Anammox is one of the main processes discovered quite recently for removal of ammonium from wastewater. Anammox process is cost effective, in that low energy and carbon source is needed. Partial nitritation is a perquisite for anammox in wastewater treatment for removal nitrogen and therefore partial nitritation/Anammox technology is studied substantially and applied in full-scale. However, the technology at present can only be used to treat high rich ammonium streams. Application of Anammox for treatment of low ammonium wastewater is not possible because of low yield of Anammox bacteria. The study aimed at devising strategies for using the Anammox technology to treat wastewater streams with low concentration of ammonium nitrogen. The objective was to get systems that could concentrate ammonium from low ammonium waste streams, so as to be able to treat it with partial nitritation/Anammox process. Two methods were used to concentrate ammonium: ion exchange and reverse osmosis. Ion exchange method was used to concentrate UASB effluents of about 24 - 40 mg NH4-N/l to 188 - 367 mg  NH4-N/l respectively which is about 9 times the initial concentrations. At VRF 5, 163 mg  NH4-N/l concentrate was attained from 41.8 mg  NH4-N/l RO feed. Results also showed that concentrates from both methods are able to be treated with partial nitritation/Anammox technology. However it took more than 32 hours to complete treatment of ion exchange concentrates while it took less than 24 hours to finish the partial nitritation/Anammox process of RO concentrates. The longer time taken can be attributed to high salinity of the concentrates which is as a result of NaCl which was used for regeneration in ion exchange process. Both ion exchange and reverse osmosis are viable methods for concentrating ammonium from UASB effluents. Dissolved oxygen was very important factor that influenced the biological process.

The drinking water plant in this case study is a combined groundwater and reverse osmosisplant in the Stockholm archipelago. The reverse osmosis purification step was added to theplant in 1995. This technique is relatively new in Sweden and there are possibilities for it tobecome a good complement to conventional drinking water treatment. The plant has used thistechnique for over 10 years with good results. It is therefore of great interest to evaluate anddocument it for the possibility to implement this technique in areas not connected toconventional drinking water production.Reverse osmosis separates the incoming water to a clean permeate and concentrate ofremoved particles, larger molecules and ions. This technique has a high purification degree. Itcan remove dissolved particles and microorganisms without disinfection. However, it isrelatively expensive due to a high electricity consumption compared to conventional drinkingwater treatment. The high electricity consumption in this kind of system depends on aphenomenon called membrane fouling caused by the constituents in the raw water, graduallybecoming enriched on the membrane surface.The aim of this thesis was to evaluate and document a drinking water plant in the Stockholmarchipelago from a social, economical, technical and environmental perspective. A socialsurvey in the form of a questionnaire was conducted to reveal opinions about the water qualityprovided by the plant. The economical evaluation was done to estimate the cost of drinkingwater production and find the water cost in Kr/m3. The technical part involved documentationof the plant layout and evaluation of its performance. To assess the performance historicalchemical and microbial analyses were evaluated. A mass balance was attempted to drawconclusions for the overall system. The environmental part of the plant assessment, includedan estimate of the electricity and chemicals use in the plant.The results revealed that from an overall perspective the water quality from the plant issatisfactory with some concerns about metal taste and turbidity that sometimes occur. Thepotential presence of dangerous algal toxins in the water was also a concern. The totalproduction cost in Kr/m3 is higher than expected and higher than sales price. In technicalterms, the plant has functioned well. However, there is a need to monitor more parameters inthe plant including; more flow parameters, concentrations of added chemicals and more waterquality parameters. Electricity consumption has been higher than expected. Control(throttling) valves in the brine reject are relatively large energy consumers and arecommendation is to investigate potential savings by changing them for pressure exchangevalves. / www.ima.kth.se

Activated carbon (AC) systems and reverse osmosis (RO) systems are commonly used point-of-use (POU) water filtration systems as the last barrier to remove trace-level contaminants in tap water to protect human health. Limited studies have been done to evaluate trace-level manganese and uranium removal in tap water. Additionally, undesired microbial growth in POU systems may reduce treatment efficiencies of POU systems and limited studies have been done to evaluate microbial growth potential in POU systems. The overall research objective of this study was to systematically evaluate the removal of metals and assimilable organic carbon in POU systems. AC systems were operated to 200% of their designed treatment capacities and RO systems were operated for three weeks. The results indicated that AC systems were generally ineffective to remove metals in drinking water, while metals were effectively removed in RO systems. The results showed that calcium and magnesium were not effectively removed in AC systems with removal efficiencies of less than 1%. Various factions of iron were removed with its removal efficiencies in AC systems ranged between 61% and 84%. Copper was effectively removed in AC systems with removal efficiencies greater than 95%, which was possibly related to its low influent concentration in drinking water (<30 μg/L). Both manganese and uranium were ineffectively removed from AC systems. Different from AC systems, RO systems were consistently effective to remove all metals. Calcium, magnesium, iron, and copper were all removed with removal efficiencies greater than 98%, while removal efficiencies of manganese and uranium in RO systems were above 95%. Assimilable organic carbon was effectively removed from all AC and RO systems and high variability of AOC removal efficiencies were observed, which may be attributed to the heterogenicity of biofilm and microbial growth in POU systems. The new knowledge generated from this study can help improve our understanding of emerging contaminant removal in POU systems and develop better strategies for the design and operation of POU systems to remove emerging contaminants in drinking water and mitigate their health risks to humans.

This dissertation introduces desalination processes in general and multistage flash (MSF) and reverse osmosis (RO) in particular. It presents the fundamental and practical aspects of neural networks and provides an overview of their structures, topology, strengths, and limitations. This study includes the neural network applications to prediction problems of large-scale commercial MSF and RO desalination plants in conjunction with statistical techniques to identify the major independent variables to optimize the process performance. In contrast to several recent studies, this work utilizes actual operating data (not simulated) from a large-scale commercial MSF desalination plant (48 million gallonsper day capacity, MGPD) and RO plant (15 MGPD) located in Kuwait and the Kingdom of Saudi Arabia, respectively. We apply Neural Works Professional II/Plus (NeuralWare, 1993) and SAS (SAS Institute Inc., 1996) software to accomplish this task. This dissertation demonstrates how to apply modular and equation-solving approaches for steady-state and dynamic simulations of large-scale commercial MSF desalination plants using ASPEN PLUS (Advanced System for Process Engineering PLUS) and SPEEDUP (Simulation Program for Evaluation and Evolutionary Design of Unsteady Processes) marketed by Aspen Technology, Cambridge, MA. This work illustrates the development of an optimal operating envelope for achieving a stable operation of a commercial MSF desalination plant using the SPEEDUP model. We then discuss model linearization around nominal operating conditions and arrive at pairing schemes for manipulated and controlled variables by interaction analysis. Finally, this dissertation describes our experience in applying a commercial software, DynaPLUS, for combined steady-state and dynamic simulations of a commercial MSF desalination plant. This dissertation is unique and significant in that it reports the first comprehensive study of predictive modeling, simulation, and optimization of large-scale commercial desalination plants. It is the first detailed and comparative study of commercial desalination plants using both artificial intelligence and computer-aided design techniques. The resulting models are able to reproduce accurately the actual operating data and to predict the optimal operating conditions of commercial desalination plants. / Ph. D.

Membrane-based filtration technologies have seen rapid inclusion in a variety of industrial processes, especially production of drinking water by desalination. Biological fouling of membranes is a challenge that leads to increased costs from efficiency reductions, membrane damage, and ultimately, membrane replacement over time. Such costs can be mitigated by monitoring and optimizing cleaning processes for better prognosis. A fluorescence-based sensor for early biofouling detection capable of measuring extracellular enzyme activity was developed. The selected fluorogen and fluorogen-substrate were characterized and down selected by in vitro screening for compatibility in seawater and profiled over relevant Red Sea desalination parameters (pH and temperature). ATP measurements are currently regarded as start-of-the-art when assessing biomass accumulation in membrane-based filtration systems Therefore, the fluorescence sensor response was measured for a range of bacterial concentrations and validated using an ATP assay. We demonstrate the efficacy of the proposed approach for the quantitative assessment of bacteria activity in seawater rapidly and sensitively. Following in vitro testing, the method was employed in a lab-scale seawater reverse osmosis (SWRO) system for suitability in monitoring biofouling formation. The sensor successfully measured bacterial biomass accumulation rapidly and non-invasively using exogenously applied fluorogen-substrates. The sensor response was corroborated with real-time in situ non-destructive imaging of the membrane surface. This approach demonstrates the practicality of prototyping an early-detection biofouling sensor in membrane based processes using extracellular enzyme activity as a measure of bacterial abundance.

Water scarcity is an issue faced across the globe that is only expected to worsen in the coming years. We are therefore in need of methods for treating non-traditional sources of water. One promising method is desalination of brackish and seawater via reverse osmosis (RO). RO, however, is limited by biofouling, which is the buildup of organisms at the water-membrane interface. Biofouling causes the RO membrane to clog over time, which increases the energy requirement of the system. Eventually, the RO membrane must be treated, which tends to damage the membrane, reducing its lifespan. Additionally, antifoulant chemicals have the potential to create antimicrobial resistance, especially if they remain undegraded in the concentrate water. Finally, the hazard of chemicals used to treat biofouling must be acknowledged because although unlikely, smaller molecules run the risk of passing through the membrane and negatively impacting humans and the environment. It is, therefore, integral to investigate techniques for prevention of biofouling and removal of mature biofilms that are effective, less damaging to the membrane, and safe for humans and the environment. A common experimental setup is biofilm antimicrobial microdilution susceptibility tests. To acquire meaningful data from these tests, however, appropriate organisms must be tested. Manuscripts 1 investigates, via semi-systematic reviews, the question of what organisms are appropriate to represent the complexity of a biofilm in antimicrobial tests. Ultimately, we recommend utilizing the model biofilm-forming, pioneer organism, Pseudomonas aeruginosa for these studies. Biofouling studies also must present data in a useful manner to the many disciplines that are interested in preventing or removing biofouling. Our goal is to investigate both via antimicrobial microdilution susceptibility tests. In Manuscript 2 we investigate the metrics of each discipline with an interest in anti-biofouling studies. Ultimately we recommend utilizing both crystal violet stain to assess total biomass removal and the LIVE/DEAD BacLight stain to assess cell vitality (including log reduction and MIC, BPC, MBIC, MBC, BBC, and MBEC), to satisfy the metrics of all interested disciplines. Finally, in Manuscript 3 we implement the recommendations from Manuscripts 1-2 for biofilm prevention and biofilm removal antimicrobial microdilution susceptibility tests. In this manuscript, we work with a subset of safer preservatives including, methylisothiazolinone, phenoxyethanol, and sodium benzoate. We found that methylisothiazolinone was the most effective antimicrobial, however, it was not the safest. Additionally, we investigated the relationship between MBIC and BPC, which was found to vary between the preservatives. Ultimately, we have provided recommendations for biofilm antimicrobial susceptibility tests that produce widely applicable and useful metrics, as well as utilized these recommendations to investigate the efficacy of safer antimicrobials. All of this work provides a framework for which even safer and effective novel antimicrobials can be investigated. / Graduate / 2021-07-22

Fouling in a nanofitration membrane module is usually a result of concentration polarization. The effect of permeate suction on the slightly negatively charged spiral wound nanofiltration membrane is investigated. According to the film theory, the mass transfer coefficient is inversely proportional to concentration polarization. The effect of permeate suction destabilizes the boundary layer. This will decrease the concentration polarization layer, and consequently will increase mass transfer through the membrane's surface. To validate the hypothesis, experiments were carried out on a NF membrane that can be described by the solution-diffusion model. This model has coefficients that can be measured experimentally. Using the membrane wall concentration in this model instead of the bulk feed concentration can help estimating the mass transfer coefficient more appropriately. Two experimental studies were carried out, one with a standard high pressure pump, and another one with the added effect of suction pressure applied to the permeate collector tube. Three different concentrations of binary dilute solutions of NaCl, MgSO4, and MgCl2, at three different pressures (low, medium, and high) were tested. For all tested solutions, permeate suction increased the diffusive Peclet number as a function of the feed concentration (x) according to the equation Pe = a1x²+b1x+c1, with R²>0.99, where x is the feed concentration in Mol/l, and a1, b1, and c1 are coefficients dependent on feed pressure for every salt solution. With the increase of the Peclet number, it was observed that the concentration polarization decreased, and both the product flow and the product quality were improved. Suction had the greatest impact at the range of 100 to 110 psi feed pressure, where the concentration polarization reduced approximately 14 to 20 %. ANOVA for the concentration polarization showed that suction was significant in reducing the calculated concentration polarization layer for all tested solutions. It was concluded that permeate suction reduced concentration polarization, increased product flow rate, and improved product quality. Thus, adding permeate suction has beneficial consequences because it reduces membrane fouling and extends its useful service life.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21308号 / 工博第4506号 / 新制||工||1701(附属図書館) / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 田中 宏明, 教授 清水 芳久, 教授 伊藤 禎彦 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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