7_Pre-treatments to reduce fouling of low pressure microfiltration (MF) membranes.pdf

Journal of Membrane Science 289 (2007) 231240

Pre-treatments to reduce foulingme

hririk

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Abstract

Despite the fact that natural organic matter (NOM) is significantly smaller than the pore size of microfiltration (MF) membranes, fouling dueto organic compounds has emerged as a problematic issue for both potable water and wastewater membrane filtration. Pre-treatment of the feedwater can be a useful strategy for reduction or mitigation of these fouling effects. The aim of this investigation was to evaluate various combinedpre-treatment methods for reducing NOM fouling of laboratory scale micro-filtration (MF) membranes, including treatment with adsorbents suchas MIEX (MIEX is a registered trademark of Orica Australia Pty. Ltd.) and powdered activated carbon (PAC) as well as coagulation withalum. Highbe a simpleexamined. Rincluding cbut did not r 2007 Else

Keywords: M

1. Introdu

Foulingnificant isspotable antration hasto foulingin the fieldthe complelack of undthe need fopossible m

Microfiltypically u

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0376-7388/$doi:10.1016/jperformance size-exclusion chromatography (HPSEC) was applied to determine molecular weight (MW) distribution and proved toanalytical technique, capable of detecting the onset of fouling by observation of the >50,000 Da colloidal peak in the water sourcesesults obtained showed that treatments that reduce the majority of bulk water dissolved organic carbon (DOC) of all MW ranges,

olloidal (very high MW) material successfully prevented short-term fouling of MF, where treatments that removed most of the DOCemove the colloidal components, were unable to prevent fouling.vier B.V. All rights reserved.

icrofiltration; MIEX; NOM; PAC; Fouling

ction

of membranes by natural organic matter is a sig-ue for the efficiency of membrane filtration in bothd wastewater treatment systems. As membrane fil-grown in prevalence, the issue of flux decline due

has determined the direction of significant research. While inorganic fouling is as much an issue, it isx and often unknown composition of NOM and aerstanding of the fouling mechanisms that has drivenr scientific investigation to address the causes and

eans of mitigation.tration (MF, pore sizes between 0.1 and 10m) issed as a clarification process for the removal of par-

ding author. Tel.: +61 8 8259 0314; fax: +61 8 8259 0228.dress: [email protected] (R. Fabris).

ticulate material. This may be as a polishing step following aconventional treatment or as a pre-treatment before a more reten-tive membrane process such as nanofiltration (NF) or reverseosmosis (RO). It is worth noting that dissolved organic car-bon (DOC) is not typically retained by MF due to the poresizes involved being much larger than component molecules;however DOC is nevertheless involved in both short and longterm fouling. Research has shown that only a small portion ofthe total NOM is responsible for irreversible fouling includinghigh molecular weight (MW) polysaccharides, colloidal mate-rial, low MW proteins and amino sugars [14], however highlyaromatic hydrophobic acids that make up the majority of typicalnatural water NOM also cause significant flux decline throughreversible fouling [5]. Recent research has highlighted the influ-ence of organic colloids in the fouling of MF membranes [610]and shows that of the fractional components of NOM in a watersource, the colloids cause the most significant flux decline [9].Colloidal fouling also appears independent of solution pH but

see front matter 2007 Elsevier B.V. All rights reserved..memsci.2006.12.003micro-filtration (MF)Rolando Fabris a,, Eun Kyung Lee b, C

Vicki Chen b, Mary Da Co-operative Research Centre for Water Quality and Treat

SA Water Corporation, PMB 3, Salisburyb UNESCO Centre for Membrane Science and Technology, School of C

University of New South Wales Sydney, NReceived 20 April 2006; received in revised form 27 Novem

Available online 8 Decembeof low pressurembranes

stopher W.K. Chow a,as aAustralian Water Quality Centre,110, Australiacal Engineering and Industrial Chemistry,052, Australia006; accepted 1 December 20066

232 R. Fabris et al. / Journal of Membrane Science 289 (2007) 231240

increases in the presence of divalent metal ions such as calcium[9,10].

Strategiful membraadsorption)onset of fotarget dailyface area (iplant footpcycles andexpense inenvironmeMembranecapacity foity. Many da hydrophiinteractionthe membrand also thhaving mucbranes with

Pre-treamodify potion of flumembranetreatmentlation/floccfiltration odirectly onon the surfa[1416]. Itreduces thetrant NOMet al. [4] reirreversibleadditionalemployed,there is extNOM levemembranetion [1722resins [23]the membrtime to fultion, the acmay createfouling [25tion with adadd to an e

The aimtreatment mfor potableusing magnusing alumand variedDOC overbeen show

pounds [2628]. While most means of evaluating membranefouling are destructive or require the removal of the mem-

from the system, it was hoped that the contributions ofs organic carbon species to the fouling could be eval-using high performance size exclusion chromatographyC) applied to the process stream waters.

terials and methods

ource waters

rce waters chosen for this investigation were both wellterised by the authors and also known to cause significant

without treatment. Source waters were also selected toe low and high range levels of DOC to assess the impact onatment and membrane fouling. The Myponga Reservoirted about 50 km south of Adelaide, Australia. The wateryponga Reservoir is sourced via surrounding catchment

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ig. 1.es to reduce fouling can include reducing flux, care-ne material selection and pre-treatment (coagulation,. Reduction of the flux can in some cases prevent theuling altogether, however in an application where aflux is required this will necessitate additional sur-

.e. membrane modules) thereby increasing both therint and capital cost. The benefits of longer filtrationless chemical cleaning may not justify the additionala purely economic sense but may become viable if

ntal sustainability is an important consideration [11].materials will have a significant effect on the foulingr any particular compound as well as the reversibil-ifferent polymer membranes are available with eitherlic or hydrophobic surface, thereby changing theirwith potential foulants [1,12]. The microstructure ofane will determine the uniformity of the pore sizee resistance to fouling with track-etched membranesh greater resistance to fouling than sponge-like mem-large pore openings and irregular pore size [13].

tment of the process stream to either remove ortential foulants is an effective method for reduc-x decline and is usually easy to implement wherefiltration is retrofitted into an existing conventionalplant. The most popular pre-treatment is coagu-ulation followed by either traditional rapid sandr direct filtration, where flocculated water is flowedto the membrane, forming a porous, low density cakece that is easily removed by scouring or backwashingis generally accepted that reduction of overall DOCpotential for fouling, however remaining recalci-

may still be available to foul the membrane. Kimuramarked that pre-coagulation alone does not mitigate

fouling, only reversible fouling. To remove theserecalcitrant components, other technologies must besuch as oxidative or absorptive processes. Whileensive literature on the use of adsorbents to reducels, studies of the effects of adsorption treatments onfouling examine mostly activated carbon applica-] and little on other adsorbents such as ion-exchange

. In most cases, the carbon is applied directly withinane reactor and may not provide sufficient contactly exploit the capacity of the carbon [24]. In addi-cumulation of the carbon on the membrane surfacedifficulties in partitioning the sources of any resultant]. Ease of implementation may also be a considera-sorbents such as activated carbon being the easiest to

xisting coagulation plant with minimal modification.of this investigation was to evaluate various pre-

ethods for reducing NOM fouling of MF membraneswater treatment, focussed on combining adsorptionetic ion exchange resin (MIEX) with coagulationor adsorption with powdered activated carbon (PAC)combinations of all three. MIEX typically removesa broad range of molecular weights while alum hasn to be effective for higher molecular weight com-

branevariouuated(HPSE

2. Ma

2.1. S

Soucharacfoulingprovidpre-treis locafrom Mand is(62 HaDam,water (catchmSydne

2.2. P

Thethree-smal ch[29]. Manionof NOavailabpaddle(B-KEwas trfor 2011mresin

Frally considered a high colour and high DOC sourceunits (HU) and 11.7 mg/L, respectively). Woronorantrast, is considered a low colour, low DOC source

and 2.2 mg/L, respectively) and is sourced from thearea of the Woronora River, serving the residents ofouthern suburbs, NSW, Australia.

eatments

bined treatments protocol (Fig. 1) was based on areatment utilising adsorbent technologies and mini-cal addition that was developed in a previous studyetic ion exchange resin (MIEX) is a macroporousange resin specifically developed for the removal

drinking water treatment. Detailed description islsewhere [3032]. Jar tests were performed on a six-g stirrer (SEM Pty. Ltd., Australia) in 2 l gator jarsPhipps & Bird, USA). Myponga Reservoir water

with 10 mL/L of MIEX by stirring at 100 rpmSettled water was decanted and filtered through ansize filter (Whatman International, UK) to remove

. The filtered water was contacted with 40 mg/L

Pre-treatment protocol for membrane fouling experiments.

R. Fabris et al. / Journal of Membrane Science 289 (2007) 231240 233

of a coal-based, steam-activated powdered activated carbon(PAC) (PICA, Australia) by stirring at 100 rpm for 30 min. A20,000 mg/L Al2(SO4)318H2O solution was used to dose coag-ulant at 40 mg/L to flocculate the PAC and/or the remainingnatural water turbidity. For coagulation treatment, samples wereflash mixed at 200 rpm for 1 min followed by 14 min of slowmixing at 25 rpm and 15 min of settling before samples weregravity filtered through 11m pore size paper filters (Grade 1,Whatman International Ltd., UK). MIEX contacted water wasalso coagulated without prior PAC treatment. For all combinedtreatments, the treated water was filtered through an 11m poresize filter to remove remaining MIEX and/or PAC, therebyminimising any further adsorption before the membrane experi-ments could commence. Samples were taken at the intermediatetreatment steps to enable partitioning of the contribution to thefouling of remaining NOM components.

2.3. Membrane congurations

A flat sheet and a hollow fibre submerged configuration wereutilized in the experiments. Schematics of the filtration set-up are

shown in Fig. 2. The flat sheet configuration consisted of a dead-end cell containing a 0.22m pore size hydrophilic flat PVDFmembrane (GVWP from Millipore) with 15.2 cm2 area. The cellwas operated in unstirred mode at 30 kPa. The pure water fluxfor the flat sheet membrane at 30 kPa was 1974 59.3 L/(m2 h)(65.8 1.98 L/(m2 h kPa)). The submerged hollow fibre (SHF)module consisted of 10 fibres (30 cm length) of 0.2m poresize hydrophilic PVDF (US Filter), potted in-house. The lowerend of the bundle was fixed and blocked while suction wasapplied in the lumen of the fibres from the top of the bun-dle. At 100 L/(m2 h), the measured transmembrane pressure(TMP) was 0.62 0.02 kPa for pure water (161.3 L/(m2 h kPa)).In both configurations, the TMP and flux were monitored usinga pressure transducer and an electronic balance connected to acomputer.

2.4. Instrumental analyses

Analysed parameters included turbidity, true colour, ultra-violet absorbance at 254 nm (UV254), DOC, molecular weightdistribution by high performance size exclusion chromatography

Fig. d (b) s2. Schematic of (a) dead-end unstirred filtration set-up in constant pressure an ubmerged hollow fibre filtration set-up in constant flux.


(HPSEC) and scanning electron microscopy (SEM). Turbid-ity was determined using a Hach 2100AN turbidimeter (Hach,USA) and is expressed in nephelometric turbidity units (NTU).Samples for true colour, UV254 and DOC were filtered through0.45m membranes. True colour was measured using a 5 cmquartz cell at 456 nm and calibrated against a Platinum/Cobaltstandard [33]. UV254 was measured through a 1 cm quartz celland DOC was measured using a Sievers 820 Portable TOCanalyser (Ionics, USA). HPSEC was analysed using a WatersAlliance 2690 separations module and 996 photodiode arraydetector (PDA) at 260 nm (Waters Corporation, USA). Phos-phate buffer (0.1 M) with 1.0 M NaCl was flowed through aShodex KW802.5 packed silica column (Showa Denko, Japan)at 1.0 mL/min. This column provides an effective separationrange from approximately 100 Da to an exclusion limit of50,000 Da. Apparent molecular weight was derived by cali-bration witstandards operformedmicroscope

2.5. Memb

The fodescribed bDarcys lawseries mod

J = (Rm

where J is tpermeate vtotal foulan(Rrev) and iRf = RrevThe resistaing pure wthen changmonitoredfiltration cein situ threcentration

only, while avoiding significant disturbance of the NOM foulinglayer. The pure water flux of the membrane was then re-evaluatedfor the determination of irreversible foulant resistance. Rf treat isdefined as the calculated total foulant resistance of the treatedwater.

3. Results and discussion

3.1. Pre-treated water quality

When comparing water quality data for the various pre-treatments (Table 1), it is clear that MIEX was very effectiveas a primary treatment for colour, UV absorbance and DOCremoval. Although initial water turbidity was not high foreither water source, treatments that reduced turbidity to around0.1 NTU in both source waters included alum coagulation, as

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Table 1Treated water

Sample

Myponga RawMyponga MIMyponga MIMyponga MIMyponga MI

Woronora RaWoronora MIWoronora MIWoronora MIWoronora MIh poly-styrene sulphonate (PSS) molecular weightf 35, 18, 8 and 4.6 kDa. Electron microscopy was

using a Hitachi S900 field emission scanning electron(Hitachi Science Systems, Japan).

rane fouling

uling behaviour of membrane filtration can bey the resistance-in-series model, which is based on. For constant pressure filtration, the resistance-in-

el is expressed as:P

+ Rf) (1)

he filtrate flux, P the transmembrane pressure, theiscosity, Rm the membrane resistance, and Rf is thet resistance. Rf is the sum of hydraulically reversiblerreversible (Rirrev) fouling resistances:+ Rirrev (2)nce of a clean membrane was determined by filter-ater until steady state was attained. The feed wased to pre-treated water and the filtrate flow rate wasin order to determine Rf. At the end of filtration, thell was emptied and the membrane was gently rinsed

e times with 50 mL of pure water to remove the con-polarisation layer contributing to reversible fouling

the abin somtreated(Tableinantlythe adfeasiblto thetion win direeffectsbranesless thwaterlargeparamhad beMF mties ofpeak,believeand cobiologusuallyprevenand aror exte

quality parameters for pre-treated Myponga Reservoir and Woronora Dam

Code pH Turbidity (NTU)MR 7.8 1.95

EX MM 6.9 0.66EX/Alum MMA 6.5 0.12EX/PAC MMP 7.3 0.24EX/PAC/Alum MMPA 6.6 0.14

w WR 6.7 0.69EX WM 6.5 0.28EX/Alum WMA 4.8 0.07EX/PAC WMP 6.6 0.25EX/PAC/Alum WMPA 4.7 0.07ents are largely incapable of turbidity removal andses (especially PAC) increase the visually apparentter turbidity prior to filtration. Reported reductions

turbidity for the adsorbent treatments were predom-to the subsequent filtration step, as partitioning of

ents and natural water turbidity was not practicallyoarse (11m) filtration was also deemed necessarytreatment procedures as the focus of the investiga-ot to observe the effects of particles and DOC, ascontact microfiltration, but rather the more isolatede dissolved organic species on fouling of MF mem-

ll combined treatment produced treated water with0 mg/L DOC for both Myponga and Woronora source% DOC removed). It is worth noting that despiterences in both DOC and traditional water quality, both Myponga Reservoir and Woronora Dam waterhown to produce significant short term fouling ofanes. Both waters also contained detectable quanti-high MW colloidal NOM. This multi-component

at the exclusion limit of the column (50,000 Da), isbe composed of some NOMmetal complexes [28]

ex amino sugars from bacterial cell walls and othersources [34,35]. The organo-metallic complexes areicative of low residence time in the catchment, whichgnificant natural photo-oxidation or biodegradation,generally detected following conventional treatmentstorage. The amino sugar component however, has

Colour (HU) UV254 (cm1) DOC (mg/L)65 0.432 11.76 0.054 3.41 0.037 2.82 0.013 1.00 0.007 0.9

3 0.035 2.21 0.013 1.22 0.021 1.11 0.005 0.40 0.005 0.4


Fig. 3. Pre-treatment DOC molecular weight distributions by HPSEC for Myponga Reservoir. Code: R, Raw; M, MIEX; A, Alum; P, PAC.

generally proved to be more difficult to remove. For the purposesof this papthe sourcegreater than

MIEXcomponentDOC (1000colloidaling high Mremoved loafter MIEXically it isremoval oftheir inabilstructure ddrance on t

3.2. Flat sheet fouling experiments

fouin F

, Mymbrent o

ancmayeatmNOMater.d infou

avetio (Rer, colloidal material is defined as the component ofwater organic matter of apparent molecular weight

50,000 Da that is detectable by UV absorbance.treatment reduced a broad range of UV-absorbing

s (Figs. 3 and 4), especially high and medium MW10,000 Da) but was not effective for very high MWNOM. Coagulation with alum removed the remain-W NOM and all detectable colloidal material. PACw to medium MW DOC (3001000 Da) when used contact but little additional colloidal material. Typ-observed that most absorbents are ineffective forcolloidal components. This could be explained by

ity to take dissolved colloidal material into the poreue to physical size, as well as possible stearic hin-he adsorbent surface.

Theshownwatersthe metreatmperformrangepost-trdenseraw w

resultegreatermay hThe raFig. 4. Pre-treatment DOC molecular weight distributions by HPSEC for Woronoralant resistance as a function of permeate volume isig. 5 for raw and treated waters. For the untreatedponga water being higher in colour and DOC foulsane more readily than Woronora water. The MIEXf Woronora water resulted in detrimental filtratione. The broken MIEX resin fines in the sub-micronnot have been completely removed by the 11ment filtration and interacted with NOM to form a-MIEX cake layer, resulting in the higher Rf thanThe MIEX treated Myponga water, in contrast,reduced fouling compared to the raw water. The

lant load with regards to the untreated Myponga watermasked any additional fouling from MIEX fines.

f treat/Rf) is plotted against (Rf) and summarizes theDam. Code: R, Raw; M, MIEX; A, Alum; P, PAC.


Fig. 5. Foulinand treated MDam water. C

benefits ofresistancethe total foof pre-treatthe relative

Compardistributionon molecuthat encomshown). Thsmall to beexaminatiodecrease wthe designative of spec

Fig. 6. Foulaand WoronoraA, Alum; P, P

and retentate samples were collected at the termination of theexperiment and therefore represent averaged water quality. Thismeans that they contain material from both before, and after theonset of fouling. In interpretation of the fouling behaviour of thevarious pre-treated waters, observation of the molecular weightdistribution would tend to propose two fouling theories. Eitherthe colloidal material is directly involved in the membrane foul-ing and therefore becomes less abundant in the permeate withincreasing volume filtered, or the membrane fouling by othercomponents causes increased retention of the colloidal mate-rial. Both theories are valid if based only on the HPSEC data,however TMP increases were only apparent in treated waterswhere the colloidal material was still present indicating that thecolloidal DOC was directly involved in the short-term foulingobserved. This further confirms the findings of Lee et al. andChen et al. [6,36]. The data presented in Figs. 7 and 8 also showthat in most cases, the amount of colloidal DOC detected inthe permea

on c

the csolual Dmbr

lk aqtersd mal Dter fts ared aIEXed thlesseg profile (foulant resistance) vs. permeate volume of (a) untreatedyponga Reservoir water and (b) untreated and treated Woronoraode: R, Raw; M, MIEX; A, Alum; P, PAC.

multiple pre-treatment in terms of reduced foulantin Fig. 6. For this investigation, Rf treat is defined asulant resistance at a permeated volume of 1000 mLed water. A ratio (Rf treat/Rf) of less than 1.0 indicatesbenefit of treatment in terms of reduced fouling.

ison with the observations of the molecular weightby HPSEC showed that MF alone had no effect

lar weight components in the 3008000 Da range

nomen

Whileout thecolloidthe methe bu

Wareducecolloidface affoulanprovidand Mobservdue topassed the majority of the UV absorbance (data notis was entirely expected as these components are tooretained by a 0.2m pore size membrane. However,n of the >50,000 Da response consistently showed aith increasing permeate volume (Figs. 7 and 8). Whileted 500 and 1000 mL samples were both representa-ific time periods during the filtration, the permeate

nt resistance benefit analysis of pre-treatments for Myponga (M)(W) water (ratio < 1.0 is a benefit). Code: R, Raw; M, MIEX;

AC.

ments thatcan also bedata and thon microfiremove retaof foulinghowever thnal resistandecrease in

Table 2Percentages o

Sample

Myponga RawMyponga MIMyponga MIMyponga MIMyponga MI

Woronora RaWoronora MIWoronora MIWoronora MIWoronora MI

Rf, foulant reste exceeded the amount in the retentate. This phe-an also be explained by the proposed fouling theory.olloidal DOC in the permeate is distributed through-tion, following the onset of fouling, the majority ofOC in the retentate is immobilised on the surface ofane (fouling layer) and is therefore less abundant inueous solution.pre-treated with MIEX + alum showed greatlyembrane fouling in parallel with high removal ofOC. This is supported by SEM of the membrane sur-ouling and washing (Fig. 9) which shows the surfacee clearly reduced with pre-treatment and that alumsignificant improvement. In comparing coagulation

pre-treatment for ultrafiltration, Son et al. [37] alsoat MIEX was less effective for reduction of foulingr removal of high MW organic matter. For the treat-included PAC, some residual particulates from PACseen which is consistent with the obtained resistancee work of Matsui et al. [24] with submicrometre PACltration. After washing of the membrane surface toined material and the filter cake (Table 2), the amountmaterial in absolute terms was clearly reduced,

e reversible component as a percentage of the origi-ce decreased with pre-treatments despite an overalltotal resistance. This suggests that although several

f reversible resistance after flat sheet filtration

Code Rf treat (1/m) %Rf reversibleMR 1.15 1012 60.9

EX MM 5.16 1011 46.4EX/Alum MMA 4.20 109 44.6EX/PAC MMP 1.05 1011 53.9EX/PAC/Alum MMPA 7.22 109 21.5w WR 4.68 1011 44.8EX WM 6.73 1011 42.9EX/Alum WMA 7.71 109 72.6EX/PAC WMP 1.55 1011 31.6EX/PAC/Alum WMPA 8.74 109 33.9istance; Rf treat, foulant resistance at 1000 mL permeated volume.


Fig. 7. Impactreated water

pre-treatmesurface foublocking co

Treatmeshowed hi(Table 2). Tefit of remmay be ovin short tersource likefines on theof DOC dupre-treatme

3.3. Subme

For the sthe waters tthe MIEXwaters. It wthe successt of flat-sheet micro-filtration fouling on retention of high molecular weight colloidaland (c) Myponga MIEX and PAC treated water.

nts were very effective for reduction of short term,ling (cake formation), there still remains some porenstituents that can contribute to longer term fouling.nt of both water sources with MIEX + PAC + alumgher Rf treat than MIEX + alum treatments alonehis indicates that at high levels of treatment, the ben-

oving additional low MW organic material by PACerweighed by the detrimental effects of PAC finesm fouling of MF. Similarly, for a low DOC waterWoronora, the detrimental effect of MIEX resinfouling may be more significant than the reduction

e to the treatment. This highlights the need to tailornt strategies for an individual water source.

rged hollow bre experiments

ubmerged hollow fibre experiments at 100 L/(m2 h),hat were analysed were both untreated source waters,

+ alum treated and MIEX + PAC + alum treatedas intended that the SHF experiments would test if

ful treatments from the flat-sheet experiments would

also prevenfluxes. Pre-the flat-shewater condfor the durtreated watlated filtratshown in Ffiltration wat constantthe foulinghigher fluximately 30more foulin

As a resthe appliedthan those asource watthe plannedincreases into the onsetNOM using (a) Myponga Reservoir water, (b) Myponga MIEX

t fouling in a more practical application and at highertreatments that failed to prevent short term fouling inet experiments were not applied. For the two treateditions, the set flux was maintained at the same TMPation of the filtration (2.5 L, 4 h), indicating that theers failed to foul the hollow fibre bundle. The accumu-ion resistances at a permeated volume of 1000 mL areig. 10. The observed fouling behaviour during SHFas similar to that of dead-end unstirred cell filtrationpressure shown in the previous section. However,resistances were less. One reason may be that the

es obtained with constant pressure filtration (approx-0 L/(m2 h)) in the flat sheet configuration producedg.

ult, it can be assumed that the low fouling potential oftreated waters extended to volumes and fluxes greaterpplied to the flat-sheet fouling experiments. The raw

er experiments were both terminated after 1.5 L of2.5 L total volume of water was filtered as appliedTMP were unable to maintain the desired flux due

of fouling. HPSEC scans of the colloidal peak reveal


Fig. 8. Impact of flat-sheet micro-filtration fouling on retention of high molecular weight colloidal NOM using (a) Woronora Dam water, (b) Woronora MIEXtreated water and (c) Woronora MIEX and PAC treated water.

Fig. 9. Electron microscopy of Woronora (W) and Myponga (M) flat-sheet membrane after fouling and rinsing. Code: R, Raw; M, MIEX; A, Alum; P, PAC.


Fig. 10. Tran (a) MM, MIEX; A

Fig. 11. ImpaWoronora Da

that by therial was verpermeate (MIEX + Ping of micrincreased tsheet experindicate thadditional r

4. Conclu

In the apexpected thorganic maeffects ofbe more ereduced thsmembrane pressure (TMP) during submerged hollow fibre (SHF) filtration of, Alum; P, PAC.ct of submerged hollow fibre microfiltration fouling on retention of high molecular wm water.

1000 mL sampling point, retention of colloidal mate-y high in both raw water sources with low levels in theFig. 11). The pre-treatment with MIEX + alum andAC + alum, successfully prevented short-term foul-oporous SHF. The addition of PAC treatment slightlyhe fouling resistance as was also observed in the flatiments; however, the SEMs of flat sheet membranesat the presence of PAC fines may contribute to thisesistance.

sion

plication of the combined treatment protocol, it wasat the removal of selective components of the sourcetter by the various treatment steps would allow thethe residual organic material on fouling of MF toasily observed. It was shown that treatments thate majority of bulk water DOC of all MW ranges,

including cMIEX + Ping of MFDOC (MIEponents, wa non-destrsignificantthe >50,000examined.be used excability to aout removaa monitorin

Reference

[1] L. Fan, Jistics of nWater Reyponga Reservoir and (b) Woronora Dam water. Code: R, Raw;eight colloidal NOM using (a) Myponga Reservoir water and (b)

olloidal (very high MW) material (MIEX + Alum,AC + Alum) successfully prevented short-term foul-, where as treatments that removed most of theX + PAC) but did not remove the colloidal com-

ere unable to prevent fouling. HPSEC proved to beuctive analytical technique, capable of detecting acontributor to membrane fouling by observation ofDa colloidal organic material in the water sources

Although it cannot provide sufficient information tolusively in the evaluation of membrane fouling, the

pply HPSEC analysis to an operating system with-l of the membrane makes it potentially attractive asg method.

s

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Pre-treatments to reduce fouling of low pressure micro-filtration (MF) membranesIntroductionMaterials and methodsSource watersPre-treatmentsMembrane configurationsInstrumental analysesMembrane fouling

Results and discussionPre-treated water qualityFlat sheet fouling experimentsSubmerged hollow fibre experiments

ConclusionReferences

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7_Pre-treatments to reduce fouling of low pressure microfiltration (MF) membranes.pdf