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CAN S-PAC CONTROL/REDUCE FOULING IN CERAMIC MF MEMBRANE?: PRE-COAT Approach

J. Z. Hamad, M.D. Kennedy, S.G.J Heijman, B.S. Hofs,

G.L. Amy and J.C. Schippers.

20 November 2009

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Ceramic Membranes: Strengths & Weakness

High Flux Operation– 150 – 210L/m2.h Resistant to High Temperature and

Chemicals (4000C & pH 1-14) Long Life (15 years) – (Polymeric 5-7

years) BW Flux – 1,700L/m2.h Can easily break (brittle)

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Limitations of Ceramic membranes

Cost almost double to polymeric Virus, NOM & SOCs - not removed

without Pre-treatment Fouling (Particulate/Colloidal, Organic)

–

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Pretreatment In-line coagulation (Panglish et al 2007) – PACl (1-

3.5mg/l) – Ruhr River (Average DOC 2.4mg/l) – with 1.5mg/l of Al dosage - 35% of DOC removal observed –Flux -200L/m2h

Adsorption with PAC (Zhao et. al 2005) – PAC (20g/l) + MF Ceramic – high Doc River water (20mg/l) - Removal of DOC was 70%. – Flux -167L/m2.h

PACl & O3 (Lehman and Li 2009) – PACL (1mg/l) + Ozone (4mg/l) – Source of water is secondary effluent with average TOC of 5mg/l. Average Removal of TOC was 30% - Flux was 170L/m2.h

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Previous Works Done

Comparison of the efficient of S-PAC & N-PAC on NOM removal

Removal of micro-pollutants with S-PAC pre-coats + Ceramic membrane

Virus Removal

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GOAL and OBJECTIVESGoal: To minimise/control fouling in

Ceramic membraneObjectives Minimising the irreversible fouling in

Ceramic membrane UV & DOC Removal Determination of the fractions of

NOM removed – (LC-OCD)

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What is S-PAC?

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N-PAC: d10=3-5; d50= 10μm

S-PAC: d10=0.3; d50=0.8 µm

N-PAC was pulverized in ball Mill for 15hrs to produce S-PAC

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MATERIAL AND METHODS

Water Source = Pre-filtered Canal Water + Tap Water 1:1

PARAMETER

Value

Turbidity (NTU) 0.5

DOC (mg/l) 5 – 5.5

UV (cm-1) 0.14 - 0.17

To remove the Turbidity and Suspended particles Canal water was pre-filtered with 1μm

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Membrane CharacteristicsDescription Parameter

Size (Diameter)

30mm (L=1 m)

Pore size 0.1μm

Surface Area (Blocked)

0.065m2

Filter Material

Aluminium Oxide (α-Al2O3)

Filtration mode

Dead end mode

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Data Logger: Q, t, P &T

PILOT PLANT

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METHODOLOGY Blocking the membrane channels (46

channels out of 55) – this reduced the use of water from 60L/h to 10L/h.

Pre-filtration of Delft canal water using 1µm filter (current DOC level is about 9 mg/l).

Mixing the pre-filtered with tap water by ratio of 1:1 - (Raw water)

Filtration of Raw water with S-PAC pre-coats (40 layers) with BW intervals of 1, 2, 3 and 4 hours (CIP was done before starting new experiment in order to restore the membrane permeability) – Average Flux of 155L/m2h was used

Sampling for DOC,UV and LC-OCD measurements

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OPERATIONAL PROCESSES OF THE PILOT PLANT

FILTRATIONCYCLE

Filtration Cycle is 1 - 4 hours. Flux = 155L/m2.h

BACKWASHING (BW)

BW Flux = 1,350L/m2.h Duration 20 seconds.

AIR FLUSHING (AF)

AF = Compressed Air (5 bar). Duration 30 seconds

FORWARD FLUSHING (FF)

FF = Feed Water at high Flux of 350L/m2.h for 1 minute. Purpose – To remove entrapped air

S-PAC Dosing in Ceramic

Dosing rate 6.7L/h. S-PAC concentration = 7.5g/l. Dosing time = 30 seconds.

CIP – Citric Acid (3%) membrane is soaked for 6 hrs followed by NaOCl (3,000ppm) 6 hrs

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Duration of Filtration Cycles & Equivalent Doses

Number of Layers = 40

FILTRATION CYCLE (Hours)

Equivalent Dose S-PAC (mg/l)

1 40

2 20

3 13.5

4 10

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RESULTS & DISCUSSIONS

Fouling ExperimentsUV & DOC Removal

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TMP increase – Blank vs 40 layers S-PAC at Ave. J = 155L/m2.h and 1 hr filtration cycle on MF Ceramic

BLANK

y = 6.0x + 137.8

0

50

100

150

200

250

0 1 2 3 4 5 6 7 8 9 10 11 12

Time (Hours)

Pres

sure

(mba

r)

With S-PAC (40 layers)

0

50

100

150

200

250

0 1 2 3 4 5 6 7 8 9 10 11 12

Time (Hours)

TMP (

mbar

)No fouling!

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TMP increase – Blank vs 40 layers S-PAC at Ave. J = 155L/m2.h and 2 hrs filtration cycle on MF Ceramic

Blank Experiments (2hours - BW)

y = 6.0x + 186.3

0

50

100

150

200

250

300

0 2 4 6 8 10 12

Time (hours)

TMP (mbar) Flux (L/m2h) Slope Linear (Slope)

With S-PAC

y = 3.5x + 141.8

0

50

100

150

200

250

0 2 4 6 8 10 12

Time (Hours)

TMP (mbar) Slope Linear (Slope)

42% Fouling Reduction

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TMP increase – 40 layers S-PAC at Ave. J = 155L/m2.h & 3 hrs filtration cycle on MF Ceramic

y = 4.3x + 188.0

0

50

100

150

200

250

300

0 3 6 9 12

Time (Hour)

TMP

(m

bar)

& F

lux

(L/m

2 h)

TMP (mbar) Flux (L/m2h) Slope Linear (Slope)

30% Fouling Reduction

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TMP increase – 40 layers S-PAC at Ave. J = 155L/m2.h & 4 hrs filtration cycle on MF Ceramic

4Hrs BW time interval - S-PAC+Ceramic

y = 5.5x + 123.7

0

50

100

150

200

250

300

0 2 4 6 8 10 12

Time (hours

TM

P (

mb

ar)

TMP (mbar) Slope Linear (Slope)

10% Fouling Reduction

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DOC Removal40 Layers S-PAC + Ceramic - J = 155L/m2h & 4 hrs

Filtration cycle (DOCraw = 5.11mg/l)

68%

45%

32%26% 23%

0%

20%

40%

60%

80%

100%

0 1 2 3 4

Time ( Hours)

% D

OC

Rem

oval

DOC Removal from Raw water (DOC =5.13mg/l) with 40 layers S-

PAC + 0.1 um Ceramic - J=155L/m2h & 1 hr Filtration cycle

0%

20%

40%

60%

80%

100%

0 10 20 30 40 50 60

Time (Minutes)

40mg/l S-PACl Blank (DOC)

60% DOC Removal

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UV Removal

40 Layers S-PAC + Ceramic - J = 155L/m2h & 4 hrs

Filtration cycle (UVraw = 0.165)

73%

59%

45%39%

34%

0%

20%

40%

60%

80%

100%

0 1 2 3 4

Time ( Hours)

%UV

Rem

oval

UV Removal (UVraw=0.142) with 40 Layers S-PAC + MF Ceramic -

J = 155L/m2h & 1 hr Filtration Cycle

0%

20%

40%

60%

80%

100%

0 10 20 30 40 50 60

Time (Minutes)

40mg/l S-PAC Blank

70% UV Removal

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Observations/Conclusions 40 layers of S-PAC pre-coats renewed after every 1 hour

(eq. dose 40mg/l) can control both reversible and irreversible fouling (minimize the use of chemicals!).

40 layers of S-PAC pre-coats renewed after every 2 hrs (eq. dose 20mg/l) reduced irreversible fouling by 42%.

40 layers of S-PAC pre-coats used for 3 hrs filtration cycle (eq. dose 13.5mg/l) reduced irreversible fouling by 30%.

40 layers of S-PAC pre-coats applied for 4 hrs filtration cycle (eq. dose 10mg/l) reduced irreversible fouling by 10%.

DOC and UV Removal of 60% and 70% was achieved respectively from surface water (DOC = 5mg/l & UV = 0.16) when 40 layers of S-PAC were used over ceramic membrane at a Flux of 155L/m2h and filtration cycle of 1 hour.

With 2,3 and 4 hours filtration cycles DOC Removal of 32%, 26% and 23% were observed respectively while UV Removal was 45%, 39% and 34% respectively

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Recomendations

Longer Fouling experiments with higher Fluxes (170 – 210 L/m2h)

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Ongoing Works

LC-OCD measurements EEM measurements

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ACKNOWLEDGEMENT

EU Techneau – Funding KWR – Pilot Plant MetaWater - membranes

.

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Air

7

6 9

Ceramic 8 Membrane Demineralised Water

(D.M)/ CEB

Permeate/ 5DM/

CEB Dosage

Pump 4 Flowmeter

PAC/Coagulant

13 Feed pump 3Raw Water CEB/CIP 1

2Zero Flow shut down

10Pressure Gauge

Valve

OPERATION:1.) Filtration – (valve 1 & 3 open)BW vessel – valves 1,3,4 & 8 open2.) BW–valves 10,2,4,9 open3.) Air Flushing – valves 2,7,10 open4.) Forward flushing–valves 1& 6 open

Filtration cycle – 1 hourBackwashing –16 seconds (3liters)Air Flushing – 30 seconds (5 bars)Forward Flushing – 1 min. (150l/h)

PILOT PLANT- CERAMIC MEMBRANE

FILTRATION

FILLING BW

BW

AFFF

2ND CYCLE

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A). CERAMIC MEMBRANE Membrane Area 0.4 m2

Stock Solution (mg/l) 7,500 Ct Number of channels 55Dosing rate (l/h) 6.7 q Unblocked channels 9

Feed rate in % 20.0Weight of PAC (g) - M 418.75 mg Ct*q*t/60

t 0.5 Dosing timeParticle diam.(um) - d 0.3 d

Density (g/cc) - ρ 0.5 ρA (m2) 0.065

Volume of PAC (cm3) - Vp 0.84 Vp = M/ρ J (l/m2.h) 150Total Volume in one channel

(cm3) - Vt 4.91 Vt=(πDc2/4)*Lm Q (l/h) 10 Q= J/A

Total Volume of all channels

in a module VT - (cm3) 44.20 VT=N.VtPercentage of PAC in a Module (R') channels 1.89% R' = (Vp/VT)*100%

Total Number of Particles in one layer:Number of unblocked channels - N 9 N Channel diam. (mm) - Dc 2.5 mm Module length (m) - Lm 1

Diameter of channel remained after PAC coat layer D1

% Percentage of channel remained after PAC dosing - R 98.11% R = 100 - R'0.981 R

Relationship between number of particles along the centre of channel (Nc) is given by D1 Dc

Nc.d = (Dc - D1)/2 ..Eq.1 where d is particle diameterIf R is % of the channel that is not covered by PAC then,Volume of remained channel Vr = R x Vt where Vt is a total Volume of a channel

Vr = R.Vt where Vt is a volume of channel

π.D12.Lm/4 = R* π.Dc

2.Lm/4 Nc

D1 = R1/2*Dc Equation 2

From Equation 1: D1 = Dc - 2Nc.d, therefore substitute D1 in Equation 2

Dc - 2Nc.d = R1/2.Dc

Nc =(Dc - R1/2.Dc)/2d = Dc(1 - R0.5)/2d

Nc = number of layers formed in one channel after PAC dosingTherefore Total number of Layers in a module (NT) = Nc x N

Nc 39.67 Dc(1 - R0.5)/2d

Number of Layers - N 40

CONTACT TIME:

CALCULATIONS OF EMPTY BED CONTACT TIME (EBCT)EBCT = Vb/QWhere Vb = Carbon BedVolume, Q = Flow rate Total Vol. collectedafter 1 hr 31.00 L/h

Q = J.A, J = Flux and A =membrane Area Weight of PAC 418.75 mg

Vb = Vp = 0.84 cm3 Equivalent dose in 1 hr13.51 mg/lQ = 10 l/h

EBCT 8.53E-05 HoursTherefore Contact Time (Seconds) EBCT 0.31 Seconds

Equivalent Dose:Time 1 5 10 15 20 30 45 60 75 90 240Volume passed 0.16 0.82 1.64 2.45 3.27 4.91 7.36 9.82 12.27 14.73 39.27Equivalent Dose 2559.03 511.81 255.90 170.60 127.95 85.30 56.87 42.65 34.12 28.43 10.66

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Pre-treatment prior to Ceramic Membrane

Adsorption (Mixing Chambers & Static mixing) + In-line coagulation (Matsui et. al 2005) )– Low DOC water (about 1.5mg/l DOC).- - 62.5L/m2.h

1.) S-PAC (1-10mg/l) + Poly Aluminium Chloride (PACl 1mg/l)

2.) N-PAC (5-40mg/l) + PACl (1mg/l)

Adsorption without Coagulation

RAW 5mg/l(S-PAC) + 1mg/l(PACl)

20mg/l(N-PAC) + 1mg/l(PACl

TOC (mg/l)

1.2 0.35 0.6

Removal

71% 50%

RAW 5mg/l(S-PAC)

20mg/l(N-PAC)

TOC (mg/l)

1.2 0.35 0.6

Removal

33% 8%

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SELECTION OF PRE-TREATMENT METHOD

Why PAC? Why S-PAC? Why Pre-coat? PAC can well remove both NOM and micro-pollutants by adsorption

Average PAC dose of 10mg/l was recommended by CRISTAL Process for removal of pesticides on Reservoir water

Fast kinetics due to smaller particles 5mg/l of S-PAC worked better than 20mg/l of N-PAC in NOM removal (Matsui et al. 2005)

No pre-loading a new layer of S-PAC is introduced when a new filtration cycle starts Exhausted layer is removed by Backwashing Form a very thinly layer on the membrane channels so contact time is < 1 second – recirculation is not needed

R