Operating parameters influencing Ultrafiltration of ... · Operating parameters influencing Ultrafiltration of organic model solutions ... Aachen 27-28th November Aquabase Workshop

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Operating parameters influencing Ultrafiltration of organic model solutions

Verónica García Molina

Technical Service and Development Dow Water Solutions

27-28th November, Aachen

®™ Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow Verónica García Molina, Aachen 27-28th November

Aquabase Workshop on Mitigation Technologies

STRUCTURE OF THE TALK

• Overview Ultrafiltration

• Experimental Results

• Conclusions



PRINCIPLES OF ULTRAFILTRATIONWhat is Ultrafiltration?

Ultrafiltration is a size exclusion membrane process that reject particles, pathogens, high molecular weight species, and ultimately lower turbidity.

However, UF does not reject any dissolved salts, dissolved organics, or other species like true color, taste & odor, etc.



PRINCIPLES OF ULTRAFILTRATIONWhat is Ultrafiltration?

Relative size of common materials [µm]0.0001 0.001 0.01 0.1 1 10 100

ionogen molecular

1000

gelatin

latex / emulsion

milled flour

dP

macromolecular

microparticle

macroparticle

sugar

asbestos

tobacco smoke yeast cells

metalion

redbloodcells

endotoxin

viruses bacteria

albumin protein

carbon blackaqueoussalts

paint pigment human hair

beach sand

activatedcarbon

indigo blue

atomicradius

syntheticdye

Pollen

UF


Why UF?Ultrafiltration membrane development has been accelerated due to more stringent drinking water rules around the world to remove pathogens from drinking water coupled with its potential of easy integrity validation.

Pathogens

Rotavirus [bar = 100 nm)F.P. Williams, U.S. EPA

Cryptospridium and Giardia [bar = 10 µm]H.D.A Lindquist, U.S. EPA

E. Coli Microcolony average cell is ~ 4 µm longJames Shapiro and Clara Hsu,University of Chicago

PRINCIPLES OF ULTRAFILTRATIONAquabase Workshop on Mitigation Technologies



PRINCIPLES OF ULTRAFILTRATIONOperation mode: Dead-end vs Cross-Flow

membrane membrane

FeedFeed Concentrate

Permeate Permeate

Dead-End Cross-Flow

Module Hollow fiber (submerged and pressurized)

Spiral wound

Application

Operation

Cleaning

Drawbacks

Feed ↓ TDS Feed ↑ TDS

Discontinuous operation Continuous operation

Back wash feasible Back wash not possible

Flux decline or feed pressure increase with time

With high TDS, higher feed spacer required



PRINCIPLES OF ULTRAFILTRATIONWhile working in Dead-End modus:

• Backwash (Reverse Filtration)o Often dosed with 15 ppm of NaClO (fouling control)o Flowrate is 200% of design flux (minimum 100 lmh)

• Air Scrubo Air pressure is <1 bar delivered at the moduleo Frequency is typically every 6 hours when necessary



PRINCIPLES OF ULTRAFILTRATIONWhile working in Dead-End modus:Chemically Enhanced Back-wash (approx. Every 72 hours)• Acid: HCl 1000 ppm

◦ Removes colloids and inorganic salt• Alkali: NaOH 500 ppm or NaClO 1000 ppm

◦ Removes organics or biofoulants from membrane

Clean in Place (every 1 to 3 months)• Acid: HCl 2000 ppm ;pH 2• Alkali: NaOH 1000 ppm or NaClO 2000 ppm; pH12



PRINCIPLES OF ULTRAFILTRATIONMain fields of applications of Ultrafiltration?

• Municipal and industrial wastewater treatment and reuse◦ Membrane Bioreactors◦ Hygienization of WWTP◦ Pre-filter before NF/RO

• Drinking water processing ◦ Pre-treatment for NF/RO

• Surface water treatment for industrial use◦ Food industry ◦ Pharmaceutical industry ◦ Metal processing industry

• Seawater pretreatment


PRINCIPLES OF ULTRAFILTRATIONCASE 1 Petrochemical Water ReclamationCASE 1 Petrochemical Water Reclamation

Item AmountCODcr（mg/L） ≤40Turbidity（NTU） ≤5.0Oil（mg/L） ≤2NH3-N（mg/L） ≤1TSS（mg/L） ≤5TDS（mg/L） ≤1000Ca2+（mg/L） ≤240

Source: Petrochemical plant wastewater

Capacity: 560 m3/h

Location: Beijing, China

Running Time: From 2005

Process: UF Pretreatment UF RO DI

UF Feed Water Quality

High COD

UF COD removal 37.5%


PRINCIPLES OF ULTRAFILTRATION

CASE 2 Microelectronics Water ReclamationCASE 2 Microelectronics Water Reclamation

Source: Plant industrial wastewater[from cut and grind process]

Capacity：90 m3/h

Location: Shanghai, China


Process: Coagulation→Sedimentation→Bag Filter→ UFParameter Unit Feed water

pH 7.5

Turbidity NTU 4847

CODcr mg/L 1122

TDS mg/L 69.1 (15.5℃)

Actived Silica mg/L 82.9

Total Silica mg/L 91.6

Oil mg/L 0.08

High turbidity

High COD value



CASE 3 High TSS Surface Water TreatmentCASE 3 High TSS Surface Water Treatment

Feed 2 ppm NaOCl before UF System

Process:Raw Water Tank UF Feed Pump Heater Exchanger OMEXELLTM UF RO

Operational Performance

High TSS raw water feed to OMEXELLTM UF directly

Turbidity is less than 0.4 NTU (100%) and less than 0.2 NTU (90%)

TMP is less than 0.5 bar (average)

CIP is only once during 2 years operation


CASE 3 Seawater PretreatmentCASE 3 Seawater Pretreatment

Source: Seawater

Capacity: 50,000 m3/d UF Permeate and 28,800 m3/d RO Water

Location: HeBei, China


Process: Disc-Filter + UF + RO


TMP is less than 0.4bar

Without CEB

BW Frequency: >30min

CIP Frequency: Once/3~4months




• Overview of Ultrafiltration


• Objective

• Experimental Device

• Discussion of results

• Conclusions



EXPERIMENTAL PARTObjective:

Study the influence of some operating parameters on the performance of an UF test unit

• Concentration of solutes in the Feed

• Pressure Applied

• pH of the solution

• Presence of Calcium



EXPERIMENTAL PARTUltrafiltration Test Cell

Stirrer Pressurized air conduction

MembraneFeed and concentrate

Permeate

Volume 400 mL

Membranes 30 kDa (cellulose), 20 kDa and 5 kDa (polyethersulfone)

Solution Dextran, Humic Acid, Fulvic Acid, NOM, Cellulose powder, Alginic Acid

Agitation 300 rpm

Pressure 1 – 3 bar

Temperature Ambient

Duration Until a certain amount of permeate is collected



EXPERIMENTAL PART

Influence of the solute concentration in the feed solution

10 20 30 40 50 60 70 80 90 100253035404550556065707580

Perm

eabi

lity

(L/m

2 hbar

)

Permeate Volume (mL)10 20 30 40 50 60 70 80 90 100

25

30

35

40

45

50

55

60

65 1 mg/L 3 mg/L 5 mg/L 8 mg/L 10 mg/L

Perm

eabi

lity

(L/m

2 hbar

)

Permeate Volume (mL)

30 kDa Cellulose membrane 20 kDa Polyethersulfone membrane

Permeability vs. Permeate volume. Dextran solutions containing from 1 to 10 mg/L

High concentrations → higher membrane fouling/cake layer formation



EXPERIMENTAL PART


- Concentration + Concentration

Feed Feed Feed

High concentrations → higher membrane fouling→ lower flow

membrane

Permeate

membrane membrane

Permeate Permeate



EXPERIMENTAL PART


0.4

0.5

0.6

0.7

0.8

0.9

1

1 3 5 7 9 11

30 kDa 20 kDa

.

20 kDa membrane Difussion Model:

↑ concentration difference ↑ Passage

Ret

entio

n

Dextran Concentration (mg/mL)

30 kDa membrane Cake layer model:

↑ Concentration ↓ Passage

feed

permeate

CODCOD

1tentionRe −=



30 kDa Membrane

20 kDa Membrane



EXPERIMENTAL PART

0 3 6 9 12 15 18 21 249

1215182124273033 1 bar 2 bar 3 bar

Flux

(mL/

m2 h)


Influence of the transmembrane pressure

Flux vs. Permeate volume. 10 mg/L of FulvicAcids solutions. 5 kDa Polyethersulfonemembrane

1 bar 2 bar 3 bar

NOM 1R101N (10 mg/mL) 5 kDa 0.65 0.57 0.45

NOM 1R108N (10 mg/L) 5 kDa 0.62 0.44 0.27

Dextran (3 mg/mL) 30 kDa 0.48 0.29 0.25

Retention values after UF of solutionscontaining NOMs and Dextran

Higher transmembrane pressure results in higher permeate production

Higher transmembrane pressure results in faster accumulation of solutes → higher passage

feed

permeate

CODCOD

1tentionRe −=



EXPERIMENTAL PART

Influence of the pH of the feed solutions

0 10 20 30 40 50 60 70 80 90 100485052545658606264 pH 4.8 pH 6 pH 8 pH 9.7

Flux

(mL/

m2 h)


Flux vs. Permeate volume. 3 mg/L of Dextran solutionsat different pH conditions.

30 kDa Cellulose membrane

-5

-4

-3

-2

-1

0

1

2 3 4 5 6 7 8 9 10pH

Zeta

Pot

entia

l [m

V]

Measured ValuesAverage

The higher the pH:

-The membrane is more negatively charged

- Dextran more negatively charged due todeprotonation



EXPERIMENTAL PART

Influence of the presence of Ca2+ in the feed solution

Flux vs. Permeate volume. 5 kDa Polyethersulfonemembrane

0 10 20 30 40 50 60 70 80 90 10020

40

60

80

100

120

140

160 3 g/L Alginic Acid 3 g/L Alginic Acid + 218.2 mg/L CaCl2.2H2O

Flux

(L/m

2 h)


Bridging characteristics of Ca2+ between:

-Solute – Solute

-Solute - Membrane

Fastest formation of a fouling layer on the surface of the membrane;

Higher resistance for the water




• Overview of Ultrafiltration


• Conclusions



CONCLUSIONS

•Conclusions

• Flux decline during UF operation still remains an issue for its further development

• Concentration in feed, applied pressure, pH and presence of divalent cations have been proved to have a direct influence on the process

• Membrane selection plays a crucial role for the success of the process



THANK YOU VERY MUCH FOR YOUR ATTENTION

Documents

Operating parameters influencing Ultrafiltration of ... · Operating parameters influencing Ultrafiltration of organic model solutions ... Aachen 27-28th November Aquabase Workshop