Natural Organics Removal Using Membranes

Schäfer, A.I.

doi:10.1201/9781420031638

Cited by 74 publications

(80 citation statements)

References 294 publications

(600 reference statements)

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“…While there is some fouling in the absence of calcium (∆P of 4 kPa) and no fouling at all at high calcium concentration (>3 mM), a peak of membrane fouling was found at low calcium concentration in the vicinity of 0.5 mM (∆P of up to 12 kPa). While a similar phenomenon has also been reported for nanofiltration [15] and microfiltration [16] membranes for water and wastewater treatment applications, the actual mechanism is still unclear. Aoustin et al [17] studied the fouling of two ultrafiltration membranes due to natural organic matter and reported negligible calcium concentration effects.…”

Section: 2supporting

confidence: 55%

“…This is further enhanced by the presence of a small amount of calcium (0.5 mM) which acts as a bridging ion and facilitates HA absorption to particulate matter and the membrane surface. HA is also known to foul membranes by gel formation and adsorption in the membrane pores [19]. High concentration of HAs within the cake layer can also result in a significant decrease in TOC retention (reduction from about 50 to 20%) as HA concentration increases (see Figure 5B).…”

Section: 4mentioning

confidence: 99%

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Fouling in greywater recycling by direct ultrafiltration

2006

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Greywater is no doubt a valuable resource that can be used to alleviate water shortage and increase water conservation in individual households. It is particularly important for arid and semi-arid regions like Australia. Treated greywater can also be used for many activities within the household such as toilet flushing, garden watering, car washing, or pavement cleansing. This study examines the fouling behaviour of submerged ultrafiltration membranes in greywater recycling under concentration variation of common greywater constituents. The results indicate that the use of ultrafiltration directly for greywater recycling in individual households is promising. As expected, increase in particulate matter concentration results in a thicker cake layer. However, hydraulic resistance of such cake layers depends on the presence of other constituents namely calcium and organic matter, which play a major role in membrane fouling. Fouling increases linearly with organic matter concentration, while the presence of a small amount of calcium may enhance fouling significantly.

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Section: 2supporting

confidence: 55%

Section: 4mentioning

confidence: 99%

Fouling in greywater recycling by direct ultrafiltration

2006

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“…A study was carried out which looked at the rejection abilities of a range of membranes targeting hematite colloids (40-500nm), NOM and cations, fouling conditions and cost of treatment of these processes with consideration of chemical pretreatment with ferric chloride [1]. In this paper the effect of membrane fouling on rejection is presented.…”

Section: Introductionmentioning

confidence: 99%

“…Of particular concern in water treatment is the removal of natural organic matter (NOM) which contains potential disinfection by-product precursors. The presence of colloids, multivalent ions and organics in surface waters may cause substantial fouling of membranes.A study was carried out which looked at the rejection abilities of a range of membranes targeting hematite colloids (40-500nm), NOM and cations, fouling conditions and cost of treatment of these processes with consideration of chemical pretreatment with ferric chloride [1]. In this paper the effect of membrane fouling on rejection is presented.…”

mentioning

confidence: 99%

Fouling effects on rejection in the membrane filtration of natural waters

Schäfer¹,

2000

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Membrane processes in drinking water applications are micro-(MF), ultra-(UF), and nanofiltration (NF). These processes remove turbidity and bacteria (MF), viruses and macromolecules (UF) and small molecules and hardness (NF). Of particular concern in water treatment is the removal of natural organic matter (NOM) which contains potential disinfection by-product precursors. The presence of colloids, multivalent ions and organics in surface waters may cause substantial fouling of membranes.A study was carried out which looked at the rejection abilities of a range of membranes targeting hematite colloids (40-500nm), NOM and cations, fouling conditions and cost of treatment of these processes with consideration of chemical pretreatment with ferric chloride [1]. In this paper the effect of membrane fouling on rejection is presented.The study was based on experiments with two MF membranes (GVWP, GVHP, 0.22 µm, Millipore), six UF membranes (1, 3, 5, 10, 30, 100 kDa, regenerated cellulose, Millipore), and four organic nanofiltration (NF) membranes (TFC-SR, TFC-S, TFC-ULP, CA-UF, Fluid Systems, U.S.).Three different types of organics (IHSS humic acid, IHSS fulvic acid and an Australian concentrated NOM) in a carbonate buffer containing calcium chloride and a background electrolyte were used. Experiments were carried out in perspex (MF, UF) and stainless steel (NF) stirred cells of a volume of 110-185 mL and a membrane area of 15.2 -21.2*10 -4 m 2 at transmembrane pressures of 1, 3, and 5 bar for MF, UF, and NF, respectively.UF removes 10 -95% of NOM depending on the molecular weight cut-off (MWCO) of the membrane. Pore sizes of < 6 nm are required to remove about 80% of NOM, where a 6 nm pore size corresponds to a MWCO of about 10 kDa. Colloids are fully rejected.NF removes NOM effectively (70 -95% as dissolved organic carbon (DOC) and 85 -98% as UV absorbance). Cation rejection is very membrane dependent and varies for the investigated membrane types between 13 and 96% for calcium and 10 to 87% for sodium. 1Fouling was also dependent on pore size and was caused by large colloids (250 nm) or coagulant flocs in MF, small colloids, organic-calcium flocs and aggregates with a dense structure (formed slowly) in UF, and by a calcium-organic precipitate in NF. The fouling influenced the rejection of colloids in MF and that of NOM in UF and NF. If a highly charged layer was deposited on the NF membranes, cation rejection was also influenced. The characterisation of permeate organics revealed that low molecular weight acids passed through the NF membranes and that the rejection of these acids was also dependent on the deposit on the membrane.The mechanisms which can explain such an increase in rejection are different for the three membrane processes. In MF, pore plugging and cake formation was found responsible for fouling. This reduces the pore size and increases rejection. In UF, internal pore adsorption of calcium-organic flocs reduces the internal pore diameter and subsequently increases rejection. In NF, the key fact...

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“…Ultrafiltration (UF) membranes permit the removal of colloidal particles, microorganisms and a considerable amount of dissolved organic matter. These membranes have been very widely utilised in drinking water treatment as an alternative technology to conventional methods of purifying water (Schäfer, 2001;Domany et al, 2002;Chang et al, 2015;Zhang et al, 2015). NOM, e.g., humic acid, poses serious hindrance to membrane flux (flow of water across a membrane) by adsorbing on the membrane surfaces in a process known as fouling, wherein the pores of the membranes become blocked with time, resulting in a lower flux of water across the membrane (Elimelech et al, 2011;Vankelecom et al, 2003;Särkkä et al, 2015;Yunos et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Synthesis of robust flexible polyethersulfone ultrafiltration membranes supported on non-woven fabrics for separation of NOM from water

Tshabalala¹,

Nxumalo²,

Mamba³

et al. 2016

WSA

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This work describes the synthesis of structurally robust ultrafiltration (UF) polyethersulfone (PES) membranes supported on three different types of non-woven fabrics (NWFs) prepared using a simple phase inversion method. The NWF supported membranes exhibited high mechanical strength compared to the unsupported PES membranes modified with polyvinyl pyrrolidone (PVP) due to the strength provided by the NWFs. The tensile strength of the supported PVP modified membranes was ~7 MPa compared to ~2 MPa observed for the PVP modified unsupported UF membranes. The use of the NWFs clearly provides robustness to the modified membranes. The membrane surfaces became hydrophilic with addition of PVP and the pore sizes increased with an increase in PVP concentration (scanning electron microscopy (SEM) results). The rejection of humic acid (as a model NOM compound) was 98% for PES on NWF1, while PES membranes supported on NWF2 and NWF3 gave rejections of 94% and 96%, respectively; all with good fouling resistance. This work demonstrates that the use of a NWF support allows for the modification of the surface of the membranes without compromising the overall strength of the membranes, but more importantly the ability of the membranes to reject HA while exhibiting high resistance to fouling.

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Natural Organics Removal Using Membranes

Cited by 74 publications

References 294 publications

Fouling in greywater recycling by direct ultrafiltration

Fouling in greywater recycling by direct ultrafiltration

Fouling effects on rejection in the membrane filtration of natural waters

Synthesis of robust flexible polyethersulfone ultrafiltration membranes supported on non-woven fabrics for separation of NOM from water

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