10 pp. / Arsenic levels are often above drinking water standards in Arizona groundwater, at levels that may affect health. Private well owners are responsible for testing and treating they own water. This publication gives an overview of arsenic well water and discusses home water treatment options, including detailed descriptions of distillation, reverse osmosis, and iron filters to lower arsenic and other common water constituents in drinking water.

No description available.

No description available.

This work introduces a systematic seawater reverse osmosis (SWRO) membrane network synthesis approach, based on the coordinated use of process superstructure representations and global optimization. The approach makes use of superstructure formulations that are capable of extracting a globally optimal design as a performance target, by taking into consideration desired process conditions and constraints that are typically associated with reverse osmosis systems. Thermodynamic insights are employed to develop lean network representations so that any underperforming solutions can be eliminated a priori. This essentially results in considerable improvement of the overall search speed, compared to previously reported attempts. In addition, the approach enables the extraction of structurally different design alternatives. In doing so, distinct membrane network design classes were established by partitioning the search space, based on network size and connectivity. As a result, corresponding lean superstructures were then systematically generated, which capture all structural and operational variants within each design class. The overall purpose is thus to enable the extraction of multiple distinct optimal designs, through global optimization. This mainly helps provide design engineers with a better understanding of the design space and trade-offs between performance and complexity. The approach is illustrated by means of a numerical example, and the results obtained were compared to previously related work. As anticipated, the proposed approach consistently delivered the globally optimal solutions, as well as alternative efficient design candidates attributed to different design classes, with reduced CPU times. This work further capitalizes on the developed representation, by accounting for detailed water quality information, within the SWRO desalination network optimization problem. The superstructures were modified to incorporate models that capture the performance of common membrane elements, as predicted by commercially available simulator tools, e.g. ROSA (Dow) and IMSDesign (Hydranautics). These models allow tracing of individual components throughout the system. Design decisions that are supported by superstructure optimization include network size and connectivity, flow rates, pressures, and post treatment requirements. Moreover, a detailed economic assessment capturing all the significant capital and operating costs associated in SWRO processes, including intake, pre and post treatment has also been accounted for. These modifications were then illustrated using a case study involving four seawater qualities, with salinities ranging from 35 to 45 ppt. The results highlight the dependency of optimal designs on the feed water quality involved, as well as on specified permeate requirements.

Deposition of calcium carbonate (CaCO3) and calcium sulfate (CaSO4) causes serious processing problems and limits the productivity of seawater reverse osmosis (RO) desalination. The interactions between CaSO4 and CaCO3 in the dynamic seawater RO systems have been neglected previously because conventional studies mainly focused on individual compounds or mixed compounds in batch systems. The present work evaluates composite fouling behavior of CaSO4 and CaCO3 in a dynamic RO unit. The fouling experiments were performed at constant pressure and velocity by a partial recycling mode which permeate was withdrawn from the system during the recirculation of retentate to simulate the increasing of water recovery level. The fouling phenomena were monitored by the decline of flux. Scanning electron microscopy (SEM) with a combination of elemental dispersive x-ray microanalysis (EDS), and x-ray powder diffraction (XRD) was used to identify the morphological features, chemical compositions and crystalline phases of foulants. The interactions of CaSO4 and CaCO3 were investigated by the comparison between individual CaSO4 or CaCO3 fouling and composite fouling, and by varying SO42-/HCO3- molar ratio of the feed. A recently developed approach, Scaling Potential Index (SPI) incorporated with measured concentration polarization modulus (CP), for assessing the fouling tendency of inorganic salts on the membrane surface was validated in the dynamic tests. In addition, the effectiveness of two generic scale inhibitors, polyacrylic acid (molecular weight =2100, PA) and sodium hexametaphosphate (SHMP) were evaluated. Some of the highlights of the obtained results are as follows: ??????The precipitation kinetics, morphology and adhesive strength of composite scales were different from pure precipitates ??????CaSO4 precipitated as gypsum while CaCO3 precipitated as two crystalline phases: calcite and aragonite ??????The crystalline phases as well as precipitation kinetics were affected by SO42-/HCO3- ratio ??????Scaling Potential Index was able to predict the fouling tendency of CaSO4 and CaCO3 accurately ??????The dosage of PA and SHMP was effective to mitigate fouling Results of this work are significant, not only because they have made contribution to the fundamental understanding of composite inorganic fouling in RO membrane systems which was ignored previously, but also because they may play a key role in the development of scale control.

Thesis (Ph.D.)--University of Wollongong, 2008. / Typescript. Includes bibliographical references.

A comparison of fouling in osmotically driven processes with that in pressure driven processes is the main focus of the thesis. Forward osmosis (FO) and reverse osmosis (RO) have received considerable attention for water treatment and seawater desalination. This research compared the nature of fouling in FO mode with that in RO starting with the same initial flux in connection with cleaning effects and then comparing to those in ultrafiltration membranes. In all cases, with cleaning as an integral part, the extent of fouling reversibility, and the question whether a critical flux could be determined were examined. The work during the first phase (undertaken at Oxford) quantified the removal of reversible fouling through rinsing by cold and hot water for a range of concentrations using the foulants dextran and carboxymethyl cellulose. The flux-TMP relationship was conventionally compared to that of the clean water flux. The later phase (at Singapore) compared the fouling in FO and RO by alginate in terms of multiple parameters using cellulose tri acetate (CTA) and thin film composite (TFC) membranes. Silica and alginate were selected as model foulants. Whilst experimental water flux profiles in the present study did not exhibit significant differences in trend between FO and RO fouling, foulant resistance for FO was found to be increasingly greater than for RO with the progression of the fouling tests. This was further corroborated by membrane autopsies post fouling tests; both foulant mass deposition density and specific foulant resistance for FO were greater than for RO. The analysis clearly revealed that FO is essentially more prone to fouling than RO which was presumably due to less flux decline in FO (or greater average flux) as compared to that in RO in result of ICP-self compensation effect which is opposite to the prevailing claim in the literature. Additionally, the present study did not find evidence that hydraulic pressure in RO has a role in foulant layer compaction. FO membrane fouling by real waters was the focus of the final phase of the research at SMTC. Pilot scale FO experiments were conducted on spiral wound CTA membrane with treated waste water obtained from a NEWater factory (Singapore) as the feed. In the second stage, experiments were repeated at bench scale with membrane coupons taken from the spiral wound membranes used earlier. The key finding was that the mass transfer coefficients in the Spiral-Wound module were around 50% lower than the corresponding values in the flat sheet unit and this severely limited the fluxes. The reason could be attributed to strong internal concentration polarisation in the former, where tightly wound spacers act to increase the structural parameter.

abstract: With the application of reverse osmosis (RO) membranes in the wastewater treatment and seawater desalination, the limitation of flux and fouling problems of RO have gained more attention from researchers. Because of the tunable structure and physicochemical properties of nanomaterials, it is a suitable material that can be used to incorporate with RO to change the membrane performances. Silver is biocidal, which has been used in a variety of consumer products. Recent studies showed that fabricating silver nanoparticles (AgNPs) on membrane surfaces can mitigate the biofouling problem on the membrane. Studies have shown that Ag released from the membrane in the form of either Ag ions or AgNP will accelerate the antimicrobial activity of the membrane. However, the silver release from the membrane will lower the silver loading on the membrane, which will eventually shorten the antimicrobial activity lifetime of the membrane. Therefore, the silver leaching amount is a crucial parameter that needs to be determined for every type of Ag composite membrane. This study is attempting to compare four different silver leaching test methods, to study the silver leaching potential of the silver impregnated membranes, conducting the advantages and disadvantages of the leaching methods. An In-situ reduction Ag loaded RO membrane was examined in this study. A custom waterjet test was established to create a high-velocity water flow to test the silver leaching from the nanocomposite membrane in a relative extreme environment. The batch leaching test was examined as the most common leaching test method for the silver composite membrane. The cross-flow filtration and dead-end test were also examined to compare the silver leaching amounts. The silver coated membrane used in this experiment has an initial silver loading of 2.0± 0.51 ug/cm2. The mass balance was conducted for all of the leaching tests. For the batch test, water jet test, and dead-end filtration, the mass balances are all within 100±25%, which is acceptable in this experiment because of the variance of the initial silver loading on the membranes. A bad silver mass balance was observed at cross-flow filtration. Both of AgNP and Ag ions leached in the solution was examined in this experiment. The concentration of total silver leaching into solutions from the four leaching tests are all below the Secondary Drinking Water Standard for silver which is 100 ppb. The cross-flow test is the most aggressive leaching method, which has more than 80% of silver leached from the membrane after 50 hours of the test. The water jet (54 ± 6.9% of silver remaining) can cause higher silver leaching than batch test (85 ± 1.2% of silver remaining) in one-hour, and it can also cause both AgNP and Ag ions leaching from the membrane, which is closer to the leaching condition in the cross-flow test. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2017

abstract: Drinking water filtration using reverse osmosis (RO) membranes effectively removes salts and most other inorganic, organic, and microbial pollutants. RO technologies are utilized at both the municipal and residential scale. The formation of biofilms on RO membranes reduces water flux and increases energy consumption. The research conducted for this thesis involves In-Situ coating of silver, a known biocide, on the surface of RO membranes. This research was adapted from a protocol developed for coating flat sheet membranes with silver nanoparticles, and scaled up into spiral-wound membranes that are commonly used at the residential scale in point-of-use (POU) filtration systems. Performance analyses of the silver-coated spiral-wound were conducted in a mobile drinking water treatment system fitted with two POU units for comparison. Five month-long analyses were performed, including a deployment of the mobile system. In addition to flux, salt rejection, and other water quality analyses, additional membrane characterization tests were conducted on pristine and silver-coated membranes. For flat sheet membranes coated with silver, the surface charge remained negative and contact angle remained below 90. Scaling up to spiral-wound RO membrane configuration was successful, with an average silver-loading of 1.93 g-Ag/cm2. Results showed the flux of water through the membrane ranged from 8 to 13 liters/m2*hr. (LMH) operating at 25% recovery during long-term of operation. The flux was initially decreased due to the silver coating, but no statistically significant differences were observed after 14 days of operation (P < 0.05). The salt rejection was also not effected due to the silver coating (P < 0.05). While 98% of silver was released during long-term studies, the silver release from the spiral-wound membrane was consistently below the secondary MCL of 100 ppb established by the EPA, and was consistently below 5 ppb after two hours of operation. Microbial assays in the form of heterotrophic plate counts suggested there was no statistically significant difference in the prevention of biofouling formation due to the silver coating (P < 0.05). In addition to performance tests and membrane characterizations, a remote data acquisition system was configured to remotely monitor performance and water quality parameters in the mobile system. / Dissertation/Thesis / Masters Thesis Engineering 2017

L’objectif de cette thèse est de mettre en évidence le comportement à l’échelle microscopique des composés organiques au cours des procédés de traitement de mélanges complexes, en particulier les procédés membranaires. Pour cela des outils expérimentaux et de modélisation ont été mis au point. Les méthodes de caractérisation expérimentale des mélanges complexes et de l’état de surface des solides utilisés sont entre autres la construction d’isothermes d’adsorption et la mesure des tensions interfaciales par la méthode de la goutte posée. Le cas étudié ici est celui de la filtration de solutions modèles de tensioactifs par osmose inverse. Nous avons montré que le comportement des composés organiques (tensioactifs) influence la performance du procédé membranaire et les propriétés de membranes. L’outil de simulation du comportement des composés en phase liquide et à l’interface liquide-solide permettant une description à une échelle plus fine que celle atteignable expérimentalement est la DPD (Dissipative Particle Dynamics). Une première étape a permis de simuler l’agrégation des tensioactifs en solution et de retrouver les valeurs expérimentales des concentrations micellaires critiques et nombres d’agrégation de tensioactifs anioniques. L’étude de l’adsorption des tensioactifs sur une membrane d’osmose inverse a été initiée, avec pour objectif de mettre en évidence l’organisation des composés à l’échelle locale. L’apport des outils développés a été démontré et leur utilisation pourra être approfondie dans des travaux ultérieurs. / The aim of this work is a better understanding of the microscopic behavior of organic matters during the wastewater treatment of complex mixtures, especially during the membrane processes. Both experimental and simulation methods were developed in this work. Experimentally, adsorption isotherms were built to study the adsorption of organic matters on the membrane surface during the filtration. The sessile drop measurement allowed investigating the surface properties (interfacial tensions) of the membrane. After the filtration of surfactants by reverse osmosis (RO), we found that the surfactants played an important role in the performance and the surface properties of the RO membrane. The DPD (Dissipative Particle Dynamics) simulation method was used to model the behavior of anionic surfactants in solution and at the solid/liquid interface from a more detailed aspect than experiments. Firstly, the micellization of three anionic surfactants in aqueous solution was simulated and the model was validated by comparing the equilibrium properties (the critical micelle concentration and aggregation number) of micelle solutions obtained from simulation to the experimental values in literature. Then the model was extended to simulate the adsorption of surfactants on the RO membrane. The construction of a system with a membrane was initiated, and the study on the organizations of surfactants at the membrane surface opens a door to further active research.