1. Name1. Name : : PornsakPornsak SamornkraisorakitSamornkraisorakit

1.1. Bachelor DegreeBachelor Degree in in Sanitary ScienceSanitary Science from from MahidolMahidol UniversityUniversity

2.2. Master DegreeMaster Degree in in Environmental EngineeringEnvironmental Engineering from from KasetsartKasetsart UniversityUniversity

- Educational Background :

2. Position : Scientist 6

3. Working for Department of Water Quality Control

Metropolitan Waterworks Authority

- Training course Yokohama Training Program in 2001Yokohama Training Program in 2001 in Japan

History of Membranes1748

Abbe Nollett discovered Osmosis1865

Fick (England) made 1st Synthetic Membrane1907

Bechold (Germany)1919

“The name of Membrane Filter”1927

MF became Commercially available1950

1st RO Membrane Created1957

US Public Health Service accepts MF for Coliform Testing

Membranes Enter Municipal Market

1950sElectrodialysis

1960sReverse Osmosis

1980sNanofiltration

1990sMembrane Filtration

A Brief US Membrane History• Prior to 1990 mostly RO in industrial applications

• Historically, smaller facilities (< 1 mgd)

• 1st Significant MF/UF System in North America in 1993 (Saratoga, CA – 3.6 mgd)

• Membrane Bioreactor emerged in early 1990’s

• In-land brackish desalination in mid 1990’s

• Over 250 Membrane WTP now on-line

• Trend is to more, and larger facilities– Minneapolis – 70 and 95 mgd– Singapore – 72 mgd

Conventionally Membrane systems are classified as

1. Microfiltration Membrane (MF)

2. Ultrafiltration Membrane (UF)

3. Nanofiltration Membrane (NF) and

4. Reverse Osmosis Membrane (RO)

based on membrane’s pore size, these membranes process which is used pressure to drive water across the membrane can be used inwater treatment, wastewater treatment and pure water plants.

The Filtration Spectrum

MF membrane UF membrane

NF membrane RO membrane

Demineralization Processes

Filtration Comparison

Conventional Filtration Membrane Filtration

FilterMedia

CoagulantParticle Particle

Membrane

Feed

Filtrate

ขอแตกตางระหวางการกรองทรายกับการกรองโดยใชขอแตกตางระหวางการกรองทรายกับการกรองโดยใช MembraneMembrane

การกรองทราย(Sand Filter) การกรองแบบ MembraneFiltration rate = 120 – 250 m/d Membrane filtration flux = 0.5

– 1 m/d per membrane pressure difference(98.1 kpa)

Filtration Area

Practically < 100 m2

Filtration Area100 – 300 m2/ พื้นทีต่ิดตั้ง 1 m2

Filtration Mechanism-Interception, collision, electrostatic attraction-Straining only happens in cake filtration

Filtration Mechanism-Concentration Polarization(ยกเวน Microfiltration(MF))-Sieving/Straining

U f

c f c w

mwc

mpc

c p δ

x

J s

J v

Δ x

B u l k F e e d W a t e r

R O / N F M e m b r a n e

P r o d u c t W a t e r

L a m i n a r F i l m

F o u l i n g L a y e r

J v

P r o d u c t W a t e r

c p U f

c f

c w

mwc

mpcx

J s

Δ x

B u l k F e e d W a t e r

R O / N F M e m b r a n e

L a m i n a r F i l m

Interfacial Processes– Chemical Fouling/Biofouling– Concentration Polarization– Scaling

Concentration PolarizationConcentration PolarizationPrecipitates salts on the membrane surface if the brine concentration becomes to great. The brine becomes saturated with dissolved minerals and tends to deposit them on the membrane.

Results in lower flux rates for both water and minerals

Remedy is to increase water flow velocity and create turbulence at the membrane boundary to encourage minerals to diffuse back into the flow stream.

Arrange pressure vessels in parallel/series arrangement. (Christmas tree flow arrangement)

Concentration Polarization EffectConcentration Polarization Effect

1. Increasing Osmotic Pressure1. Increasing Osmotic Pressure

2. Decreasing2. Decreasing Water Flux Water Flux

3. Increasing Salt Flux3. Increasing Salt Flux

4. Decreasing RO Element Age4. Decreasing RO Element Age

5. Precipitation CaCO5. Precipitation CaCO33 or CaSOor CaSO44

Membranes comparisonMembranes comparison

By membrane material and pore size.By driving forces employed and feed flow direction. By mechanisms of separation.By the application in industries.By the geometric configuration.

PressurePressure--Driven Membrane ProcessesDriven Membrane Processes

Low Pressure: Microfiltration(MF), Microfiltration(MF), Ultrafiltration(UFUltrafiltration(UF))– Turbidity and microbial contaminant control.– Hybrid Sorption/Membrane Processes for Control of

Dissolved Contaminants

High Pressure: Nanofiltration(NFNanofiltration(NF), Reverse Osmosis(RO)), Reverse Osmosis(RO)– Desalination– Softening– Control of Dissolved Trace Contaminants

RORO

NF

UF

MF

OPERATINGPRESSURES

RECOVERY PRIMARYAPPLICATION

125 TO 1,200

PSIG

80 TO 120

PSIG

5 TO 30

PSIG

5 TO 15

PSIG

50 TO 85

PERCENT

70 TO 90

PERCENT

80 TO 95

PERCENT

80 TO 95

PERCENT

DESALTING

SOFTENING

NOM REMOVAL

SWTR

NOM REMOVAL

SWTR

Pressure Driven Membrane Processes

Membrane Materials

Polyethylene

Cellulose acetate (CA) and(CA) and Cellulose Triacetate (CTA)Cellulose Triacetate (CTA)

Polyamide

Polyethersulfone

1. Organic Membrane

2. Inorganic Membrane

Zirconium Oxide ( ZrO3)

Aluminium Oxide (Al2O3)

Titanium Oxide ( TiO2)

Membrane PolymersMembrane PolymersCellulose Acetateand Derivatives

Polyamides

Reverse Osmosis Membrane Reverse Osmosis Membrane Structure and CompositionStructure and Composition

Two common type of membranes:

– Cellulose acetate – older designs

– Thin Film Composites – newer designs

Cellulose Acetate (CA) and Cellulose Triacetate (CTA)

ขอดี

1. ทนทานตอการทําลายจากพวก Bacteria

2. ทนทานตอสาร Oxidizing Agent เชน Cl2 สามารถทนความเขมขนของ Cl2 ไดสงูถึง 1 mg/l ในชวงเวลาสั้นๆ3. สกัด Salt Rejection ไดถงึ 95 %4. ราคาคอนขางต่ําเมื่อเทียบกับ Membrane ชนิดอื่นๆ

ขอเสีย

1. ใชงานไดในชวง pH 4.5 - 7 ถาเกิน 7 ผิว Membrane จะเสีย2. ความดนัที่ใชในการกรองคอนขางสูงทําใหสิ้นเปลอืงพลังงาน3. ทนทานตออุณหภมูิไดไมเกิน 30 องศาเซลเซียส

Thin Film Composite (TFC) or Aromatic Polyamide

ขอดี

1. ใชงานไดในชวง pH 2 - 102. ทํางานไดที่อณุหภมูสิูง 45 องศาเซลเซียส3. สกัด Salt Rejection ไดถงึ 99 %4. ความดนัที่ใชในการกรองต่ําเมื่อเทียบกับ CA และ CTA

ขอเสีย

1. ทนทานตอการทําลายจากพวก Bacteria ไดนอยกวา CA และ CTA2. ไมทนทานตอสาร Oxidizing Agent เชน Cl2 ความเขมขน 0.1mg/l ก็มีผล3. ราคาสูงกวา CA และ CTA

5. มีโอกาสถูกเคลือบ/อุดตัน (fouling) จากสารอินทรียต่ํา

Reverse Osmosis Membrane Structure and Composition

Characteristics Cellulose Acetate Thin film Composite

Net Driving Pressures: 400 psi 200 psi

NaCl Rejection: 92-97% 98 - 99%

Flux Rate at 200 psi, 77°F 25 GFD 25 - 30 GFD

Operating pH range: 4.0 - 6.0 3.0 - 10.0

Cleaning pH range: 3.0 - 6.0 2.0 - 12.0

Cost relative to tin film composite membrane: Lower -

Allowable feedwater chlorine concentration: 1.0 mg/L none

Maximum operating temperature: 104°F (40°C) 113°F (45°C)

Salt Passage increase after 3 years 2X <30%

Subject to biological attack Not subject to biological attack

Subject to hydrolysis Higher fouling rates than CA

Higher rejection and flux rates than CAMost suitable for treatment of municipal wastes and some heavily pretreated surface water supplies (due to lower fouling rate vs. thing film)

Sensitive to oxidants in feedwater

Comparison of Membrane Characteristics

1. Organic Membrane

- Microfiltration (MF)- Ultrafiltration (UF)

- Nanofiltration (NF)

- Reverse Osmosis (RO)

2. Inorganic Membrane

- Microfiltration (MF)- Ultrafiltration (UF)

Membrane Materials

Different material

Membrane can be classified by its material: one is organic material such as organic polymers : cellulose acetate (CA) , polyamide (PA) , polysulfide (PS), vinvlidene fluoride (VF),acrylonitrile (AN), etc… and another type is inorganic material such as ceramic stainless steel etc …

Polyvinylidene-fluoride(PVDF)Medium shown at 3000X

magnification

Polytetrafluoroethylene(PTFE) Medium shown at 3000X magnification

Nylon Medium shown at 3000X magnification Hollow fiber ultrafiltration medium shown at 300X magnification

Types of Media Nylon, PVDF, PTFE, and hollow fiber ultrafiltration media are recommended for use in DI water

applications. Photomicrographs of these media are shown here.

Membrane Construction Options

Composite

Asymmetric

Symmetric

Skin layerSkin layer

Composite layerComposite layer

No Skin layerNo Skin layer

No Skin layerNo Skin layer

เปนเมมเบรนพวก CrosslinkedCrosslinked Aromatic PolyamideAromatic Polyamide

ThinThin--Film Composite MembranesFilm Composite Membranes

Polyester Fiber Backing ~120 μm

Polysulfone Support ~50 μm

Active NF/RO Layer

Active Layer ~50-250 nm

Polysulfone Layer Pore Size ~20-30 nm

Polyamide ultrathin barrierlayer (approx. 0.2µm)

Polysulfone microporousSupport (approx. 40µm)

Polyester non-woven webCarrier (approx. 120µm)

Thin Film Composite Membrane

Membrane Filtration Type

- quickly clogging and fouling

- low energy consumption

- high energy consumption

- prolong clogging and fouling

1. Dead end Filtration

2. Cross-Flow Filtration

DEAD END FILTRATIONDEAD END FILTRATION

FILTER MEDIA

FEED WATER

FILTEREDWATER

FF

tt

Direct Flow Configuration

FilterCake Membrane

Feed Flow

Filtrate

DEAD END FILTRATIONDEAD END FILTRATION

•• HIGH CAKEHIGH CAKE--LAYER BUILD UPLAYER BUILD UP

•• UNIT MUST BE STOPPED UNIT MUST BE STOPPED PERIODICALLY FOR PARTICLE PERIODICALLY FOR PARTICLE REMOVAL OR FILTER REPLACEMENTREMOVAL OR FILTER REPLACEMENT

•• BY NATURE A BATCH PROCESSBY NATURE A BATCH PROCESS

CROSSFLOW FILTRATIONCROSSFLOW FILTRATION

FEED

PERMEATE

RETENTATE

FF

tt

Crossflow Configuration

Flow

FilterCake

Filtrate

RecycleStream

Membrane

CROSSFLOW FILTRATIONCROSSFLOW FILTRATION

•• CAKECAKE--LAYER DOES NOT BUILD LAYER DOES NOT BUILD INDEFINITELYINDEFINITELY

•• HIGH FLUXES MAINTAINED OVER HIGH FLUXES MAINTAINED OVER PROLONGED TIME PERIODSPROLONGED TIME PERIODS

•• EFFECTIVE IN CONTROLLING EFFECTIVE IN CONTROLLING CONCENTRATIONCONCENTRATION--POLARIZATION ANDPOLARIZATION ANDASSOCIATED CAKE BUILD UPASSOCIATED CAKE BUILD UP

Membrane GeometryMembrane Geometry

4. Spiral Wound Module4. Spiral Wound Module

3. Hollow Fiber 3. Hollow Fiber ModuleModule

2. Tubular 2. Tubular ModuleModule

1. Sheet Module1. Sheet Module

Sheet Sheet ModuleModule

Tubular ModuleTubular Module

PermeatePermeate

FeedFeed

ConcentrateConcentrate

Tubular ModuleTubular Module

Tubular Membranes (OD > 3 mm)Tubular Membranes (OD > 3 mm)

Mostly used in Industrial MF

Membranes ClassificationMembranes Classification(Configuration)(Configuration)

Ultrafiltration Membranes

Hollow fiber UF Membrane—Inside-out Hollow fiber UF Membrane—Outside-in

Hollow Fiber Hollow Fiber ModuleModule

Hollow Fiber MembranesHollow Fiber Membranes

Hollow Fiber Membranes (ID < 1.5 mm)Hollow Fiber Membranes (ID < 1.5 mm)

Membranes ClassificationMembranes Classification(Configuration)(Configuration)

Mostly used in MF & UF

Hollow Fiber Membrane

Feed

Filtrate

Concentrate

Hollow Fiber Flow Patterns

Feed

Feed

Feed

INSIDE - OUT

OUTSIDE - IN

Hollow Fiber Module : Hydracap for UF (Hydranautics)

Hydrophilic Polyethersulfone

Lumen (Feed Side)

Filtrate

Concentrate

Spiral Wound Spiral Wound ModuleModule

BRINE SPACERBRINE SPACER

PRODUCT WATER

PRODUCT WATER SIDE BACKING WITH MEMBRANES

ON EACH SIDE

Spiral Wound Membranes

Flat Sheet (SpiralFlat Sheet (Spiral--wound)wound)

Mostly used in Reverse Osmosis & Nanofiltration

Membranes ClassificationMembranes Classification(Configuration)(Configuration)

The Structure

Of

Module

Permeate Pipe

Membrane Body

element cover

membraneinternal spacer

external spacer

perforation

permeate pipe

Raw Water

Permeate

Reverse Osmosis SystemsSystem technology and

operation parameter

Reverse Osmosis SystemsSystem technology and

operation parameter

Osmosis is the natural passage of water through a semi-permeable membrane from a weaker solution to stronger solution, to equalize the chemical potentials in the membrane-seperated solution, Osmotic pressure is the driving force for osmosis to occur.

Reverse Osmosis

Osmosis – Normal flow from low to high concentration

Fresh WaterConcentrated Solution

Osmotic Pressure

Membrane

Reverse Osmosis is the external pressure greater than the osmotic pressure is applied to the solution, causing water to flow against the natural direction through the membrane, thus producing high-quality demineralized water

Reverse Osmosis

Reverse Osmosis – Flow reversed by application of pressure to high concentration solution

Concentrated Solution

Membrane

Fresh Water

Reverse OsmosisReverse Osmosis•• force water through membraneforce water through membrane•• removes many contaminantsremoves many contaminants

OSMOTIC PRESSURE OSMOTIC PRESSURE (π)(π)

THUMB RULE:THUMB RULE:ππ = 1 = 1 psipsi per 100 mg/l TDSper 100 mg/l TDS

Example:Example:Osmotic pressure will be 25.5 Osmotic pressure will be 25.5 psipsi of a of a

solution containing 2550 mg/l TDS.solution containing 2550 mg/l TDS.

OSMOTIC PRESSURE OSMOTIC PRESSURE (π)(π)

ACCURATE CALCULATIONACCURATE CALCULATIONππ = 14.7 * C * R * T= 14.7 * C * R * T

where C = Solution TDS in moles/lwhere C = Solution TDS in moles/lR = Gas constant R = Gas constant

= 0.08206 (= 0.08206 (l.atm/l.atm/ooK.molesK.moles) ) T = Temperature in degree KelvinT = Temperature in degree Kelvin

= (= (ooCC + 273) + 273) ooKK

OSMOTIC PRESSURE OSMOTIC PRESSURE (π)(π)

Example:Example:ππ = 14.7 * C * R * T = 23.76 = 14.7 * C * R * T = 23.76 psipsi

where C = 0.065 moles/l TDSwhere C = 0.065 moles/l TDSR = Gas constant R = Gas constant

= 0.08206 (= 0.08206 (l.atm/l.atm/ooK.molesK.moles) ) T = Temperature in degree KelvinT = Temperature in degree Kelvin

= (30 + 273) = (30 + 273) ooK = 303 K = 303 ooK K

คําจํากดัความตางๆในระบบคําจํากดัความตางๆในระบบ Reverse OsmosisReverse Osmosis

1.1. Feed waterFeed water คือน้ําที่สงเขาระบบคือน้ําที่สงเขาระบบ RO RO เพื่อผลิตน้ําที่ตองการเพื่อผลิตน้ําที่ตองการ

2.2. RO ProductRO Product หรือหรือ Permeate Permeate คือน้ําที่ผานการกรองจากคือน้ําที่ผานการกรองจาก RORO

3.3. RO Reject, Concentrate RO Reject, Concentrate หรอืหรอื BrineBrine คือน้ําที่เหลือจากการกรองคือน้ําที่เหลือจากการกรอง RO RO และมีความเข็มขนของสารละลายและมีความเข็มขนของสารละลาย ( (TDSTDS)) สงูสงู4.4. Recovery RateRecovery Rate คือคือ อัตราสวนเปอรเซ็นตของอัตราสวนเปอรเซ็นตของ RO Product RO Product กบักบั Feed Water Feed Water เชนเชน ระบบระบบ RO RO มีมี Recovery Rate 70 % Recovery Rate 70 % หมายถงึหมายถงึ สงสง Feed Water Feed Water เขาไปเขาไป 100 100 สวนสวน จะไดจะได RO Product 70 RO Product 70 สวนสวน อกีอกี 30 30 สวนสวน

เปนเปน RO RejectRO Reject5.5. Percent Salt RejectionPercent Salt Rejection คือคือ จํานวนเปอรเซ็นตที่จํานวนเปอรเซ็นตที่ RO RO membrane membrane สามารถสกัดเอาสารละลายไวไดสามารถสกัดเอาสารละลายไวได เชนเชน Feed water Feed water มีมี โซเดียมโซเดียม 100 100 สวนสวน ในใน RO Product RO Product มีมี โซเดียมเหลือโซเดียมเหลือ 5 5 สวนสวน ดังนั้นดังนั้น Sodium Sodium rejection rejection มีคามีคา 95 %95 %

6.6. RO Element, RO Module RO Element, RO Module หรือหรือ RO RO CatridgeCatridge คือคือ RO RO membrane membrane ที่ประกอบสําเร็จแลวพรอมที่จะใชงานที่ประกอบสําเร็จแลวพรอมที่จะใชงาน

7.7. Pressure VesselPressure Vessel คือคือ ทอความดนัสําหรบัใสทอความดนัสําหรบัใส RO Element RO Element เพื่อทําเพื่อทํา

การกรองน้ําการกรองน้ํา มขีนาดบรรจุไดตั้งแตมขีนาดบรรจุไดตั้งแต 11 ถึงถึง 77 Elements Elements วัสดุทําดวยวัสดุทําดวย PVC, PVC, Fiber Glass Fiber Glass หรือหรือ Stainless Steel

8.8. StageStage คือคือ จํานวนครั้งที่น้ําไหลผานระบบจํานวนครั้งที่น้ําไหลผานระบบ RORO

-- Single StageSingle Stage หมายถงึหมายถงึ น้ําไหลผานระบบน้ําไหลผานระบบ RO RO ครั้งเดียวครั้งเดียว

ซึ่งอาจจะเปนซึ่งอาจจะเปน BrineBrine--staging staging ซึ่งหมายถึงซึ่งหมายถึง reject reject จากจาก stage stage แรกถูกสงเขาไปในแรกถูกสงเขาไปใน Stage Stage ที่สองที่สอง เพื่อเพิ่มเพื่อเพิ่ม recovery rate recovery rate

หรืออาจจะเปนหรืออาจจะเปน Product staging Product staging ซึ่งหมายถึงซึ่งหมายถึง RO Product RO Product จากจาก StageStage แรกเพื่อขจัดสารละลายเพิ่มขึ้นแรกเพื่อขจัดสารละลายเพิ่มขึ้น

-- Two StageTwo Stage หมายถึงหมายถึง น้ําไหลผานระบบน้ําไหลผานระบบ RO RO สองครั้งสองครั้ง

9.9. ArrayArray หมายถึงหมายถึง จํานวนจํานวน pressure vessel pressure vessel พรอมดวยพรอมดวย RO RO ElementsElements ที่ติดตั้งเปนชดุและมีความสัมพันธกับการที่ติดตั้งเปนชดุและมีความสัมพันธกับการ Staging Staging

ตัวอยางเชนตัวอยางเชน -- Array = 2,0Array = 2,0 หมายถึงหมายถึง RO RO ชุดนี้เปนชุดนี้เปน single stage single stage และมีและมี pressure pressure vesslevessle 2 2 ชดุชดุ-- Array = 3,1Array = 3,1 หมายถึงหมายถึง RO RO ชุดนี้เปนชุดนี้เปน 2 stage 2 stage และมีและมี pressure pressure vesslevessle ในใน stagestage แรกแรก 3 3 ชุดและในชุดและใน stage stage ที่สองที่สอง 1 1 ชุดชุด-- Array = 3,2,1Array = 3,2,1 หมายถงึหมายถงึ RO RO ชุดนีม้ีชุดนีม้ี 3 stage3 stage

10.10. RORO BankBank หมายถึงหมายถึง ชุดของชุดของ RO Pressure Vessels RO Pressure Vessels ถูกจัดมาถูกจัดมา

รวมกลุมกันและติดตั้งอยูในโครงรองรับรวมกลุมกันและติดตั้งอยูในโครงรองรับ (Supporting Frame) (Supporting Frame) เดียวกันเดียวกัน เชนเชน Array 3,1 Array 3,1 จะถูกติดตั้งอยูในจะถูกติดตั้งอยูใน Bank Bank เดียวกันเดียวกัน

11.11. CleanClean--InIn--Place (CIP)Place (CIP) คือคือ ระบบสําหรับลางทําความสะอาดระบบสําหรับลางทําความสะอาด RO RO Elements Elements ซึ่งอาจจะติดตั้งอยูกับที่ติดตั้งระบบซึ่งอาจจะติดตั้งอยูกับที่ติดตั้งระบบ RO RO หรืออาจเปนระบบลอเลื่อนหรืออาจเปนระบบลอเลื่อน

เข็นเขามาใชเมื่อตองการทําความสะอาดเข็นเขามาใชเมื่อตองการทําความสะอาด

Membrane Performance and Properties

Described Mathematically:

– Water Flux = Water Perm x (Membrane ΔP – Osmotic ΔP)

– Mineral Flux = Mineral Perm x (Conc Gradient across membrane)

Water and Mineral Permeability constants are characteristics of the particular membrane

Definition of Flux

Rate of water flow through a membrane– Gallons per sq ft per day (GFD)– Grams per second per sq centimeter (gm/cm-sec)

Average flux rate determines cleaning frequency of the membrane.

Feedwater Source Flux Rate, GFDIndustrial/Municipal Waste 8 – 12Surface Water 8 – 14Well 14 - 20

Calculate Flux Rate

The permeate flow through an arrangement (or array) of RO membrane pressure vessels is 1,330,000 gallons per day.

Feedwater first flows to 33 vessels operating in parallel. The concentrate from the 33 first-pass vessels is combined and sent to a set of 11 second-pass vessels.

Each element (or tube) contains six membrane elements. Each element is 8 inches in diameter and 40 inches long, thus providing 325 sq ft of membrane surface area per element.

Calculate the average membrane flux rate for the system in gallons per day per sq foot (GFD).

Calculate Flux Rate

KnownPermeate Flow, GPD 1,330,000

No. of Vessels 44 (33 + 11)

No of Elements 6

Membrane Area per 325 Element, sq ft

UnknownAverage Flux Rate, GFD

Calculate Flux Rate

1. Determine total membrane area in the system.

Membrane = No. of x No. of x Surf AreaArea, Sq Ft Vessels Elements per Element

= (44 Vessels) x (6 elements) x (325 ft3/element)

= 85,800 Ft3

Calculate Flux Rate

2. Calculate average membrane flux rate for system

Avg Flux = Permeate Flow, GPDRate, GFD Membrane Area, Sq Ft

= 1,330,000 GPD85,800 sq Ft

= 15.5 GFD

What means Recovery ?

Recovery = permeat flow [m3/h]raw water flow [m3/h]

x 100 %

Recovery

A measure of the efficiency of the membrane to produce clean water.

Recovery, % = Product Flow x 100%Feed Flow

Recovery rates limited by two factors:

1. Desired product water quality

2. Solubility of minerals in the brine

Recovery = premeate flow in relation toraw water flow

R

K

P

25% drain to waste

75% permeate100% raw water

concentrate recycling

What means salt passage ?

Salt passage (%) = Permeat salt concentration x 100Feed salt concentration

Salt rejection (%) = 100 – Salt passage

Mineral Rejection

Mineral rejection is the measure of the membrane’s ability to remove minerals from the water.

Rejection, % = 1 - Product ConcentrationFeedwater Concentration

X 100%

Effects of Feedwater Temperature and pH on Membrane Performance

Flux rates decrease as temperature decreases. (Very steep curve! Flux rates reported based on standard reference temperature (example: 25°C)

Hydrolysis accelerated by increase in temperature for CA membranes (not a problem with thin film membranes). (Mineral rejection capacity decreases as temperature increases)

Slightly acid conditions reduce rate of hydrolysis.

Membrane Design Membrane Design การออกแบบควรพิจารณาหลกัเกณฑดงันี้การออกแบบควรพิจารณาหลกัเกณฑดงันี้

1. Membrane Filtration Flux

2. Water Temperature < 45 oC

Water Temperature↓ water viscosity↑ membrane filtration flux ↓

Water Temperature ↑ water viscosity ↓ membrane filtration flux ↑

3. Transmembrane Pressure Difference

membrane filtration flux ↑ Transmembrane Pressure Difference ↑

membrane filtration flux ↓ Transmembrane Pressure Difference ↓

0.5 – 1 m3/d.m2 per membrane pressure difference(98.1 kpa)

4. Recovery

5. Water Quality input

เฉพาะเมมเบรนทีท่ําจากเฉพาะเมมเบรนทีท่ําจาก Cellulose AcetateCellulose Acetate (CA)(CA) และและ Cellulose Triacetate (CTA)Cellulose Triacetate (CTA)

85%85%

75%75%

50%50%

10%10%

L/mL/m22.hr.hr

SDIWhat is the SDI (Silt Density Index or fouling index) ?The SDI is the best parameter to determine colloidal fouling potential of RO feed water. Colloidal matter in general means that the substance is not dissolved but also not really suspended as such. These substances can seriously impair the performance of the RO unit by lowering productivity and sometimes salt rejection.

The source of colloidal fouling is varied and often includes bacteria, clay, colloidal silica, organics and iron corrosion products. Additionally, pre-treatment chemicals used in a clarifier such as alum, ferric chloride or cationic polyelectrolytes can also cause colloidal fouling if not removed properly prior to the RO.

The general worlwide rule is that reliable operation of an RO system can only be granted at SDI < 3

SDI

SDIHow is SDI measured ?First of all a special measuring device consisting of ball valve, pressure regulator, pressure gauge and filter holder incl. 0.45µm pore filterpaper(see figure 1) plus a 500ml measuring cylinder and a stop watch is needed.

The measurement can then be taken as following:- Connect this device to the feed water pressure line.- Place the filterpaper on the filter holder and bleed water pressure on- Adjust feed pressure to 2.1 bar (30 psi) and measure initial time t0necessary to filter 500ml of sample water (keep feed pressure constantat 2.1 bar all times)

- Keep filter in operation for 15 minutes under 2.1 bar (30 psi) feedpressure, discharge the filtered water

- After 15 minutes measure again time t1 necessary to filter 500ml.- The SDI can then be calculated: SDI = [1-t0/t1] x 100/15

Silt Density Index Silt Density Index

Direct SDI - Complete, Portable and Affordable SDI Measurement

Filters for Direct SDI (SDI-1000)

EZ & Enhanced Automatic SDI Monitors Spare Parts for Y-EZSDI, Y-EZSDIC, & Y-ENHSDI

SIMPLE SDI Kit

Test Kits and Meters

Chlorine Test Kit pH Tester

Main parameters causing problems in the feed water of the RO are:

CaF2, BaSO4, CaCO3, SrSO4, CaSO4increasing solubility

Softening or antiscalant dosing has to be applied to prevent scalingof these sparingly soluble salts onto the membranes. The most common problem is scaling by CaCO3. The parameter to judge whether CaCO3 will precipitate on the membranes is the so called LSI (Langelier saturation index): LSI = log [Ca2+] x [CO32-](L = solubility product) L

Permissible values of LSI:LSI ≤ -0.2 without any scale inhibitorLSI ≤ 0.5 with sodium hexametaphosphateLSI ≤ 1.8 with organic scale inhibitor

ขอควรตระหนกัเกี่ยวกับเงื่อนไขการติดตั้งระบบขอควรตระหนกัเกี่ยวกับเงื่อนไขการติดตั้งระบบ

1. คุณภาพน้ําดิบ หากไมนับสวนสารตกตะกอน และเชื้อราตางๆ ตองมีคุณสมบัติเหมาะที่จะเปนน้ําประปา

2. เปนจุดทีม่ีไฟฟา3. อยูในตําแหนงที่เหมาะสมตอการจายน้ําไปยังจุดทีม่ีความตองการรับน้ํา4. พื้นทีด่ินมีความมัน่คง5. เปนสถานทีท่ี่สามารถควบคุมสุขลกัษณะได6. มีพื้นที่เหลอืเพียงพอในการดําเนินการติดตั้ง ตรวจเช็คหรือเปลีย่น membrane module

7. การจัดตําแหนงของอุปกรณเอื้ออํานวยตอการทํางานของระบบ8. สามารถปลอยน้ําออกสูธรรมชาติได9. มีอุบตัิภัยทางธรรมชาติ เชน อทุกภัย ฟาผา เกิดขึ้นยาก

1.1. Pre TreatmentPre Treatment

2.2. Pre DisinfectionPre Disinfection

3.3. DeDe--chlorinationchlorination

5.5. Anti Anti –– ScalingScaling SystemSystem

4.4. pH AdjustmentpH Adjustment

6.6. Cartridge FilterCartridge Filter

7.7. RO RO –– Feed PumpFeed Pump

ระบบระบบ Reverse OsmosisReverse Osmosis และสวนประกอบและสวนประกอบ

8.8. RO Module & Pressure VesselRO Module & Pressure Vessel

9.9. Frame Structure and SkidFrame Structure and Skid--MountMount

10.10. RO Product StorageRO Product Storage

11.11. CIP SystemCIP System

12.12. RO PipingRO Piping

13.13. Accessory :Accessory : Flow meter, Back Pressure Valve, Flow meter, Back Pressure Valve, Pressure Gauge, TDS Meter, Conductivity Meter, Pressure Gauge, TDS Meter, Conductivity Meter, Temperature meterTemperature meter

ระบบระบบ Reverse OsmosisReverse Osmosis และสวนประกอบและสวนประกอบ

MEMBRANE PROCESSMEMBRANE PROCESS

FEEDFEED PERMEATEPERMEATE

CONCENTRATECONCENTRATE

Christmas Tree ArrangementChristmas Tree Arrangement

Vessel 1

Vessel 2

Vessel 3

Vessel 4

Vessel 5

Vessel 6

Vessel 7Brine to Waste

Feedwater

Product Water

Membrane Filtration Enhancements

Organic + CoagulantMatter

Ferrous + Oxidant

Hydrogen + OxidantSulfide

Organic + PACCompounds

MembraneFiltration

ParticleRemoval

TreatedWater

Pre - TreatmentPre Pre -- TreatmentTreatment RO ProcessRO ProcessRO Process

PretreatmentPretreatment

Purpose:– Remove turbidity/suspended solids

– Adjust pH and temperature

– Remove materials to prevent scaling or fouling

– Disinfect to prevent biological growth

RO Pretreatment RO Pretreatment -- WhyWhy

Feed water limiting conditions Feed water limiting conditions •• SDI less than 5SDI less than 5•• Turbidity less than 1 NTUTurbidity less than 1 NTU•• Temp. less than 45 deg CTemp. less than 45 deg C•• Bacteria and organics nilBacteria and organics nil•• Oil & Grease nilOil & Grease nil•• Free chlorine nilFree chlorine nil•• Fe, Fe, MnMn less than 0.1 mg/lless than 0.1 mg/l•• Al less than 0.1 mg/lAl less than 0.1 mg/l

Components of a Reverse Osmosis Unit

Membrane Filtration Process

Membrane

Re - CycleStrainer

Cleaning Tank

Waste

Filtrate

Feed

Backwash

Christmas Tree Arrangement

Membrane StagingMembrane Staging

SINGLE STAGESINGLE STAGE

Feed PermeateConcentrate

PARALLELPARALLEL STAGESTAGE

Feed Permeate

Concentrate

FeedConcentrate

DOUBLE STAGEDOUBLE STAGE

Concentrate

Permeate

Permeate

Membrane Filtration Process

2 Racks with each 12 dizzer 5000 modules(Capacity of 238 GPM per rack)

Filtrate storage tank

Feed buffer tank

Residential Components

1. PVC Pressure Vessels Max pressure 200 psi

2. Stainless Steel Pressure Vessels Max pressure 400 psi

3. Fiberglass Pressure Vessels Max pressure 400 - 1500 psi

Pressure VesselsPressure Vessels

UF or MF Performance

Physical BarrierRemoves ParticlesPhysical Disinfection

Reliable PerformanceAutomated OperationConsistent Performance

DESIGNDESIGN

CHARACTERISTICCHARACTERISTIC SpiralSpiral--WoundWound

Hollow FibersHollow Fibers TubularTubular Plate & FramePlate & Frame

CostCost LowLow LowLow HighHigh HighHigh

Packing DensityPacking Density HighHigh UFUF--HighHighRO Very HighRO Very High

LowLow ModerateModerate

Pressure CapabilityPressure Capability HighHigh UF-LowRORO--HighHigh

UF-LowRO-Medium

HighHigh

Membrane PolymerMembrane PolymerChoicesChoices

ManyMany FewFew FewFew ManyMany

Fouling ResistanceFouling Resistance FairFair UFUF--GoodGoodRORO--PoorPoor

Very GoodVery Good Fair

Clean abilityClean ability GoodGood UFUF--Very GoodVery GoodRORO--PoorPoor

Very Good GoodGood

RO NF UF MF

Advantages It can removal ions. Salt in high removal efficiency

It can removal of required organics, bacteria or viruses, and provides salt rejection from 50% to 90%

It can treat ground water ,separate selected component from mixed solution, low pressure .Pretreat influent before RO or NF

It can separate selected component Relative long life Pretreatinfluent before UFLow operation pressure.low cost

Disadvantages High cost ,short using life Backwash frequently ,fouling problem

Cost relative lower than RO, fouling problem, short using life

Middle costClog problemShort using life

Clog problemit can’t remove small

particles

Applied areas Semi conducting Pure water plantIon recovery in industry wastewater

Concentrate and partially demineralize liquid whey . Partial ion recovery

Water and waste water treatment . wildly applied in food, pharmaceutical chemical industries

Food industry PharmaceuticalChemicals separation and recovery as well as concentration of hazardous waste from wastewater. Oil removal.

Small System Operator

Good Operators

are BORED with their

work

Microfiltration (MF) System

24 Module HYDRABLOC

Industrial InstallationUltrafiltration (UF) SystemUltrafiltration (UF) SystemUltrafiltration (UF) System

Ultrafiltration (UF) SystemUltrafiltration (UF) System

Hydranautics has been a world leader Hydranautics has been a world leader in custom engineered RO systemsin custom engineered RO systems

Reverse Osmosis

6 MGD Facility500 gpd Facility

1. AMI Membranes

2. Replacement Membranes

3. Hydranautics Membranes

4. Koch Membranes

5. FilmTec (DOW) Membranes

6. Retrofit FilmTec Membranes for DuPont Permeators

7. Toray Membranes

MembranesMembranes Market Market

Market Share by MakerMarket Share by Maker

Sea Water RO membrane market SizeSea Water RO membrane market Size

0

50

100

150

200

250

1986

1990

1997

1998

1999

2000

2001

2002

2003

FILMTEC34%

HYDRAN-AUTICS

22%

FLUIDSYSTEM

15%

OTHERS29%

Unit:MilU$

Year

Yearly Marlet Size

Reference: “The 1998 Guide to the US Membrane Industry”(Desalination Sea Water TFC Membrane Market)

CSM SW membrane

Growth of the IndustryGrowth of the IndustryNorth American MF/UF Installations - Drinking Water

0

50

100

150

200

250

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Year

Num

ber o

f Fac

ilitie

s

Growth of the IndustryGrowth of the IndustryNorth American MF/UF Installations - Drinking Water

0

100

200

300

400

500

600

700

800

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Year

Cum

ulat

ive

Cap

acity

(mgd

)

Desalination Is Growing As WellDesalination Is Growing As Well

SWROSWRO

BWROBWRO

EDREDR

BWROBWRO

SWROSWROEDREDRBWNFBWNF

25020 15 71110

9244110BWNFBWNF

Number of Installations Capacity (mgd)

Specification comparison of Sea Water ROSpecification comparison of Sea Water RO

Rejection(%) Flux(GPD) Surface Area(ft2)

RE-8040SN 99.2 6200 330

RE-8040SR 99.6 6000 380

HSR(Development) 99.8 5200 380

Model

SW30-8040 99.1 6000 300

SU820 99.75 4000 295

(Filmtec)

SW30HR-380 99.6 6000 380

SWC3 99.6 5900 370

SWC4 99.8 5200 370

SU820FA 99.75 5000 335

CSM SW membrane

SystemSystemTransmembrane Transmembrane

Pressure Operating Pressure Operating Range (Range (psipsi))

Feed Water TDS Feed Water TDS Range (mg/l)Range (mg/l) Recovery Rates (%)Recovery Rates (%)

Sea WaterSea Water 800 800 –– 1,5001,500 10,000 10,000 –– 50,00050,000 15 15 –– 5555

Standard PressureStandard Pressure 400 400 -- 650650 3,500 3,500 –– 10,00010,000 50 50 –– 8585Low PressureLow Pressure 200 200 -- 300300 500 500 –– 3,5003,500 50 50 –– 8585NanofiltrationNanofiltration 45 45 -- 150150 Up to 500Up to 500 75 75 -- 9090

Source : AWWA, 1990, Water Quality and Treatment

General process of Sea Water desalination by RO membraneGeneral process of Sea Water desalination by RO membrane

CSM SW membrane

CSM SW membrane

OPERATING PARAMETERSOPERATING PARAMETERS

pHpH

pHpHpH

CCC

CC

PPP

PP

FF

FFF

TT

P

FEEDFEED

PERMEATEPERMEATE

REJECTREJECT

RecoveryRecoveryConcentration FactorConcentration FactorSalt PassageSalt PassageSalt RejectionSalt RejectionDifferential Differential PresurePresure

OPERATING PARAMETERSOPERATING PARAMETERS

PERFORMANCE PROBLEMSPERFORMANCE PROBLEMS

SCALINGSCALINGFOULINGFOULINGCHEMICAL ATTACKCHEMICAL ATTACKPREMATURE MEMBRANE PREMATURE MEMBRANE REPLACEMENTREPLACEMENTINEFFECTIVE CLEANINGINEFFECTIVE CLEANING

Symptoms of FoulingSymptoms of Fouling

Higher than Design Differential PressureHigher than Design Differential PressureHigher than Design Feed PressureHigher than Design Feed PressureLower than Projected FluxLower than Projected FluxLower than Projected RejectionLower than Projected Rejection

FoulantsFoulants :: Plugging or deposition or bonding of dissolved/suspended matter on the membrane surface. It typically occurs at the front end of each pressure vessel when the feed enters the membrane.

Scaling :Scaling : The precipitation of sparingly soluble salts within the feed side of the membrane. It typically occurs at the end of each pressure vessel where concentration is greatest

General Rule of TroubleshootingGeneral Rule of Troubleshooting

First Stage Problem First Stage Problem -- FoulingFoulingLast Stage Problem Last Stage Problem -- ScalingScaling

Membrane Blocking

FoulingFouling ScalingScaling

Biological Fouling

- Bacteria

- Algae

- Fungi

Suspended Particle

-Colloidal

-Organic Material

- CaCO3

- CaSO4

- BaSO4

- Silica or Silicate

Fouling and Scaling

Membrane Fouling MechanismsMembrane Fouling Mechanisms

Organic & InorganicOrganic & InorganicParticulate & SolubleParticulate & SolubleVarious MechanismsVarious Mechanisms

Surface & PoreSurface & PoreAdsorption, precipitation, coagulationAdsorption, precipitation, coagulation

Membrane FoulingMembrane Fouling

Membrane PerformanceMembrane Performance

TMP

More

Fouli

ng

Fouling is Part of MembranesFouling is Part of Membranes

All membranes are subject to fouling, no All membranes are subject to fouling, no exceptionexceptionFouling is acceptable as long as it is Fouling is acceptable as long as it is reversible and manageable (i.e., can be reversible and manageable (i.e., can be removed in a reasonable fashion) removed in a reasonable fashion)

Potential Fouling MaterialPotential Fouling MaterialNatural Organic MatterNatural Organic Matter

NOM with high SUVA NOM with high SUVA TOC > 4 mg/L would be a concernTOC > 4 mg/L would be a concernOrganic fouling is Organic fouling is ““stickysticky”” and difficult to cleanand difficult to cleanOrganic may serve as Organic may serve as ““cementcement”” to bind other to bind other particulates and form a strong cake layerparticulates and form a strong cake layerCaustic cleaning (e.g. NaOH) and strong Caustic cleaning (e.g. NaOH) and strong oxidant (e.g. Hoxidant (e.g. H22OO22) are effective for NOM ) are effective for NOM fouling cleaningfouling cleaning

Potential Fouling MaterialPotential Fouling MaterialParticulate/ColloidsParticulate/Colloids

Inorganic particles alone would not cause much Inorganic particles alone would not cause much foulingfoulingInorganic particle cake layer could be easily Inorganic particle cake layer could be easily removed by backwashremoved by backwashExcessive turbidity could clog membrane fiber Excessive turbidity could clog membrane fiber lumenslumensInorganic particles mixed with NOM could cause Inorganic particles mixed with NOM could cause substantial foulingsubstantial foulingOrganic colloids could cause significant fouling Organic colloids could cause significant fouling and could be difficult to cleanand could be difficult to clean

Potential Fouling MaterialPotential Fouling MaterialInorganic MaterialInorganic Material

Precipitation of Ca, Mn, Mg, Fe, and Al Precipitation of Ca, Mn, Mg, Fe, and Al could cause significant foulingcould cause significant foulingFine inorganic colloids (< 0.05 Fine inorganic colloids (< 0.05 μμm) could m) could clog membrane pores and cause fouling clog membrane pores and cause fouling Prefer a negative Prefer a negative LangelierLangelier Index Index Acid, EDTA, SBS cleaning could be Acid, EDTA, SBS cleaning could be effective for inorganic foulingeffective for inorganic fouling

Langelier Index = Actual pH – Saturation pHSaturation pH = 2.18 - log[Ca+2] - log[HCO3

-]L.I. > 0 : Oversaturated (tend to precipitate)L.I. < 0 : Undersaturated (tend to dissolve more)

Potential Fouling MaterialPotential Fouling MaterialSynthetic PolymersSynthetic Polymers

Polymers used for coagulant/filter aids & Polymers used for coagulant/filter aids & backwash water treatmentbackwash water treatmentPresence of polymers in feed water could cause Presence of polymers in feed water could cause dramatic fouling, and sometimes irreversibledramatic fouling, and sometimes irreversibleFree residual polymer is worse than particleFree residual polymer is worse than particle--associated polymerassociated polymerCationic polymers are worstCationic polymers are worstSome polymers can be easily cleaned with Some polymers can be easily cleaned with chlorine and therefore are consider compatible chlorine and therefore are consider compatible with membraneswith membranes

Fouling MitigationFouling MitigationPretreatmentPretreatment

Reduce TOC level (< 4 mg/L)Reduce TOC level (< 4 mg/L)Reduce Turbidity (< 5 NTU)Reduce Turbidity (< 5 NTU)Reduce Hardness (< 150 mg/L)Reduce Hardness (< 150 mg/L)Avoid substantial change in water Avoid substantial change in water chemistry, such as pH and other chemistry, such as pH and other pretreatment chemicalspretreatment chemicalsPrevent Oil and Polymers from entering Prevent Oil and Polymers from entering the feed waterthe feed water

Fouling MitigationFouling MitigationOperationOperation

Use Use crossflowcrossflow if turbidity is high (For if turbidity is high (For InsideInside--out membranes)out membranes)Bleed a portion of the concentrate to Bleed a portion of the concentrate to avoid solid buildupavoid solid buildupOperate at a lower flux (lower TMP)Operate at a lower flux (lower TMP)Enhance pretreatmentEnhance pretreatment

Fouling MitigationFouling MitigationCleaning StrategyCleaning Strategy

1.1. Frequent BW (shorter filtration cycle)Frequent BW (shorter filtration cycle)2.2. Longer BW durationLonger BW duration3.3. Higher BW pressure Higher BW pressure 4.4. Add cleaning chemicals in BW waterAdd cleaning chemicals in BW water5.5. Frequent chemical cleaningFrequent chemical cleaning

Colloidal

Common Foulants Common Foulants -- 11

Cleaning frequency is directly related to the Cleaning frequency is directly related to the feedwater quality specifically colloidal feedwater quality specifically colloidal particles and organic materialparticles and organic materialCan be controlled by pretreatment process Can be controlled by pretreatment process selection and may be assisted by the selection and may be assisted by the application of application of antiscalantsantiscalants with dispersing with dispersing propertiesproperties

Biological

Common Foulants Common Foulants -- 22

Causes high differential pressuresCauses high differential pressuresReduces turbulent flow through the feed Reduces turbulent flow through the feed spacers and traps colloidal particlesspacers and traps colloidal particles

Causes

Membrane BiofoulingMembrane Biofouling

High Bioactivity level in feedwaterHigh Bioactivity level in feedwaterIneffective PretreatmentIneffective PretreatmentIntermittent System Operation Intermittent System Operation Ineffective Cleaning Ineffective Cleaning ProgrammeProgramme

Chemical Fouling

Common Foulants Common Foulants -- 33

Often causes reduction in flux and Often causes reduction in flux and increase in rejection characteristics of the increase in rejection characteristics of the membranemembraneTypically associated with the use of Typically associated with the use of Cationic and Anionic materials or Cationic and Anionic materials or filming materials such as oils or greasesfilming materials such as oils or greases

Causes

Chemical FoulingChemical Fouling

Overdosing of Pretreatment CoagulantsOverdosing of Pretreatment CoagulantsIncompatible Chemicals being SelectedIncompatible Chemicals being SelectedContamination of Chemicals Contamination of Chemicals Inappropriate Cleaning MaterialsInappropriate Cleaning MaterialsContamination of feed sourceContamination of feed source

Common ScalingCommon Scaling

Causes high differential pressures and Causes high differential pressures and reduces turbulent flow through the feed reduces turbulent flow through the feed spacersspacersCan affect rejection characteristics of Can affect rejection characteristics of thin film composite membranes and thin film composite membranes and reduce flux reduce flux During cleaning deposits may cause During cleaning deposits may cause abrasion of membrane surfacesabrasion of membrane surfaces

Inorganic Scale

Inorganic Scale FormationInorganic Scale Formation

High Alkalinity and High SilicaHigh Alkalinity and High SilicaHigh Hardness or Metal Oxide ContentHigh Hardness or Metal Oxide ContentHigh pHHigh pHHigh RecoveryHigh RecoveryDosing System FailureDosing System FailureIncorrect Pretreatment ChemicalsIncorrect Pretreatment Chemicals

Causes

Causes

Membrane DamageMembrane Damage

Incomplete Removal of OxidantsIncomplete Removal of OxidantsExposure to Extreme pH/TemperaturesExposure to Extreme pH/TemperaturesInappropriate Chemical SelectionInappropriate Chemical SelectionSurface AbrasionSurface AbrasionExcessive Cleaning FrequencyExcessive Cleaning Frequency

Troubleshooting Guide 1Troubleshooting Guide 1

Permeateflow

Saltpassage

Differentialpressure

Direct cause Indirectcause

Oxidationdamage

Chlorineozone

CorrectivemeasureReplaceelement

Membraneleak

PermeateBackpressureOr Abrasion

ReplaceElementImprovefiltration

“O” Ringleak

ImproperInstallation

Replace“O” Ring

LeakingProductTube

Damagedduringloading

Replaceelement

PermeateFlow

Saltpassage

DifferentialPressure

DirectCause

Indirectcause

Correctivemeasure

Scaling InsufficientScalecontrol

CleaningScale control

ColloidalFouling

Insufficientpretreatment

CleaningImprovepretreatment

Biofouling ContaminatedRaw water

Cleaning &disinfectionImprovepretreatment

Troubleshooting Guide 2Troubleshooting Guide 2

Permeateflow

Saltpassage

Differentialpressure

DirectCause

IndirectCause

Correctivemeasure

Organicfouling

Oil/GreasesHMWPolymers

CleaningImprovepretreatment

Compaction Waterhammer

Replaceelement orAddelements

Troubleshooting Guide 3 Troubleshooting Guide 3

Taking the Total System Taking the Total System ApproachApproach

Troubleshooting StepsTroubleshooting Steps-- InvestigateInvestigate-- EvaluateEvaluate-- SolveSolve-- PreventPrevent

Membrane Cleaning

Membrane Cleaning• Hydraulic Cleaning (10~30 minutes)

– Water/Air Backwash– Air Scouring– Water Flushing

• Chemical Cleaning (1~8 weeks)– Free Chlorine (Sodium Hypochlorite)– Acid/Base– Other strong oxidants, such as H2O2

– Reducing agent, such as SBS– Chelating chemicals, such as EDTA– Proprietary Chemicals (surfactants)

Summary of Fouling Material & Cleaning Chemicals

Cleaning Chemical For Fouling Material

NaOCl Biological; NOM; Synthetic polymers

Acids (HCl, H2SO4, Citric Acid) Inorganic deposits

NaOH NOM

Sodium bi-sulfite (SBS) Reducible metals (Fe, Mn)

H2O2 NOM

EDTA Metals

Membrane Cleaning

Periodic cleaning is included in the design

Cleaning is performed:– To keep operating pressures low

– To keep flux rates up

– To keep salt removal rates up

Typically, cleaning solution is pumped into pressure vessels and returned to solution tanks at the end of the process (about 1 hr)

Various types of cleaning solutions are used depending on type of fouling that occurs.

Safety

Chemicals routinely used in RO systems:– Acid

– Chlorine

– Sodium hexametaphosphate

– Formaldehyde

– Citric acid

– Numerous cleaning agents

Electrodialysis (ED)

Typically for brackish water applications

Advantages:– Proven technology

– Efficient removal of inorganic constituents

– Waste brine contains only salts removed plus acid used for pH control.

Energy required for process is 0.2 – 0.4 kWh/1000 gals

Electrodialysis (ED)

Electrodialysis (ED)

Common Problems– Scaling or fouling

– Precipitation of magnesium hydroxide or calcium carbonate

This may cause increased electrical resistance and damage the membranes

Acid is usually fed to ensure scale-free operation

Electrodialysis Reversal (EDR)

Electrodialysis Reversal (EDR)

Electrodialysis (ED)

Electrodialysis (ED)

Math Assignment

Read and work the problems in Section A.34 Demineralization.

Conclusion• Today membrane technology is widely used in mixture separation, pollution

control, exhaust gas treatment, water treatment, wastewater treatment, pure water generation etc. The main challenging of industrial use membrane is the membrane price and the membrane clogging problems.

• The selective of different type of membrane for a typical design is base on target material to be removed and the characteristic of the membrane. These will affect the removal efficiency, effluent quality, back washing, chemical treatment, capital and operating cost. In the industrial utility of membrane, normally different types of membranes are intergraded. For example, in the water treatment plant, MF can be used to remove fine partial first, UF can be used as partially deification, and then NF and RO can be used to remove ions. This can improve efficiency of the whole system; increase the solid loading rate, hydraulic loading rate

uestuestionsions ??