Bøger i IHE Delft PhD Thesis Series serien

This book is about increasing the flexibility of adaptation responses in urban flood risk management systems. It will serve as a guide to those who are involved in planning and implementing adaptation responses in an urban context. It is a synthesis of flexible adaptation practices from several disciplines such as information technology methodologies, automobile and aerospace manufacturing and modelling in the financial sector. It elaborates on the flexible adaptation planning process for identifying how and what kind of flexibility is necessary; where flexibility can be incorporated; and when is the appropriate time to implement the flexible adaptation responses.

High fluoride concentration in groundwater has made many drilled boreholes unusable for drinking in parts of Northern region of Ghana. Treatment of the groundwater by adsorption is also hampered by the lack of suitable locally available adsorbents. This thesis highlights through principal component analysis and saturation indices calculations that predominant mechanisms controlling the fluoride enrichment probably include calcite precipitation and Na/Ca exchange processes, which deplete Ca from the groundwater, and promote the dissolution of fluorite. Additionally, aluminium oxide coated media is capable of reducing fluoride in water, suggesting it is a promising defluoridation adsorbent.

Water resources in tourist islands have been severely threatened, especially in the Galápagos Islands, where the increased local population has generated attractive income from the tourist services. This study investigates water supply and demand in Santa Cruz, the most populated island of Galápagos. The research encompasses a thorough assessment of the water supply crisis, as well as the quantification of water demand from different categories (domestic, tourist, restaurants and laundries) through surveys, in the absence of water metering. The results yield a wide range of water consumption, questioning the current assumption of water scarcity.

Recent years have seen a growing interest in the application of chalcogenide nanoparticles (NPs), e.g. Se, Te, CdSe and CdTe NPs, in various industrial sectors including energy, petroleum refining and in the field of biology and medicine. Moreover, due to the high toxicity of chalcogen oxyanions, their release into the environment is of great concern. Thus, emphasis was given in this study on the development of a novel microbial synthesis process of chalcogenide NPs by combining biological treatment of Se/Te containing wastewaters with biorecovery in the form of Se NPs, Te NPs and CdSe NPs. Enrichment of Se-oxyanion reducing microorganisms was carried out to simultaneously remove selenite (Se(IV)) and cadmium (Cd(II)) from wastewaters by combining bioremediation of toxic Se-rich wastewater with the biorecovery of Se as CdSe NPs. The results showed compositional changes in the extracellular polymeric substances (EPS) matrix of the anaerobic granular sludge upon exposure to Cd(II) and Se(IV) and identified the roles of EPS fractions in the biogenesis of CdSe NPs. Besides, it was found that the EPS on the surface of the biogenic Se NPs play a major role in lowering the bioavailability and toxicity of biogenic Se(0) compared to chemogenic Se(0) NPs. An upflow anaerobic sludge blanket (UASB) reactor was used for the first time to continuously remove tellurite from wastewater and recover biogenic Te(0).

The main objective of this research was to optimize the electron donor supply in sulphate reducing bioreactors treating sulphate rich wastewater. Two types of electron donor were tested: lactate and slow release electron donors such as carbohydrate based polymers and lignocellulosic biowastes. Biological sulphate reduction was evaluated in different bioreactor configurations: the inverse fluidized bed, sequencing batch and batch reactors. The reactors were tested under steady-state, high-rate and transient-state feeding conditions of electron donor and acceptor, respectively. The results showed that the inverse fluidized bed reactor configuration is robust and resilient to transient and high-rate feeding conditions at a hydraulic retention time as low as 0.125 d. The biological sulphate reduction was limited by the COD:sulphate ratio (< 1.7). The results from artificial neural network modelling showed that the influent sulphate concentrations synergistically affected the COD removal efficiency and the sulphide production. Concerning the role of electron donors, the slow release electron donors allowed a biological sulphate reduction > 82% either using carbohydrate based polymers or lignocellulosic bio-wastes, in batch bioreactors. The biological sulphate reduction was limited by the hydrolysis-fermentation rate and by the complexity of the slow release electron donors.

Waste electrical and electronic equipment (WEEE) generation is a global problem. This PhD research investigates novel metal recovery technologies from WEEE.

Seawater desalination is a rapidly growing coastal industry that is increasingly threatened by algal blooms. Depending on the severity of algal blooms, desalination systems may be forced to shut down because of clogging and/or poor feed water quality. To maintain stable operation and provide good feed water quality to seawater reverse osmosis (SWRO) systems, ultrafiltration (UF) pre-treatment is proposed.This research focused on assessing the ability of UF and other pre-treatment technologies to reduce biofouling in SWRO systems. An improved method to measure bacterial regrowth potential (BRP) was developed and applied at laboratory, pilot and full scale to assess the ability of conventional UF (150 kDa) and tight UF (10 kDa) alone and in combination with a phosphate adsorbent to reduce regrowth potential and delay the onset of biofouling in SWRO.The improved bacterial regrowth potential method employs a natural consortium of marine bacteria as inoculum and flow cytometry. The limit of detection of the BRP method was lowered to 43,000 ┬▒ 12,000 cells/mL, which is equivalent to 9.3 ┬▒ 2.6 ┬╡g-Cglucose/L.The reduction in bacterial regrowth potential after tight UF (10 kDa) was 3 to 4 times higher than with conventional UF (150 kDa). It was further reduced after the application of a phosphate adsorbent, independent of pore size of the UF membrane. Pilot studies demonstrated that the application of tight UF (10 kDa) coupled with a phosphate adsorbent consistently lowered the bacterial regrowth potential and no feed channel pressure drop increase was observed in membrane fouling simulators (MFS) over a period of 21 days. The study also showed that non-backwashable fouling of UF membranes varied strongly with the type of algal species and the algal organic matter (AOM) they release. The presence of polysaccharide (stretching -OH) and sugar ester groups (stretching S=O) was the main cause of non-backwashable fouling.In conclusion, this study showed that an improved BRP method is suitable for the assessment of SWRO pre-treatment systems and it can be a useful tool to develop potential strategies to mitigate biofouling and improve the sustainability of SWRO systems.

The role of small hydropower is becoming increasingly important on a global level. Increasing energy demand and environmental awareness has further triggered research and development into sustainable low-cost technologies. In developing countries, particularly in rural areas, the possibility of local power generation could considerably improve living conditions. With this in mind, the development of a next generation low-head hydropower machines was subject of investigation in the EU-project HYLOW. Being part of the research lines of that project, this thesis presents a numerical modelling approach to improve the design of machines like water wheels for increased hydraulic efficiency. Nowadays, Computational Fluid Dynamics (CFD) enables numerical models to be quite accurate and incorporate physical complexities like free surfaces and rotating machines. The results of the CFD simulations carried out in this research show that a change in blade geometry can result in higher torque levels, thereby increasing performance. Numerical simulations also enabled to determine the optimal wheel-width to channel-width ratio and further improve performance by modifying the channel bed conditions upstream and downstream of the water wheel. With a power rating in the low kilowatt range, low-head hydropower machines like optimised water wheels seem to have a clear potential for small-scale energy generation, thereby contributing to achieving the Sustainable Development Goals by providing local energy solutions.

The magnitude and urgency of the need to adapt to climate change is such that addressing it has been taken up by the United Nations as one of the sustainable development goals - Goal 13 (SDG13) in 2015. SDG13 emphasises the need to strengthen resilience and adaptive capacity to climate related hazards and natural disasters. Coping with urban floods is one of the major needs of climate adaptation, where integration of climate change responses into flood risk management policies, strategies and planning at international, national, regional and local levels is now the norm. However, much of this integration lacks effectiveness or real commitment from stakeholders involved in adaptation planning and implementation. Hence this research has focused on integrating flexibility based adaptation responses into an urban flood risk management context. The research has synthesised flexible adaptation practices from several disciplines including information technology, automobile and aerospace manufacturing. The outcomes of the research are brought together in a framework for structuring local adaptation responses and an adaptation planning process based on flexibility concepts. The outcomes provide a way to assist with the identification of the appropriate nature and type of flexibility required; where flexibility can best be incorporated; and when is the most appropriate time to implement the flexible adaptation responses in the context of urban flooding.

Water resources in tourist islands have been severely threatened, especially in the Galápagos Islands, where the increased local population has generated attractive income from the tourist services. In addition, the data regarding water supply and demand are scarce. This study investigates water supply and demand in Santa Cruz, the most populated island of Galápagos. The research encompasses a thorough assessment of the water supply crisis, as well as the quantification of water demand from different categories (domestic, tourist, restaurants and laundries) through surveys, in the absence of water metering. Also, specific water demand was assessed by installing 18 water meters. The results yield a wide range of water consumption, questioning the current assumption of water scarcity. Furthermore, a prognosis of water supply and demand was carried out, and also several intervention strategies were proposed such as rainwater harvesting, greywater recycling, leakage reduction, water meter installation, water demand reduction, as well as seawater desalination to cope with the future population growth. Due to the fragility of the ecosystem, these strategies were assessed through a Multi-Criteria Decision Analysis, considering environmental, technical, economic and social aspects, as well as relevant stakeholders’ perspectives. finally, the water supply network of Puerto Ayora was evaluated in order to understand the need of the current intermittent supply regime. A methodology was developed to estimate the overflow of the domestic roof tanks (a common incidence amongst local population). The results question the practicality of individual household storage. The final results show that the current situation in terms of the lack of water quantity may not be real, as it has been thought for the last decades. The water issues refer more importantly to the water quality, as well as to the lack of proper water management practices.

This research focused on investigating the occurrence of pharmaceuticals and personal care products (PPCPs) and clinically relevant fungi in public swimming pools. Anthropogenic contaminants can be reduced by promoting hygienic behaviour and application of UVOX.