Impact of SWMM Fouling and Position on the Performance of SWRO Systems in Operating Conditions of Minimum SEC.

Due to water stress in the world in general desalination technologies are becoming increasingly important. Among the available technologies, reverse osmosis (RO) is the most widespread due to its reliability and efficiency compared to other technologies. The main weakness of RO is the loss of performance due to membrane fouling, which usually affects the water permeability coefficient (A), causing it to decrease. In RO desalination plants, fouling does not affect all spiral wound membrane modules (SWMMs) in the pressure vessels (PVs) in the same way. This will depend on the type of fouling and the position of the SWMM inside the PV. In this study, the impact of A and the position of the SWMM on the performance of the RO system is analyzed. For this purpose, decrements of up to 50% have been assumed for the seven SWMMs in series considering nine commercial SWMM models. The operating point analyzed is that which minimizes the specific energy consumption (SEC), a point obtained in a previous work carried out by the authors. The results show how the impact of A on the SWMM in the first position is more significant than the impact on modules that are in another position for the nine SWRO models studied. A drop of 50% in the coefficient A of the first element produces a permeate loss in the pressure pipe between 0.67 and 1.35 m3 d-1. Furthermore, it was observed that the models with the lowest coefficient A exhibited the highest performance losses in terms of permeate production when A was decreased.

Efficient Photocatalytic Degradation of Organic Pollutant in Wastewater by Electrospun Functionally Modified Polyacrylonitrile Nanofibers Membrane Anchoring TiO2 Nanostructured.

In this study, polyacrylonitrile (PAN_P) nanofibers (NFs) were fabricated by electrospinning. The PAN_P NFs membrane was functionalized with diethylenetriamine to prepare a functionalized polyacrylonitrile (PAN_F) NFs membrane. TiO2 nanoparticles (NPs) synthesized in the laboratory were anchored to the surface of the PAN_F NFs membrane by electrospray to prepare a TiO2 NPs coated NFs membrane (PAN_Coa). A second TiO2/PAN_P composite membrane (PAN_Co) was prepared by embedding TiO2 NPs into the PAN_P NFs by electrospinning. The membranes were characterized by microscopic, spectroscopic and X-ray techniques. Scanning electron micrographs (SEM) revealed smooth morphologies for PAN_P and PAN_F NFs membranes and a dense cloud of TiO2 NPs on the surface of PAN_Coa NFs membrane. The attenuated total reflectance in the infrared (ATR-IR) proved the addition of the new amine functionality to the chemical structure of PAN. Transmission electron microscope images (TEM) revealed spherical TiO2 NPs with sizes between 18 and 32 nm. X-ray powder diffraction (XRD) patterns and energy dispersive X-ray spectroscopy (EDX) confirmed the existence of the anatase phase of TiO2. Surface profilometry da-ta showed increased surface roughness for the PAN_F and PAN_Coa NFs membranes. The adsorption-desorption isotherms and hysteresis loops for all NFs membranes followed the IV -isotherm and the H3 -hysteresis loop, corresponding to mesoporous and slit pores, respectively. The photocatalytic activities of PAN_Coa and PAN_Co NFs membranes against methyl orange dye degradation were evaluated and compared with those of bare TiO2 NPs.The higher photocatalytic activity of PAN_Coa membrane (92%, 20 ppm) compared to (PAN_Co) NFs membrane (41.64%, 20 ppm) and bare TiO2 (49.60%, 20 ppm) was attributed to the synergy between adsorption, lower band gap, high surface roughness and surface area.

Model Based Simulation and Genetic Algorithm Based Optimisation of Spiral Wound Membrane RO Process for Improved Dimethylphenol Rejection from Wastewater.

Reverse Osmosis (RO) has already proved its worth as an efficient treatment method in chemical and environmental engineering applications. Various successful RO attempts for the rejection of organic and highly toxic pollutants from wastewater can be found in the literature over the last decade. Dimethylphenol is classified as a high-toxic organic compound found ubiquitously in wastewater. It poses a real threat to humans and the environment even at low concentration. In this paper, a model based framework was developed for the simulation and optimisation of RO process for the removal of dimethylphenol from wastewater. We incorporated our earlier developed and validated process model into the Species Conserving Genetic Algorithm (SCGA) based optimisation framework to optimise the design and operational parameters of the process. To provide a deeper insight of the process to the readers, the influences of membrane design parameters on dimethylphenol rejection, water recovery rate and the level of specific energy consumption of the process for two different sets of operating conditions are presented first which were achieved via simulation. The membrane parameters taken into consideration include membrane length, width and feed channel height. Finally, a multi-objective function is presented to optimise the membrane design parameters, dimethylphenol rejection and required energy consumption. Simulation results affirmed insignificant and significant impacts of membrane length and width on dimethylphenol rejection and specific energy consumption, respectively. However, these performance indicators are negatively influenced due to increasing the feed channel height. On the other hand, optimisation results generated an optimum removal of dimethylphenol at reduced specific energy consumption for a wide sets of inlet conditions. More importantly, the dimethylphenol rejection increased by around 2.51% to 98.72% compared to ordinary RO module measurements with a saving of around 20.6% of specific energy consumption.

Thermodynamic Limitations and Exergy Analysis of Brackish Water Reverse Osmosis Desalination Process.

The reverse osmosis (RO) process is one of the most popular membrane technologies for the generation of freshwater from seawater and brackish water resources. An industrial scale RO desalination consumes a considerable amount of energy due to the exergy destruction in several units of the process. To mitigate these limitations, several colleagues focused on delivering feasible options to resolve these issues. Most importantly, the intention was to specify the most units responsible for dissipating energy. However, in the literature, no research has been done on the analysis of exergy losses and thermodynamic limitations of the RO system of the Arab Potash Company (APC). Specifically, the RO system of the APC is designed as a medium-sized, multistage, multi pass spiral wound brackish water RO desalination plant with a capacity of 1200 m3/day. Therefore, this paper intends to fill this gap and critically investigate the distribution of exergy destruction by incorporating both physical and chemical exergies of several units and compartments of the RO system. To carry out this study, a sub-model of exergy analysis was collected from the open literature and embedded into the original RO model developed by the authors of this study. The simulation results explored the most sections that cause the highest energy destruction. Specifically, it is confirmed that the major exergy destruction happens in the product stream with 95.8% of the total exergy input. However, the lowest exergy destruction happens in the mixing location of permeate of the first pass of RO desalination system with 62.28% of the total exergy input.

Management based on grading of animation deformity following implant-based subpectoral breast reconstruction

Subpectoral breast reconstruction using implants and meshes have been used widely in Europe, the United States and the United Kingdom. Although this technique has several advantages, animation deformity is a well-documented problem. We propose a new grading system to classify breast animation in patients undergoing subpectoral implant based breast reconstruction. We also discuss different techniques to avoid and correct animation deformity.

Developed Hybrid Model for Propylene Polymerisation at Optimum Reaction Conditions.

A statistical model combined with CFD (computational fluid dynamic) method was used to explain the detailed phenomena of the process parameters, and a series of experiments were carried out for propylene polymerisation by varying the feed gas composition, reaction initiation temperature, and system pressure, in a fluidised bed catalytic reactor. The propylene polymerisation rate per pass was considered the response to the analysis. Response surface methodology (RSM), with a full factorial central composite experimental design, was applied to develop the model. In this study, analysis of variance (ANOVA) indicated an acceptable value for the coefficient of determination and a suitable estimation of a second-order regression model. For better justification, results were also described through a three-dimensional (3D) response surface and a related two-dimensional (2D) contour plot. These 3D and 2D response analyses provided significant and easy to understand findings on the effect of all the considered process variables on expected findings. To diagnose the model adequacy, the mathematical relationship between the process variables and the extent of polymer conversion was established through the combination of CFD with statistical tools. All the tests showed that the model is an excellent fit with the experimental validation. The maximum extent of polymer conversion per pass was 5.98% at the set time period and with consistent catalyst and co-catalyst feed rates. The optimum conditions for maximum polymerisation was found at reaction temperature (RT) 75 °C, system pressure (SP) 25 bar, and 75% monomer concentration (MC). The hydrogen percentage was kept fixed at all times. The coefficient of correlation for reaction temperature, system pressure, and monomer concentration ratio, was found to be 0.932. Thus, the experimental results and model predicted values were a reliable fit at optimum process conditions. Detailed and adaptable CFD results were capable of giving a clear idea of the bed dynamics at optimum process conditions.

Multiphasic Reaction Modeling for Polypropylene Production in a Pilot-Scale Catalytic Reactor.

In this study, a novel multiphasic model for the calculation of the polypropylene production in a complicated hydrodynamic and the physiochemical environments has been formulated, confirmed and validated. This is a first research attempt that describes the development of the dual-phasic phenomena, the impact of the optimal process conditions on the production rate of polypropylene and the fluidized bed dynamic details which could be concurrently obtained after solving the model coupled with the CFD (computational fluid dynamics) model, the basic mathematical model and the moment equations. Furthermore, we have established the quantitative relationship between the operational condition and the dynamic gas⁻solid behavior in actual reaction environments. Our results state that the proposed model could be applied for generalizing the production rate of the polymer from a chemical procedure to pilot-scale chemical reaction engineering. However, it was assumed that the solids present in the bubble phase and the reactant gas present in the emulsion phase improved the multiphasic model, thus taking into account that the polymerization took place mutually in the emulsion besides the bubble phase. It was observed that with respect to the experimental extent of the superficial gas velocity and the Ziegler-Natta feed rate, the ratio of the polymer produced as compared to the overall rate of production was approximately in the range of 9%⁻11%. This is a significant amount and it should not be ignored. We also carried out the simulation studies for comparing the data of the CFD-dependent dual-phasic model, the emulsion phase model, the dynamic bubble model and the experimental results. It was noted that the improved dual-phasic model and the CFD model were able to predict more constricted and safer windows at similar conditions as compared to the experimental results. Our work is unique, as the integrated developed model is able to offer clearer ideas related to the dynamic bed parameters for the separate phases and is also capable of computing the chemical reaction rate for every phase in the reaction. Our improved mutiphasic model revealed similar dynamic behaviour as the conventional model in the initial stages of the polymerization reaction; however, it diverged as time progressed.

Polypropylene Production Optimization in Fluidized Bed Catalytic Reactor (FBCR): Statistical Modeling and Pilot Scale Experimental Validation.

Propylene is one type of plastic that is widely used in our everyday life. This study focuses on the identification and justification of the optimum process parameters for polypropylene production in a novel pilot plant based fluidized bed reactor. This first-of-its-kind statistical modeling with experimental validation for the process parameters of polypropylene production was conducted by applying ANNOVA (Analysis of variance) method to Response Surface Methodology (RSM). Three important process variables i.e., reaction temperature, system pressure and hydrogen percentage were considered as the important input factors for the polypropylene production in the analysis performed. In order to examine the effect of process parameters and their interactions, the ANOVA method was utilized among a range of other statistical diagnostic tools such as the correlation between actual and predicted values, the residuals and predicted response, outlier t plot, 3D response surface and contour analysis plots. The statistical analysis showed that the proposed quadratic model had a good fit with the experimental results. At optimum conditions with temperature of 75 °C, system pressure of 25 bar and hydrogen percentage of 2%, the highest polypropylene production obtained is 5.82% per pass. Hence it is concluded that the developed experimental design and proposed model can be successfully employed with over a 95% confidence level for optimum polypropylene production in a fluidized bed catalytic reactor (FBCR).

Coronary artery disease in patients undergoing valve replacement at a tertiary care cardiac centre.

OBJECTIVE: To determine the prevalence of coronary artery disease in patients undergoing valve surgery at a tertiary care cardiac centre. METHODS: The medical records of 144 consecutive patients who underwent mitral, aortic or dual (mitral and aortic) valve replacement surgery at the Tabba Heart Institue between January 2006 to December 2008 were retrospectively reviewed. All patients underwent coronary angiogram. Significant coronary artery disease (CAD) is defined as coronary stenosis of > or = 50%. RESULTS: There were 74 (51.4%) males and 70 (48.6%) females in the study. The mean age was 51.64 +/- 11 years. Of all, 73 (50.7%) underwent mitral valve replacement, 47 (32.6%) had aortic and 24 (16.7%) had dual valve replacement. Out of 144 patients, 99 (68.8%) had < 50% coronary stenosis and remaining 45 (31.3%) had > or = 50% stenosis. In patients who had undergone mitral valve replacement (MVR), significant coronary disease was found in 32.9%, whereas in patients who had undergone aortic valve replacement (AVR) and dual valve replacement (DVR) the prevalence of coronary disease was 31.9% and 25% respectively. CONCLUSIONS: Our results suggest that the overall prevalence of coronary artery disease in patients undergoing valve surgery in our population is comparable with prevalence reported in international data.

Doppler derived gradient of St. Jude mechanical prosthesis, early postoperative assessment.

OBJECTIVE: To determine the doppler derived mean gradients of St Jude mechanical prosthesis in early postoperative period in patients undergoing valve replacement at a tertiary care cardiac centre. METHODS: Medical records of 190 consecutive patients who underwent 233 mitral, aortic or dual (mitral and aortic) valve replacement by St Jude bileaflet mechanical prosthesis at Tabba Heart Institute, between March 2006 to December 2008 were reviewed. Doppler derived mean gradients were assessed predischarge and recorded. RESULTS: There were 98 (51.5%) males and 92 (48.5%) females in the study cohort. The mean age was 40 +/- 14 years. Of the total, 101 (53%) had mitral, 46 (24.2%) had aortic and 43 (22.6%) patients had dual valve replacement. Doppler derived mean gradient was assessed across 144 mitral and 89 aortic St Jude mechanical prosthesis. Doppler derived mean gradient for St Jude mitral prosthesis was 3.5 mm Hg and for St Jude aortic prosthesis was 10.2 mm Hg. CONCLUSIONS: The study determines baseline gradients across mitral and aortic St Jude mechanical prosthesis in our population. These can be used as reference gradients to assess St Jude prosthetic valve function in patients who did not have early postoperative doppler assessment.

Association of ST segment depression >5 min after exercise testing with severity of coronary artery disease.

OBJECTIVE: To determine the association of prolonged ST segment depression after an exercise test with severity of coronary artery disease. METHODS: A cross sectional study of 100 consecutive patients referred to the cardiology laboratory for stress myocardial perfusion imaging (MPI) conducted between April-August 2008. All selected patients were monitored until their ST segment depression was recovered to baseline. ST segment recovery time was categorized into less and more than 5 minutes. Subsequent gated SPECT-MPI was performed and stratified according to severity of perfusion defect. Association was determined between post exercise ST segment depression recovery time (<5 minutes and >5 minutes) and severity of perfusion defect on MPI. RESULTS: The mean age of the patients was 57.12 +/- 9.0 years. The results showed statistically insignificant association (p > 0.05) between ST segment recovery time of <5 minutes and >5 minutes with low, intermediate or high risk MPI. CONCLUSION: Our findings suggest that the commonly used cut-off levels used in literature for prolonged, post exercise ST segment depression (>5 minutes into recovery phase) does not correlate with severity of ischaemia based on MPI results.

Prevalence and factors associated with HCV (hepatitis C virus) seropositivity in Islamabad, Pakistan.

An estimated 150-200 million people worldwide are infected with hepatitis C. Prevalence is higher in some countries in Asia and Africa. Only limited information about the epidemiology of Hepatitis C Virus (HCV) infection especially in females is available. The aim of this study is to determine the prevalence of anti-HCV antibodies and the possible factors for transmission in the female population of a largely urban city Islamabad. A cross sectional study was conducted from May 2006 to August 2006 in Islamabad. We select 252 female households (n=252) following the selection criteria. The primary outcome variables were HCV seropositivity and factors like history of major surgical procedure, blood transfusion, Intravenous drug use etc. The results showed mean age of the sample was 33.21 (±9.95) years and HCV seropositivity was present in 62 (24.6%) females. Final Forward Stepwise multiple logistic regression showed blood transfusion [OR, 10.094 95% CI 1.950-52.257], dental procedure [OR, 5.381 95% CI 2.315-12.507] and dilation and curettage [OR, 3.869 95% 1.867-8.015] were significantly associated with HCV seropositivity in females. The study highlights poor quality of care provided and a massive need to educate general population including patients as well as health professionals and allied health workers.

Role of serum troponin-I in identifying left ventricular ejection fraction of

OBJECTIVE: To determine the serum levels of troponin-I in identifying left ventricular ejection fraction (LVEF) of 63.5 ng/ml predicted LVEF of 87.5 ng/ml predicted LVEF < 40% with a sensitivity of 86% and specificity of 100%. CONCLUSION: Troponin-I concentration of > 63.5 ng/ml and > 87.5 ng/ml can predict LVEF

Primary percutaneous coronary aspiration of thrombus from infarct related artery.

We are reporting the case of a 48-year-old man hypertensive, and smoker presenting with acute inferoposterior ST elevation myocardial infarction (STEMI) with right ventricular infarction. He underwent diagnostic angiogram which revealed total occlusion of mid right coronary artery (RCA) by thrombus. Multiple runs of aspiration were performed using Export Aspiration Catheter-6F and thrombus was aspirated from RCA. Postaspiration stenting was deferred due to absence of any significant obstructive lesion. Some thrombus had migrated to distal right posteriolateral branch (RPLB). He was started on glycoprotein (GP) IIb IIIa inhibitors which had to stopped after a few hours due to upper gastrointestinal bleed. After 48 hours a re-look angiogram demonstrated good flow in RCA with resolution of the residual thrombus.

Effects of chemotherapy on patients with unresectable or metastatic adenocarcinoma of gallbladder.

OBJECTIVE: To evaluate the effect of combination chemotherapy on disease status, toxicity and survival of patients with unresectable locally advanced or metastatic adenocarcinoma of gallbladder. METHODS: Single arm study of twenty patients, with unresectable locally advanced or metastatic adenocarcinoma of gallbladder, who presented to oncology clinic at Ziauddin Hospital Nazimabad Karachi from January 1997 to December 1998. Patients received combination of 5-Fluorouracil (5FU) and Folinic Acid daily for five days. RESULTS: Out of twenty patients, two (10%) were males and eighteen (90%) were females. Twelve (60%) patients showed symptomatic relief for a mean duration of 4.7 +/- 3.2 months. Disease remained stable in ten (50%) patients, progressed in nine (45%), and one (5%) showed partial remission of disease. Toxicity with chemotherapy was acceptable, without severe side effects. None of the patients suffered from febrile neutropenia. Overall survival was 13.6 +/- 12.3 months. CONCLUSION: 5-Fluorouracil with Folinic acid therapy does not result in significant objective responses, however, stabilization of disease process occurred in 55% of patients. Symptomatic relief was observed more frequently. This combination deserves further evaluation.