Rosacea is a chronic skin disorder, characterized by redness and flushing of the cheeks, nose, chin or forehead. It has been proposed that rosacea is a result of frequent blushing (Miller, 1921; Klaber & Whittkower, 1939). However, the relationship between rosacea and blushing is uncertain. The aim of the present research was to investigate the relationship between psychological stress and vascular disturbances in rosacea. Five studies were conducted. The first study explored the relationship between rosacea and mental health while the next two investigated vascular responses in rosacea sufferers and controls to acetylcholine (which induces endothelial vasodilatation and axon reflexes) and psychological stress (embarrassment). The fourth study aimed to examine the relationship between psychological indicators and rosacea symptoms on a daily basis. The fifth study consisted of three case studies looking at the use of Cognitive Behavioural Therapy (CBT) and Task Concentration Training (TCT) with rosacea sufferers presenting with social anxiety and fear of blushing symptoms. In study 1, sixty-two participants were asked to complete the Blushing Propensity Scale (BPS), Fear of Negative Evaluation (FNE), Depression, Anxiety and Stress Scale (DASS), Social Interaction Anxiety Scale (SIAS) and Social Phobia Scale (SPS). Outcomes from the first study indicated that Type 2 rosacea sufferers (n= 12) perceived themselves as blushing more frequently and intensely than Type 1 rosacea sufferers (n=19) or controls (n=31). This suggested that Type 2 rosacea sufferers experiencing frequent blushing may have a lower sensitivity threshold to blushing episodes. In addition, Type 2 rosacea sufferers perceived themselves as more stressed than Type 1 rosacea sufferers or controls, possibly indicating that managing the condition can be stressful. Contrary to previous reports (Gupta et al., 2006; National Rosacea Society, 2005) severity of rosacea was not associated with depression, social anxiety or fear of negative evaluation. However, a few participants who reported high social anxiety and stress scores were offered psychological intervention (Study 5). The aim of the second study was to investigate vascular responses in rosacea sufferers. Cutaneous endothelial and axon reflex function was assessed using an acetylcholine dose response curve. The axon reflex was assessed by inducing a flare with ACh iontophoresis. Outcomes from this study indicated that Type 2 rosacea sufferers had a greater axon reflex response than Type 1 rosacea sufferers. Thus over-reactivity of the axon reflex in Type 2 rosacea sufferers might contribute to prolonged vasodilatation. However, cutaneous endothelial responses to ACh were similar in rosacea and control groups. The results suggested that neural pathways mediated the flushing response rather than cutaneous endothelial function. The third study investigated facial blood flow while participants attempted laboratory induced embarrassment tasks. Type 2 rosacea sufferers were found to have a greater blood flow in the facial region than Type 1 rosacea sufferers during singing and speech tasks, suggesting that Type 2 rosacea sufferers blushed more than type 1 rosacea sufferers or controls. Furthermore, Type 2 rosacea sufferers reported higher embarrassment and blushing ratings than Type 1 rosacea sufferers. This indicated that Type 2 rosacea sufferers perceived themselves as emotionally more aroused than other participants. Taken together, it would appear that a combination of physiological and cognitive factors increased facial blood flow in Type 2 rosacea sufferers in laboratory induced embarrassment tasks. The fourth study explored the relationship between stress and symptoms of rosacea. Using a diary, 15 rosacea sufferers recorded their stress, anxiety and mood and their intensity of rosacea symptoms daily. Stress was associated with increased stinging/facial redness on the same day for 1 to 2 months. Furthermore, it was associated with increased stinging ratings the next day. However, feeling anxious or having low mood was not related to increase stinging the next day. The presence of increased stress found in rosacea participants on the day where stinging and redness occurred should be taken into consideration when formulating psychological interventions for rosacea sufferers. In study 5, individual psychological intervention was provided to three participants experiencing stress, fear of blushing and social anxiety symptoms. Cognitive Behavioural Therapy (CBT) and Task Concentration Training (TCT) were helpful in managing stress, anxiety and fear of blushing symptoms in individual rosacea sufferers. Encouragingly, all participants reported a gain in their repertoire of strategies and showed a decrease in anxiety symptoms on assessment questionnaires following their intervention. Replication of the intervention protocol and investigation of other psychological approaches are required to establish best practise outcome for rosacea sufferers who require psychological interventions. The present findings suggest that over-reactivity of axon reflexes contributes to facial flushing. In addition, emotional flushing in rosacea sufferers appears to be maintained by a combination of cognitive and physiological factors. On a clinical level, the study recommends that emotional stress associated with facial flushing in rosacea sufferers to be targeted for psychological intervention.

The overall objective is to improve the one-dimensional numerical prediction of the fine and non-cohesive bed material load in alluvial rivers, especially during high intensity episodes during which sediment beds are strongly remobilized. For this reason, we attempt to reduce the major inaccuracy sources coming from the alluvial resistance and bed material load relations needed to close the mathematical system. Through a shared parameter called the control factor m, the interactions occurring in alluvial rivers are incorporated more deeply into the mathematical model and more particularly into the closure laws: bed material load (SVRD, Suction-Vortex Resuspension Dynamics) and the energy slope (Verbanck et al. 2007). The control factor m is assumedly related to the Rossiter resonance modes of the separated flow downstream the bed form crest. To further improve the representation of the flow-sediment-morphology interactions, a fully coupled model approach has been naturally chosen. In this work the terminology fully coupled means that the three equations forming the system are solved synchronously and that the terms often neglected by more traditional decoupled models are kept. The feasibility of the new closure methodology has been drawn up by reproducing numerically the silt-flushing experiment conducted by the Yellow River Conservancy Commission (Y.R.C.C.) in the Lower Yellow River (LYR) in Northern China. The objective of the silt flushing experiment is to reverse the aggradation trend of the Lower Yellow River which, in the last decades, has become a perched river. The numerical simulation specifically reproduces the silt-flush effects in a reach of LYR located in the meandering part of the river. This reach (around 100 km) is delimited by Aishan and Luokou hydrometric stations. Since the SVRD formulation has been developed from flume observations, the law has first been confronted to river datasets. The confrontation has revealed that the SVRD law becomes less suitable for fine sediment fluxes (ratio of water depth over median particle size > 5000). Therefore, a modified equation SVRD-2 has been built to enlarge the validity range. The suitability of the SVRD-2 equation to predict fine sediment fluxes has been tested on data available from several hydrometric stations located in the meandering reach of the LYR: historical observations and measures collected during the flushes. The SVRD-2 has also been compared with relations specifically calibrated for this configuration. The comparison has pointed out that the performance of the two formulas is similar, which is encouraging for the SVRD-2 approach as it has not been calibrated on those data. The closed equation system has been written on its quasi-linear form and is solved by a Finite Volume Method combined with a linearized Riemann algorithm. The numerical model has been checked up on two test cases: deposition upstream of a dam and the aggradation experiment conducted by Soni 1975. As it is not yet possible to predict dynamically the value of the control factor m, a possible solution would be to extract its value from the measured data at the inlet cross section. Unfortunately, the necessary data are not measured locally. Moreover, a uniform value of the control factor m may not suffice to reproduce the flow along the whole reach. Therefore, it has been proposed to work temporarily in the reverse way. From the comparison between the numerical results and the experimental data, a time evolution of the control factor m has effectively been extracted and it has been shown that it varies along the reach. At Aishan, the evolution of the control factor m corresponds to the evolution expected from the data analysis previously conducted on other data sets: the value of the control factor m decreases during the flush as it tries to reach the optimal value m=1. The time evolution at Luokou behaves differently to the one at Aishan, but remains in agreement with m evolution patterns observed historically for the river section flowing round Jinan City walls. For Luokou, the highlighted differences may come from three dimensional effects coming from the meander bend upstream the station. Generally, the results obtained for the hydraulics, the sediment transport and bed adaptation are encouraging but still need improvements and additional feeding from the experimental data. The results for the concentration and therefore the bed elevation are very sensitive to the value of the control factor m as it influences most of the terms of the bed material load equation (SVRD-2). The major remaining difficulties are, firstly, to deal with the rapid transients for which the model is less suitable and, secondly, to improve the prediction of the value of control factor m. Before paying more attention into the transients, enhancements concerning the flow along the reach (initial condition and discharge rates during the first days of the flush) must be conducted in priority. Indeed as the prediction of the bed or the cross section evolutions depend directly on the quality of the prediction of the sediment concentration and the hydraulics, one should first improve these aspects. To perform this study, more information about the water levels or sediment concentrations is necessary at some intermediate stations. One solution is to lengthen the studied reach, upstream to Sunkou and downstream to Lijin, totaling a river length of 456 Km. A more entire signal of the energy slopes and the associated bed configurations at different stations would enlighten how the control factor m evolves along the reach during the silt-flush events.

The industrial solvent trichloroethylene (TCE) and petroleum hydrocarbons (e.g., fuel oil) are among the most ubiquitous organic compounds found in subsurface contaminated environment. The developed treatment train system included the first stage of groundwater and surfactant flushing followed by the second stage of chemical oxidation such as potassium permanganate (KMnO4) and Fenton-like treatment. The third stage was the application of enhanced bioremediation for the further removal of residual contaminants after the first two treatment processes. The objectives of this study were to (1) assess the applicability of treatment train system for the remediation of organic compounds contaminated subsurface environment, (2) determine the optimal operational conditions of the three-stage treatment system, and (3) evaluate the effects of residual surfactant Simple GreenTM (SG) and hydrogen peroxide (H2O2) after chemical oxidation stage on the efficiency of bioremediation process. In this study, three different surfactants [SG, Triton X-100, and Tween 80] were evaluated in batch experiments for their feasibility on contaminants removal. Results from the surfactant biodegradation and microbial enumeration study indicate that SG was more biodegradable and was able to enhance the microbial activity of the intrinsic microorganisms. Thus, SG was applied in the following batch or column experiments of the treatment train system. Results from this study indicate that approximately 87.6% of TCE in the system (with initial concentration of 40 mg L-1) could be removed from the simulated dense non-aqueous-phase liquids (DNAPLs) system after groundwater flushing followed by biodegradable surfactant (1 g L-1 of SG) flushing, while the TCE concentrations dropped from 40 to 4.96 mg L-1 at the end of the flushing experiment. Moreover, approximately 10.7% of the remaining TCE could be removed from the system after the oxidation process using KMnO4 as the oxidant. Results from the oxidation process show that TCE was reduced from 4.96 to 0.69 mg L-1, and chloride concentation was increased from ND to 0.88 mg L-1 with the presence of 1 g L-1 of SG. The residual 1.7% of the TCE could be further remediated via the enhanced bioremediation stage, and the TCE concentrations dropped from 0.69 mg L-1 to below detection limit at the end of the bioremediation experiment. Results also indicate that the remaining KMnO4 had no significant inhibition on bacterial growth and TCE biodegradation. Thus, SG flushing and KMnO4 oxidation would not cause adverse effect on subsequent bioremediation process using intrinsic bacteria. Thus, complete TCE remediation was observed in this study using the three-stage treatment scheme. Results from the column experiment reveal that a complete TPH removal could be obtained after the application of three consecutive treatment processes. Results show that TPH concentration could be reduced from 50,000 mg kg-1 to below detection limit. This indicates that the treatment train system is a promising technology to remediate fuel-oil contaminated soils. Results from the column study indicate that approximate 80.3% of initial TPH in the soil could be removed after the SG [50 pore volumes (PVs)] followed by groundwater (30 PVs) flushing. The Fenton-like oxidation (with 6% of H2O2 addition) was able to remove another 15.0% of TPH. The observed first-order reaction rate constant of TPH oxidation was 2.74¡Ñ10-2 min-1, and the half-life was 25.3 min during the first 40 min of reaction. The residual 4.7% of the TPH could be further remediated via the aerobic bioremediation process. Thus, complete TPH removal was obtained in this study using the three-stage treatment scheme. The proposed treatment train system would be expected to provide a more efficient and cost-effective alternative to remediate chlorinated solvent and petroleum hydrocarbons contaminated sites.

This thesis deals with the application of the electrical impedance spectrometry (EIS) method and the implemented Z-meter III device, Z-meter IV device respectively, while observing the infiltration of simulated flushing water with the aim of assessing the possibility or the appropriateness of its use. The experiment was carried out in the Laboratory of Water Management Research.

Due to the combined effect of intense rainfall events together with the expected impact of climate change, this will put pressure on the existing and future infrastructure for storm water management. One of the challenges related to this is the combined sewer system which is still operating in large areas of many cities worldwide. In Stockholm, combined sewer represents around 50% of the total sewer pipe length. In a Combined sewer system, once the conveyed discharge exceeds the system capacity, the system overflows, which can result in a diverse range of health and environmental problems. The cause of overflow has been strongly linked to runoff from intense rainfall events. Therefore, a key proposal to overcome this problem is to disconnect runoff from hard surfaces. This research aims to investigate the impact of applying a rainwater harvesting (RWH) and reuse system to collect runoff water from roof surfaces in areas with combined sewer system. A simulation water balance model for a rooftop RWH system was developed and two reuse purposes were considered, which entails toilet flushing and garden irrigation within the property. The study area consists of one building block within Kungsholmen area in Stockholm. The obtained results indicate that applying such systems can reduce runoff to the sewer system. Toilet flushing reuse shows a higher reduction impact on sewer flow than the use for irrigation. Toilet flushing reuse reduces annual runoff volumes to sewer in a range of 49.5% - 93.4% while irrigation provided reduction in a range of 11.6% - 26.3%. Regarding number of times that overflow from the combined sewer system occurs, toilet flushing reuse demonstrated reduction of 40% - 100% while 20% to 60% was reduced by irrigation reuse. For overflow volume, a reduction rate of 11% to 100% was reached through toilet flushing in contrast to 9% to 43% reduction from irrigation reuse. 19% to 37% of toilet flushing water demand was covered by the tank, while arange of 48% to 100% was covered for irrigation demand. All these parameters were found to be sensitive to change in tank size where increasing the size result in higher flow reduction rates. When considering implementing a reuse system, it is important to consider the applicability of RWH and reuse within the specific property. In areas that are under development, either of the two reuses can be considered depending on local conditions. However, in already built up area it is difficult to introduce a system that requires significant adjustment to existing pipe networks, such as reuse systems for toilet flushing. Systems for outdoor irrigation are possible to implement in most situations. When it comes to tank size, the optimal size will depend on the intended reuse, the catchment area and the objective of the system. For example, if the main objective is to reduce potable water consumption, a smaller tank can be used compared to where the main objective is to reduce sewer overflow. Hence, when considering implementing a rainwater reuse systems, each project will need to consider the local conditions as well as the individual objectives when determining the optimal reuse purpose and tank size. A cost-benefit analysis should also be considered when determining the optimal tank size for the intended use.

On December 27, 1657, the men of Flushing, Long Island, signed a letter of protest addressed to the Governor-Director of New Netherlands. Though the law of the colony demanded otherwise, the men of Vlissengen pledged to accept all persons into their township, regardless of their religious persuasion. Their letter, called the Flushing Remonstrance, not only defied the laws of one of the most powerful, religious governors of the colonial age, it articulated a concept of religious freedom that extended beyond the principles of any other contemporary document. Given its unique place in early American colonial history, why have historians not devoted more research to the Flushing Remonstrance? The answer to that question had roots in suppositions widely accepted in the academic community. This thesis addresses and refutes these assumptions in full historical context.

Niacin is a highly effective, lipid regulating drug associated with a number of metabolically induced side effects such as prostaglandin (PG) mediated flushing and hepatic toxicity. In an attempt to reduce the development of these adverse effects, scientists have investigated differing methods of niacin delivery designed to control drug release and alter metabolism. However, despite successful formulation of various orally based capsule and tablet delivery systems, patient adherence to niacin therapy is still compromised by adverse events such as PG-induced flushing. While the primary advantage of orally dosed formulations is ease of use, alternative delivery options such as transdermal delivery or polymeric micro/nanoparticle encapsulation for oral administration have shown promise in niacin reformulation. However, the effectiveness of these alternative delivery options in reducing inimical effects of niacin and maintaining drug efficacy is still largely unknown and requires more in-depth investigation. In this paper, we present an overview of niacin applications, its metabolic pathways, and current drug delivery formulations. Focus is placed on oral immediate, sustained, and extended release niacin delivery as well as combined statin and/or prostaglandin antagonist niacin formulation. We also examine and discuss current findings involving transdermal niacin formulations and polymeric micro/nanoparticle encapsulated niacin delivery.

Idag spolar den stora majoriteten av alla invånare i Sverige med dricksvattnen itoaletten. Spolning med regnvatten i WC är något som på flera håll i världenanvänds flitigt främst i områden med någon slags vattenbrist. Men i Sverige harregnanvändande anläggningars popularitet inte riktigt slagit igenom ännu.Orsaken till detta kan härledas till flera faktorer. De viktigaste och de sompåverkar mest är; den goda tillgången och således låga priset på dricksvatten iSverige, samt begränsad konkurrens bland företag och återförsäljare vilket ger etthögt investeringspris på regnanvändande anläggningar för konsumenten.Fokus i detta examensarbete ligger på att göra en grundläggande analys avregnvatten och möjligheterna att genom en regnanvändande anläggning kunnaanvända regnvatten istället för dricksvatten för att spola i toaletten med.Tillvägagångssättet har varit att genom en studie av olika källor sammanställainformation relevant till ämnet regnvatten och regnvattenanvändning till WCspolning,följt av en analys och jämförelse av hur ekonomiskt hållbar enregnanvändande anläggning i ett standardhus beläget i Malmö är, i förhållande tillsamma standardhus med en traditionell dricksvattenförsörjning för WC-spolning.Resultatet av analysen visar tydligt att en regnvattenanvändande anläggning ifallet med standardhuset i dagsläget inte går att rättfärdiga ur ekonomisksynpunkt, men även att det finns möjlighet till en realistisk ekonomisk förtjänst iandra byggnader eller i framtiden. / The vast majority of the Swedish population today flushes their toilet withdrinking water. Flushing the toilet with rain water is used diligently on multiplelocations around the world, typically where there is a shortage of fresh water. InSweden though, the popularity of rain water harvesting has not yet beensuccessful. The cause of this can be deducted to several factors, where the mostimportant and the most influential are the abundant source, and therefore low cost,of fresh water in Sweden and the lack of competition among retailers, whichresults in a high investment cost of rain water harvesting equipment for theconsumer.The focal point of this Bachelor’s Degree project is to make a fundamentalanalysis of rain water and the possibilities of using rain water instead of drinkingwater for flushing the toilet. The procedure of the project has consisted of a studyof sources, a compilation of information relevant to rain water and the use of rainwater as flushing water in the toilet and an analysis of a calculated average housein Malmo, Sweden, and a comparison between a traditional toilet flushing systemand a rain water toilet flushing system of the same average house.The result of the analysis clearly shows that a rain water toilet flushing systemcan not be justified from a economical standpoint in the case of the average house,but also that there is a realistic chance of an economical profit in the future or ifused with other building types.

Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: When desalinating brackish water by reverse osmosis (RO) or other techniques, high overall water recoveries are essential to minimize brine production and the associated disposal costs thereof. As the overall water recovery increases, concentrations of sparingly soluble salts (e.g. barium sulphate, calcium sulphate) reach levels above saturation, especially near the membrane surface, drastically increasing the scaling propensity. Antiscalants are typically dosed into the feed water to prevent such scaling during RO desalination. However, the carry-over of antiscalant into the concentrate stream can complicate subsequent salt precipitation processes that may be used to increase overall water recovery. These precipitation techniques are sometimes used to reduce the levels of super-saturation in the RO concentrate prior to a subsequent RO desalination step. The purpose of this study was to assess the feasibility of reducing calcium sulphate scaling on RO membranes, by using periodic permeate flushing when feeding a lab-scale RO unit with a supersaturated calcium sulphate solution in the absence of anti-scalant. The overall water recovery was increased by recycling the concentrate, after an intermediate de-supersaturation step. This simulated a multiple-stage RO system, typical of processes used in high-recovery acid mine drainage (AMD) treatment plants. De-supersaturation of the concentrate intermediate was achieved with direct seeded gypsum precipitation, in the absence of any antiscalant. On the membrane surface inside the membrane unit, calcium sulphate concentrations greatly exceeded saturation levels – a combined consequence of the normal concentration process and the well-known surface-based concentration polarisation phenomenon. Therefore, periodic forward-flushing of the supersaturated solution from the membrane unit was performed with permeate. In theory, the periodic flushing removes the highly concentrated layer at the membrane surface during every flush, before scaling can occur. Various flushing regimes were evaluated to assess the effectiveness of the process. A lab-scale desalination unit with a 0.106 m2 flat sheet polyamide RO membrane was designed and constructed. The unit could operate at a feed rate of 12-14 L/h and at permeate fluxes of 12-24 LMH. Super-saturated feed solutions were prepared by mixing sodium sulphate and calcium chloride dihydrate salts with demineralised water, with an initial salinity of ± 5300 mg/L TDS, corresponding to a gypsum saturation index (SIg) of 1.2 for most experiments. The total production time, net permeate production and flux decline were used to compare the flushing efficiency in different experimental runs. Initial tests showed that scaling could be prevented (when operating the unit in full recycle mode, i.e. where both concentrate and permeate were recycled to feed), at flushing frequencies between 12 and 2.4 h-1, when the membrane feed and concentrate were slightly under-saturated (SIg = 0.9) and slightly super-saturated (SIg = 1.1) respectively. However, when switching the same system to non-flushing mode after 24 hours of operation, membrane scaling occurred within 2-3 hours, as indicated by a strong decline in flux. However, when operating the system in concentrate recycle mode (i.e. permeate is withdrawn) with super-saturated feed solutions (e.g. SIg = 1.2), and thus a notably more super-saturated solution in the membrane concentrate, scaling could not be prevented (albeit delayed for some time) with intermittent permeate flushing. A fractional 25-1 factorial design was used to determine which factors had the most significant effect on total production time and permeate production rate, testing five factors: 1) flushing frequency, 2) flushing volume, 3) permeate soak time, 4) permeate flux and 5) instantaneous recovery. The ANOVA analysis showed that total production times were, not surprisingly, primarily affected by the permeate flux, where operation at 24 LMH resulted in a lower net permeate production between 3.0 - 4.2 L, compared to 7.6 - 9.7 L at 12 LMH. Higher permeate fluxes clearly resulted in higher levels of concentration polarisation at the membrane surface, thus increasing the propensity for membrane scaling. Flushing frequency and instantaneous recovery also affected the net permeate production, where 6 h-1 and 10 % were the optimal values respectively within the range of test conditions. The lowest permeate production rate resulted in the highest net permeate volume production (i.e. also longest total production time), confirmed by a least squares regression. In summary: This study showed that periodic permeate flushing could delay the membrane scaling process. However, it failed to prevent membrane scaling completely when operating the system with supersaturated calcium sulphate solutions in the absence of antiscalants. The flushing technique effectively delayed the onset of precipitation, but scaling eventually occurred if the lab-scale RO system was operated in concentrate recycle mode with oversaturated feed solutions (SIg = 1.2). Additional experiments at different cross-flow velocities during permeate flushing, while using an optimised RO test cell flow channel design, are recommended for future studies. / AFRIKAANSE OPSOMMING: Gedurende die ontsouting van brakwater deur tegnieke soos tru-osmose (TO), is ʼn maksimum herwinning van water noodsaaklik om die produksie, en die gepaardgaande kostes van verwydering, van die sout/brak neweproduk te minimeer. Soos die herwinning van water verhoog, so ook verhoog die konsentrasie van moeilik-oplosbare soute (soos bariumsulfaat, kalsiumsulfaat) in die sout konsentraat stroom, totdat die soute uiteindelik superversadiging bereik. Hierdie superversadiging gebeur veral naby die membraanoppervlak, waar dit lei tot ʼn verhoogde kans van presipitasie en skaalvorming. Om dit te voorkom word die voerwater na ʼn TO stelsel tipies gedoseer met antiskaalmiddels. Hierdie antiskaalmiddels verlaat die stelsel saam met die konsentraat, waar hulle gevolglike die presipitasie van soute bemoeilik. Presipitasie van soute uit die konsentraat kan tipies gebruik word om die vlak van superversadiging in die konsentraat te verlaag, waarna verdere TO behandeling gebruik word om selfs ʼn hoër algehele waterherwinning te bewerkstellig. Die doel van hierdie studie was om die vatbaarheid van die vermindering van kalsiumsulfaat (gips) skaalvorming in die afwesigheid van antiskaalmiddels op TO membrane te toets. Dit is bewerkstellig deur ʼn laboratoriumskaal TO eenheid te voer met ʼn superversadigde kalsiumsulfaat oplossing en die membraan periodies met skoon produkwater (permeaat) te was. Die algehele waterherwinning is verhoog deur met ʼn tussenstap die versadigingsvlak van gips in die konsentraat te verlaag, waarna dit hersirkuleer is na die voertenk. Sodoende is ʼn multi-stadium TO stelsel nageboots, soos dit tipies in hoë herwinningsaanlegte, soos met die herwinning van suur mynwater (E: acid mine drainage, AMD), gebruik word. ʼn Verlaging in superversadiging van die konsentraat in die tussenstap is behaal deur die konsentraat direk aan gipskristalle bloot te stel om presipitasie te bewerkstellig in die afwesigheid van enige antiskaalmiddels. Gedurende eksperimente het die soutkonsentrasie op die membraanoppervlak in die TO eenheid superversadigingsvlakke vêr oorskry, as gevolg van die natuurlike konsentrasie proses en die bekende konsentrasie polarisasie oppervlaksverskynsel. Om hierdie superversadiging teen te werk is periodiese saamstroom spoeling van die membraan met skoon produkwater uitgevoer. In teorie het die periodiese spoeling die hoogs gekonsentreerde oplossing van die membraan oppervlak verwyder voor skaalvorming kan plaasvind. Verskillende spoelpatrone is ondersoek om die doeltreffendheid van die spoeling te bepaal. Om die eksperimente uit te voer is ʼn laboratoriumskaal ontsoutingsaanleg met ʼn maklik verwyderbare 0.106 m2 plat-vel poli-amied TO membraan ontwerp en gebou. Die aanleg kan vloeistof voertempo’s tussen 12-24 L/h hanteer en skoon produkwater teen 12-24 LHM lewer. Die superversadigde voer oplossings, soos gebruik in die meerderheid van die eksperimentes is voorberei deur natriumsulfaat en kalsiumchloried-dihidraat soute te meng in gedemineraliseerde water, tot ʼn soutgehalte van ± 5300 mg/L TDS bereik is. Hierdie soutgehalte stem ooreen met ʼn gips versadigingsindeks (E: gypsum saturation index, SIg) van 1.2. Die skoon produkwater totale produksietyd en netto produksie, asook die membraan vloed afname, is gebruik as veranderlikes om die spoel doeltreffendheid tussen eksperimentele lopies te vergelyk. Aanvanklike toetse het getoon dat skalering voorkom is by effens onderversadigde (SIg = 0.9) en effens superversadigde (SIg = 1.1) voer oplossings met die onderskeie spoel frekwensies van 12 en 2.4 h-1, (terwyl die aanleg in algehele hersirkulasie bedryf is, m.a.w. wanneer beide die konsentraat en produkwater gedurig na die voertenk hersirkuleer word). ʼn Effens-superversadigde eksperiment is ook sonder spoeling uitgevoer vir 24 uur. In hierdie geval het skaalvorming binne twee tot drie uur gebeur, soos bevestig deur ʼn skerp afname in die membraan vloed. Skaalvorming kon nie verhoed word terwyl die aanleg bedryf word met superversadigde (SIg = 1.2) voeroplossings en slegs konsentraat hersirkulasie nie (m.a.w. skoon produkwater word opgevang), alhoewel skaalvorming vertraag kon word. Hierdie operasie het tot beduidend meer gekonsentreerde oplossings in die membraan gelei. Om te bepaal watter faktore die grootste invloed op totale produksietyd en netto produksie van skoon produkwater het, is ʼn fraksionele faktoriaalontwerp van 25-1 uitgelê wat vyf faktore toets, naamlik: 1) spoel frekwensie, 2) spoel volume, 3) skoon produkwater weektyd, 4) membraanvloed en 5) oombliklike herwinning. ʼn AVOVA analise het getoon dat totale produksietyd hoofsaaklik deur membraanvloed beïnvloed is, soos verwag kan word. Dit word gestaaf deurdat die aanleg, bedryf teen 24 LMH, slegs 3 - 4.2 L netto produkwater gelewer het, teenoor 7.6 - 9.7 L by 12 LMH. Hoër membraan vloedtempo’s het tot hoër vlakke van konsentrasie polarisasie op die membraanoppervlak gelei, wat ʼn groter neiging tot skaalvorming tot gevolg gehad het. Spoelfrekwensie en oombliklike herwinning het ʼn invloed op die netto produksie van skoon produkwater gehad, met 6 h-1 en 10 % as die onderskeie optimale waardes. ʼn Kleinstekwadraat regressie het aangedui dat die laagste produksietempo van skoon produkwater die hoogste netto produksie van skoon produkwater gelewer het, (asook die langste produksietyd). In opsomming: Hierdie studie het getoon dat gereelde spoeling met skoon produkwater die membraan skaalproses kan vertraag. Gedurende bedryf met superversadigde kalsiumsulfaat oplossings sonder enige antiskaalmiddels is daar gevind dat skaalvorming nie geheel en al vermy kon word nie. Die spoeltegniek, soos gebruik in hierdie studie, het die aanvang van skaalvorming in die laboratorium skaal TO eenheid vertraag, maar bedryf met konsentraat hersirkulasie en superversadigde oplossings (SIg = 1.2) het steeds skaal gevorm. Bykomende eksperimente teen verskeie kruisvloei snelhede gedurende die spoel stap word aanbeveel vir toekomstige studies.

A distribuição e a variabilidade de propriedades termohalinas e a circulação tridimensional do estuário do rio Curimataú foram estudadas com a aplicação do modelo numérico de simulações Delft3D-Flow, validado com dados experimentais medidos durante dois ciclos consecutivos de maré de quadratura e de sizígia. Duas grades numéricas foram aplicadas com o intuito de observar as diferenças entre as simulações nos modos barotrópico e baroclínico. As condições iniciais de simulações tais como: salinidade, velocidade, densidade e coeficientes cinemáticos de viscosidade, difusividade horizontal e vertical foram obtidas mediante resultados de simulações sob condições iniciais homogêneas. A seguir, o modelo numérico foi utilizado em condições mais realistas que foram comparadas aos dados experimentais. As simulações para a estrutura de salinidade, no modo barotrópico na maré de sizígia, apresentaram os melhores resultados, em comparação com os resultados experimentais, confirmado pelo índice de validação Skill igual 0,96; no modo baroclínico as simulações também foram de boa qualidade e o Skill foi muito próximo ao anterior (0,94). As simulações teóricas do campo de velocidade também foram de boa qualidade, comparativamente aos dados experimentais; os índices de validação médios foram muito próximos para os modos barotrópico e baroclínico (0,80 e 0,79). Esses valores do índice de validação confirmam que a dinâmica e os processos de mistura de natureza advectiva e difusiva foram bem representados matematicamete. Durante a maré de quadratura os resultados teóricos dos modos barotrópico e baroclínico não foram de boa qualidade (índice skill próximo a 0,60), devido às dificuldades de imposição de condições de contorno adequadas para a alta descarga fluvial que ocorreu durante os experimentos. Além das simulações por intervalos de tempo de 25 h, que foram utilizadas para validação com os dados experimentais, também foram feitas simulações inéditas horárias das características termohalinas, da circulação e do transporte advectivo de sal em séries temporais de 16 e 90 dias nos modos baroclínico e barotrópico, respectivamente. Aos resultados simulados das estruturas de salinidade e de velocidade, no modo baroclínico e maré de sizígia, foram aplicadas as metodologias rotineiramente utilizadas no processamento e análise de dados experimentais, com a finalidade de interpretar o comportamento dinâmico e os processos de mistura e transporte. No modo baroclínico, durante ambas as marés de sizígia e quadratura, a região inferior do estuário foi classificada como parcialmente misturado (tipo 2a), com valores baixos para os parâmetros de estratificação O(10-2)<pe< O(10-3) e com o parâmetro de circulação variando consideravelmente entre valores altos (pc&#61627;50) e baixos (pc&#61627;2). A análise da variabilidade dos coeficientes cinemáticos de viscosidade e difusividade no canal estuarino do rio Curimataú indicou que esses coeficientes variaram no seguinte intervalo: 10-3 m2 s-1 a 1,2x10-2 m2 s-1. A energia cinética turbulenta e as taxas de energia dissipada por unidade de massa, nas proximidades da boca do estuário, apresentou os maiores valores com ordens de grandeza de 6,5x10-3 m2 s-2 e 2,4 m2 s-3, respectivamente. / The distribution and variability of the termohaline properties and the three-dimensional circulation of the Curimataú river estuary had been studied with the application of the numerical model of simulations Delft3D-Flow, validated with experimental data measured during two consecutive cycles of neap and spring tide. Two numerical grids were applied with the intention of observing the differences between the barotropic and baroclinic simulations. The initial conditions such as: salinity, velocity, density and the horizontal and vertical kinematic coefficients of viscosity and difusivity had been undertaken through the results under homogeneous initial conditions. After that, the numerical model had been used in more realistic conditions which were compared with the experimental data. The simulations of the structure of salinity, in the barotropic model during the spring tide, showed better results when compared with the experimental data, validated by the Skill equal to 0.96; in the baroclinic model the simulations also had presented a good quality and the Skill was very close to those one (0.94). The theoretical simulations of the field of velocity were also of a good quality, comparatively the experimental to the experimental data; the mean Skill had been very close the barotropic and baroclinic models (0.80 e 0.79). Those values of the Skill confirm that the dynamic and the mixing process of advective and diffusive nature had been well presented mathematically. During the neap tide the theoretical results of the barotropic and baroclinic models had not been of a good quality (Skill 0.60), due to the difficulties of imposition of suitable boundary conditions to the high river discharge during the experiments. Besides the simulations with time intervals of 25 h, which were used to the validation with the experimental data, also had been realized hourly simulations of the termohaline features, of the circulation and the advective salt transport into temporal series of 16 and 90 days in the barotropic and baroclinic models respectively. To the simulated results of the salinity and velocity structures, in the baroclinic model and under spring conditions, had been applied the aim methodology used in process and analyzes of experimental data, with the finality of interpretation of the dynamic behavior and the mixing process and the transport. In the barolinic model, during both tides, neap and spring, in the lower reaches of the estuary was classified as partially mixed (tipe 2a), with low values to the stratification parameters O(10-2)<pe< O(10-3) and with the circulation parameter varying considerably between high values (pc&#61627;50) and low values (pc&#61627;2). The analyses of the variability of the Kinematic and diffusivity coefficients in the Curimataú river channel indicated that those coefficients had been in the interval of: 10-3 m2.s-1 a 1.2x10-2 m2.s-1. The kinetic turbulent energy and the rate of energy dissipation had indicated that in the vicinity mediations of the estuary mouth are concentrated the highest values: 6,5x10-3 m2 s-2 and 2,4 m2 s-3, respectively.