Membrane processes in drinking water...

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MEMBRANE FILTRATION PROCESSES

Membrane processes in drinking water treatment

Microfiltration (MF) and Ultrafiltration (UF)

2nd French-Serbian Summer School

09/10/2007 I WATER QUALITY DIVISION WATER TREATMENT MEMBRANE PROCESSES 2

Principles of membrane processesDrivers for expansion of membrane technology in Eur ope

� More stringent water quality regulations� Turbidity� Cryptosporidium (regulated in UK)� Pesticides� …

� Efforts from private companies to: � Exceed current/anticipated regulations� Provide sustainable solutions� Make technology available (reliability/cost) for municipal

applications through strong R&D efforts� Minimize O&M cost for small remote plant and maintain high

water quality

� Higher consumer expectations� Lack of fresh water resource in Mediterranean region and

Islands (�desalination)

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1988 1990 1992 1994 1996 1998 2000 2002 2004

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Principles and Theory


Principles of membrane processes Contents

� Principles and Theory

� Principles of membrane processes

� Membrane disinfection properties

� Filtration modes, materials and geometry

� Membrane operating parameters

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Hardness X X

Sulfates X X

Monovalent ions (fluorine, nitrates,…) X

Parameters MF UF NF RO

Turbidity X X

Bacteria and cysts (Giardia, Cryptosporidium…) X X

Virus X

Color X X

Organic matter and disinfection by-products X* X

Micropollutants (pesticides, taste+odor) X

X*

X*

* Removal by CristalTM process (Aquasource UF membranes combined with powdered activated carbon)

Principles of membrane processesApplications


Principles of membrane processesTypes of membrane filtration processes

desalinationdiscoloration removal of pesticides, taste + odor, nitrates

90-99 % ions99 % organic molecules

Reverse osmosisRO

softeningpartial desalinationdiscoloration removal of pesticides, taste + odor, sulfates

95% bivalent ions30-60% monovalent ions99% organic molecules (molar weight > 200 – 400 )

NanofiltrationNF

clarificationdisinfectionpretreatment for NF and RO

some macro-moleculesUltrafiltration

UF

clarificationpretreatment for NF and RO

All particles except some virusesMicrofiltrationMF

Applications in drinking water treatment

Effectiveness of treatmentType of filtration

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n = number of analysesND :none detectedn = 10

n = 10

n = 10

Raw waterFiltered water

MS2 Bacteriophages

MFB 0.2 µmMFA 0,2 µm UF 0.01µmAquasource

1E+00

1E+01

1E+02

1E+03

1E+04

1E+05

1E+06

1E+07

1E+08

1E+09

MS

2 B

acte

rioph

ages

, pfu

/ml

ND

Membrane disinfection propertiesComparing disinfection by Micro- vs. Ultra- filtratio n

UF is effective for virus removal

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Membrane disinfection propertiesDisinfection by UF vs. conventional disinfectants

Viruses8 mg/l.min

4 log13 mg/l.min

2 log1,6 mg/l.min

4 logEscherichia Coli bacteriophage

Protozoa

9 logPolio virus Type I

> 5 logBacteriaColiformsThermo tolerant coliforms Fecal EsteptocoquesClostridium

Aerobic microorganisms (22 –37°C)

> 5 log70 mg/l.min2 log

7200 mg/l.min10 mg/l.min4 log

Cryptosporidium cysts

10 mg/l.min4 log

18 mg/l.min2 log

2,4 mg/l.min4 log

Giardia cysts

4 - 5 log20 mg/l.min2 mg/l.minAmeba cysts

UFChlorine dioxide

ChlorineOzone








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Filtration modes, materials and geometryHollow fiber internal vs. external filtration

Internal filtration

inlet water Permeate

concentrate

External filtration

inlet water

concentrate

Permeate


Filtration modes, materials and geometryDead end vs. Cross flow filtration

Dead-end filtration

Cross-flow filtration

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Filtration modes, materials and geometryImmersed vs. pressurized filtration

Pressurized filtration

Immersed filtration

Aeration

Permeate

for

backwash

. … ..

.. . .. ..

. .. . ..

. … ..

.. . .. ..

. .. . ..


Filtration modes, materials and geometryMembrane materials

organic film + mineral supportHybrid

alumina, silicium carburate, titanium oxide, zirconium...

Inorganic (Mineral)

cellulose acetate, polysulfone, polypropylene, polyacrylonitrile, polyester, polymide, Polyether sulfonepolytétrafluoroethylene, vinylidene polyfluorure

Organic (Polymers)

Polymeric membrane are mainly used for drinking water treatment

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Filtration modes, materials and geometryUF & MF membrane materials

Cellulose Poly(ether)sulphone

Hydrophilic Hydrophobic / Hydrophilic

Fouling (organic adsorption) Low Fair/Medium

pH tolerance Narrow (3 - 8.5) Wide (2 - 13)

Biological degradation yes no

Chemical resistance Low (Chlorine) Good

Aquasource HydraCap


Filtration modes, materials and geometryMembrane configurations

� Flat membranes (organic)

� spiral modules

� plate modules

� Cylindrical membranes (organic, mineral)

� hollow fiber or capillary fiber modules

� tubular modules

Hollow fiber are mainly used for drinking water treatment

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Filtration modes, materials and geometryExample of advantages/disadvantages of UF configuration

Tubular Capillary Plate&Frame Spiral-Wound

Cost/area High Low High Low

Flow Good Good Low Low

Packing density, m²/m3 Poor Excellent Good Good

Energy consumption High Low Medium Medium

Fouling Excellent Good/Fair Good/Fair Medium


Filtration modes, materials and geometryFlat - spiral membrane

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Filtration modes, materials and geometryFlat – spiral membrane: Filmtec module


Filtration modes, materials and geometryHollow fiber membrane – typical pressurized module

Hollow fibersSupport grid

ResinInlet waterunder pressure

Filtered water outlet

Outlet for removed particles

Aquasource ND 300 – 64 m²

HYDRACap 60– 46 m²

Hollow-fiber capillary membrane

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Filtration modes, materials and geometryHollow fiber membrane


Filtration modes, materials and geometryHollow fiber immersed membrane – Gentle vacuum

external film

ZeeWeed®

module

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Filtration modes, materials and geometryTubular membrane – TAMI modules

Permeate

Concentrate








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Permeate(filtrate)

Concentrate(retentate)

Feed(raw water) Pump

PIN

POUT

PP

Membrane

Module

Valve

QF

QP

Membrane operating parametersMembrane language


Membrane operating parametersMembrane filtration phenomena

Permeate

Filtration

Feed

Concentrate

Backwash

Fouling ⇔⇔⇔⇔ Permeability (Lp) ↓↓↓↓

TransMembrane Pressure (TMP)↑↑↑↑

Clogging ⇔⇔⇔⇔ Head loss (∆∆∆∆P)↑↑↑↑

Permeate

Waste

Waste

Removal of reversible fouling ⇔⇔⇔⇔ Permeability ↑↑↑↑, TransMembrane Pressure ↓↓↓↓, Head loss ↓↓↓↓

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Without backwash With backwash

Irreversible fouling

Permeability (L p 20°C )

Time

Reversible fouling

Membrane operating parametersMembrane performance evolution with time


Market and development for membrane technology

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Membrane technology market and development Contents

� Market and development for membrane technology

� Major manufacturers / suppliers

> Norit

> Aquasource

> Memtec

> Zenon

> Kalsep

� Market growth

� Costs


Major manufacturers / suppliers Overview

� 8 major membrane manufacturers/suppliers

� Organic hollow fiber technology dominates

� No ceramic technologies implemented for drinking water production since 1991

� Ultrafiltration is the preferred technology for drinking water applications

� Netherlands, France, and UK represent 85% of the contracted MF/UF capacity in Europe

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Major manufacturers / suppliers Suppliers identified in Europe for municipal applic ations

Manufacturer Process Type Backwash Material

X-Flow (The Netherlands) MF/UF module Int Water PES

Aquasource (France) UF module Int Water CA

Memtec (Australia) MF module Ext Air PP

Acumem (UK) MF module Ext Water PES

Zenon (Canada) UF cassette Ext Air/water PVDF

Hydranautics (USA) UF module Int Water PES

Asahi Pall (Japan) MF/UF module Int Air/water polyacril on.


Major manufacturers / suppliers Norit membranes: X-Flow modules

8 inch modulesSurface area 22 � 35 m2

Reference: Clay Lane1st stage: 1 536 modules, 160 000 m 3/d2nd stage: 144 modules (concentrate treatment)

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Major manufacturers / suppliers Aquasource membranes

DN300 Modules: 55 m 2 64m2

Lausanne, Switzerland(396 modules, 40 000 m 3/d)

DN450 Modules :125 m 2

Rouen, France(96 modules, 24 000 m 3/d)


Major manufacturers / suppliers Memtec membranes

CMF system (pressurized)

CMF-S system (submerged)

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Major manufacturers / suppliers Zenon membranes

ZeeWeed Organic fibers0,035 µm cut-off450 m2

excesssludge

permeate

Feed


Major manufacturers / suppliers Zenon cassette trains

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Major manufacturers / suppliers Kalsep membranes

HYDRAcap module

HYDRAcap systemBirchtrees WTW 1.6 Ml/d





� Market growth

� Costs

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Market growth Application of membrane technology in municipal wat er treatment in Europe (growth)

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1988 1990 1992 1994 1996 1998 2000 2002 2004

Hydranautics 2001Kalsep 2000Pall 1998Norit 1995Acumem 1996Zenon 1994Memtec1993Aquasource 1988

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Market growth Application of membrane technology in municipal wat er treatment in Europe (figures)

Total installed plant Application

NA : Not available

Acumen UF 46 4 21 100 -Aquasource UF 120 65 32 100 -Hydranautics UF 19 20 5 100 -Kalsep UF 16 9 5 100 -Memtec MF 92 14 21 100 NAPall MF 4 12 2 - 100Norit UF 142 43 43 100 -Zenon UF 31 29 12 1 99

Total 8 468 196 43 93 7

Largest PlantProcess Capacity Number Capacity Drinking water Wastewat er

mgd mgd % capacity % capacity

1 MGD = 3 785 m3/day

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<5

5-10

10-25

>25

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Market growth Municipal WTP's in Europe using membrane technology


Market growth Municipal WTP's in Europe using membrane technolog yDistribution by country

0 100 200 300

DenmarkNorwayIrelandPoland

HungaryBelgium

SpainSlovenia

ItalyGermany

NetherlandsFrance

UK

Drinking waterWastewater

Capacity, mgd

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� Market growth

� Costs


Costs Capital and operating costs for membranes processes

Total water costTotal water cost Capital costCapital cost

€/m€/m33 €/m€/m33.d.d

MF/UFMF/UF 0.15 0.15 -- 0.3 0.3 150 150 -- 450450

NFNF 0.3 0.3 -- 0.5 0.5 400 400 -- 600600

RORO 0.45 0.45 -- 1 1 900 900 -- 13001300

Costs highly depend on facility capacity

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Costs Operating cost distribution for membranes processes

� MF

� UF

� NF

� RO

� RO desalination

pressure bar

energykwh/m 3

0,1

0,1

0,4

0,6

2,4/3,1

cost$/m3

0,01

0,01

0,04

0,06

0,30

membranes$/m3

0,03

0,03

0,02

0,02

0,02

2

2

7

12

65/90


Membrane processes in drinking water treatment

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Membrane development within SE

1985

R&D CIRSEE

1ère réalisation: Amoncourt 1991

Orléans 200540 000 m3/j L’Apié

25 000 m3/j

Vigneux55 000 m3/j

Helbarron16 000 m3/j

55 usines exploitées

par LdE

1988

1997

19962004


Membrane processes Contents

� Membrane processes in drinking water treatment

� Design considerations

� Typical treatment train� Direct filtration

� Polishing: Clarification + UF

� Polishing: Clarification + GAC + O3 + UF

� Pretreatment for Reverse Osmosis

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DesignHow designing a membrane system?

� To clearly define the future WTP objectives�Treated water quality�Water production capacity and anticipated annual variations

As hydraulic performance of a membrane systemclosely depends on the quality of water to be treated

⇒⇒⇒⇒ To do a CASE BY CASE design

� To characterize raw water quality and identify peak periods during the year

� To carry out a pilot study on future raw water to w ork out:�Process design parameters�Operating conditions


DesignHow define the WTW size ?

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1-jan

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1-m

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1-no

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Flux 180 LMH Flux 150 LMH LAR 2002

� To clearly define the need of the WTW in terms of quantity

� Historical data

� Alternative supply

� Adjust design considering flow variation though out the year (water quality, temperature, …)

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DesignHow characterizing raw water quality?

� TOC : Total Organic Carbon

� DOC : Dissolved Organic Carbon

� UV : absorption UV @ 254 nm

� Algae

� Turbidity

� Temperature

� Iron, Manganese, Aluminium, silica

Organic fouling

Mineral fouling

Productivity

Main parameters with an impact on membrane performance:

Filtration mode

Establish the design on appropriate water quality data


DesignMeasuring organic matter

� UV absorbance measures levels of aromatic and unsaturated organic matter

� The UV/TOC ratio is often correlated to certain treatment parameters such as potential for formation of trihalomethanes (THM's) or other organic matter content such as PHA

UV/COT ~ 1 - 2 mg/l low

2,0 - 4 medium

> 4 - 5 high (humic matter)

• high amount of PHA (polyhydroxy-aromatics)

• high and irreversible affinity with membrane material

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DesignRaw water quality impact on membrane operating cond itions

Categories Tub, NFU Filtration mode Flux, LMH @ 20°C Ba ckwash, min. CC, nbr/yr

0 <0.5 Dead-end 120 to 150 60 to 90 1 to 21 < 2 + spike Dead-end 100 to 120 60 to 90 1 to 22.1 < 6 + spike Cross-flow 90 to 110 30 to 45 4 to 62.2 2 to 4 + spike Cross-flow 80 to 100 30 6 to 82.3 < 6 + spike Cross-flow 70 to 80 30 63.1 > 6 + spike Cross-flow 60 to 70 30 6 to 123.2 > 6 + spike Cross-flow 40 to 50 30 12

Example: water categories for Aquasource membranes

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DOC (mg/l)

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UV

/DO

C

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2.1 3.1

3.2

2.3

3.1

3.2

2.2


DesignConstraints of membrane technology as clarification stage

� If raw water quality is out of the recommended ranges,

a pre-treatment is necessary:

� Turbidity > 300 NTU �� Settling

� Organic matter TOC > 4 mg/L �� pretreatment and PAC/UF

� Algae > 6 - 10 x 106 /L �� Flotation, O 3, PAC/UF

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Membranes in drinking water treatmentDifferent configurations according to raw water qua lity

Type of Raw Water

POLISHING AFTER CONVENTIONAL TREATMENT (Disinfection)

PRE-TREATMENT FOR REVERSE OSMOSIS

DIRECT FILTRATION (Clarification + Disinfection)

Surface waterLake / clean

surface waterGroundwater

Combined membrane treatment

Ultrafiltration

Cl2

With or without PAC

or

Cl2

Coagulant

Polymer

Sandfiltration Ultrafiltration

Settlingor flotation

(O3)

With orwithout PAC

(CAG)

Cl2

MF/UF NF/RO(O3)

With orwithout PAC

(CAG)


Membranes in drinking water treatmentWhy injecting PAC upwards the UF membranes?

Applications:

• For treating raw water containing:High organic matter concentrationsMicro-pollutants

• For polishing:Removal of organic matterRemoval of taste & odor precursors

Operating conditions:

• Cross-flow filtration• Dosing rates 5 to 20 g/m 3

• Continuous dosing• Dosing depending on thresholds of turbidity, TOC, U V

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Membranes in drinking water treatmentEffect of injecting PAC upstream the UF membranes

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600

800

1 000

1 200

1 400

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Time (days)

arrêt injection CAP avant le préfiltre

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400

600

800

1 000

1 200

1 400

0 1 2 5 7 8 9 10 11

Shut-down PAC injection prior to pre-filter


DesignWhy conducting a pilot study?

1/ To confirm theoretical process design on a specific case

⇔ To follow the evolution of permeability with time, depending on raw water quality

2/ To fine tune design parameters

⇔ To conduct lab test (adsorption isotherm & kinetics) to determine the PAC contact time and doses for specific water

3/ To determine optimal operating conditions (max flow rate, min water losses)

⇔ To increase, by steps, flux and filtration cycles and follow up permeability vs time

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DesignPilot study: a viable option for plant design ?

Flu

x, L

/h.m

², P

erm

éabi

lity,

L/h

.m².

bar

WQ 1 WQ 2

15 - 27/11/01 19 - 25/09/020

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100

150

200

250

300

Jp Jp à 20°C Lp à 20°C

To study the impact of the water quality to be trea ted

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0,5

1,0

1,5

2,0

2,5

CO

T (

mg/

L) e

t U

V (

DO

/m)

0

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400

600

800

1 000

1 200

Par

ticul

es/m

L -

SD

I*10

0TOC UV Particles SDI

15 - 27/11/01 19 - 25/09/02

WQ 1 WQ 2

� Difficult to predict fouling behavior only with water characteristic

� Compounds not identify thru TOC / UV even SDI





� Typical treatment train� Direct filtration




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Membranes as direct filtrationExample: L’Apié WTP, France (28 000 m 3/d)

Chlorine

PAC10 mg/L

Pre filter 200 µm

Discharge(to DENSADEG)

8 x 20 modules

DN300

Lakewater

Raw water (lake):- low turbidity- micropollutants (pesticides, nitrates, …)- organic matter- microbial contamination


Membranes as direct filtrationExample: L’Apié WTP, France (28 000 m 3/d)

Raw water Treated waterAverage (Min-Max)

Turbidity (NTU) 1,2 (0,4 - 107) < 0,1

Color (mg/L Pt/Co) 4 (2,5 - 10) < 2,5

TOC (mg/L) 2,4 (1,6 – 4,1) 0,9 (0,7 - 1)

Total coliforms (n/100 mL) 100 (10 - 1000) 0

Fecal streptococci(n/100 mL) 16 (0 - 17) 0

Algae (nb/L) 0,5 106

(0,25 106 - 2 106) 0

Water Quality

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� Direct filtration





Membranes as polishing (clarification + UF)Example: Bexar Met WTP, USA (35 000 m 3/d)

coagulationfloculation

PAC

chlorination

Superpulsatorclarifier

7 x 48 modules of 55 m 2

PAC

Lagunes

recycling at inlet of clarifier

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Membranes as polishing (clarification + UF)Example: Bexar Met WTP, USA (35 000 m 3/d)

min. - max. averageCoagulant dose(ferric chloride) 10 - 100 35 g/m3

Flow rate 50 - 140 95 l/h.m2 at 20°C

Backwash 30 – 90 min 40 min

Operating conditions

Water quality

Turbidity raw water 5 to > 1000clarified water 0,4 to 10filtered water 0,01 to 0,06









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Membranes as polishing (clarification+GAC+O 3+UF)Example: Vigneux WTP, France (55 000 m 3/d)

Set of 28 modules of individual surface area = 55m 2

PAC storage bin2 Ozonation U tubes

Parameters Units Mean Min-Max

Temperature °C 16 1 - 29.5

Turbidity ntu 16 5 – > 150

DOC mg/L 3.6 3.2 - 4.9

UV254 m-1 5.6 4.6 - 19

Surface Water, Seine River


Membranes as polishing (clarification+GAC+O 3+UF)Example: Vigneux WTP, France (55 000 m 3/d)

coagulationfloculation

PAC

chlorination

Pulsator& Superpulsator

clarifiers

GAC filters

8 x 28 modulesof 55 m 2

Cristal™ Process

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with Cristal™ process



Membranes as polishing (clarification+GAC+O 3+UF)Impact of Cristal™ process on organic matter remov al

Coagulation -Floculation Settling GAC

Filtration

OzonationPAC

Chlorination

SeineRiver

Parameter Raw water Treated waterCOT 2,0 - 3,3 % removal 20-30% -

mg/l (2,0 - 2,6) -45 - 60% - 70 - 75%(0,9 - 1,6) - (0,5 - 0,9)

CODB 0,9 - 1,0 mg/l 0,5 - 0,8 -<0,2 - <0,2

UV254nm 4,5 - 6,5 % removal 30 - 40% 50 - 60%D-O (2,8 - 3,6) (1,9 - 2,7)

70% 80% 85 - 90%(1,4 - 1,8) (0,9 - 1,5) (0,4 - 0,7)



Membranes as polishing (clarification+GAC+O 3+UF)Impact of Cristal™ process on taste and odor remov al

Coagulation -Floculation Settling GAC

Filtration

OzonationPAC

Chlorination

SeineRiver

Parameter Raw water Treated waterLimitodor 5 (musty - silt – stagnant water) odor: 1 - 2

taste: 1 - 3Nonylphenols traces absenceDimethyl trisulfure 2 - 5 ng/l 1 - 3 ng/lMIB 2 - 6 ng/l 2 - 5 ng/l

odor: 1 - 2 0 chlorinetaste: 1 - 2 0 chlorineabsence absence1 - 3 ng/l absence2 - 5 ng/l < 1ng/l

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Conventionnel CristalO3 + CAG O3 + CAP/UF

CAPEX 8.2 M€ 11.7 M€- Ozone 4.4 M€ 4.4 M€- Polishing 3.8 M€ 7.3 M€*

OPEX 0.03 €/m3 0.06 €/m3

- Ozone 0.01 €/m3 0.02 €/m3

- Polishing 0.02 €/m3 0.4 €/m3**

* Racks UF : 21; Civil engineering : 9; Equipments : 18** Energy : 0.1; PAC : 0.13; Membrane : 0.16

Membranes as polishing (clarification+GAC+O 3+UF)Cost comparison









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Membranes as pretreatment for ROExample: Heemskerk plant, Netherlands (70 000 m 3/d)

UF treatment objectivesDisinfectionRO pretreatment

RO treatment objectiveshardnesssalinitypesticidestaste and odornutrients bacteria

Ijssel Coagulation Sedimentation RSF UF RO Neutralizatio nLake


Microcoagulation

Improvement of UF competitiveness

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Background

1999microcoagulation

patent

2004Première

File

2004Air

backwash patent

End of 2005

Capex optimisation of UF solution

“Dead end” Microcoagulation

Improvement of cleaning procedures efficiency

� Water Backwash

� Flush

� Drain backwash

� Air backwash

Delivered to business

Equipment Process


Microcoagulation processWithout

microcoagulation

1 mm

With microcoagulation

� Selected coagulant : FeCl3� Coagulant dosage : # 1 mg/L as FeCl 3

� Injection type : in line� Contact time & energy : preferably before feeding pump

Microcoagulation process and benefits

Agglomerate the diffused particules in raw water

In filtration : form a non uniform cake layer

Improve filtration flow

Reduction of membrane area required

Air backwash is necessary to prevent clogging and secure the UF system

Cleaning efficiency : optimise the removal of “cake”

� Water backwash� Flush� Drain backwash� Air backwash

Process Backwash

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Application fieldMicrocoagulation is not a continuous process well adapted to water with a large range of quality

variation : � Temperature ⇒ cold water < 15°C� Water quality ⇒ peak of dissolved NOM : abs UV 254 nm : 5-7 m-1

� Microcoagulation has no effect on settled water but may be slightly efficient on settled-filtrated water

� Warning ! ! ! : wash water contains Fe(OH) 3

Reduction of membrane area :

≥≥≥≥ 20%

Flux @ 6-15°C=

Flux @ 20°C

Lake waterSurface waterKarstic water

Sea water

Potential benefitFlux design Type of water

In case of water temperature > 15°C :

� less than 10% of operation time

� except DTG acceptance

� Design influenced by temperature

Reduction of membrane area :

≥≥≥≥ 20%

Design on “good” water quality

Lake waterSurface waterKarstic water

Potential benefitFlux design Type of water

� Design influenced by water quality (peak of dissolved NOM)

� drinking water criteria remains


Seine river (pH = 7.6, turbidity = 5-10 NTU, COT = 2-3 mg/L, ab s UV 254 nm = 5-7 m-1)

Permeability

Flux

without

with

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Open intake seawater (pH = 8.1, turbidity = 0.5-1 NTU, COT = 0.3-0.5 mg/ L, UV 254 nm = 0.75-1 m -1, SDI = 13-24%/min)

Permeability

Flux

without

with


Loue river (pH = 7.7, turbidity = 4-7 NTU, COT = 1.5-1.9 mg/L, abs UV 254 nm= 3-5 m-1)

Permeability

Flux

without

with

Membrane processes in drinking water...

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