A reverse osmosis (RO) membrane followed by a packed tower aerator and rapid sand filter are used by an agricultural company in Emmen to treat brackish groundwater to supply water for growing crops and cleaning purposes. The iron removal by the treatment plant is sufficient most of the time throughout the year. However, the farmer periodically (once per year) reported yellowish treated water, indicating insufficient iron removal. Nevertheless, it is still not clear what is the cause of the insufficiency of the iron removal. This thesis aimed to investigate the iron removal in the water treatment plant in Emmen and propose a solution to improve the iron removal. The iron removal of the treatment plant was investigated through a set of batch iron oxidation, flocculation, and filtration experiments. The pH of the water was the main parameter that influenced the oxidation of Fe(II). It was found that within the retention time that was available in the treatment plant’s tower aerator and the rapid sand filter (20 minutes), the Fe(II) was not fully oxidized and flocculated. At pH of the permeate in the range of 6 – 7, only <11.5% of the initial Fe(II) was oxidized in 20 minutes. Increasing the pH to 8 accelerated the oxidation of Fe(II), and the Fe(II) was completely oxidized within 30 minutes.Although removal of iron that is dominated by floc filtration was not achieved, the treatment plant also removed the iron through adsorption on iron hydroxide deposit in the packed tower aerator and sand particle. However, the Fe(II) adsorption capacity of adsorbents was low at low pH. The regeneration of the adsorption capacity was achieved through oxidation of the adsorbed Fe(II) which is also influenced by pH. COMSOL model showed that without regeneration, the adsorption capacity of new sand and iron oxide-coated sand was exhausted after 24 hours and 230 hours, respectively.When the concentration of CO2 in the permeate is in equilibrium with air, the pH of the permeate should be in the range of 7.9 – 8. However, the maximum pH of the permeate was 7 after aeration because the contact time of the tower aerator was not sufficient to completely strip the CO2. The tower aerator was also clogged by iron deposits that reduces the airflow and causes short-circuiting that decrease the CO2 stripping efficiency over time.Installation of a bubble column reactor was proposed to improve the CO2 stripping and increase the pH of the permeate. The Phreeqc model showed that the CO2 could be stripped until approx. 1 mg/L within 4 minutes, and the pH also increased to approx. 7.9. Moreover, the bubble column reactor will provide additional retention time for Fe(II) oxidation, and approx. 20 – 30% of the initial Fe(II) concentration can be oxidized within 4 minutes. The bubble column was considered preferable compared to the packed tower aerator because it was not susceptible to clogging by iron deposits and requires lower maintenance.

This work investigated which NOM fraction from secondary wastewater effluent were causing competition with metoprolol and clarithromycin for adsorption site on high silica zeolites (HSZ). This thesis works with five commercially available HSZ frameworks (FAU, MOR, BEA, MFI and FER). Adsorption batch test were performed with demi water, wastewater and nano filtrated wastewater with molecular weight cutoff around 400 Da. The competition between two organic micro pollutant (OMP) metoprolol and clarithromycin in demi water were not obvious for FAU type high silica zeolite. Metoprolol is adsorbed much better than clarithromycin regardless of the water type or high silica zeolite framework. Adsorption of clarithromycin was the best with MOR and BEA in demi water, but the removal deteriorated severely in secondary wastewater effluent. Clarithromycin adsorption on BEA and MOR in micro filtrated wastewater and nano filtrated wastewater seems to be comparably impaired. Metoprolol on the other hand showed counter intuitive results. It adsorbs worse in nano filtrated wastewater compared to micro filtrated wastewater for MOR and BEA.

In this study simultaneous and continuous inline dosing of PAC and coagulant in UF was investigated. Surface water was directly treated with PAC-UF and performance of the system was assessed by looking at membrane fouling and organic micropollutants removal. Combining adsorption and membrane processes in one technique, hybrid membrane processes, enhances performance of OMP removal by membrane processes. Powdered activated carbon (PAC) combined with coagulation and ultrafiltration (UF) is a possible treatment technique for surface water. Permeability in UF-membranes remains steady, when dosing coagulant. Only a small increase in irreversible fouling of 0.2-0.7*109 m-1h-1 is visible. However, absence of coagulant dosing causes irreversible fouling to increase to 8.7*1010 m-1h-1 and can not be easily reversed with a chemically enhanced backwash (CEB). Inline dosing of PAC alone causes an irreversible fouling of 11.4*1010 m-1h-1 and highest increase in reversible fouling of 11.7*1010 m-1h-1. Addition of coagulant (1.2 mg/l) lowers reversible fouling compared to no dosing, on the other hand addition of PAC to coagulant shows no clear increase or decrease in reversible fouling. Coagulation has a negative effect on capillary blocking, an increase of 4-8% compared to no coagulant or adsorbent. PAC and no dosing did not influence pore blocking. Highest removal of low to good adsorbable OMP was 10-63% for continuous and simultaneous dosing of 12 mg PAC/l and 1.2 mg FeCl3/l. Increasing filtration time (30 to 60 min) showed highest removal efficiency of 75% of Sotalol and 5-Methyl-1H-Benzotriazole, both good adsorbable OMP. Removal of PFAS varies between a few percent and 37%. Continuous dosing of coagulant (1.2 mg/l) with PAC (10 mg/l) has a negative impact on OMP adsorption including PFAS. With a higher PAC dose (15 mg/l) removal efficiency was not affected. Addition of coagulant with PAC-UF showed to be effective to prevent irreversible fouling, with direct surface water treatment. However, coagulation is responsible for blocking of capillaries even resulting in a small decrease of permeability. Removal of OMP including PFAS was much lower compared to other PAC-UF systems and therefore PAC-UF with simultaneous and continuous inline dosing of PAC is not a good set-up. Adjustments in set-up should be made in order to make this configuration work. Possible improvements are increase of filtration time between backwash and dosing sequence of PAC and coagulant.

The increase in greenhouse gas emissions change the precipitation behaviour causing either extreme wet- or dry weather. This impacts the fresh water supply for clean water production. Evides B.V., one of the Dutch water companies, anticipates to these changes with the sewer mining concept called ‘RINEW’ (Rotterdam Innovative Nutrients and Energy Watermanagement). RINEW studies various ways to recover valuable substances in direct decentralized sewage treatment. The treatment scheme involves the pre-treatment microscreen, coagulation and ceramic Microfiltration (cMF) for the water purification step Reverse Osmosis (RO). Since the application of cMF for sewage treatment is a novel concept, the objective of present thesis is to gain insight into technical aspects of cMF (a cMF fouling indicator and effect of oxygen on RO biofouling) and potential financial feasibility of the RINEW concept in the Netherlands. To study the potential of a fouling indicator for the cMF, irreversible fouling rates and feed water quality results are obtained over a two month period. The feed water quality is digitally monitored and characterized on COD, NTU and EC. The parameter ‘COD’ (chemical oxygen demand) is considered the most suitable as fouling indicator due to the relative large particle size of organic matter and sticky properties of biopolymers. Relating the fouling rates to the feed water quality results in a linear trend where higher irreversible fouling rates occur at higher COD concentrations. Yet, the trend result is scattered significantly since the operational flux was highly instable over time. The feed pump is originally designed for a Nanofiltration (NF) application which may explain the deviant cMF operation. The effect of oxygen in cMF permeate is studied on the (bio)fouling development on spiral wound Reverse Osmosis (RO). The study is done in duplicate each time using two parallel Membrane Fouling Simulator (MFS) which are fed by cMF permeate. In one MFS setup the water is depleted from oxygen by adding Sodium Bisulfite (NaHSO3). The pressure drop results in the MFS fed by aerobic water indicate a significant unstable fouling rate. The fouling rates obtained from the MFS fed by oxygen depleted water compare to similar studies done with NF permeate and tap water. This suggest a significant stable RO biofouling can be obtained if Sodium Bisulfite treatment is applied to RO feed water. The potential financial feasibility is studied via a concept study. Concept 1 is the RINEW concept providing high quality water (e.g. demi water) to an industry. Since it is a sewer mining concept the water transport costs are neglected. In concept 2 an equal high quality water flow is produced from secondary effluent by a MF/UF+RO combination at a central Sewage Treatment Plant (SWTP). The water transport from the central SWTP to the industry is taken into account in concept 2. The difference in specific costs [EURm-3] between the two concepts is estimated which is recalculated into a breakeven the high quality water transport distance of approximately 20 km. In other words, if an industry demands high quality water and sewage is the only water source, concept 2 is more financial feasible within a range of 20 km from a SWTP. In relation to the Netherlands the SWTP density is discussed as too high for the RINEW concept to be financial feasible. Similar realized treatment plants in the Netherlands show higher importance to aspects like water source, current expertise and existing facilities in the decision-making of treatment plant.

This thesis constitutes a part of the "IMPRESS" project which is aiming at the production of bio-plastics by utilizing hemicellulosic hydrolysates. The hydrolysate stream, after following the steps of acid hydrolysis and neutralization, consists of monosaccharides (C5/C6 sugars), salt and sugar degradation products. The C5/C6 sugars need to be concentrated by a factor of 10 to be purified afterwards in downstream processes. Evaporation has been the most dominant technology in the sugar treatment sector, however the current study aimed to investigate tubular nanofiltration (NF) and vacuum membrane distillation (VMD) units for concentrating the C5/C6 sugars, as more sustainable alternatives. Synthetic solutions with C5/C6 sugars and salt were used to assess the performance of the NF and MD membranes in terms of sugar and salt rejection before the experiments with the real hydrolysate solution. Among the different NF and MD membranes, the one that met the C5/C6 sugar rejection requirements (>90 %) during the synthetic solution experiments was tested for concentrating the C5/C6 sugars. The most suitable technology for concentrating the C5/C6 sugars was also assessed for its energy consumption. Additionally, single filtration tests were conducted to characterize the NF membranes, while surface tension and contact angle measurements were performed to predict the membrane wetting phenomena during the VMD operation. Based on the C5/C6 sugar rejection values (range of 22-81 %) obtained with ceramic and polymeric NF membranes, it was deduced that the tubular NF membranes were not capable of meeting the C5/C6 sugar concentration goals. The polymeric membranes performed better than the ceramic ones in terms of C5/C6 sugar rejection, with a maximum sugar rejection of 81 %. However, the polymeric membranes were found to be more prone to fouling, showing a maximum decrease of 34 % in the water permeability after 4 hours of operation with the hydrolysate solution. Additionally, the characterization of the NF membranes based on the Donnan Steric Pore Model (DSPM) revealed membrane pore sizes larger than those provided by the manufacturer. On the contrary, the 0.2 μm MD membrane showed >99 % of C5/C6 sugar rejection and was used for the sugar concentration tests. The maximum C5/C6 sugar concentration factor (CF) achieved with the VMD was 8 with a negligible sugar loss (<1 %) in the permeate, indicating that concentrating the C5/C6 sugars by a factor of 10 is feasible with this technology. Surface tension and contact angle measurements disclosed inconsistencies in the hydrophobicity of the MD membrane, which can be linked to the membrane wetting phenomena occurred during the VMD operation. The fouling of the MD membrane (50 % of flux decrease after 39 hours of operation) was found to be reversible with complete flux recovery after chemical cleaning and drying of the membrane. The energy assessment of the VMD technology showed that the main energy consumer was the cooler, contributing to 96 % of the total consumed energy. Based on the cooler's efficiency, the energy consumption of the VMD unit was calculated to be in the range of 207-736 KWh/m3 of distillate. When compared with multi-effect evaporators with up to three effects, the VMD was found to be more energy efficient. Investigating less energy-intensive alternatives for concentrating the C5/C6 sugars, experiments with electrodialysis (ED) showed 90 % removal of both acid and salt from the raw and neutralized hydrolysate water, respectively, making it feasible for reverse osmosis (RO) membranes to be further tested for concentrating the C5/C6 sugars. Therefore, a treatment scheme of ED and tubular RO membranes is proposed for further research on concentrating the C5/C6 sugars. Overall, a pre-treatment step with the most permeable ceramic NF membrane is suggested, as evinced by the high color removal achieved (elimination of big foulants) and the high permeation of the C5/C6 sugars and salt.

The aim of this research was to evaluate the feasibility of direct hollow fiber nanofiltration membranes for drinking water purposes. The experiments were performed on the dNF40 pilot provided by NXF. The fouling potential and the ion retention of the dNF40 pilot were determined by continuous filtration experiments using raw IJssellake water under different operational conditions. The performances (ion retention and fouling potential) of the dNF40 on raw IJssellake water were compared with the dNF40 performances on pre-treated water from Waterwinstation Prinses Juliana (WPJ) (previously done at PWNT). The WPJ pre-treated water has undergone extensive pre-treatment consisting of drum screens, flocculation, sedimentation, rapid sand filtration (RSF) and granular activated carbon (GAC). The OMP retention of the dNF40 pilot was determined by full recirculation experiments using WPJ pre-treated water under two different operational conditions with elevated concentrations 'spiked solution'. Limited to no fouling impact was observed on the membrane performance when feeding the pilot with raw IJssellake water. The membrane performance parameters (mass transfer coefficient (MTC), trans membrane pressure (TMP) and normalized pressure drop (NPD)) were stable over time. In addition, limited to no fouling impact was observed on the membrane when feeding the pilot with WPJ pre-treated water. However, membrane performance (i.e. MTC) was better for raw IJssellake water (1 year old membrane) compared to WPJ pre-treated water (virgin membrane). This implies that the active outer layer of the membrane has undergone a change in properties leading to these higher MTC values. An increase in recovery, flux and crossflow velocity resulted in a decrease in ion retention. However, a decrease in ion retention with elevated crossflow velocity is unusual. Higher crossflow velocities should actually lead to an increase in ion retention due to reduced ion build-up next to the membrane surface (i.e. lower concentration polarization effect). However, the lower ion retention can be attributed to the elevated MTC during experiments. The removal of natural organic matter (NOM) was consistently above 90% and was not influenced by a change in operational condition. Ion retention was higher for WPJ pre-treated water (virgin membrane) compared to raw IJssellake water (1 year old membrane). This can be attributed to the increase in MTC of 1.5 LMH/bar in raw IJssellake water (compared to WPJ pre-treated water) potentially caused by a change in the properties of the active outer layer. For determining the OMP retention of the dNF40 membrane, a spiked solution containing per- and polyfluoroalkyl substances (PFAS) and pharmaceutical compounds was analyzed. The PFAS compounds of the spiked solution were retained very well (above 80%). As expected, the retention increased with increasing MW. The adsorption percentage of PFAS was between 40%-90%. The pharmaceutical retention was around 30%, although all pharmaceuticals analyzed had a MW below the MWCO of the membrane. A 5-stage full-scale dNF40 plant was designed based on a permeate flow of 15 M m3/year, a total hardness concentration in the permeate stream below 1.4 mmol/L and a recovery percentage of 85%. Based on the 5-stage full-scale dNF40 plant an economical analysis was performed and compared to the full-scale UF-RO in Heemskerk. The total cost (OPEX and CAPEX) were cheapest for the full-scale dNF40 plant fed with raw IJssellake water (12 ct/m3), followed by the dNF40 plant fed with WPJ pre-treated water (32 ct/m3) and most expensive for the UF-RO plant (35 ct/m3). The major factors in the OPEX was the membrane replacement cost for the dNF40 plant and the energy and chemical cost for the UF-RO plant.

The new concept of sewer mining which utilizes the ceramic nanofiltration (C-NF) membranes offers a compact solution for water and other resources recovery. However, since it has very limited pre-treatment process, membrane fouling is a common problem due to the direct contact between the membrane and sewage water. Sewage water contains a lot of extracellular polymeric substances (EPS) that can block the membrane pores. One of the most persistent EPS is sodium alginate which responsible for the gel layer formation on the membrane surface. Removal of the alginate gel layer can be done by implementing chemical cleaning. However, too frequent chemical cleaning can damage the membrane and environmentally dangerous. Therefore, to make this new concept of sewer mining more feasible, the correct cleaning method to remove the fouling layer need to be found. From this point, the research objective for this research is formulated as “Investigation of fouling control methods that can prolong the time before chemical cleaning needs to be performed to achieve higher water production.” Several methods such as forward flush, iron coating and calcium carbonate coating were investigated. Alginate filtration was done under constant pressure experiment and the effectivity of each cleaning method was calculated by measuring the change in water permeability after the cleaning. The results show that the iron and calcium carbonate coating followed by 5 min forward flush are able to achieve a permeability recovery of 40 to 90 %. Iron coating required 400 mg/l of iron hydroxide to be dossed and a minimum of 5 min reaction times with hydrogen peroxide to have a high permeability recovery. On the other hand, only 1 minute is required by 200 mg/l calcium carbonate dosing concentration with citric acid as a cleaning solution to achieve a similar improvement as the iron hydroxide coating. Both of the processes produce higher water productivity in 2 h of experiment than the chemical cleaning with 0.1 % sodium hypochlorite. In the end, a theoretical projection on the real sewage water filtration was made to study the economic and environmental impact of the coating process. The results show the cost of production per m3 of clean water is 0.22 euro for iron hydroxide and only 0.12 euro for calcium carbonate. Furthermore, environmental impact assessment using Chain Management by Life Cycle Analysis (CMLCA) software which produced by Leiden University with Eco-indicator 99 (EI-99) categorization shows that calcium carbonate has less environmental burden than iron hydroxide coating.

Globally, drinking water sources are polluted with poly- and perfluoroalkyl substances (PFAS). The toxicity and persistent properties of these industrial chemicals raised concerns about environmental and public health. As a result, drinking water companies are removing PFAS from drinking water using separation technologies. Anion exchange and nanofiltration membranes have been proven to be effective drinking water treatment methods for the removal of PFAS. However, these drinking water technologies produce large volumes of PFAS-containing waste streams, which poses new challenges for the drinking water industry. To prevent toxic PFAS from re-entering the environment, these waste streams must be treated. This can be done by PFAS destruction, however, due to the large volumes of the waste streams, this is very expensive and energy-intensive. Therefore, concentrating the drinking water waste streams before destruction is desired. This research examined existing PFAS-concentration technologies and compared their PFAS removal efficiency, volume reduction, and cost-effectiveness in concentrating the PFAS waste streams produced during drinking water treatment. These waste streams include the concentrate of nanofiltration and the brine from anion exchange. The analysed concentration technologies are foam fractionation, adsorption of PFAS onto DEXSORB+ and all-silica BEA zeolites, and nanofiltration. Foam fractionation removes PFAS from the waste stream by injecting air bubbles. Two laboratory setups were made for the injection mechanism of the air bubbles. First, by passing pressurized air through an air stone, and second, by adding pressurized water (i.e. white water) to the waste stream. The adsorbents were tested in the laboratory by conducting equilibrium batch experiments with different adsorbent dosages. The laboratory experiments were performed on both drinking water waste streams. The performance of concentrating the anion exchange brine solution with nanofiltration membranes was evaluated with the use of IMS Design models.

Water is the most dominant substance on the planet and has always been a synonym for life. On this planet, water has always been plentiful. Therefore, the conclusion of the United Nations in 2015 was even more shocking. The United Nations estimated that in 2030 a water gap would exist of 40%. The withdrawal of fresh water would be 40% larger than the amount that is replenished every year. We are living on borrowed time, and we need to close this gap. Since most water on the earth is saline, desalination could be a possible solution. Unfortunately, desalination is an energy-intensive process, and it will always be. There are different methods. However, energy consumption would always be rather large. Much of our energy is still created by fossil fuels in most areas in the world. Our increasing demand for fresh water can lead to a further large fossil footprint and therefore more climate change. Climate change negatively impacts our water supplies. A negative spiral could be the result. The world is consuming a large amount of energy. Unfortunately, this is not done efficiently. It is estimated that 72% of worldwide energy consumption is lost after conversion. Waste heat is an unwanted product as a result of this inefficient conversion. It is estimated that 63% of this waste heat has a temperature of 100 degrees Celcius or lower. A temperature that is not even sufficient to boil an egg, but it is energy nonetheless. If this energy could be harvested, the water gap could be closed by desalination without increasing the carbon footprint. However, how to do this? A solution could be found in Japan and your dry cleaner. In the seventies, when the oil crisis was at its peak, Japan had a problem. It has a high need for air conditioning which has a high need for energy. A device was created that could use waste heat to create cooling with silica gel. The general public knows silica gel as moist eaters that are included in your dry cleaning. By placing silica gel in a closed environment, liquid water could be evaporated. Evaporation needs energy, and this could create cooling. In early 2000, some folks in Singapore realised that this technology could also be used to desalinate. Adsorption Desalination was born. Adsorption desalination (also known as AD) is a boiling point elevation and vapour pressure lowering desalination technique. Silica gel has a high affinity to adsorb water vapour. Since this is done in a closed environment, the pressure is lowered till boiling. When an energy source is placed inside the liquid, an equilibrium can be found without lowering the pressure further. Once the silica gel is saturated, it is heated till a certain temperature that it starts to desorb the vapour again. This vapour is collected and condensed into a clean product. The mass transport takes place by a pressure difference. Since the evaporation takes place in vacuum conditions, it is around room temperature. Therefore it can have a low sensitivity for erosion. Since it is an evaporation technique, it also has a low sensitivity for fouling. On paper, it can be a desalination technology with low operational costs compared to others. In reality, a couple of barriers have to be conquered. One of the barriers is the characteristics of the core element of this technology, the silica gel. The reason that silica gel can adsorb water vapour so well is due to two main elements. First, it is an incompletely dehydrated polymeric structure of colloidal silica acids. Therefore it can create hydrogen bonds, polar bonds and weak electron bonds with other molecules. Water is a bipolar molecule, and therefore silica gel can adsorb water exceptionally well. It can create hydron bonds efficiently, and due to the bipolar nature of water, multiplayer on top of each other can be formed. The second element is the high specific surface of silica gel. It has many pores, and therefore a specific surface equal to human lungs can be formed. In the end, the best qualities can adsorb until 40% of their body weight. These two elements determine the maximum amount of vapour silica gel can adsorb. However, two parameters determine if silica gel can adsorb. These two parameters are the temperature and vapour pressure. If the temperature is high, the vapour pressure has also to be high to ensure adsorption and the other way around. The same account for the opposite effect. Therefore energy transfer is vital for smooth operation. Unfortunately, the thermal conductivity of silica gel is extremely low. Besides energy transfer to change the temperature of silica gel to go from adsorping to desorbing and reverse, much energy has to be transported during the adsorption and desorption phase. During adsorption, water vapour transforms from a gas phase to a semi-solid phase. In this phase, the energy level is lower. Since energy cannot be destroyed, this energy has to be removed. The same applies to the opposite. If the heat exchanger is not well designed, the adsorption and desorption phase are prolonged, and the daily water production diminished. Even if the whole set-up is well designed, there is still one element of silica gel that can also diminish the water production of the set-up: the degradation of silica gel. Multiple mechanisms can degrade silica gel, but the two most important are fragmentation and pore pollutions by metal ions. Fragmentation (the breaking up into smaller parts) occurs by the high thermal stress the silica gel endures and the pollutions by the feed. A part of the sorption ability is destroyed or temporarily inhibited. The use of acid water can remove the pollution, so maintenance on the silica gel is necessary. Replacing the silica gel by other sorbents like zeolite is possible. Unfortunately, it has a lower adsorption capacity which leads to a less compact device and is, therefore, more expensive. Another unfortunate fact is that zeolite desorbs at a higher temperature. When using zeolite, adsorption desalination can no longer use waste heat of low quality to desalinate. The last problem with using silica gel, but also other sorbents, are the instabilities with the sorption characteristics in vacuum conditions. The sorption characters depend as said before on the temperature and the vapour pressure. Inside vacuum conditions, a disturbance of the vapour pressure can negatively influence the sorption characteristics and can lead to desorption at the wrong moment. Since it is done in a closed environment, it can lead to condensation which lowers the vapour pressure further. A complete breakdown of performance can be the result. Disturbances can happen through air leakage, which is are a common problem in industries. There are some solutions, but in the end, the permanent one is a high-quality vacuum system and intensive maintenance. Even with these barriers, adsorption desalination is still an attractive technology due to its relationship with its own energy consumption pattern. The energy consumption is high but stable and barely sensitive to change in conditions like feed salinity and recovery. Its energy consumption stays around the 40 $kWh/m^3$ in most cases. Only a small part, around 1.38 $kWh/m^3$ or even less has to be mechanical energy. All others can come from waste heat. If the other operating costs are kept low, it is an exciting technology to use, especially for brine treatment since waste heat is an inexpensive energy source. Some researcher claim it is a free energy source, but that statement cannot be valid. To use waste heat, infrastructure is necessary to collect it and transport it. It is not the same as putting a plug in the wall. There is probably enough waste heat in the world to close the water gap. As an example, the Netherlands is the second biggest producers of waste heat in Europe and creates enough to produce probably more 850 $km^3$ potable water. Unfortunately, there are some uncertainties. Waste heat is only classified in three rough categories, low, medium or high. Low is everything below 100 degrees Celcius. It could be that most energy is trapped in waste heat with a temperature of 30 degrees. More validation is necessary since the future of adsorption desalination is intertwined with waste heat. Without waste heat, it cannot be an inexpensive desalination technique. Since it is still an experimental technology, not a lot of data is available to create a solid picture of the costs involved with adsorption desalination. Only two studies exist today, and both estimate that the cost for seawater desalination using adsorption desalination is between 50% and 70 % of the cost while using reverse osmosis. Only one study gives insight into the different sectors of cost. What is notable is that the other costs, replacement cost for parts and chemical cost for adsorption desalination are kept at zero. A strange conclusion since silica gel can degrade and replacement can be necessary, chemicals are necessary for the heating and cooling water AD uses. No conclusion can be made about the final costs of AD, but it the conclusion of these studies seems unlikely. For seawater desalination, the costs are probably in the same range as reverse osmosis. Furthermore, there is a strong case that AD can remove biological pollutants since it is an evaporation technique where temperatures are reached until 80 degrees Celcius. There are a few remarks and only solid empirical data can prove these claims. The original intent of this research was to research these claims. Unfortunately, the set-up was not functioning properly due to practical problems like air leakages. Even with this result, much knowledge was gained, and a few remarks and conclusions can be made. To conclude, adsorption desalination is a newly emerging technology with many interesting aspects. It can provide an alternative for standard desalination techniques while being sustainable. There are a few barriers to overcome, but it deserves attention. Further developments should be stimulated since the water should be close in an environmentally friendly matter. Adsorption desalination is a sustainable solution that should always be considered.

Natural Organic Matter (NOM) is always present in the drinking water sources such as rivers, lakes and reservoirs. It causes several problems, including the unfavourable colour and odour of water, formation of disinfectant by-products and harmful microbial growth. In drinking water treatment, anion exchange (anion-IEX) is used for NOM removal. However, the regeneration of anion-IEX produces a brine, which is a high saline waste stream containing the desorbed NOM and anions (i.e. sulphate) as well as the residual sodium chloride added during the regeneration process. One possible approach to manage the waste brine is to recover the valuable compounds from the brine, and consequently, reduce the brine volume that has to be disposed. The separation could be done by ceramic nanofiltration (NF) membranes. However, the separation performance of ceramic NF membranes at high salinity conditions is still not fully understood. Therefore, the use of ceramic NF membranes to treat the brine-like wastes that contain NOM and high salt concentrations were investigated. Commercial 500 Dalton(Da) ceramic NF membranes were used in the salt experiments. Several experimental conditions such as pH and ionic strength were investigated to understand their influence on the rejection of sulphate (SO42-) and chloride (Cl-). The results show that the salt rejection was governed by charge effect, and it changed depending on pH and ionic strength. When ionic strength was 0.1M, the mitigated charge effect led to a low rejection of SO42- (<20%) and Cl- (<5%) by the 500Da membranes. On the other hand, the 560Da membrane used in salt&NOM experiments exhibited more than 95% rejection of NOM but less than 25% rejection of both SO42- and Cl- when ionic strength was 1M. Since the 500Da membranes were unable to reject divalent ions at high ionic strength, it is suggested to decrease the membrane pore size to achieve the separation of SO42- and Cl-. The size of pores in ceramic membranes can be narrowed down by an approach called Atomic Layer Deposition (ALD) (Shang et al., 2017). In this study, the vacuum TiO2 ALD was applied to coat thin films on the commercial ceramic NF membranes that have Molecular weight cut-off (MWCO) ranging from 600Da to 900Da. After the first coating, the water permeability of the membranes decreased dramatically while the MWCO of the membranes decreased slightly. After the second coating, an increased MWCO was observed, which might be attributed to the plugging of small pores. In addition, the flux distribution and pore size distribution were theoretically analysed to investigate the change of the membrane pores before and after ALD.

As freshwater resources are predicted to become more scarce in the future, desalination will become a more prevalent treatment method. Microbial desalination, defined as the use of microbial processes to remove ions from a saline solution, may have potential as a new desalination method to produce water for domestic, agricultural or industrial purposes. This research explored the theory, performance, application and feasibility of microbial desalination. It consists of three research lines. Firstly, the performance and optimal conditions for microbial desalination were examined in batch experiments. In the second research line, the use of microbial ion transport proteins in a biomimetic membrane was proposed and the microbial light powered transport protein SyHr was genetically designed and expressed for this purpose. Finally, two models weremade which evaluate the feasibility ofmicrobial desalination at full scale; one which compares the costs of microbial desalination in sequencing batch reactors to seawater reverse osmosis and one to calculate the recovery and required size of a biomimetic membrane as described in the second research line. Based on the results of all research lines, it was concluded that microbial desalination is be a promising new technology for desalination, which should be further developed.

Due to climate change and growing cities, water scarcity is becoming one of the futures biggest problems. On top of that, the population and prosperity of cities around the equator are growing fast. Meaning that the need for electricity, cooling and drinking water will grow fast in the following decades. ROTEC’s vision is that these growing problems require a sustainable approach for the future. A solution to these challenges can be found in the oceans temperature difference. The top layer of the ocean is heated by the sun, while the deeper layer remains cold. This causes around the equator a temperature difference of more than 20 degrees over the ocean’s depth. This offers a lot of opportunities. It can be used as a vast source for electricity production (OTEC), large scale drinking water production (ROTEC) and for cooling (SWAC). Indonesia is one of the best locations worldwide, due to the easy access of cold deep sea water and the abundant presence of hot surface water. North-Sulawesi has a unique access to these sources. Due to the steep slope of the seabed the cold deep seawater can easily be reached. Team ROTEC conducted a research in Manado for two months and came up with several solutions that can contribute to a more sustainable and beneficial future of North Sulawesi. There was mainly focussed on performing a need assessment for the capital Manado and the touristic Bunaken Island. This pointed out that Manado can reduce their electricity usage during peak loads by implementing a new way of cooling of malls and hotels along the boulevard. Bunaken needs electricity and drinking water in a way that is more easy to maintain and operate. Data analysis and measurements showed that both Bunaken and Manado have a high theoretical potential, since cold deep seawater is close to shore and found at relative shallow depths. For Manado a new seawater district cooling system is proposed. This system uses cold deep seawater to cool the large buildings along the boulevard, instead of conventional chiller-cooling-tower units. The solution reduces their electricity usage for cooling by 96% and more electricity is left for the grid of Manado. The yearly costs for the operation of the cooling is 92% cheaper and the investment for the installation is earned back within 6 years after construction. Peak loads in the grid are decreased and emissions reduced; equivalent to 19,000 tons CO2 per year. For Bunaken an integrated drinking water and electricity solution is found. By just using the temperature difference in the ocean, to produce clean and constant electricity and drinking water from seawater. The proposed installation provides the base load (80kW) for Bunaken for the same price as current solar PV and diesel generators together. Clean drinking water for the villagers is 12 times cheaper than Aqua Danone and 1.4 times cheaper than the not drinkable water from fresh water wells on the island. Such a kind of installation can produce 24/7, is stable and that without the need of fuels.

New techniques are urgently demanded to remove organic micropollutants (OMPs) such as endocrine disrupting compounds, pharmaceuticals and pesticides from our drinking water sources. With increasing salinity of surface waters in coastal regions, salt removal has also become an issue in the production of drinking water. When advanced oxidation processes are combined they are capable to remove OMPs to a large extent, but without the removal of salts. Dense membranes like reverse osmosis (RO) or flat-sheet nanofiltration (NF) membranes – which require an extensive pretreatment – can sufficiently remove OMPs and salts, but only at low permeabilities and by producing a saline waste stream. Hollow fiber NF membranes seem very promising in this respect as they have higher permeabilities, lower energy consumptions and can be applied directly. In this study, the removal of salts and OMPs from synthetic surface water and real lake water from the Valkenburgse Meer (VM) by the polyelectrolyte multilayer (PEM) coated dNF40 membrane was studied in order to make it suitable for dune infiltration water. This type of membrane is fabricated by depositing polycations and polyanions alternately on a porous support medium, also known as the layer by layer (LbL) technique, which enables control of the membrane’s surface charge and permeability. Hollow fiber NF membranes have the ability to separate ions or solutes with smaller sizes and hydraulic radii than the pore size of the membrane due to electrostatic repulsion. The membrane is negatively charged at neutral pH. The dNF40 membrane showed ion retentions of up to 27% for Cl-, 98% for SO42-, 87% for Mg2+, 76% for Ca2+ and 17% for Na+ in once-through configuration with a hydraulic permeability of 5.8 Lm-2h-1 and molecular weight cut-off (MWCO) of ~200 Da. However, lower ion retention values were observed for filtration of real lake water, except for SO42-. Retentions were unaffected by cross-flow velocity, but increased with increasing permeate flux. Moreover, the ion retentions reduced considerably when the system recovery increased to 75%. In addition to the salt retentions, the retention of a mix of 20 distinctively different pharmaceuticals, both positively charged, negatively charged and neutral OMPs with molecular weights between 119 and 748 gmol−1, was investigated. An average retention as high as 79% and 89% was reached for SW (no natural organic matter (NOM)) and VM water (11.6 mgL-1 of NOM), respectively. As expected, the negatively charged pharmaceuticals were retained best as a result of electrostatic interactions with the negatively charged membrane, followed by the positively charged compounds, of which repulsion is probably promoted by underlying polycation layers in the membrane structure. Neutral compounds were retained less. The dNF40 membrane showed to be resistant to fouling, while no extensive pretreatment was applied, making it suitable for direct treatment of surface water. Furthermore, OMPs were largely removed, hardness was partially reduced and NOM was almost completely removed, but insufficient NaCl was retained to meet dune infiltration water standards. Therefore, an additional step becomes necessary in the pretreatment of surface water. Four suggestions were provided.

Fog harvesting is a sustainable drinking water solution for arid climates. Previous studies have developed an analytical model to predict the fog water collection efficiency as a product of aerodynamic and deposition efficiency as independent factors. In this study, we tested the assumption that deposition efficiency stays unchanged when the geometry of the fog catcher is adjusted. We assessed the collection efficiency of both straight and curved fog water collectors using computational fluid dynamics models and performed controlled experiments in a climatic wind tunnel on sample fog water collectors. The analytical model disregards convex fog harvesters because their lower drag coefficient reduces the aerodynamic efficiency of the fog harvester. The results of the CFD models show that efficiency can be doubled if fog catchers are built convex facing the wind. The wind tunnel experiments support the results from the CFD models. The results of this study show that for convex fog harvesters, although less fog passes through the net, the deposition efficiency increases resulting in a net increase of water collection.

In this thesis, direct application of hollow fiber nanofiltration on surface water is suggested as an efficacious method for surface water treatment. This thesis was carried out as a collaborative effort between Lenntech B.V. and TU Delft. The current research aims to assess the performance of these membranes as a potential solution for surface water treatment and to gain a meaningful understanding of rejection performance and fouling tendencies of these modules through lab-scale experimentation of a low MWCO hollow fiber membrane. Direct application of nanofiltration on surface water was carried out on a lab-scale using the dNF-40 hollow fiber nanofiltration membrane supplied by NXFiltration B.V. Enschede. This membrane is fabricated using a technique called Layer-by-Layer (LbL) polyelectrolyte deposition which consists of an assembly of alternatingly deposited polycationic and polyanionic nanolayers on a polyethersulfone (PES) ultrafiltration support. The dNF-40 membrane is negatively charged at neutral pH. The main objective of the research was to determine the effectiveness of the dNF40 membrane for surface water treatment in terms of three key performance parameters viz. rejection, membrane fouling and concentration polarization. Membrane characterization was carried out by measuring the pure water permeability, Molecular Weight Cut Off (MWCO) of the membrane and rejection of single salt solutions. The pure water permeability of a pristine membrane was 1.53×10^{-14} m. The MWCO was measured using PEG filtration method and was found to be 200 Da. The membrane performance is limited in terms of the flux due to concentration polarization. CP factor was measured experimentally and compared with Sherwood analytical model. Since the flow through the fibers in laminar, high cross-flow velocities are required to reduce CP are high (< 0.5 m/s) due to which hydraulic pressure losses along the feed channel are high. A pressure drop of 0.2 bar was measured for a pristine membrane at a cross-flow velocity of 0.5 m/s. Filtration experiments were carried out with two kinds of surface waters: Delft Schie water and Biesbosch reservoir water. The influence of flux and cross-flow velocity on the rejection of ions were investigated. The removal of Natural Organic Matter (NOM)in both surface waters was between 80 and 85%. The rejection of divalent cations viz. Ca2+and Mg2+was higher at low system recoveries (upto 30%) but a severe drop in rejection was observed at higher recoveries (80%). The final permeate collected at 80% recovery contained 37 mg/L of Ca2+and less than 1 mg/L of NOM. 98%rejection of SO42- was observed irrespective of the feed composition and operating conditions. The dNF-40 membrane exhibited high fouling-resistance during surface water filtration showing no mass transfer coefficient(MTC) decline during 6-hour experimental cycles with surface water. To test for fouling fractions of surface water,additional tests were carried out with model foulant solutions including sodium alginate, humic acid and bovine serum albumin with varying foulant concentrations and ionic strengths; of the three, alginate fouling was most severe in terms of flux decline. Irreversible fouling was observed during the alginate filtration tests. Fiber-blocking was also observed during alginate filtration due to aggregation of alginate and Ca2+. Chemical cleaning with 200 ppm NaOCl solution at pH 12 completely re-stored the permeability. The results presented in this thesis demonstrate that the dNF-40 hollow fiber membrane with the LbL structure can treat surface water with-out pre-treatment. These membranes are ideal for applications such as production of drinking water where partial removal of hardness and complete removal of organic matter is required.

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

The drinking water company PDAM Tirtawening has two pipelines that supply raw water to the treatment plant. The pipelines stretch out for 31 kilometers from Chikalong(small nearby town) to the treatment plant in Badaksinga in Bandung. For one of those pipelines the current flow to the treatment plant is well below the design flow. The original design flow of the pipeline is 850 liters per second, currently the pipeline transports roughly 580-650 liters per second. This is not a critical problem at the moment because the treatment plant does not have the capacity to treat and distribute more water, but in the nearby future PDAM Tirtawening wants to increase its capacity and supply more water to the people of Bandung. This means that the supply of raw water to the treatment plant also needs to be increased. From the study it can be concluded that the flow drop was caused by human decisions to throttle the flow, based on the fact that there was severe burst (“explosion”) of the pipeline somewhere in the year 2005. The burst was caused by a water hammer incident, occurring during maintenance. During this maintenance period the water flow was stopped and a water body was standing stagnant in the lower end of the pipeline. When the operators opened valve again at the intake point, to start up the flow in the pipeline, the water mass accelerated downwards towards the stagnant water body below. The air trapped between these two water bodies could not escape in time thereby being compressed causing peak pressures. These pressures where of a much higher magnitude than the pressure which the pipeline was designed for, causing the “explosion” of the pipe. The reason why the trapped air could not escape through the air valves is because they are sealed to reduce the chance of locals stealing water. To avoid air entrapment and thereby reducing the risk on water hammer the following three throttling locations along the pipeline where investigated. • keep regulating the inflow at the intake point at Chikalong. • regulate inflow at the first intersection (OVS1) 3 kilometres downstream of Chikalong. • regulate inflow downstream at Badaksinga at the outflow point of the pipeline. From these three options throttling at OVS1 is preferred. The peak pressures along the pipeline stay well below the design pressure. However, throttling at preset at Chikalong has gone ’sufficient’ looking at PDAM’s standards for more than 25 years already. Regulating at Badaksinga (throttling and closing) is not feasible. Very high pressures and problems with cavitation of the intake valve will increase the chance on pipe bursts and damage to the valve. Also, it is recommended to PDAM to slowly open the valve at the intake point after maintenance in order to slowly increase the volume of the flow. This action will insure that the pipeline will slowly fill up with water thereby giving the trapped air the chance to escape, this will decrease the chance on peak pressures and “explosions” in the future.