass, iron, and steel, and can also act as a cleaner heat source. Achieving net-zero emissions by 2050 will likely require sectors that currently depend on fossil fuels for high-temperature applications and feedstocks to adopt blue or green hydrogen instead. Today, certain industrial applications still use gray hydrogen, derived from fossil fuels and contributing to carbon emissions. However, blue hydrogen captures and stores the CO2 generated, while green hydrogen is emissions-free, produced using renewable energy. In essence, some processes will need to transition from gray to blue or green hydrogen, while many others will shift from fossil-fuel-based processes to hydrogen-based alternatives.

However, the timing and extent of the hydrogen transition are uncertain as they are heavily influenced by external factors such as hydrogen prices, available subsidies, and alternative decarbonization options. Additionally, industrial plant owners may be reluctant to disclose decarbonization plans due to competitive pressures, adding another layer of demand and participant uncertainty that complicates infrastructure planning.

This thesis addresses the planning of hydrogen infrastructure within an industrial port cluster (IPC). IPCs are defined by their proximity to water and concentration of industrial activities related to a specific sector. In order to effectively address spatial constraints, this thesis will plan the hydrogen networks along the current road network within IPCs. Current infrastructure planning methods have a time horizon of ten years. However, as the expectation is that the hydrogen demand will increase towards 2055, a time horizon of ten years can increase the total costs of the network when the network is implemented over time between 2025-2055. This introduces the following research question:

“How can a cost-efficient, robust pipeline network for an industrial port cluster be developed over time under uncertainty?”

To answer this question, the robust backtracking planning method (RBPM) is developed. This method aims to minimize costs over the 2025-2055 time frame while facilitating the hydrogen to the demanding plants. Because the demand for hydrogen is likely to grow over time, this method finds a robust network that is able to facilitate the demand in many possible future demand scenarios of 2055.

The robust network is then implemented incrementally for 2035, 2045, and 2055 using a backtracking approach. In this context, backtracking means that when an industrial plant transitions to hydrogen in one stage, pipelines are installed with the robust networks’ capacity, rather than just the minimum required to meet that plant’s immediate needs. This extra capacity ensures that if other plants transition in later years, the existing network can accommodate the increased demand without needing costly pipeline extensions. By preemptively building capacity, this approach reduces future installation costs and enhances the network’s ability to adapt to evolving demand patterns.

The RBPM is tested on simulations of multiple simplified IPCs. By testing different IPC simulations, it is studied how the difference in industrial plants determines the development of the network. The RBPM is compared to the results of a traditional planning approach which only plans the networks with a time horizon of ten years.

The results show that the RBPM incurs lower costs over 30 years, but it requires a higher investment in 2035 due to the greater capacity installed at that time. This thesis finds that the total potential hydrogen demand and the physical size of an IPC significantly affect the performance of the RBPM compared to the traditional planning approach. Additionally, the projected installation and operational costs over time also impact the RBPM’s performance relative to the traditional planning approach.

For IPCs with comparatively low hydrogen demand — typically clusters with fewer iron and steel facilities, chemical plants, or refineries — the RBPM emerges as the most economical approach. This method requires only slightly higher investment by 2035 but ultimately generates substantial savings by 2055. By installing sufficient pipeline capacity upfront, the RBPM avoids the need for additional pipelines every ten years, leading to long-term cost efficiency through 2055.

For IPCs with high hydrogen demand—typically found in iron and steel plants, basic chemical plants, or refineries—the initial installation costs and ongoing operational expenses of RBPM make it less advantageous. While RBPM may offer slightly better economic profitability over a 30-year period, the substantial investment required in 2035 compared to traditional planning makes implementation challenging due to budget constraints. In these high-demand clusters, the decision between RBPM and the traditional approach for developing a hydrogen pipeline network depends on the cluster’s budget, anticipated future installation costs, and projected operational expenses over time.

Opportunities for further research include the application of the RBPM to a real case study to validate the result, increasing the amount of possible future scenarios by incorporating uncertainty in installation and operating costs and increasing the demand and participant uncertainty range. Lastly, another research direction to explore is the generation of different robust network methods and their performance.