Effects of MF membranes deformation and permeability on filtration of clay suspension and its solution chemistry

Emergency Events Database (EM-DAT) indicates global increase in the frequency and intensity of natural disasters from 1900 to 2013. This is due to combinations of factors: climate change phenomena and population growth in vulnerable regions. One of first priorities after disaster is to provide safe drinking water to the affected. Membrane technology offers several advantages over conventional treatment. It provides better water quality, much more compact system, more flexible, less dependent on electricity and low cost. Microfiltration (MF) membranes have been regarded as one of the oldest separation technique and used extensively for the removal of particles, turbidity and microorganisms in water treatment. However, membrane fouling and membrane deformation due to blocking and hydrostatic pressure respectively, are limiting factors in water treatment. In understanding this issue, low pressure filtration of clay suspension for water treatment purposes is investigated in this work. The effects of permeability due to variation in solution chemistry of clay suspension, and deformation due to hydrostatic pressure are the parameters studied. Clay is used as solid contaminant; one of multi-components of natural waters and hence, one of the major factors that limits the use of MF for surface water treatment because it causes membrane fouling. Clays are complex colloidal materials, thus their presence in water alter the performance of membranes due to their reactions with variations in solution chemistry as well as with water. Darcy’s law could be used to explain apparent permeability change by changing the concentration of salt. This would explain the electro-viscous effects by altering zeta potential and double layers measurement, and also membrane resistance towards water. This study is important because membrane permeability control might prolong the lifetime of the membrane for water treatment. Membrane deformation is investigated by measuring pure water flux measurement prior to filtration experiment, and hysteresis phenomenon to be observed whether reversible or irreversible membrane deformation has occurred

Filtration of natural organic matter using ultrafiltration membranes for drinking water purposes: circular cross-flow compared with stirred dead end flow

Application of ultrafiltration membranes for removal of humic acids is investigated below. Membrane filtration processes were compared using two different set-ups: circular flow and stirred dead end flow. The transmembrane pressure, temperature, feed concentration, pH, ionic strength and shear stresses applied on the membrane surfaces were kept constant whilst the permeate flux and solute rejection were measured during the experiments with both set-ups. It was shown that the rejection (both the observed and the true rejection) in the case of circular flow was higher than in the case of dead end flow. The mass transfer coefficients were determined for both set-ups. In the case of stirred dead end, it ranged in from 2.14 to 4.72 × 10−6 m/s; however, for circular cross flow system, the mass transfer coefficients were found in the range 2.24–3.22 × 10−5 m/s. Comparison of the mass transfer coefficients obtained for both systems showed that it was significantly higher for circular flow systems as compared with stirred dead end system at similar operating conditions. Energy consumed per volume of purified water by circular flow system (0.345 kW) was found to be much lower when by stirred dead end system (0.955 kW). This proved that the performance of circular flow system was more efficient in terms of rejection, mass transfer coefficient and energy consumption

Membrane-based point-of-use water treatment (PoUWT) system in emergency situations: a review

During emergency situations, effective and quick reactions are vital in order to supply safe and unpolluted drinking water within approved guidelines Point-of-use water treatment (PoUWT) system, for instance, portable membrane-based water treatment devices, could help affected people to survive while waiting for aids to arrive. In the context of portable membrane-based water purification devices, it is also found that the most literature does not mention particle depositions and interactions, and membrane fouling mechanisms that might occur in these devices. The latter is especially important if the device is for private use for certain type of contaminant. It is found that the information available in the literature is mostly based on the performance of devices in terms of the following: bacteria/viruses/particles removal, cost efficiency including maintenance and repair, capacity and flow rate of permeate and producing company. These are discussed briefly as well

A comparative study between stirred dead end and circular flow in microfiltration of china clay suspension

A well-defined comparative study between stirred dead end and circular crossflow for microfiltration of china clay suspension has been undertaken. The comparisons have been made with respect to convective mass transfer coefficients, permeation and rejection rates, and energy consumption. Similar operating and hydrodynamic conditions were implemented for the comparison. According to our experimental data circular crossflow module was proven to perform better as compared with the stirred dead end system due to the higher mass transfer coefficients, higher permeation rates and lower energy consumption. The mass transfer coefficients observed are comparable to previously found in vortex flow filtration and dead end flow filtration. The presence of Dean vortices in circular crossflow module promotes flow instabilities in the curved channel flow path which reduce concentration polarization effect during the filtration process. The concentration polarization effect however deteriorated due to solute build up (high solute concentration at the membrane surface) and decrease of the shear stress, i.e., the particle lift forces on the membrane surface. This resulted in deposition of particles on the membrane surface. In terms of energy consumption, for the same energy cost the limiting flux reached in circular crossflow is found higher than in stirred dead end uni

Characteristics of Ultrasensitive Hexagonal-Cored Photonic Crystal Fiber for Hazardous Chemical Sensing

This research article was published by MDPI 2022A highly sensitive non-complex cored photonic crystal fiber sensor for hazardous chemical sensing with water, ethanol, and benzene analytes has been proposed and is numerically analyzed using a full-vector finite element method. The proposed fiber consists of a hexagonal core hole and two cladding air hole rings, operating in the lower operating wavelength of 0.8 to 2.6 μm. It has been shown that the structure has high relative sensitivity of 94.47% for water, 96.32% for ethanol and 99.63% for benzene, and low confinement losses of 7.31 × 10−9 dB/m for water, 3.70 × 10−10 dB/m ethanol and 1.76 × 10−13 dB/m benzene. It also displays a high power fraction and almost flattened chromatic dispersion. The results demonstrate the applicability of the proposed fiber design for chemical sensing applications

Improvement of Properties and Performances of Polyether sulfone Ultrafiltration Membrane by Blending with Bio-Based Dragonbloodin Resin

Polyethersulfone (PES) is the most commonly used polymer for membrane ultrafiltration because of its superior properties. However, it is hydrophobic, as such susceptible to fouling and low permeation rate. This study proposes a novel bio-based additive of dragonbloodin resin (DBR) for improving the properties and performance of PES-based membranes. Four flat sheet membranes were prepared by varying the concentration of DBR (0–3%) in the dope solutions using the phase inversion method. After fabrication, the membranes were thoroughly characterized and were tested for filtration of humic acid solution to investigate the effect of DBR loading. Results showed that the hydrophilicity, porosity, and water uptake increased along with the DBR loadings. The presence of DBR in the dope solution fastened the phase inversion, leading to a more porous microstructure, resulted in membranes with higher number and larger pore sizes. Those properties led to more superior hydraulic performances. The PES membranes loaded with DBR reached a clean water flux of 246.79 L/(m2 ·h), 25-folds higher than the pristine PES membrane at a loading of 3%. The flux of humic acid solution reached 154.5 ± 6.6 L/(m2 ·h), 30-folds higher than the pristine PES membrane with a slight decrease in rejection (71% vs. 60%). Moreover, DBR loaded membranes (2% and 3%) showed an almost complete flux recovery ratio over five cleaning cycles, demonstrating their excellent antifouling property. The hydraulic performance could possibly be enhanced by leaching the entrapped DBR to create more voids and pores for water permeation

Confounding effect of wetting, compaction, and fouling in an ultra-low-pressure membrane filtration: A review

Ultra-low-pressure membrane (ULPM) filtration has emerged as a promising decentralized water and wastewater treatment method. It has been proven effective in long-term filtration under stable flux without requiring physical or chemical cleaning, despite operating at considerably lower flux. The use of ultra-low pressure, often simply by hydrostatic force (often called gravity-driven membrane (GDM) filtration), makes it fall into the uncharted territory of common pressure-driven membrane filtration. The applied polymeric membrane is sensitive to compaction, wetting, and fouling. This paper reviews recent studies on membrane compaction, wetting, and fouling. The scope of this review includes studies on those phenomena in the ULPM and how they affect the overall performance of the system. The performance of GDM systems for water and wastewater treatment is also evaluated. Finally, perspectives on the future research direction of ULPM filtration are also detailed

Investigation on the hydrodynamics of a circular crossflow membrane filtration for purification of drinking water

With increasing frequency and intensity of disasters reported around the world, no doubt the developing countries would suffer considerable damages such as environmental, infrastructure, economy, population displacement, etc., compared to the developed countries. It is well known that in the events of emergency situations, e.g. natural disasters, one of the most basic requirements for human survival is the supply of clean and safe drinking water. However, it is impossible to supply when the facilities and infrastructures required are not functioning effectively. Hence, there is an urgency to develop a decentralized water treatment system to answer such problems in the aftermath of disasters, which undoubtedly require immediate response while waiting for aid to arrive. In order to address these issues, experiments involving contaminants which are commonly found in natural waters (e.g. clay, humic acid, and bacteria) were carried out using commercially available microfiltration (MF) and ultrafiltration (UF) membranes. [Continues.

Supercontinuum generated high power highly nonlinear photonic crystal fiber for medical and optical communications applications

This paper investigates a supercontinuum generated high power highly nonlinear photonic crystal fiber for medical and optical communication applications. The full vector finite difference method with perfectly matched layer is used as an analysis tool. Numerical simulation results show that it is possible to achieve high nonlinear coefficient, near zero ultra-flattened dispersion, low confinement loss and supercontinuum spectrum with high power. Moreover, numerical results show that short length of the proposed photonic crystal fiber is achieved. The numerical simulation results of supercontinuum generation is conducted by solving the generalized nonlinear Schrödinger equation with the split-step Fourier method. It is observed adequate supercontinuum spectrum that broaden from 960 to 1870 nm by considering center wavelengths of 1.06, 1.31, and 1.55 μm into silica based index guiding photonic crystal fiber. This simulation results prove that the proposed design of a highly nonlinear photonic crystal fiber is a great solution for broad supercontinuum generation with high power

Feasibility Studies of Rainwater Harvesting System for Ablution Purposes

For countries with an abundance of rain, there is definite potential to implement a rainwater harvesting system for different applications. This paper describes feasibility studies of an open-pond rainwater harvesting system for ablution purposes, analysing the quality of harvested rainwater and formulating a rainwater harvesting model with suitable performance measures. The formulated model can be used to analyse the feasibility of the system in any locality by inputting local meteorological data. Quality analysis has shown that the harvested rainwater can be used safely for ablution purposes, albeit with a slightly acidic pH below 6.5. At a depth of 1.0 m and using the current pond configuration of a local mosque, the reliability of the system is 62.5% (228 days per year), and the amount of water saved is 345 m3, which is 60.7% of the water demand. It has been shown that a pond surface area of 60–70 m2 provides optimum reliability and water saving, and more water savings can be expected with a more economical usage of water during ablution. These results indicate the feasibility of implementing a rainwater harvesting system for ablution purposes in religious institutions to help curb the water shortage crisis