Search

Organic matter (OM) is the most important factor influencing the effectivity and efficiency of micropollutant (MP) ozonation in wastewater effluents. The importance of the quantity of OM is known, because of this, total organic carbon (TOC) is generally used to determine the required ozone dose for any water sample. Still, the effect of OM type on MP ozonation is not well understood. In this study, effluents from five wastewater treatment plants were collected and the organic matter in these effluents was fractionated using membranes (F1-4) and resin (HI, HOA, HON and HOB). Fractions were diluted to the same TOC concentration, spiked with MPs and ozonated at three ozone doses. Our results show that all five effluents had comparable OM compositions and similar MP removal, confirming the suitability of OM quantity (TOC) to compare the ozone requirements for wastewater effluents. From the 19 analysed MPs, three groups were identified that showed similar removal behaviour. The strongest differences between the groups were observed around MP ozone reactivities of 102, 104 and 106 M−1 s−1. This indicates the presence of three OM groups in the samples that interfere with the removal of different MPs. MP removal in the resin fraction HON were higher for MPs with high and medium ozone reactivity, indicating a low interference of OM in this fraction with MP ozonation. OM in the resin fractions HOA and HI showed higher interference with MP ozonation. Therefore, removing the HOA and HI fractions prior to ozonation would result in a lower required ozone dose and a more efficient removal of the MPs. MP removal correlated with the OM characteristics A300, SR and fluorescence component comp 2. These characteristics can be used as inline tools to predict the required ozone dose in water treatment plants.

The reuse of polymer flooding produced water (PFPW) generated in oil and gas industry is limited by its salt content, making desalination by electrodialysis a promising treatment option. Therefore, this study aimed to 1) assess the technical feasibility of employing electrodialysis to desalinate PFPW generated in assorted scenarios, and 2) evaluate the reuse of the electrodialysis-desalted water to confect polymer-flooding solution. The experimental work involved desalting two kinds of synthetic PFPW solutions, one with relatively low salinity (TDS=5000 mg/L, brackish PFPW), and another with high salinity (TDS=32,000 mg/L, sea PFPW), at two different temperatures, and later reusing the desalted solution to prepare viscous solutions. For the electrodialysis runs, the effects of feed composition and temperature on water transport, energy consumption and current efficiency were analyzed. It was found that the presence of polymer did not significantly influence the water transport rate or the specific energy consumption for the seawater cases, but had a measurable effect when desalting brackish water at 20 °C. It was also found that some polymer remained in the stack, the loss occurring faster for the brackish PFPW. Still, both kinds of reused PFPW probed adequate to be employed as a basis for preparing n polymer solution.

Concentration polarization and fouling hamper the desalination of polymer-flooding produced water (PFPW) via electrodialysis (ED). This water is an abundant by-product from the oil and gas industry. A common technique to mitigate both problems is the application of pulsed electric field (PEF), which consists in supplying a constant current during a short time (pulse) followed by a time without current (pause). Accordingly, this work evaluated the application of PEF during the ED of PFPW to improve the process performance and to reduce fouling incidences. The experimental work consisted in performing ED batch runs in a laboratory-scale stack containing commercial ion exchange membranes. Synthetic PFPW was desalinated under different operating regimes until a fixed number of charges were passed. After each experiment, a membrane pair was recovered from the stack and analyzed through diverse techniques. The application of PEF improved the ED performance in terms of demineralization percentage and energy consumption, the latter having reductions of 36% compared to the continuous mode. In general, the shorter the pulses, the higher the demineralization rate and the lower the energy consumption. Regarding the application of different pause lengths, longer pauses yielded lower energy consumptions, but also lower demineralization. Amorphous precipitates composed of polymer and calcium fouled most on the anion and cation exchange membranes, independently of the applied current regime, but in a moderate amount. Finally, the present study relates the observed effects of PEF application to the electrophoresis and diffusion of HPAM, and shows that PEF is a sound option to enhance the desalination of PFPW.

Desalination is known to have considerable energy, economic, and environmental impacts. Treatment trains are receiving increased interest for their potential to meet produced water standards while both minimizing impacts and increasing the range of eligible input salinities. However, determining which technologies to combine and predicting their performance is both difficult and case specific. This research will present a unique hybrid-modelling framework (DESALT) for evaluating and comparing desalination treatment trains based on the same customizable inputs. This comprehensive discrete-based approach generates treatment trains and then systematically evaluates them using physics-based evaluation methods that are reflective of changes in operating conditions. DESALT also accounts for technology limitations, product water requirements, and user preferences. The modelling outputs are filtered using a combination of a Pareto front analyses and DEA decision support. The result is a list of eligible and preferred treatment trains with their corresponding operating conditions. The framework's performance was tested by applying two different technologies (electrodialysis and brackish water reverse osmosis) to a brackish water case study. While the methodology was able to capture the trade-offs between treatment trains and individual technologies, the results are highly reliant on the accuracy of the evaluation methods used.

Hypothesis Anion exchange membranes (AEMS) are particularly prone to fouling when employed to desalinate polymer flooding produced water (PFPW), an abundant sub-product from the oil and gas industry. The formation of fouling on an AEM will be affected by the composition of the solution, which includes various dissolved salts, partially hydrolyzed polyacrylamide (HPAM), crude oil, and surfactants. Experiments Electrodialysis experiments were performed to desalinate feed solutions with different compositions, aiming to distinguish between their individual and combined effects. The solutions contained diverse mono- and divalent ions. The analysis included data collected during the desalination and characterization of the fouled AEMs by diverse analytical techniques. Findings HPAM produced the most severe effects in terms of visible fouling and increase of resistance. This polyelectrolyte fouls the AEM by adsorbing on its surface and by forming a viscous gel layer that hampers the replenishment of ions from the bulk solution. Ca and Mg have a large influence on the formation of thick HPAM gel layers, while the oily compounds have only a minimal influence acting mainly as a destabilizing agent. The membranes also presented scaling consisting of calcium precipitates. The effects of the gel layer were minimized by applying current reversal and foulant-free solution.

The presence of multivalent ions in polymer-flooding produced water (PFPW) hampers its recycling mainly because i) they increase the risk of scaling and reservoir souring (sulfate), ii) they interfere with the viscosifying effect of the fresh polyelectrolyte. It is desirable to achieve the removal of most multivalent ions without completely desalting the stream. With the adequate process conditions, electrodialysis could help to achieve this goal, so this work focused on evaluating the removal of divalent ions from synthetic PFPW through varying operational conditions. The experimental work consisted on batch experiments run in an electrodialysis-stack composed of strong Neosepta ion-exchange membranes. Synthetic PFPW solutions containing a mixture of monovalent and divalent ions were desalted at four different current densities, and three different temperatures. Additionally, the effect of the dissolved polymer on the removal was assessed by performing half of the experiments on polymer-containing solutions and half of them on solutions without it. Our results demonstrate that it is possible to achieve preferential removal of divalent cations (calcium and magnesium) through electrodialysis, especially when employing low current densities (24 A/m2) and high temperature (40 °C). The removal of sulfate, a divalent anion, is also accelerated in these conditions. The presence of polyelectrolyte did not significantly affect the removal rate of divalent ions. Thus, it is concluded that meticulous application of ED to minimize concentrations of divalent ions in PFPW is a potential effective way for water and polymer recycling in enhanced oil recovery situations, as an alternative to the use of other non-selective desalination technologies.

As water shortages are increasing, the need for sustainable water treatment and the reuse of water is essential. Water reuse from wastewater can be accomplished in a membrane bioreactor (MBR) in the secondary activated sludge stage of a wastewater treatment plant. To remove viruses, dissolved organics and inorganics still present in the MBR permeate, nanofiltration (NF) can be applied. Nevertheless, the major drawback of nanofiltration membranes is the production of a concentrate stream that cannot be discharged to the environment. In this research we investigate the concept of a combined MBR and NF system with NF concentrate recirculation back to the MBR to produce reusable water in a sustainable way. Long-term continuous operation (1 year) shows that the NF permeate quality is riot impacted by the recirculation. Fouling on the NF membrane is mostly the result of inorganics, while organics (e.g. humic acids) do not have a major impact on NF fouling. In fact, the flux of the NF was enhanced by the presence of humic acids due to recirculation. However, the MBR showed increased fouling and consequently more frequent membrane cleaning. The results presented show that the continuous production of reusable water from wastewater in a combined MBR and NO process with NO concentrate recirculation can be successful. (C) 2013 Elsevier B.V. All rights reserved

The high total phosphorus content of raw domestic wastewater with its significant eutrophication potential offers an excellent possibility for phosphate recovery. Continuous recirculation of NF concentrate to an MBR and simultaneous phosphate recovery from the NF concentrate can be applied to produce reusable water, recovering phosphates, while at the same time decreasing the scaling potential of the recirculated NF concentrate, prolonging the retention times of slowly biodegradable soluble compounds (e.g. micropollutants) and recirculating multivalent cations to promote the bio-flocculation. Here we introduce an electrochemical system to recover phosphates. An electrochemical cell was divided into an anode and a cathode compartment separated by a cation exchange membrane. Precipitation of phosphates from nanofiltration concentrate was induced by locally increasing the pH at the cathode surface by water electrolysis and thereby creating supersaturated conditions at the cathode. 70–95% recovery of total phosphate was achieved at a pH of 8–10 near the cathode. Ion analysis, XRD and ATR-FTIR spectra indicated that the precipitate consisted of amorphous calcium phosphate (ACP) and minor proportions of amorphous calcium carbonate (ACC). The amount of ACC was dependent on the pH. Calcium phosphate scaling at the cathode surface did not occur due to H2-gas formation preventing nucleation and growth at the cathode.

A plant-wide simulation study is presented in which we investigated the feasibility of a novel centralized municipal wastewater treatment system design as previously proposed by Khiewwijit et al. (2015). This design includes processes as bioflocculation (BF), anaerobic digestion (AD), partial nitritation (PN) and Anammox (ANA). We specifically investigate the effects of operational conditions (SRT, HRT, dissolved oxygen set point and temperature) on carbon recovery potential and ability to meet N discharge criteria according to European legislation. The results suggest that BF-AD can be a promising technology combination for carbon recovery. However, PN-ANA is as yet not suitable for European conditions within the context of studied design at the current state of technology development.

High loaded MBRs (HL-MBR) can concentrate sewage organic matter by aerobic bioflocculation for subsequent anaerobic conversion to methane or volatile fatty acids. In the range of very short solid retention times (SRT), the effect of SRT on bioflocculation and EPS production in HL-MBR was investigated. This short SRT range was selected to find an optimum SRT maximising recovery of organics by aerobic bioflocculation and minimizing losses of organics by aerobic mineralization. Bioflocculation was studied in five HL-MBRs operated at SRTs of 0.125, 0.25, 0.5, 1 and 5 d. The extent of flocculation, defined as the fraction of suspended COD in the concentrate, increased from 59% at an SRT of 0.125 d to 98% at an SRT of 5 d. The loss of sewage organic matter by biological oxidation was 1, 2, 4, 11 and 32% at SRT of 0.125-5 d. An SRT of 0.5-1 d gave best combination of bioflocculation and organic matter recovery. Bound extracellular polymeric substances (EPS) concentrations, in particular EPS-protein concentrations, increased when the SRT was prolonged from 0.125 to 1 d. This suggests that these EPS-proteins govern the bioflocculation process. A redistribution took place from free (supernatant) EPS to bound (floc associated) EPS when the SRT was prolonged from 0.125 to 1 d, further supporting the fact that the EPS play a dominant role in the flocculation process. Membrane fouling was most severe at the shortest SRTs of 0.125 d. No positive correlation was detected between the concentration of free EPS and membrane fouling, but the concentration of submicron (45-450 nm) particles proved to be a good indicator for this fouling.

Ion exchange membranes (IEMs) are used for selective transport of ions between two solutions. These solutions are often different in concentration or composition. The membrane resistance (R-M) is an important parameter affecting power consumption or power production in electrodialytic processes. In contrast to real applications, often R-M is determined while using a standard 0.5 M NaCI external solution. It is known that R-M increases with decreasing concentration. However, the detailed effect of a salinity gradient present over an IEM on R-M was not known, and is studied here using alternating and direct current. NaCl solution concentrations varied from 0.01 to 1.1 M. The results show that R-M is mainly determined by the lowest external concentration. R-M can be considered as two resistors in series i.e. a gel phase (concentration independent) and an ionic solution phase (concentration dependent). The membrane conductivity is limited by the conductivity of the ionic solution when the external concentration, c(ext) 0.3 M, then differences of R-M are small. A good approximation of experimentally determined R-M can be obtained. The internal ion concentration profile is a key factor in modeling Rm. (C) 2014 Elsevier B.V. All rights reserved.

Hypothesis Anion exchange membranes (AEMS) are particularly prone to fouling when employed to desalinate polymer flooding produced water (PFPW), an abundant sub-product from the oil and gas industry. The formation of fouling on an AEM will be affected by the composition of the solution, which includes various dissolved salts, partially hydrolyzed polyacrylamide (HPAM), crude oil, and surfactants. Experiments Electrodialysis experiments were performed to desalinate feed solutions with different compositions, aiming to distinguish between their individual and combined effects. The solutions contained diverse mono- and divalent ions. The analysis included data collected during the desalination and characterization of the fouled AEMs by diverse analytical techniques. Findings HPAM produced the most severe effects in terms of visible fouling and increase of resistance. This polyelectrolyte fouls the AEM by adsorbing on its surface and by forming a viscous gel layer that hampers the replenishment of ions from the bulk solution. Ca and Mg have a large influence on the formation of thick HPAM gel layers, while the oily compounds have only a minimal influence acting mainly as a destabilizing agent. The membranes also presented scaling consisting of calcium precipitates. The effects of the gel layer were minimized by applying current reversal and foulant-free solution.

This article has been removed: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This article has been removed at the request of the Executive Publisher.This article has been removed because it was published without the permission of the author(s).

Hypothesis Anion exchange membranes (AEMS) are particularly prone to fouling when employed to desalinate polymer flooding produced water (PFPW), an abundant sub-product from the oil and gas industry. The formation of fouling on an AEM will be affected by the composition of the solution, which includes various dissolved salts, partially hydrolyzed polyacrylamide (HPAM), crude oil, and surfactants. Experiments Electrodialysis experiments were performed to desalinate feed solutions with different compositions, aiming to distinguish between their individual and combined effects. The solutions contained diverse mono- and divalent ions. The analysis included data collected during the desalination and characterization of the fouled AEMs by diverse analytical techniques. Findings HPAM produced the most severe effects in terms of visible fouling and increase of resistance. This polyelectrolyte fouls the AEM by adsorbing on its surface and by forming a viscous gel layer that hampers the replenishment of ions from the bulk solution. Ca and Mg have a large influence on the formation of thick HPAM gel layers, while the oily compounds have only a minimal influence acting mainly as a destabilizing agent. The membranes also presented scaling consisting of calcium precipitates. The effects of the gel layer were minimized by applying current reversal and foulant-free solution.

The presence of multivalent ions in polymer-flooding produced water (PFPW) hampers its recycling mainly because i) they increase the risk of scaling and reservoir souring (sulfate), ii) they interfere with the viscosifying effect of the fresh polyelectrolyte. It is desirable to achieve the removal of most multivalent ions without completely desalting the stream. With the adequate process conditions, electrodialysis could help to achieve this goal, so this work focused on evaluating the removal of divalent ions from synthetic PFPW through varying operational conditions. The experimental work consisted on batch experiments run in an electrodialysis-stack composed of strong Neosepta ion-exchange membranes. Synthetic PFPW solutions containing a mixture of monovalent and divalent ions were desalted at four different current densities, and three different temperatures. Additionally, the effect of the dissolved polymer on the removal was assessed by performing half of the experiments on polymer-containing solutions and half of them on solutions without it. Our results demonstrate that it is possible to achieve preferential removal of divalent cations (calcium and magnesium) through electrodialysis, especially when employing low current densities (24 A/m2) and high temperature (40 °C). The removal of sulfate, a divalent anion, is also accelerated in these conditions. The presence of polyelectrolyte did not significantly affect the removal rate of divalent ions. Thus, it is concluded that meticulous application of ED to minimize concentrations of divalent ions in PFPW is a potential effective way for water and polymer recycling in enhanced oil recovery situations, as an alternative to the use of other non-selective desalination technologies.

The reuse ofpolymer floodingproduced water (PFPW) generated inoil and gas industryis limited by its salt content, makingdesalinationbyelectrodialysisa promising treatment option. Therefore, this study aimed to 1) assess the technicalfeasibilityof employing electrodialysis to desalinate PFPW generated in assorted scenarios, and 2) evaluate the reuse of the electrodialysis-desalted water to confect polymer-flooding solution. The experimental work involved desalting two kinds of synthetic PFPW solutions, one with relatively lowsalinity(TDS = 5000 mg/L, brackish PFPW), and another with high salinity (TDS = 32,000 mg/L, sea PFPW), at two different temperatures, and later reusing the desalted solution to prepare viscous solutions. For the electrodialysis runs, the effects of feed composition and temperature on water transport, energy consumption and current efficiency were analyzed. It was found that the presence of polymer did not significantly influence the water transport rate or the specific energy consumption for the seawater cases, but had a measurable effect when desaltingbrackish waterat 20 °C. It was also found that some polymer remained in the stack, the loss occurring faster for the brackish PFPW. Still, both kinds of reused PFPW probed adequate to be employed as a basis for preparing n polymer solution.

Alternative water sources such as brackish water or wastewater have become increasingly investigated for non-potable applications. However, choosing the most appropriate reuse scheme is complex due to the diversity of potential sources, requirements of non-potable applications, quality dynamics, and range of treatment technology capabilities. Additionally, the resulting social, economic, and environmental considerations can further complicate the decision-making process. Therefore, the aim of this research is to evaluate the complexities and opportunities for alternative water use as well as the methods of treatment which can connect sources and end uses. Through a critical review of the existing literature, it was found that alternative water use is primarily focused on municipal source and domestic end uses, even though their high human-exposure potential can pose a large risk. While treatment methods can help remove these harmful contaminants, the impacts of these technologies to the environment are not always clear. Therefore, a unique hybrid-modelling framework was developed for the purpose of evaluating technologies on a systems-level bases. The performance of these configurations were then compared on the basis of technical, economic, and environmental indicators. Due to the large number of results and the variance in indicator performance, a decision support tool was generated to assess these treatment configurations and compare them to other alternative sourcing methods (e.g. offsite water exploitation and transport). Throughout this research, it was noted that the focus of alternative water sourcing is almost exclusively from the perspective of product water feasibility. However, this can limit options for brine disposal or reuse and can lead to environmental impacts. A small exercise was pursued which visualized that indeed approaching water reuse from a bine requirement perspective had the potential to reduce economic and environmental impacts while also improving the range of possibilities for product water use. Therefore, it is recommended that future research reframe alternative water use to meet brine requirements first and then match the product water with potential cross-sectoral applications

Freshwater scarcity and emerging organic (micro)pollutants in the water bodies create challenges for the ecosystem. In addition, the development of the industrial sector enhances freshwater consumption enormously. Closing the water cycle by reusing the treated wastewater is essential to meet several sustainable goals. Cooling towers in the industries are one of the largest freshwater consumers and discharge large volumes of saline wastewater as cooling tower blowdown water (CTBD). Reuse of the CTBD could reduce freshwater footprint and enable them to become an eco-efficient and sustainable industry. The CTBD contains a complex mixture of salts and organic compounds. The research project described in this thesis was designed to study advanced oxidation processes (AOPs) to remove the organic compounds (OCs) in this saline condition. In this research, four different AOPs, namely- electrooxidation, photocatalytic degradation, heat-activated persulfate oxidation, UVC/vacuum UV process, have been studied. A special focus has been given on the effectiveness of removing the OCs and the influence of chloride ions. The thesis has eight chapters, including six experiment chapters, a general introduction, and a general discussion. Chapter one gives a general introduction about freshwater water consumption, pollutants, the necessity of treatment, principles of AOPs. Chapter two presents the possibilities and limitations of electrochemical oxidation to removed OCs in the presence of chloride. Chapters three and four focused on strategies to minimize the bottleneck of electrochemical oxidation in the presence of chloride ions. Chapters five and six focused on the influences of chloride ions on photocatalytic degradation, heat-activated persulfate oxidation, and UVC/vacuum UV AOPs. Chapter seven described a complete technology train to treat the CTBD. The train includes wasteland, nanofiltration, reverse osmosis, and electrochemical oxidation. A comprehensive overview of chloride chemistry in all state-of-the-art AOPs has been summarised in chapter eight to guide the end-user to select appropriate AOPs in saline conditions. Zoetwater is een integraal onderdeel van het ecosysteem: het ondersteunt menselijk leven, landbouw en economische activiteiten. Toch wordt zoetwater steeds schaarser door toenemende populaties, economische activiteiten en klimaatverandering. Vervuiling van zoetwaterbronnen door opkomende (micro)verontreinigingen resulteert in uitdagingen voor ecosystemen en onze gezondheid. De ontwikkeling van industrie versnelt de consumptie van zoetwater. Daarom is het van vitaal belang om de watercyclus te sluiten door hergebruik van behandeld afvalwater. Industriële koeltorens zijn een van de grootste zoetwater verbruikers en lozen grote volumes zout afvalwater, beter bekend als koeltoren spuiwater (KSW). Het hergebruik van KSW kan zoetwater verbruik verminderen en de eco-efficiëntie en duurzaamheid van industrieën verbeteren. Dit hergebruik is alleen niet eenvoudig, want KSW bevat een complex mengsel van zouten en organische stoffen. Het onderzoeksproject dat in deze thesis beschreven wordt is ontworpen geavanceerde oxidatieprocessen (GOP) te onderzoeken die organische stoffen (OS) kunnen verwijderen in de zoute omstandigheden.

Groundwater, together with glaciers and polar icecaps, are the main reservoirs of freshwater in the world. In the Netherlands, more than half of the drinking water is being produced by using groundwater. Recent studies have shown that despite the lower exposure of the groundwater, some contaminants such as pesticides, are present in groundwater systems at micropollutant concentrations. Bioremediation is an environmentally friendly technology that relies on living organisms to biodegrade contaminants. In-situ micropollutants remediation represents a very promising but also delicate measure, because drinking water sources need to be protected from any activity that could represent a risk for drinking water production. Bioremediation processes in groundwater can be limited by the oligotrophic environmental conditions in combination with the low pesticides concentration. Bioremediation technologies that rely on pesticides biodegradation have previously been presented as a possible solution to remove pesticides from groundwater systems, making clear that more research is necessary before safe and effective application. The main goal of this thesis was to better understand the biological and environmental factors playing a role in the biodegradation of pesticides at micropollutants concentration in groundwater systems used for drinking water production in the Netherlands. The different chapters of this book contributed to: (a) create an overview of molecular tools that facilitate anaerobic pesticide monitored natural attenuation, (b) determine which groundwater microbial communities are present in the field and what are the environmental factors exerting selective pressure on them, (c) discover the metabolic potential for the biodegradation of pesticides of microbial communities in the field, (d) understand which environmental factors can facilitate pesticides biodegradation by indigenous microorganisms present in natural groundwater systems, (e) comprehend the fate of an added degrading inoculum to an stable groundwater column system. Finally, a general discussion is presented as well as some recommendations and further research lines are proposed to continue exploring the potential of microbial communities for the biodegradation of pesticides at micropollutants in groundwater systems used for drinking water production. Grondwater is één van de voornaamste bronnen van zoetwater ter wereld, naast gletsjers en de poolkappen. In Nederland wordt meer dan de helft van ons drinkwater geproduceerd uit grondwater. Recente studies hebben aangetoond dat verontreinigingen, zoals pesticiden, aanwezig zijn in grondwater systemen als microverontreiniging, namelijk in concentraties van nanogram to microgram per liter. Deze verontreinigingen bereiken tegenwoordig nog steeds het grondwater systeem, ondanks de restricties in het gebruik van pesticiden in de laatste decennia. Biodegradatie is een natuurlijk proces dat bijdraagt aan de verwijdering van microverontreinigingen. Bioremediatie is een natuurvriendelijke technologie welke afhankelijk is van levende organismen om verontreinigingen biologisch af te breken. In-situ bioremediatie van microverontreinigingen is een veelbelovende maatregel, maar in-situ remediatie is een gevoelig onderzoeksonderwerp omdat drinkwaterbronnen dienen te worden beschermd tegen elke activiteit welke een risico kan vormen voor de productie van drinkwater. Biologische afbraakprocessen in grondwater kunnen worden gelimiteerd door over de diepte veranderende redox condities en een zuurstofarme en nutriënt-arme omstandigheden. Het voornaamste doel van deze thesis was om de biologische en milieufactoren die een rol spelen in de biologische afbraak van pesticiden in microverontreiniging-concentraties in grondwatersystemen beter te doorgronden, met als uiteindelijk doel om deze informatie te gebruiken om beter in staat te zijn om biologische afbraakprocessen in drinkwaterbronnen te beoordelen en stimuleren.

Water is indispensable for sustaining life on Earth and the uneven distribution of freshwater resources is impacting water availability. Additionally, climate change and rapid urbanization restrict water availability, causing global water scarcity. The Bengal delta is the largest delta in the world and is suffering from economic water scarcity. Sea level rise, salinity intrusion, discharge of untreated wastewater degrades surface water quality and threaten the availability and quality of drinking and irrigation water. Urban water defined as a combination of greywater and sealed surface runoff often has been widely used in agriculture as an alternative source of irrigation. Reuse of urban water offers a cost-effective solution by enhancing the socio-environmental sustainability of water resources. However, adequate planning and in-depth understanding of the socio-economic, health and technological aspects are necessary for successfully implementing reuse projects.Considering the growing demand for quality irrigation water in the Bengal delta, this research explored the possibilities and barriers related to safe urban water reuse in agriculture. Khulna, the coastal city in Bangladesh, the most vulnerable to climate change, has been taken as a case study. Several quantitative and qualitative research methods were employed to gather data from the study area.Chapter 1 starts with the global overview on water availability and narrows down to the negative impact of climate change and rapid urbanization on growing water scarcity in different regions. Literature was consulted to illustrate the history, major trends and achievements in urban water reuse worldwide.In Chapter 2, the urban water reuse potential in peri-urban agriculture was quantitatively assessed. Firstly, the irrigation water requirement of Boro rice during the dry season was assessed using the FAO AquaCrop model. Then the greywater and sealed surface runoff generation were calculated. The analysis indicated that the urban water could positively contribute to the irrigation water demand of peri-urban agriculture while the net irrigation requirement of Boro rice has declined over the last decades (1984-2017). The water requirement is highest during February and March and the lack of rainfall in these months fails to satisfy the total irrigation demand. However, with the introduction of storage systems, urban water could supply the required amount throughout the year. The results provided a solid quantitative assessment of the matching potential of urban water to sustain agricultural activities.In Chapter 3, the spatio-temporal variability in macro-chemical surface water quality was analyzed and the subsequent usability in agriculture was mapped. Statistical analysis to correlate the water quality with urban land uses and mapping using ArcGIS were carried out. The negative impact of direct discharge of urban wastewater and solid waste on water quality is reflected by elevated values of the related parameters such as solids (TSS), organic matter (BOD5, COD) and low DO concentrations. The adjacent salt-carrying tributary rivers impact the water quality which is evident in elevated saltwater influenced parameters such as TDS, Na+ and Cl−. Results showed that the current surface water quality does not meet FAO guideline. The influence of surrounding land use was evident which can be used to improve surface water quality and future planning strategies. The method of integrating water quality information at a spatial scale provided valuable insights on the variability of water quality and usefulness, restrictions and treatment requirements for further use in agriculture.In Chapter 4, the microbial and heavy metal contamination in the surface water was assessed through laboratory analysis and subsequent risk was assessed. A screening level QMRA was performed for assessing the health risk of farmers considering E. coli concentrations in water. Results show that the mean concentrations of microbial indicators exceeded the thresholds of the WHO and local guidelines for safe irrigation. However, no such significant thresholds were observed for heavy metals. The health risk assessment suggested that the existing surface water quality poses a health risk for farmers as they are in direct contact with the polluted surface water and do not use any protective equipment. However, farmers do not prioritize their health due to their longstanding practices and lack of alternative irrigation sources. A multi-barrier approach containing reduction of pathogen concentrations and awareness among farmers was discussed to lower the risk. The results further reiterated the need for the necessary treatment of wastewater for ensuring safe use.In Chapter 5, the governance aspects of urban water reuse were investigated employing several participatory methods such as questionnaire survey, Key Informant Interview and Focus Group Discussion. Results indicated a high level of awareness among urban citizens (80%) about the negative impacts of wastewater discharge. There is a positive attitude towards urban water reuse as an alternative to combat irrigation water scarcity. Citizens are willing to pay for the treatment and the willingness of citizens is influenced by their socio-economic conditions. Several governmental agencies are parallelly involved in urban water-related issues; however, there is no clear strategy to work together on an interdisciplinary issue like urban water reuse. Adjustments in existing rules and regulations are necessary for the organization to collaborate and work together cohesively.Finally, in Chapter 6, the findings of this thesis were synthesized and four socio-technological scenarios for treating and reusing urban water in agriculture were illustrated. The potential and drawbacks of urban water reuse were discussed to highlight the need for proper treatment infrastructures. An extensive literature review was carried out to list the crucial factors that need to be considered for selecting suitable treatment technologies and defining a proper technical collection and treatment strategy including storage and redistribution to agriculture. The chapter also identifies several limitations of current research and provided suggestions for future research.Considering the future uncertainties around the provision of freshwater supply, planned urban water reuse presents a viable alternative to meet the growing water demand in agriculture. Improvement of existing water quality with adequate treatment and infrastructures for collection, storage, and supply would ensure safe urban water reuse. Supportive governance arrangement and stakeholder participation in the decision-making process could ensure the implementation of urban water reuse projects for sustaining agricultural activities in the Bengal delta.

This thesis presents the development of mathematical models of water and nutrient balances in aquaponic systems, aimed at improving our understanding of this production method towards an efficient use of resources.Our current food production systems have large social and environmental impacts, which are commonly externalized in the context of industrial production and global trade. Aquaponics is an option for sustainable food production that combines aquatic species (aquaculture) with soilless plants (hydroponics). The main challenge in aquaponics consists of balancing optimal conditions for multiple species: aquatic organisms, plants and beneficial micro-organisms. To facilitate achieving this balance, decoupled aquaponic systems have been proposed, consisting of two separate recirculating water loops. In this way, the production loop for fish operates independently from the production loop for plants, each with their own optimal conditions. Nutrient-rich water from the fish loop can be supplied to the plants continuously or at selected times, reducing fertilizer requirements. Similarly, water from the plants loop can be recovered and supplied to the fish, reducing fresh water demand.Managing water and nutrient exchange in aquaponic systems requires continuous information about the concentrations of chemical elements (nutrients). Some nutrients, like nitrogen and phosphorus, are excreted in abundance by fish and can be used by plants. Other nutrients, like calcium and sodium, are also present in fish water, but they can easily reach harmful levels for plants. Sensors to continuously monitor these concentrations are costly and thus uncommon in commercial applications. Therefore, mathematical models combined with available measurements (semi-physical models), are suitable to support management and control of aquaponic systems.Mathematical models for aquaculture and hydroponic systems are widely available in literature. However, they do not describe the dynamics of nutrients. Furthermore, measurements of nutrients in the components of aquaponic systems are not always available and typically show large uncertainties.In this context, further elaborated in Chapter 1 - General introduction, the objective of this thesis was to investigate the dynamics of water and nutrient balances in decoupled aquaponic systems and their uncertainties. The research questions formulated for this purpose aim at identifying the main challenges and opportunities in closing water and nutrient cycles, and in modelling nutrient balances under uncertainties. Chapters 2 and 3 present system-level studies. Chapters 4 and 5 focus on mathematical modelling under uncertainty, applied to biological production systems.Chapter 2 presents a model-based study coupling a recirculating aquaculture system (RAS) for tilapia with a nutrient film technique (NFT) hydroponic system for tomato. The simulation results show that fish can provide 26% of the nitrogen requirements for plants. Furthermore, it is shown that variations in nitrate concentrations in the fish loop, can be decreased by 35%, using a water management strategy that sends water from fish to plants based on amounts proportional to the fish feed.Chapter 3 presents a model-based study supported by a demonstration aquaponic system in Abtshagen, Germany. The model helped identifying imbalances in the system design. It predicted excess concentrations of total suspended solids (TSS) for fish, and excess sodium, calcium, magnesium, and ammonium for plants. The model was used to develop an improved management strategy, preventing excess TSS, sodium, and ammonium, decreasing fertilizer requirements, and achieving water efficiencies similar to commercial aquaculture and hydroponic systems.Chapter 4 presents an algorithm proposed for the calibration of mathematical models applied to biological production systems. The algorithm is based on the set-membership approach, which is a suitable alternative to statistical methods in the presence of limited and uncertain experimental data. The algorithm uses Voronoi tessellation, a novel method that characterises the feasible parameter space with (hyper)spheres, quantifying deviations from experimental data.Chapter 5 studied the dynamics and uncertainties fish growth and excretion of macronutrients. A model was developed and calibrated using the Voronoi set-membership algorithm. Uncertainty propagation was assessed using Monte Carlo simulations. The model prediction explained 84% of the literature data variability for fish growth, 75% for digestive system content, and 28% for ammonia excretion rate. The uncertainty assessment helped identifying suitable experimental conditions for future research.Chapter 6 - General discussion, reflects on the research questions, explaining the limitations identified in each research chapter, and suggestions for future research.From a system design perspective, closing water and nutrient cycles requires a comprehensive quantitative analysis, using indicators that reflect the trade-offs occurring when trying to balancing optimal conditions between the fish and plant loops. A list of suggested indicators for future research is provided. From a system operation perspective, several specific problems and proposed solutions were identified. Solids should be removed from fish water by combining mechanical filtration and sedimentation, to better regulate water exchange from fish to plants, and to stabilize nutrient concentrations for plants. Water storage between fish and plant loops should be aerated to prevent nitrogen loss via denitrification. Fish feed should be selected based on the mineral concentrations in local fresh water, to prevent excess of nutrients harmful for plants, which decrease the potential for nutrient reuse.There is high multidisciplinarity involved in model development of aquaponic systems. Studies with a gradual increase in complexity are thus suggested. Future research on nutrient balances, for example, could consider the chemical form of nutrients and their bioavailability for fish and plants. Mathematical models of aquaponic systems and their components should consider simultaneously multiple variables with multiple time scales.The discussion is extended to the more general field of modelling biological production systems, providing a framework for the development of mathematical models under uncertainty, combining set-membership calibration with uncertainty propagation assessment, to identify critical variables for future experimental measurements.Finally, the discussion is brought back to the general socio-economic context. It is suggested to investigate whether the risks of aquaponics are most sensitive to the fish production loop. If that is the case, financial incentives for production should focus on the expansion of existing aquaculture farms to include hydroponic production. Furthermore, it is necessary to improve communication between researchers and producers.

The world still runs on oil and such an oil-based society with a yearly increase in global demand urge to explore new oil sources. As a result, oil exploration and extraction have been moved to the deeper ocean marine environments. Oceans are a vital part of the ecosystem, contain phytoplankton and other crucial microorganisms responsible for CO2 absorption, O2 production, the global carbon cycle, and global climate control. While technologies for oil exploration and extractions in more remote and hard-to-reach locations such as deep marine environments have been developed, technologies for potential oil spill mitigation and clean-up remained under-developed and relied on the knowledge, experiences, and technologies adjusted for surface water oil spills. As a result, mitigation and cleaning up the deep marine oil spills often occur by unadjusted methods and technologies, which can cause unforeseen long-term negative impacts on the oceans and disturbing their performance in ecological and many other ecosystem functions.One example of a deep marine oil spill was the Deepwater Horizon (DWH) oil spill, which occurred 1500 m below the water surface in the Gulf of Mexico in 2010. The clean-up technology applied for this first very deep marine oil spill was the injection of Corexit, an oil chemical dispersant, at the oil wellhead. Chemical dispersants have been used frequently for mitigating surface water oil spills. The application of dispersants to break down the oil into smaller droplets is based on the formation of smaller oil droplets that more readily dissolve into waters, and the dissolved oil compounds are then biodegraded rapidly by oil-degrading bacteria and other microorganisms. Injection of Corexit at the DWH wellhead as well as to the water surface kept the spilled oil in the water column and reduced the pollution of the shorelines. However, in the aftermath of the DWH and researching the consequences to the marine ecosystem, it was discovered that a significant portion of the oil ended up at the seafloor through unknown or not well understood processes and mechanisms. This lack of understanding was the main driver for setting up a research program called C-IMAGE (Center for Integrated Modeling and Analysis of Gulf Ecosystems) on the fate and effects of such deep-water oil spills, which this PhD research was part of it.This PhD thesis offers a broad picture and aims at building a step-wise understanding of some critical processes determining the fate and biodegradation of oil in deep marine oil spills and the influence of chemical dispersants in each step. The DWH oil spill was taken as the practical example to refer to in our studies, which are described in six chapters.Chapter 1 (the introduction) provides a brief overview of the state of the art knowledge of oil spills history, oil composition and compound's behavior in water, weathering processes, clean-up technologies, and compares surface and deep oil spill scenarios. Chapters two to five provide results and discussions of specially designed laboratory experiments to allow a step-wise elucidation of the fate and biodegradation of oil in deep marine spills in the absence and presence of chemical dispersants. In these experiments, the field conditions during and after the DWH spill were mimicked as far as possible, using several sets of batch and microcosms experimental systems. The batch experiments were at the scale of 10–100 milliliters, dedicated to oil compound's dissolution by Corexit, interactions with mineral and organic particles, and impacts on biodegradation of oil compounds. The microcosms experiments were performed in microcosm systems at 10–1000 liters scale dedicated to oil-organic particle-biota interactions mimicking conditions in the water column and in and at the seafloor.In Chapter 2, biodegradation of oil compounds by two bacterial cultures (n-alkane and aromatic degraders) in the absence and presence of Corexit with various dispersants to oil ratios was studied. Our results show that the presence of Corexit does not in all cases enhances biodegradation of (all or some) oil compounds. When the Corexit was at the highest application concentration, the biodegradation was inhibited, especially when only the n-alkane degrading bacterial culture was present. However, with two bacterial cultures, the inhibition was not effective after ten days. This indicates that the initial inhibition of oil biodegradation can be overcome when different bacteria are present in the environment. We conclude that the observed inhibition is related to the enhanced dissolution of aromatic compounds into the water, inhibiting the n-alkane degrading bacteria.In Chapter 3, the biodegradation of oil compounds was studied in batch experiments, while the oil interacted with marine snow, clay particles, and Corexit. Marine snow are organic particles produced by algae and plankton in the upper layers of the ocean water column, a natural process essential for the whole functioning of the marine ecosystem. During the DWH oil spill and application of chemical dispersants, excessive production of marine snow was observed in the field. Results of our lab experiments show that the presence of marine snow particles enhances oil biodegradation. On the other hand, the presence of Corexit alone or in combination with organic or mineral particles (clay) hampers oil biodegradation. Clay and Corexit have a synergistic effect in increasing the dissolution of benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds in the water and cause a delay in biodegradation of oil compounds through increasing the dissolution of toxic oil compounds. However, the delay in recovery of the biodegradation was reduced by the presence of marine snow particles that adsorbed toxic BTEX compounds from the water phase.In Chapter 4, the effect of marine snow on the biodegradation of oil compounds in the sediment layer is described based on the results from microcosm experiments. These results show that the presence of marine snow reduces the depletion of oil n-alkanes by 40% on top sediments due to the preferred biodegradation of marine snow organics. Biodegradation of marine snow reduces the oxygen concentration in the sediment layers, resulting in a lower biodegradation of oil compounds in the sediment.In Chapter 5, invertebrates were included in the microcosm experiments to study the effects of settled oil-associated marine snow. Benthic invertebrate survival and behavior were investigated and compared to the biodegradation of oil compounds in the presence and absence of invertebrates. Bioturbation activities by invertebrates strongly contribute to the oxygenating and nutrient cycling in the sediment layers and ease the aerobic biodegradation. Sedimentation of oil disturbs the benthic ecosystem by slowing down the bioturbation activity and inhibits the biodegradation of the oil compounds in the sediment. The benthic system itself is affected and has a reduced ability to restore conditions favourable for the biodegradation of oil compounds at the seafloor, presumably leading to long-term impacts on sediment ecosystem functioning through the oil at the seafloor.In Chapter 6, the results from previous chapters are discussed and placed in a broader context. In short, deep marine injection of chemical dispersants in the DWH oil spill protected the shorelines and their habitats from oil pollution. However, the side effect is that this clean-up response puts the deep parts of the marine ecosystem in danger. The most pronounced effects of such an approach are the intensive oil dissolution in the water column, oil components toxicity and stress impulses to the marine (micro) organisms, excessive formation of marine snow, and scavenging of oil particles from the water column to extensive oil sedimentation towards the seafloor. This new understanding generated in our studies suggests that it may be better to design clean-up strategies that are so-called "nature-based", which means using naturally occurring processes that support the self-healing capacities of the environment. This would also entail no or very limited use of chemical dispersants, and if these are used, it should be done with a full understanding of the effects of these dispersants on the complete deep marine system. In this way, seafloor pollution and long-term consequences on the marine ecosystem will be diminished.We need to improve our understanding of deep marine systems and their response to oil spills much further. The various environmental conditions and processes are far from completely elucidated, and this is needed for a careful evaluation of scenarios for the specific environmental conditions that may dictate the oil spill behavior. This knowledge is required to further minimize damages from future deep oil spills. Though limiting petroleum oil consumption and transition to a non-fossil economy is a fundamental and final solution for oil pollution, however, inevitably, we will still live for decades in a society that will use fossil oil as an energy and chemical resource. If we transform to a renewable and biobased economy, biofuels and bio-lubricants may gradually replace fossil oils; hence, oily compounds are likely to stay in the world's economy. This pleads for budgets to continue this type of research also when the full attention of the global society is focused on climate mitigation and the energy transition. Such research is highly needed to offer the knowledge base to protect our seas and oceans during the coming transition decades and thereafter.&nbsp

In this thesis a modelling approach for the design of water supply networks using alternative regional water resources is developed. The thesis departs from the notion that water use should be compatible with the local environment, meaning that the renewable rates at which local water resources are replenished should not be exceeded. New modelling approaches are developed and tested on an industrial case study in the region of Zeeuws-Vlaandering in the south of the Netherlands.The novel modelling approach, WaterROUTE, incorporates the effects of land use on pipeline infrastructure costs with the optimization of water supply network planning. Methods from geographic information science and mathematical programming are connected with hydrological models. The proposed method connects modelling of the natural water system with decision making.WaterROUTE shows how the optimal configuration of a water supply network changes depending on the amount of water required, the maximum allowed salinity of water reaching the demand location, and the inclusion of harvested rainwater from urban areas. Groundwater availability and salinity is estimated up to 2110 with hydrological models and the rainwater harvesting potential from urban areas is estimated based on daily precipitation data for a wet and a dry year.WaterROUTE is suited to identify when the optimal water supply network layout changes significantly due to small changes in demand quantity or quality. This functionality makes the proposed methodology a valuable tool to evaluate multiple water supply scenarios/alternatives and for long term regional planning.

The occurrence of organic micropollutants in the aquatic environment is ubiquitous. They comprise compounds from diverse application areas such as pharmaceuticals, personal care products, pesticides or compounds used during industrial processing each containing a variety of sub-classes and substances.Several micropollutants have negative impact on the environment due to their toxicity, persistence and bioaccumulation potential. For this reason, European legislations such as the Water Framework Directive require the observation of such harmful micropollutants. For some of them, environmental quality standards (legal thresholds) are already in place and it is expected that the number of micropollutants that will require monitoring and have environmental quality standards will grow in the near future.Therefore, water managers are confronted with new challenges: to measure and evaluate the occurrence of organic micropollutants in surface waters and to find adequate measures to mitigate them in the water cycle. Thus, an application-oriented research was accomplished with the aim to understand the origin, transport and fate of wastewater associated organic micropollutants and moreover to find a “ready-for-implementation” measure to reduce these emissions to the environment.The research was conducted in the Swist basin, a small and well-defined catchment area within the greater rhine river catchment, close to the city of Bonn in North Rhine-Westphalia, Germany.In Chapter 2, emissions entering the river are assessed. Concentrations of carbamazepine, diclofenac and metoprolol were studied in the effluent of the four sewage treatment plants within the Swist river catchment. It is found that the concentrations of these pharmaceuticals vary a lot within (and between) the treatment plants (33 – 55% standard deviation). This is related to the hydraulic retention time of the wastewater in the sewage treatment plants. The hydraulic retention time in turn is dependent on the amount of sewage treatment plant inflow and thus the hydraulic situation which is heavily affected by the precipitation in the catchment area. A linear relation of concentrations and hydraulic retention time is observed, showing the dilution effect which increases at high sewage treatment plant inflow volumes. Additionally, it was demonstrated that these dilution-induced concentration ranges can be reliably determined with inhabitant specific loads obtained from literature. At hydraulic retention times greater than 80 hours, the concentrations of biodegradable micropollutants (in this case metoprolol and diclofenac) are decreasing due to enhanced removal in the treatment plant. After dry periods and during subsequent storm events with high inflow volumes, it was revealed, that the dilution effect is delayed. This can be explained by incomplete mixing of wastewater in the tanks of the sewage treatment plant.In Chapter 3, micropollutants in the river are assessed. Besides the effluent of the four sewage treatment plants, the river Swist was investigated for the occurrence and short-term concentration variability of carbamazepine, diclofenac, 1H-benzotriazole and galaxolide. It was found that during dry weather conditions, with stable emission input concentrations, the concentrations in the river are fluctuating within the course of a day. Reasons for these diurnal concentration variations are varying sewage treatment plant effluent volumes and in situ removal in the river trajectory. The fate of micropollutants is described by combining mass balances studies and water quality modelling. By applying this method, it is demonstrated that carbamazepine and 1H-benzotriazole are persistent in the river, whereas diclofenac is removed mainly by photodegradation process and galaxolide is removed by diverse removal processes.In Chapter 4 and 5 retention soil filters, a mitigation measure to remove micropollutants from the effluent of a sewage treatment plant is presented. Retention soil filters are a special configuration of vertical flow constructed wetlands, and widely used in Germany and in particular in North Rhine-Westphalia for the treatment of combined sewer overflow and separate sewer outlets. Two kinds of retention soil filter have been investigated for a period of three years for their potential in micropollutant removal from a sewage treatment plant effluent: a conventional retention soil filters with sand, calcium carbonate, planted with reed and a retention soil filter with granular activated carbon as additive. In Chapter 4 it is demonstrated that retention soil filters with granular activated carbon can reduce concentrations of a broad range of different organic micropollutants from sewage treatment plant effluent to below limits of quantification (95% median removal). The conventional retention soil filters can remove micropollutants as well, with best results for galaxolide, diclofenac 4-hydroxy, metoprolol and clarithromycin (75 – 79%). By monitoring the different layers of the retention soil filters individually, it is revealed that the upper layer with highest organic matter content is most effective.In Chapter 5 the effluent polishing as studied in Chapter 4 is combined with the treatment of combined sewer overflow. These represents the intended application of a new generation of constructed wetlands: the retention soil filter for the combined usage of sewage treatment plant effluent treatment during dry weather and of combined sewer treatment in case of storm and overflow events. It is shown that total organic carbon, dissolved organic carbon, nutrients and several micropollutants can be efficiently removed from combined sewer. After the treatment with combined sewer, some compounds (e.g. metformin) were washed out from the filter material at subsequent treatment with sewage treatment plant effluent. It is determined that with a dry period of 18 h between the two treatment cycles, this wash out effect can be prevented. Finally, it is concluded that both combined sewer overflow and sewage treatment plant effluent can be treated with the same retention soil filter without any negative long-term effects on its performance.In Chapter 6 the advantages and challenges of combining scientific and application-oriented work is discussed with regard to monitoring, pilot plant studies and environmental fate research conducted at a whole river basin, all under the influence of uncontrollable environmental conditions. It is shown how the results of this work are implemented by the water board Erftverband, and how the results and conceptual findings can be translated to the wider context of the “science for impact” approach and more specifically the organic micropollutant management in river basins.

This thesis explores the use of electrodialysis, an electrical and membrane-based technology, to partially desalinate polymer-containing produced water (PFPW) generated in the oil and gas industry. Chapter 1 includes an introduction to polymer flooding, explains its water needs in terms of quality and quantity, and enlists some possible treatments to reach the desired water quality. It is also explained how, by partially desalinating PFPW while retaining the viscosifying polymer, electrodialysis would allow reusing the water for polymer flooding, while significantly decreasing the amount of new polymer to be added when preparing viscous solutions. The chapter also includes some possible constraints for the implementation and enlists the research questions that are answered in the subsequent chapters.In Chapter 2, we assessed electrodialysis to desalinate PFPW generated in different scenarios and evaluated the reuse of the desalted water to confect the polymer-flooding solution. The experimental work involved desalting two kinds of synthetic PFPW solutions, one with relatively low salinity (TDS=5000 mg/L, brackish PFPW), and another with high salinity (TDS= 32,000 mg/L, sea PFPW), at two different temperatures, and later reusing the desalted solution to prepare viscous solutions. The analysis for the ED-step included the effects of feed composition and temperature on water transport, energy consumption, and current efficiency. It was found that the presence of polymer did not significantly influence the water transport rate nor the specific energy consumption for the seawater cases, but had a measurable effect when desalting brackish water at 20°C. It was also found that some polymer remained in the stack, the loss occurring faster for the brackish PFPW. Still, both kinds of reused PFPW probed adequate to be employed as a basis for preparing polymer solutions.Chapter 3 addressed the selective removal of divalent cations from PFPW through a variety of operational conditions. The chapter starts by explaining how the presence of multivalent ions in PFPW hampers its recycling mainly because i) they increase the risk of scaling and reservoir souring (sulfate), ii) they interfere with the viscosifying effect of the fresh polyelectrolyte. Then, the chapter explains the experimental work, which consisted of batch experiments run in an electrodialysis-stack. Synthetic PFPW solutions containing a mixture of monovalent and divalent ions were desalted at four different current densities and three different temperatures. Additionally, the effect of the dissolved polymer on the removal was assessed by performing half of the experiments on polymer-containing solutions and half of them on solutions without it. The results demonstrated that it is possible to achieve preferential removal of divalent ions (calcium, magnesium, sulfate) through electrodialysis, especially when employing low current densities (24 A/m2) and high temperature (40 °C). The presence of polyelectrolyte did not significantly affect the removal rate of divalent ions. It was concluded that the precise application of ED to minimize concentrations of divalent ions in PFPW is a possible a more effective way for water and polymer recycling in enhanced oil recovery situations, then the use of other non-selective desalination technologies.Chapters 4 and 5 address the influence of the feed composition on the fouling formed on anion and cation exchange membranes, respectively. The composition of the solution, which includes various dissolved salts, partially hydrolyzed polyacrylamide (HPAM), crude oil, and surfactants. Electrodialysis experiments were performed to desalinate feed solutions with different compositions, aiming to distinguish between their individual and combined effects. The solutions contained diverse mono- and divalent ions. The analysis included data collected during the desalination and characterization of the fouled AEMs by diverse analytical techniques. Chapter 4 shows that HPAM produced the most severe effects in terms of visible fouling and increase of resistance. This polyelectrolyte fouls the AEM by adsorbing on its surface and by forming a viscous gel layer that hampers the replenishment of ions from the bulk solution. Ca and Mg have a large influence on the formation of thick HPAM gel layers, while the oily compounds have only a minimal influence acting mainly as a destabilizing agent. The membranes showed scaling consisting of calcium precipitates. The effects of the gel layer were minimized by applying current reversal and foulant-free solutions. Regarding the CEMs, Chapter 5 showed that fouling was detected on most CEMs and occurred mainly in the presence of the viscosifying polyelectrolyte. Under normal pH conditions (pH~8), the polyelectrolyte fouled the concentrate side of the CEMs, as expected due to electrophoresis. Precipitation occurred mostly on the opposite side of the membrane, with different morphology depending on the feed composition.In Chapter 6, we evaluated the application of pulsed electric field (PEF) during the electrodialysis of PFPW, that is, to supply a constant current during a short time (pulse) followed by a period without current (pause). This operation mode aimed to improve process performance by reducing fouling incidences. The experimental work consisted of ED batch runs in a laboratory-scale stack containing commercial ion-exchange membranes. Synthetic PFPW was desalinated under different operating regimes until a fixed amount of charges was passed. After each experiment, a membrane pair was recovered from the stack and analyzed through diverse techniques. The application of PEF improved the ED performance in terms of demineralization rate and energy consumption, the latter having reductions of 36% compared to the continuous mode. In general, the shorter the pulses, the higher the demineralization rate, and the lower the energy consumption. Regarding the application of different pause lengths, longer pauses yielded lower energy consumptions but also lower demineralization. Amorphous precipitates composed of polymer and calcium fouled on the anion and cation exchange membranes, independently of the applied current regime, but in a moderate amount. Finally, the chapter related the observed effects of PEF application to the electrophoresis and diffusion of HPAM. It showed that PEF is a sound option to enhance the desalination of PFPW.Under the premise that process performance is limited by fouling occurring on the anion-exchange membranes, Chapter 7 aimed to correlate the properties of different AEMs with their performance while desalinating PFPW. The study made use of six stacks containing different homogeneous, commercially available AEMs, which were employed to desalinate synthetic PFPW during 8-days ED experiments operated in reversal mode. The AEMs recovered from the stacks were analyzed in terms of water uptake, ion-exchange capacity, permselectivity, and area resistance, and compared against virgin AEMs. Relatively small changes were measured for most of the parameters evaluated. For most AEMs, the water uptake and resistance increased, while the IEC and permselectivity decreased during operation. Ultimately, AEMs with high area resistance were linked to the fast development of limiting current conditions in the stack, so this property turned out to be the most relevant when desalinating PFPW.Considering the most favorable conditions assessed in previous chapters, Chapter 8 addresses the experimental evaluation of different operational conditions to increase water recovery while keeping a low energy consumption. The experimental work included the evaluation of applying a continuous constant voltage operation versus the use of PEF, as well as comparing the performance of stacks composed by either aromatic or aliphatic membranes. The results were analyzed in terms of operative time, water recovery, and energy consumption and serve to indicate under which conditions specific types of membranes would be preferred. At last, the collected data was used to perform an economic analysis. It indicated that although further optimization should be possible, achieved settings already made ED desalination of polymer-flooding produced water, a sound case from an economic point of view.Chapter 9 assessed the contribution of the desalination and the pumping energy to the total energy consumption desalinating streams with high viscosities, i.e., above the one of water (1 cP). The assessment included the influence of other important parameters, namely the salinity of the feed and the type and thickness of the spacer. It was found that the type of spacer did not significantly influence the energy required for desalination. Regarding the pumping energy, it was higher than predicted by models found in the literature, but in most cases, it was minimal compared to the energy for desalination. Only when using very thin spacers (300 µm) or very viscous feeds (12 cP) energy for pumping equalized that of desalination of feeds with 1 g/L NaCl. Thus, it was concluded that the main contributor to the energy consumption of these viscous solutions is still the desalination energy, and it is recommended to use spacers of a thickness between 450 and 720 µm to keep pumping energy low.At last, Chapter 10 starts by recalling the main areas of investigation that were defined in Chapter 1 (influence of polymer-flooding produced water composition and conditions, removal of multivalent ions, fouling, preservation of polymer integrity) and discuss the findings presented in this thesis. Then, a full-scale polymer flooding case is introduced and based on the results of the previous chapters, an economic analysis performed. In the three scenarios analyzed, introducing a produced water desalination step would have a positive return on investment. In two of them, the payback time is sooner than six years. Finally, the chapter includes some last remarks about the investigation and recommendations for future research.

In view of urbanization, climate change, resource depletion and the impacts associated with resource extraction, processing and consumption, it is of great importance that cities foster the sustainable management of resources. For urban planning and design to contribute to sustainable resource management, a detailed and insightful understanding of urban resource flows and stocks is required. Urban metabolism (UM) assessments are considered valuable for providing insight in urban resource flows and stocks. Scholars acknowledge the potential of UM assessments generally and material flow analysis specifically for informing evidence-based, resource conscious urban planning and design, but they also point to the shortcomings that hinder the exploitation of this potential. Therefore, this research: (I) studies how comprehensiveness and resolution of analysis affect the potential of UM assessments in providing insightful understanding of UM, and (II) investigates the factors and mechanisms that underlie resource flows and stocks, to advance understanding of the systemic characteristics of cities and their metabolism. Energy and water were chosen as main resources of interest. This research is of transdisciplinary nature, integrating knowledge from different academic disciplines with knowledge from actors outside academia. Stakeholder input is acquired in a case study of Amsterdam, which is central to this research. Other case-specific parts of this research consists of analyses of empirical data, including a material flow analysis at the municipal level and analyses using more detailed spatial units such as neighbourhoods. UM-related literature with a wide range of research designs is taken into account, to engage with knowledge from relevant disciplines such as urban ecology and environmental history.It is conclude that for UM assessments to provide insightful evidence of UM for resource-conscious urban planning and design, a city’s metabolism and its underlying factors of influence should be assessed comprehensively and at several spatial and temporal resolutions. This thesis shows that a comprehensive, ‘grey-box’ MFA provides a deeper understanding of UM than a conventional MFA. Such a comprehensive assessment is instrumental to evaluating the sustainability of a city’s UM and can inform urban strategies that aim to enhance the sustainability of an urban area. Higher resolution assessments are needed to inform the implementation of interventions, as stakeholders need a more detailed insight in resource flow variability for this. To ensure that UM assessments generate meaningful results for resource-conscious urban planning and design, it is foremost essential to provide a solid underpinning of the chosen resolution(s) of UM assessment. Taking such a comprehensive, multi-scale approach is also essential to provide a systemic understanding of a city and its metabolism. This thesis show that the relationship between consumption patterns and factors is case and scale dependent, and consumption patterns are a reflection of place-specific interconnections between factors in time and space. Combining the methods and perspectives from different academic disciplines with stakeholder knowledge is essential to acquire an in-depth understanding of a city’s metabolism. Moreover, a place-based and multi-scale perspective in UM research is essential to advance our understanding of (case-specific) consumption patterns and their underlying case- and scale-specific mechanisms of influence.

This thesis looks into the impact of data uncertainty on the techno-economic decisions of the actors in a future energy system, with flexibility sources. It looks into the problem from the view point of three actors, namely, the distribution system operator, aggregators (as potential operators of a demand response program), and end-users, such as building energy managers and residential consumers. A comprehensive analytical sensitivity analysis framework is developed to quantify and monetize the impact of data uncertainty on the operation of different stylized energy systems with flexible resources.The proposed framework consists of four mathematical models: a data pre-processing module, an optimisation algorithm to model the operation of the energy system and the flexibility provider, a local (analytical) sensitivity analysis (LSA), and a global sensitivity analysis (GSA). Together, the framework is used to investigate the impact of uncertainty on the operation of a market-based energy system in the future, as well as the requirement of the existing and the emerging actors in such environment.

Fields such as water and wastewater treatment, dredging, mining, food processing, textile and paper making, petroleum and chemical industries face the challenge of particle removal from (waste) water. The removal of solids from these water streams is generally achieved via the coagulation/flocculation process, which is a simple and effective way to destabilise, agglomerate and remove particles from water and wastewater. Currently, this process is widely accomplished with the use of inorganic coagulants and fossil-based organic flocculants. Flocculants are particularly important because they are efficient at low dosages and able to form strong flocs. However, most synthetic flocculants biodegrade poorly and some of the degradation products/monomer residues are toxic, with acrylamide from polyacrylamide as a well-known example to have carcinogenic and neurotoxic effects. Besides, unreacted toxic chemicals used to synthesise the monomer units, such as formaldehyde, epichlorohydrin, and dimethylamine, have been found as sources of contaminants in treated water. Hence, the use of synthetic flocculants can hardly be considered a sustainable (waste) water treatment approach, especially in open systems such as in surface water treatment, dredging and mining.As an alternative, bioflocculants have gained increasing attention for water treatment since they are generally safe, biodegradable, and can effectively flocculate particles with performances sometimes comparable with synthetic flocculants. However, a class of promising bioflocculants yet to be fully explored are microbial extracellular polymeric substances (EPS). EPS are products of microbial biochemical secretions, comprising different macromolecules such as polysaccharides, proteins, lipids and humics substances. The high molecular weight of EPS coupled with their net negative charge make them anionic polyelectrolytes that can be applied in several fields such as for particle flocculation and heavy metal adsorption. Although EPS are already being produced from pure microbial strains (commercial exopolysaccharides such as alginate and xanthan gum), their high cost, due to the need for sterile conditions and expensive substrates such as glucose, limit their use to specialty applications such as food, feed, medicine and cosmetics.To produce cost-effective EPS that can be applied as flocculants, we established a mixed-culture approach that requires non-sterile cultures and feedstocks by using (industrial) wastewater as both carbon and nutrient source. Here, one uses the potential of cooperative growth and symbiotic relationships in mixed cultures of EPS-producing and non-EPS–producing bacterial strains as found in wastewater sludge. Moreover, this approach allows the combination of biological organic pollutant removal from wastewater with the production of EPS as a useful product. By converting most of the organics that would have been mineralised to EPS, wastewater treatment plants (WWTPs) can benefit from a reduced quantity of produced sludge, which is expensive to dispose of, and can also lower their CO2 footprint.The aim of this thesis was to valorise selected industrial wastewaters to extracellular polymeric substances (EPS) that can be employed as bioflocculants, heavy metal adsorbents and for other applications. To achieve this, it was important to study three aspects of the technology value chain: the production, characteristics and applications of EPS as flocculants and heavy metal adsorbents.EPS production was combined with fresh and saline wastewater treatment, using substrates such as glycerol, glucose, acetate and ethanol to mimic different industrial wastewaters. Under nitrogen-limited conditions, as much as 30 - 69 % wastewater-COD could be recovered as EPS-COD. Moreover, EPS produced under such nitrogen-limited conditions were mainly composed of polysaccharides, possessed higher molecular weights (1 - 4 MDa) and showed better flocculation performances than EPS produced from excess nitrogen. Highly charged anionic EPS (≥ 5 meq/g EPS) were also shown to have very high capacity to adsorb and recover heavy metals such as Cu, Pb, and Au.

Antibiotics are being used intensively for humans and livestock worldwide and led to the presence of antibiotics and antibiotic resistance genes (ARGs) in the environment. The existing wastewater treatment plants (WWTPs) are not designed to remove them. Consequently, surface water is a potential receptor of antibiotics and ARGs. Therefore, additional treatment technologies are needed to overcome the current drawbacks of our WWTPs. In this thesis, antibiotics and ARGs were measured in the surface water up to 20 km after being treated by a WWTP (with a post-treatment). A significant contribution of antibiotics and ARGs were observed in the environment. Therefore, treatment technologies based on natural systems, physicochemical technologies, or advanced biological technologies were selected to explore their effectiveness for reducing antibiotics and ARGs. Based on these findings, we can understand the occurrence of the antibiotics and ARGs in the environment, and the potential of these technologies for removing them. Deze thesis ‘Antibiotica en antibiotica resistente genen in afvalwater: Verspreiding en verwijderingstechnologieën’ beschrijft de verspreiding van antibiotica en ARGs in het afvalwater en in het milieu, en de verwijderingscapaciteit van verschillende fullscale technologieën. Onderscheid is gemaakt tussen de volgende RWZI onderdelen: primaire behandeling (verwijdering van vaste deeltjes door middel van filtratie en sedimentatie), secundaire behandeling (verwijdering van organisch materiaal en nutriënten door middel van biologische processen), tertiaire behandeling (verwijdering van verontreinigingen door middel van fysisch-chemische technieken) en quaternaire en/of nabehandeling (verwijdering van microverontreinigingen en pathogenen). De volgende full-scale technologieën zijn geselecteerd: (1) geavanceerde biologische technologieën (voor secundaire behandeling) zoals aeroob korrelslib; (2) fysisch-chemische technologieën (voor tertiaire behandeling) zoals actief kool en (3) natuurlijke behandelingstechnologieën (voor nabehandeling) zoals helofytenfilters.

Industries, such as leather tanning, agro-food, fisheries, petroleum, petrochemical and textile dyeing produce saline wastewater. As a result approximately 5% of the globally generated wastewater is hypersaline (salinity above 3.5%). Because salts have a negative effect on microbial activity, biological treatment processes are usually not considered for such wastewaters and they are treated with more expensive physical-chemical processes. Hence, there is a need to broaden the application of more sustainable biological treatment methods. In particular, anaerobic biological treatment should be considered due to possibility of converting organics into biogas, low energy requirements for operation, and production of small amounts of bio-solids. Amongst the anaerobic biological treatment technologies those based on formation of granular sludge are of special interest. This is due to superb settling velocities and a high methanogenic activity of the granules, which allows for a compact reactor design capable of handling high volumetric organic loading rates. Before this research, anaerobic granular sludge was reported to be unsuitable for treatment of highly saline wastewater because methanogens are inhibited by the salinity and sludge granules disintegrate/do not form. The main objective of this thesis was to accomplish anaerobic granulation at high salinity from dispersed biomass and to investigate strategies of overcoming salt toxicity to microorganisms. In Chapter 2 we investigated the possibility to form granules from dispersed biomass at low (5 g Na+/L) and high salinity (20 g Na+/L) in upflow anaerobic sludge blanket (UASB) reactors under other conditions known to improve fresh water granulation. The wastewater contained a complex, energy rich and proteinaceous substrate – a mixture of glucose, acetate and tryptone. This allowed a surprisingly fast development of anaerobic granules (within 45 days), even at 20 g Na+/L (~ 50 g/L NaCl). Although the COD (chemical oxygen demand, a measurement for organic pollution) removal efficiency was slightly better at 5 g Na+/L compared to 20 g Na+/L, at both salinities the removal efficiency exceeded 98% at organic loading rates as high as 16 g COD/L/d. To remain viable at high salinity, most prokaryotes synthesize or take up from bulk liquid small organic molecules called osmolytes. Uptake of osmolytes from bulk liquid is energetically more favourable compered to synthesis. Furthermore, it is known that methanogens mainly use nitrogen containing molecules, such as amino acids or their derivatives for osmoprotection. Also, extracellular polymeric substances (EPS) – the structural gluing material of granules - in anaerobic granular sludge consist of a large weight fraction of proteins (up to 90%). Thus, we hypothesized, that proteinaceous substrate in Chapter 2 potentially provided bioenergetically favourable synthesis precursors of osmolytes and EPS. This hypothesis was investigated in Chapters 3-5. In Chapter 3 proteins and amino acids were inspected for their potential to alleviate osmotic shock stress of acetoclastic methanogens in granular sludge. Aspartate, glutamate, gelatine and tryptone could all alleviate the negative effects of high salinity on methanogens. Furthermore, analysis of nitrogen containing osmolytes accumulated by salt adapted granular sludge revealed glutamate and N-acetyl-β-lysine as the major osmolytes. This could in part explain the positive effect of amino acids on methanogenic activity: glutamate could be taken up directly from the bulk liquid, while N-acetyl-β-lysine could be synthesized from aspartate after uptake in the cell. Hydrolysis of a protein (gelatine) and a peptide (tryptone) potentially could also provide both of these amino acids, thereby explaining their positive effect on methanogenic activity. In Chapter 4 the (positive) effect of proteinaceous substrates on the rate of anaerobic sludge granulation was investigated. In UASB reactor experiments, glucose and acetate were present in the wastewater, together with a third co-substrate that was different for each reactor. If proteinaceous compounds (tryptone or gelatine) were added as the third substrate, granulation at 20 g Na+/L already was observed after 40-50 days. With starch as the third substrate well settling granule-alike aggregates formed. However, this was only possible after a much longer period (~180 days) than with the proteinaceous substrate. Still, apparently methanogenic adaptation and sludge granulation can be achieved at high salinity even without addition of proteins implying that a broader spectrum of saline wastewater is amenable for anaerobic granular treatment without the need of protein dosing. In Chapter 5, the possibility to estimate the amount of proteinaceous substrate for enhanced granulation based on osmotic pressure calculations was studied. The experimental results agreed with calculations, which allowed for a nine fold decrease of protein concentration compared to the arbitrary chosen amounts in Chapter 2 and Chapter 4. In Chapter 6 microbial molecular and microscopy analyses revealed that in sludge granules of reactors supplied with proteinaceous substrate the dominant methanogenic archaea at two different salinities (5 and 20 g Na+/L) belonged to Methanosaeta in its filamentous form. Interestingly, also the dominant bacteria were present as filaments (Streptococcus at 5 g Na+/L and bacterium belonging to Defluvitaleaceae at 20 g Na+/L). An experiment was also performed in which the granulation at 20 g Na+/L from dispersed biomass was studied without a proteinaceous substrate, but with amino acids leucine and proline instead. In this reactor, the bacteria belonging to Defluvitaleaceae disappeared and the granulation was not achieved. In Chapter 7, ion exchange membranes were prepared with EPS extracted from high salinity adapted granules and shown to selectively transport cations and partially repel anions. Interestingly, EPS exhibited a higher selectivity for potassium transport compared to sodium, even though potassium and sodium have the same valence and similar physical-chemical properties. As potassium selectivity has commercial relevance, future studies focusing on the reason for this selectivity perhaps can result in the development of commercial potassium selective membranes. For microbial cells such improved transport of ions through EPS seems to have a negative effect. In methanogenic activity assays potassium was much more toxic compared to sodium suggesting that cation toxicity may be influenced by properties of EPS, i.e. the better the ion can diffuse through the EPS, the more toxic it is (Chapter 7). Finally, in Chapter 8 the results of this research are discussed in a broader context and future research directions are proposed.

The increasing legislation pressure, risks associated with micropollutants, and the insufficient efficacy of conventional WWTPs on their removal have formed a joint driving force that is boosting studies on more efficient treatment technology. The general objective of this thesis is to contribute to a better understanding and further development of photochemical treatment processes for micropollutant removal from aqueous streams. Emphasis of this thesis is given to two topics: (1) Further development of UV/TiO2 technique by application of TNA as immobilized catalyst; (2) Development of alternative photochemical water treatment technique for micropollutant removal from wastewater. This thesis demonstrates that: (1) TiO2 nanotube array is a promising immobilized photocatalyst for the removal of micropollutants; (2) Red light induced methylene blue photosensitization provides an efficient process for micropollutants removal.

Pharmaceutical compounds, originating mainly from industrial production and public consumption, are detected at extremely low levels (ng·L-1 –µg·L-1) in groundwater, surface water, and wastewater. So far, the adverse effects of pharmaceuticals and their intermediates have been widely reported, and include toxicity to humans and ecosystem, and enhancement of antimicrobial resistance. These effects call for the elimination of pharmaceuticals from water. This can be done by both abiotic and biotic degradation in the presence of oxygen (aerobic conditions) or in the absence of oxygen (anaerobic conditions). The technologies under anaerobic conditions are generally more sustainable and attractive because they require less energy and produce less pollutants, such as greenhouse gas, compared to technologies under aerobic conditions. Anaerobic degradation with metal oxides such as manganese (Mn) or iron (Fe) oxides has clear advantages in both drinking water treatment and wastewater treatment. Therefore, anaerobic degradation of pharmaceuticals in water with Mn or Fe is promising to study and develop into applicable techniques. This thesis investigates the feasibility of anaerobic degradation of pharmaceuticals in Mn- and Fe-mediated systems via both abiotic removal processes and by biodegradation. In Chapter 1, the scientific and technological motivation of the thesis is proposed. Applications and scientific developments of Mn- or Fe-based technologies to remove pharmaceuticals from water are reviewed and discussed in Chapter 2. Based on the removal mechanisms found in nature and technical systems, these Mn- or Fe-based technologies can be classified into 3 groups – physico-chemical removal, chemical removal, and biologically-related removal. A review of previous research indicates that pharmaceutical removal with Mn- or Fe-based technologies from water is efficient, and the removal efficiency varies whit the different technologies applied. Positive and negative aspects of these processes, such as (non-)specificity, treatment conditions, formation of and effects of intermediates and by-products, and effects of Mn or Fe compounds were evaluated. Based on that, new and promising Mn- or Fe-based technologies are proposed as future potential effective and sustainable pharmaceutical removal technologies. Among these proposed technologies, the dissimilatory Mn or Fe reduction is identified as a most attractive, sustainable, and low-cost technology because this novel technology requires neutral conditions and the bacteria involved are able to completely mineralize the pharmaceuticals. The anaerobic biodegradation of pharmaceuticals coupled to dissimilatory Mn(IV) or Fe(III) reduction is tested with different types of Mn(IV) and Fe(III) (Chapter 3). With a mixture of adapted sediment to metoprolol and chemically synthesized Mn(IV), anaerobic biodegradation with amorphous, chemically synthesized Mn(IV) can effectively remove caffeine (26%) and naproxen (52%) after 42 days of incubation. Further experiments with Mn(IV) obtained from drinking water treatment plants show that this type of Mn(IV) can be used to remove metoprolol and propranolol, with respectively 96% and 31% after 72 days of incubation. The inoculum can also use Fe(III) as alternative electron acceptor to degrade metoprolol. Results show that metoprolol degradation with insoluble chemically synthesized Fe(III) and soluble Fe(III)-citrate reaches 57% and 52%, respectively. No significant removal is observed in all the abiotic controls, showing that the biodegradation is the main removal mechanism in pharmaceutical removal with Mn(IV) or Fe(III). Abiotic removal of selected pharmaceuticals with MnO2 is compared under aerobic conditions and anaerobic conditions (Chapter 4). Results show that anaerobic conditions promote diclofenac removal, while it inhibits removal of metoprolol and propranolol. In demineralized water (demiwater), diclofenac removal under anaerobic conditions is 78%, and higher than the 59% found under aerobic conditions. In 50 mM phosphate buffer, and under aerobic conditions, the diclofenac removal achieves complete removal. Under anaerobic conditions the observed removal is similar as in demiwater. Preliminary investigation shows that diclofenac removal with MnO2 under anaerobic condition is better at acidic pH (pH 4 – 5) and the removal is higher when applying amorphous MnO2 compared to applying crystalline MnO2. The key factors determining the extent of pharmaceutical removal with MnO2 under anaerobic conditions are the following: the chemical structure and molecular properties of the pharmaceuticals, and the properties and activity of reactive sites on the MnO2 surface. Applying MnO2 under anaerobic conditions to remove diclofenac from water is further investigated (Chapter 5). Results show that increasing the temperature from 10 to 30°C leads to an increase in the diclofenac removal, whereas further increase of temperature to 40°C results in a decrease in the removal. The latter effect is possibly due to Ostwald ripening and/or aging processes. Increasing the amount of MnO2 increases the diclofenac degradation, as this provides more reactive sites for diclofenac conversions. Further shifting the molar ratio of MnO2 and diclofenac from 2200:1 to 8900:1, however, does not further increase diclofenac removal, probably due to limited oxidation capacity of MnO2. The presence of metal ions strongly inhibits the diclofenac removal following the order of Mn2+> Ca2+ ≈ Mg2+ >Fe3+. The metal ions appear to adsorb onto the MnO2 surface and compete with diclofenac for reactive sites. Phosphate has a diverse effect on diclofenac degradation: low concentrations inhibit and high concentrations promote the removal. The humic acids significantly promotes diclofenac removal, probably caused by affecting MnO2 reactive surface sites. To reuse the Mn or Fe during pharmaceutical removal under anaerobic conditions, biological production of Mn(IV) or Fe(III) is investigated under oxygen-limiting conditions, or with nitrate as electron acceptor (Chapter 6). Mn(IV) is successfully produced with Mn(II)-oxidizing bacteria under O2-limiting conditions, and the produced Mn(IV) is amorphous. Pharmaceutical removal with the Mn(II)-oxidizing bacteria is not observed. In abiotic pharmaceutical removal, using Mn(IV) from a drinking water production plant, is effective to remove metoprolol and propranolol. The successful production of Fe(III) is also observed under NO3--reducing conditions via biological processes. The biologically produced Fe(III) is also amorphous. There is no significant removal of pharmaceuticals coupled to the biological Fe(III) production. When comparing the biologically produced Fe(III) and other types of Fe(III), only Fe(III) from a drinking water production plant and one Fe(III)-based sorbent can remove propranolol. Finally, the outcomes of this thesis are discussed and provide insights into the application of anaerobic degradation of pharmaceuticals with mediation of Mn and Fe oxides (Chapter 7). The removal mechanisms include adsorption, chemical oxidation, and biodegradation and are identified to contribute to the different removal processes. The anaerobic Mn(IV)- and Fe(III)-mediated pharmaceutical degradation processes are evaluated on the basis of removal performance, environmental and operational conditions, sustainability of the processes, as well as the Mn and Fe types involved. Results described in this thesis provide a proof of principal for anaerobic Mn(IV)- or Fe(III)-mediated degradation in removing pharmaceuticals from water. To translate the process into a pharmaceutical removal technology for water treatment, three steps are proposed including (1) exploring the limits of anaerobic Mn- or Fe-mediated pharmaceutical degradation processes; (2) simulating the process in practice with a controlled systems, and (3) translating the processes to a pilot-scale system before a full-scale application. In addition, research topics are identified that can help to meet these challenges in the future. In summary, anaerobic Mn(IV)- or Fe(III)-mediated systems can remove pharmaceuticals from water through both abiotic removal and biotic degradation. These are promising processes which can be developed into a robust, sustainable, affordable, and environmentally friendly technology to remove pharmaceuticals from water.

The occurrence of pharmaceuticals in the environment has become a worldwide environmental concern. After administration and excretion, pharmaceuticals end up in wastewater treatment plants. These plants, typically employing biological treatment, are not designed for their removal. Hence, numerous pharmaceuticals are emitted into the environment. Chemical treatment processes like ozonation can effectively remove pharmaceuticals, however these costly processes have disadvantages such as high energy consumption and by-product formation. On the contrary, biological treatment processes are less effective for pharmaceutical removal, but can complement chemical process by for instance by-product removal. In this dissertation the combination of biological and chemical treatment processes for pharmaceutical removal was therefore studied. We found complementariness between various combinations of biological and chemical processes, resulting in the design of cost-effective combined treatment processes for enhanced pharmaceutical removal from wastewater treatment plant effluents.

A constructed wetland (CW) is an integrated and enhanced version of natural ecosystem for fate and transport of pharmaceutically active compounds (PhAC). This thesis demonstrates removal mechanisms of PhACs in CWs and their application as post-treatment processes to eliminate PhACs from wastewater effluent. Four main subjects were investigated in this thesis: 1) mechanisms of PhAC removal in individual processes in CWs, including photodegradation, sorption, biodegradation, and phytoremediation and their interactions; 2) effect of important environmental factors (i.e. dissolved organic matter, redox conditions) on the removal processes; 3) enhancement of photodegradation and biodegradation capacity in CWs; 4) fate and distribution of PhACs in CWs by using chemical and toxicological analytical tools.