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IMPLICATIONS OF PARTICLE SIZE TO TRANSIENT STAGE OF DEEP BED FILTRATION
Vigneswaran, S,Prasanthi , H,Dharmappa, H B 한국화학공학회 1996 Korean Journal of Chemical Engineering Vol.13 No.6
This study was aimed at investigating the effect of particle size, mostly in the submicron range, on break-through stage of filtration. Latex beads, with diameters ranging from 0.46- to 2.967-㎛ were filtered through filter grains of diameters 0.1-, 0.175- and 0.45-㎜. Experimental conditions were chosen so as to obtain breakthrough curves. The experimental results showed that the initial efficiency follows the pattern reported by previous experimental and theoretical studies, i.e., lower efficiency for 0.825-㎛ particles which fall in the range of critical size. However, the particle removal during the transient stage increased with an increase in particle size for the range of sizes studied. This pattern is qualitatively confirmed by the theoretical predictions of Vigneswaran and Chang (1986) model. This study also provides experimental verification of the effect of the ratio of particle size and grain size at different stages of filtration.
S Vigneswaran,권대영 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.6
In Cross-Flow Microfiltration (CFMF), suspended particles deposit to form a cake layer on the membrane surface, which provides a resistance to permeate flow. The cake resistance, which plays an important role on the performance of CFMF, is mainly determined by the packing porosity of the cake and, the physical and chemical properties of particles. This study aimed at understanding the porosity and the specific filtration resistance of the cake for a given condition. These properties have been studied using experiments under a constant permeate flux. Factors such as permeate flux and ionic strength were investigated in terms of the particles deposition and cake formation. This study also adopted a force balance model to predict the deposit rate of particles and then compare with the experimental results. Inter-particle forces (electric double layer repulsion force and Van der Waals attraction force) were incorporated into the calculation of cake structure (cake porosity and specific resistance) together with the equilibrium condition of hydrodynamic forces. The experimental results showed that the higher the permeate flux led to the greater amount of particles deposit and the denser structure of cake. The porosity of cake decreased with the increase in ionic strength (0~0.01M) and then increased sharply afterwards (0.01~0.1M). The hydrodynamic force balance model estimated well the tendency of variation in cake structure depending on the ionic strength.
Urban stormwater quality and treatment
Sarvanamuthu Vigneswaran,Rupak Aryal,Jaya Kandasamy,Ravi Naidu 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.5
Stormwater runoff from urban and suburban areas generates numerous pollutants. The areas include residential areas, parks, commercial areas, industrial areas and road/highways. Land use and human activities largely determine the nature and level of pollutants. Among the various types of pollutants that can contribute to adverse water quality impact in receiving water bodies, of concern are suspended solids, heavy metals, polycyclic aromatic hydrocarbons and nutrients. This paper provides a critical review of the characteristics and sources of urban stormwater pollutants and the manner in which the pollution occurs. Treatment systems for urban stormwater runoff and for urban stormwater harvesting are discussed.
Bilateral single cord of the brachial plexus in an adult female cadaver of South Indian origin
Uma Viswanathan,Vigneswaran Madhivadhany,Nachiket Shankar 대한해부학회 2013 Anatomy & Cell Biology Vol.46 No.3
The occurrence of a brachial plexus united into a single cord is very rare. During routine dissection of an elderly female cadaver, the brachial plexus united into a single cord was observed bilaterally. On the left side, C4, C5, and C6 roots combined to form the upper trunk, the C7 root continued as the middle trunk, and C8 and T1 united to form the lower trunk. All three trunks almost immediately fused to form a single cord. On the right side, C5 and C6 roots joined to form the upper trunk, which divided into anterior and posterior divisions. C7, C8, and T1 roots combined to form the lower trunk. The anterior and posterior divisions united with the lower trunk to form a single cord. On both sides, the subclavian artery was superior to the single cord. Supraclavicular brachial plexus injuries in such individuals may have serious clinical manifestations.
Choi, Y.,Vigneswaran, S.,Lee, S. Elsevier 2016 Desalination Vol.389 No.-
Pressure retarded osmosis (PRO) is an osmotically-driven membrane process to utilize salinity gradient power (SGP), which is renewable energy originated from the different salt concentration between seawater and fresh water. However, PRO suffers from membrane fouling, leading to decreased water permeability and energy density. Although prediction of fouling is important for its mitigation and control, little information is available on fouling potential in PRO process. Accordingly, this study aims at the investigation of fouling propensity of PRO membranes under different conditions. Feed solutions that have different fouling potential were used in a laboratory-scale PRO system. Silt density index (SDI) and modified fouling index (MFI) were applied as indicators for assessing PRO membrane fouling. Results showed that the power density of PRO decreases with an increase of the fouling potential of the feed waters. MFI was proposed to be a fouling index for PRO because it showed a better correlation with the power density than SDI and turbidity. When MFI value is lower than 1400s/L<SUP>2</SUP>, the efficiency is higher than 70%, indicating that 30% loss in energy recovery compared to the case with D.I. water. This suggests that pretreatment requirements for PRO may be determined based on MFI results.
Effect of Flocculation in Membrane‐Flocculation Hybrid System in Water Reuse
Shon, H.,Guo, W.,Vigneswaran, S.,Ngo, H.,Kim, In Taylor Francis 2005 Separation science and technology Vol.39 No.8
<P>Preflocculation reduces the fouling of membranes in cross‐flow microfiltration (CFM) thus leading to high quality product water at economic filtration flux. As such, this hybrid system will have a major impact in treating the biologically treated sewage effluent. The preflocculation achieved through the floating medium flocculation (FMF) was found to increase the phosphorus removal up to 96%. The decline in microfiltration permeate flux with time was reduced by the incorporation of flocculation. However, the improvement in the removal of dissolved organic carbon (DOC) was marginal (from 20% with membrane alone to 46% with the membrane‐flocculation hybrid system). The flocculation followed by adsorption as pretreatment helped to increase the DOC removal as high as 98%. Flocculation was found to remove more than 66% of colloidal effluent organic matter (EfOM). An attempt was also made to quantify the hydrophobic fraction in the pretreated effluent and to identify the molecular weight (MW) range of organics removed by the flocculation. The pretreatment of flocculation was found to remove 68.5%, 61.8%, and 62.9% of hydrophobic, hydrophilic, and transphilic organic matter. The MW size distribution analysis indicated that flocculation with ferric chloride removed a majority of organic matter in the MW range of 300–5000 Da.</P>