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Nigel Graham - One of the best experts on this subject based on the ideXlab platform.
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Combining Magnetic Ion Exchange Media and Microsand before Coagulation as Pretreatment for Submerged Ultrafiltration: Biopolymers and Small Molecular Weight Organic Matter
ACS Sustainable Chemistry & Engineering, 2019Co-Authors: Mengjie Liu, Nigel GrahamAbstract:In order to reduce the fouling of ultrafiltration (UF) systems caused by influent organic matter and microbial activities in the Membrane Tank, a novel pretreatment process has been evaluated involving the combination of magnetic ion exchange media (MIEX), microsand, and alum coagulation. Using a continuous flow bench-scale UF Membrane apparatus and synthetic water, the influence of MIEX and microsand with alum pretreatment on Membrane fouling was studied in comparison to a conventional pretreatment by alum alone. It was found that the continuous addition of low doses of MIEX and microsand substantially reduced (∼50%) Membrane fouling for nearly 60 days of operation, both in terms of reversible and irreversible fouling. MIEX adsorption increased the removal of dissolved organic matter, particularly hydrophobic and proteinaceous substances, and some fractions of humic-type substances, while the addition of microsand increased the density of flocs, and thus improved the removal of flocs and microorganisms (...
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Prevention of UF Membrane fouling in drinking water treatment by addition of H2O2 during Membrane backwashing
Water Research, 2018Co-Authors: Nigel Graham, Ting LiuAbstract:Abstract Although conventional coagulation pre-treatment can mitigate the fouling of ultrafiltration (UF) Membrane when treating raw waters, it is insufficient to restrict the development of irreversible fouling and reversible fouling to a low level. In this paper we demonstrate that the intermittent addition of H2O2 into the Membrane Tank during backwash events (after coagulation pre-treatment) successfully prevented the development of any significant Membrane fouling. Laboratory-scale tests were undertaken using two Membrane systems operated in parallel over 60 days, one serving as a reference coagulation-ultrafiltration (CUF) process, and the other receiving the H2O2 (CUF-H2O2), with a decreasing dose in three successive phases: 10, 5 and 2 mg/L. The results showed that the addition of H2O2 (via a separate dosing tube) during a 1 min backwash process (at 30 min intervals) reduced the growth of bacteria in the Membrane Tank, and the associated concentrations of soluble microbial products (SMP, including protein and polysaccharide). This resulted in a much reduced cake layer, which contained significantly less high MW organic matter (>50%), such as EPS, thereby improving the interaction between particles in the cake layer and/or particles and the Membrane surface. There was also less organic matter, of all MW fractions, adsorbed in the Membrane pores of the CUF-H2O2 system. The addition of H2O2 in the Membrane Tank appeared to alter the nature of the organic matter with a conversion of hydrophobic to hydrophilic fractions, which induced less organics adsorption within the hydrophobic PVDF Membrane pores, and a reduced bonding ability for particles. There was no physico-chemical evidence of any deterioration of the Membrane from exposure to H2O2, which indicates the feasibility of applying this novel method of fouling control for full-scale UF based water treatment processes.
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Evaluation of ferrate as a coagulant aid/oxidant pretreatment for mitigating submerged ultrafiltration Membrane fouling in drinking water treatment
Chemical Engineering Journal, 2016Co-Authors: Yunjia Yang, Nigel GrahamAbstract:Abstract Although pre-coagulation can mitigate ultrafiltration (UF) Membrane fouling in the treatment of surface waters for drinking water supply, biological activities (‘biofouling’) can induce a continuous increase in Membrane fouling. To meet this challenge, potassium ferrate, K 2 FeO 4 , a combined oxidant and coagulant, was evaluated as a pre-treatment chemical for controlling submerged UF Membrane fouling in water treatment. Ferrate use as an alternative to- (phase 1: ∼23 days), and in combination with- (phase 2: ∼30 days), conventional FeCl 3 , have been studied using parallel continuous bench-scale submerged Membrane systems, using FeCl 3 as the reference. The poorer performance of ferrate (alone) as a pre-treatment compared to FeCl 3 (phase 1) was the result of a lower coagulation efficiency, which outweighed the beneficial impact of the ferrate on bacterial inactivation. The net reduction in pre-treatment performance led to an increase in the concentration of residual, active bacteria in the Membrane Tank, and bacteria associated large molecular weight (MW) organic substances, such as extracellular polymeric substances (EPS) or biopolymers, which were the principal cause of the higher rate of Membrane fouling observed. In contrast, ferrate performed best as a coagulant aid/oxidant (FeCl 3 /K 2 FeO 4 ) (phase 2), with the rate of Membrane fouling (increase in transMembrane pressure) 4.5 times lower than conventional FeCl 3 pre-treatment. This pre-treatment arrangement resulted in less bacteria (and EPS) and suspended solids in the Membrane Tank, and less accumulation of materials in the cake layer and within the Membrane pores. The results indicated clearly the potential benefit of applying ferrate as a coagulant aid/oxidant with a coagulant, in UF pre-treatment, with the control of bacteria and EPS a key factor in reducing Membrane fouling.
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Application of polyacrylamide flocculation with and without alum coagulation for mitigating ultrafiltration Membrane fouling: role of floc structure and bacterial activity
Chemical Engineering Journal, 2016Co-Authors: Ting Liu, Nigel Graham, Yuanlong Lian, David Rooney, Kening SunAbstract:Abstract There is a growing interest in the use of ultrafiltration (UF) for the treatment of micro-polluted surface waters for drinking water supplies. Effective pretreatment is required to mitigate Membrane fouling and in this paper we have evaluated the application of polyacrylamide (PAM) flocculation with alum coagulation. Bench scale tests were conducted over extended periods with two types of PAM (different molecular weights (MW)) applied with, and without alum coagulation, in order to investigate their impact on Membrane fouling. The structure of the resulting flocs formed in the process and the activity of bacteria within the Membrane Tank were identified as two key factors influencing UF system performance. It was found that development of the cake layer and hydraulic resistance of the Membrane were influenced by the floc properties, which were in turn related to the MW and dose of the PAM. Coagulation and flocculation using the larger MW PAM formed amorphous flocs with a lower fractal dimension, which contributed to a lower density of the cake layer and lower rate of increase in trans-Membrane pressure. PAM flocculation without alum coagulation induced severe Membrane fouling by forming a continuous gel-like layer on the Membrane surface. By alum-PAM dosing it was found that the concentration of bacteria present in the Membrane Tank and adhering to the cake layer, was sufficient to remove nearly all of the ammonia and around 80% phosphorus in the raw water. These results demonstrate that the combination of a high MW PAM with alum as a pretreatment method of UF process can effectively improve the floc properties and cake layer structure for controlling Membrane fouling and producing high quality treated water.
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coagulation and oxidation for controlling ultrafiltration Membrane fouling in drinking water treatment application of ozone at low dose in submerged Membrane Tank
Water Research, 2016Co-Authors: Wenzheng Yu, Nigel Graham, G D FowlerAbstract:Abstract Coagulation prior to ultrafiltration (UF) is widely applied for treating contaminated surface water sources for potable supply. While beneficial, coagulation alone is unable to control Membrane fouling effectively in many cases, and there is continuing interest in the use of additional, complementary methods such as oxidation in the pre-treatment of raw water prior to UF. In this study, the application of ozone at low dose in the Membrane Tank immediately following coagulation has been evaluated at laboratory-scale employing model raw water. In parallel tests with and without the application of ozone, the impact of applied ozone doses of 0.5 mg L −1 and 1.5 mg L −1 (approximately 0.18 mg L −1 and 0.54 mg L −1 consumed ozone, respectively) on the increase of trans -Membrane pressure (TMP) was evaluated and correlated with the quantity and nature of Membrane deposits, both as a cake layer and within Membrane pores. The results showed that a dose of 0.5 mgO 3 L −1 gave a Membrane fouling rate that was substantially lower than without ozone addition, while a dose of 1.5 mgO 3 L −1 was able to prevent fouling effects significantly (no increase in TMP). Ozone was found to decrease the concentration of bacteria ( especially the concentration of bacteria per suspended solid ) in the Membrane Tank, and to alter the nature of dissolved organic matter by increasing the proportion of hydrophilic substances. Ozone decreased the concentration of extracellular polymeric substances (EPS), such as polysaccharides and proteins, in the Membrane cake layer; the reduced EPS and bacterial concentrations resulted in a much thinner cake layer, although the suspended solids concentration was much higher in the ozone added Membrane Tank. Ozone also decreased the accumulation and hydrophobicity of organic matter within the Membrane pores, leading to minimal irreversible fouling. Therefore, the application of low-dose ozone within the UF Membrane Tank is a potentially important approach for fully mitigating Membrane fouling.
G D Fowler - One of the best experts on this subject based on the ideXlab platform.
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coagulation and oxidation for controlling ultrafiltration Membrane fouling in drinking water treatment application of ozone at low dose in submerged Membrane Tank
Water Research, 2016Co-Authors: Wenzheng Yu, Nigel Graham, G D FowlerAbstract:Abstract Coagulation prior to ultrafiltration (UF) is widely applied for treating contaminated surface water sources for potable supply. While beneficial, coagulation alone is unable to control Membrane fouling effectively in many cases, and there is continuing interest in the use of additional, complementary methods such as oxidation in the pre-treatment of raw water prior to UF. In this study, the application of ozone at low dose in the Membrane Tank immediately following coagulation has been evaluated at laboratory-scale employing model raw water. In parallel tests with and without the application of ozone, the impact of applied ozone doses of 0.5 mg L −1 and 1.5 mg L −1 (approximately 0.18 mg L −1 and 0.54 mg L −1 consumed ozone, respectively) on the increase of trans -Membrane pressure (TMP) was evaluated and correlated with the quantity and nature of Membrane deposits, both as a cake layer and within Membrane pores. The results showed that a dose of 0.5 mgO 3 L −1 gave a Membrane fouling rate that was substantially lower than without ozone addition, while a dose of 1.5 mgO 3 L −1 was able to prevent fouling effects significantly (no increase in TMP). Ozone was found to decrease the concentration of bacteria ( especially the concentration of bacteria per suspended solid ) in the Membrane Tank, and to alter the nature of dissolved organic matter by increasing the proportion of hydrophilic substances. Ozone decreased the concentration of extracellular polymeric substances (EPS), such as polysaccharides and proteins, in the Membrane cake layer; the reduced EPS and bacterial concentrations resulted in a much thinner cake layer, although the suspended solids concentration was much higher in the ozone added Membrane Tank. Ozone also decreased the accumulation and hydrophobicity of organic matter within the Membrane pores, leading to minimal irreversible fouling. Therefore, the application of low-dose ozone within the UF Membrane Tank is a potentially important approach for fully mitigating Membrane fouling.
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Coagulation and oxidation for controlling ultrafiltration Membrane fouling in drinking water treatment: Application of ozone at low dose in submerged Membrane Tank
Water Research, 2016Co-Authors: Nigel Graham, G D FowlerAbstract:Coagulation prior to ultrafiltration (UF) is widely applied for treating contaminated surface water sources for potable supply. While beneficial, coagulation alone is unable to control Membrane fouling effectively in many cases, and there is continuing interest in the use of additional, complementary methods such as oxidation in the pre-treatment of raw water prior to UF. In this study, the application of ozone at low dose in the Membrane Tank immediately following coagulation has been evaluated at laboratory-scale employing model raw water. In parallel tests with and without the application of ozone, the impact of applied ozone doses of 0.5 mg L(-1) and 1.5 mg L(-1) (approximately 0.18 mg L(-1) and 0.54 mg L(-1) consumed ozone, respectively) on the increase of trans-Membrane pressure (TMP) was evaluated and correlated with the quantity and nature of Membrane deposits, both as a cake layer and within Membrane pores. The results showed that a dose of 0.5 mgO3 L(-1) gave a Membrane fouling rate that was substantially lower than without ozone addition, while a dose of 1.5 mgO3 L(-1) was able to prevent fouling effects significantly (no increase in TMP). Ozone was found to decrease the concentration of bacteria (especially the concentration of bacteria per suspended solid) in the Membrane Tank, and to alter the nature of dissolved organic matter by increasing the proportion of hydrophilic substances. Ozone decreased the concentration of extracellular polymeric substances (EPS), such as polysaccharides and proteins, in the Membrane cake layer; the reduced EPS and bacterial concentrations resulted in a much thinner cake layer, although the suspended solids concentration was much higher in the ozone added Membrane Tank. Ozone also decreased the accumulation and hydrophobicity of organic matter within the Membrane pores, leading to minimal irreversible fouling. Therefore, the application of low-dose ozone within the UF Membrane Tank is a potentially important approach for fully mitigating Membrane fouling.
Wenzheng Yu - One of the best experts on this subject based on the ideXlab platform.
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coagulation and oxidation for controlling ultrafiltration Membrane fouling in drinking water treatment application of ozone at low dose in submerged Membrane Tank
Water Research, 2016Co-Authors: Wenzheng Yu, Nigel Graham, G D FowlerAbstract:Abstract Coagulation prior to ultrafiltration (UF) is widely applied for treating contaminated surface water sources for potable supply. While beneficial, coagulation alone is unable to control Membrane fouling effectively in many cases, and there is continuing interest in the use of additional, complementary methods such as oxidation in the pre-treatment of raw water prior to UF. In this study, the application of ozone at low dose in the Membrane Tank immediately following coagulation has been evaluated at laboratory-scale employing model raw water. In parallel tests with and without the application of ozone, the impact of applied ozone doses of 0.5 mg L −1 and 1.5 mg L −1 (approximately 0.18 mg L −1 and 0.54 mg L −1 consumed ozone, respectively) on the increase of trans -Membrane pressure (TMP) was evaluated and correlated with the quantity and nature of Membrane deposits, both as a cake layer and within Membrane pores. The results showed that a dose of 0.5 mgO 3 L −1 gave a Membrane fouling rate that was substantially lower than without ozone addition, while a dose of 1.5 mgO 3 L −1 was able to prevent fouling effects significantly (no increase in TMP). Ozone was found to decrease the concentration of bacteria ( especially the concentration of bacteria per suspended solid ) in the Membrane Tank, and to alter the nature of dissolved organic matter by increasing the proportion of hydrophilic substances. Ozone decreased the concentration of extracellular polymeric substances (EPS), such as polysaccharides and proteins, in the Membrane cake layer; the reduced EPS and bacterial concentrations resulted in a much thinner cake layer, although the suspended solids concentration was much higher in the ozone added Membrane Tank. Ozone also decreased the accumulation and hydrophobicity of organic matter within the Membrane pores, leading to minimal irreversible fouling. Therefore, the application of low-dose ozone within the UF Membrane Tank is a potentially important approach for fully mitigating Membrane fouling.
Nigel. J. D. Graham - One of the best experts on this subject based on the ideXlab platform.
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Prevention of PVDF ultrafiltration Membrane fouling by coating MnO_2 nanoparticles with ozonation
Scientific Reports, 2016Co-Authors: Matthew Brown, Nigel. J. D. GrahamAbstract:Pre-treatment is normally required to reduce or control the fouling of ultrafiltration (UF) Membranes in drinking water treatment process. Current pre-treatment methods, such as coagulation, are only partially effective to prevent long-term fouling. Since biological activities are a major contributor to accumulated fouling, the application of an oxidation/disinfection step can be an effective complement to coagulation. In this study, a novel pre-treatment method has been evaluated at laboratory scale consisting of the addition of low dose ozone into the UF Membrane Tank after coagulation and the use of a hollow-fibre Membrane coated with/without MnO_2 nanoparticles over a test period of 70 days. The results showed that there was minimal fouling of the MnO_2 coated Membrane (0.5 kPa for 70 days), while the uncoated Membrane experienced both reversible and irreversible fouling. The difference was attributed to the greatly reduced presence of bacteria and organic matter because of the catalytic decomposition of ozone to hydroxyl radicals and increase of the hydrophilicity of the Membrane surface. In particular, the MnO_2 coated Membrane had a much thinner cake layer, with significantly less polysaccharides and proteins and much less accumulated organic matter within the Membrane pores.
Shigeo Wada - One of the best experts on this subject based on the ideXlab platform.
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elastic force of red blood cell Membrane during Tank treading motion consideration of the Membrane s natural state
International Journal of Mechanical Sciences, 2010Co-Authors: Kenichi Tsubota, Shigeo WadaAbstract:The elastic force of a red blood cell (RBC) Membrane during its Tank-treading motion was estimated using a three-dimensional spring network model. An RBC Membrane was modelled by an assembly of triangular elements in which stretch/compression and bending springs were placed to express planar shear and out-of-plane bending deformations, respectively. An areal incompressibility of the Membrane and a volumetric constraint on the entire RBC were taken into account. Different natural states of an RBC Membrane were considered by adjusting reference lengths and angles of the stretch/compression and bending springs, respectively. An elastic motion simulation was conducted using the spring network model to reproduce a Tank-treading motion of the Membrane for a constant biconcave discoid RBC under a fluid shear force. Given the simulated Tank-treading motion, an additional Membrane elastic force due to the motion was determined from the elastic energy changes during the motion. It was confirmed that the natural state of the RBC Membrane should be nonuniform to generate the additional elastic force. Greater spring constants and greater natural state nonuniformity induced a greater additional elastic force, and the elastic force was regarded as a resistance against the Tank-treading motion. Additional elastic forces due to the Membrane Tank-treading motion for different sets of spring constants and natural state nonuniformity values were determined, and they were compared with fluid shear forces at shear rates within the range of which a transition between Tank-treading and tumbling motions of an RBC occurs in experiments. The results suggested that for the experimentally measured elastic moduli, natural state nonuniformity in a physiological state is moderate between that for a spherical or flat shape and that for the biconcave shape. Moderate nonuniformity was also confirmed by a simulated RBC shape in a minimum state of elastic energy.