Mbr Design

Kubota Submerged Membrane Units 【 Design 】

November, 2009

Kubota Corporation 1

1.Outline of Kubota Membrane Unit

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Conventional Process - Membrane Process Recycle Screen, GC

Primary Clarifier

Deni

Sedimenatio n

Nitri

SF

UV

Influent

Conventional Process RAS

Membrane Process

Influent

Recycle

Excess Sludge

Effluent

Screen GC Excess Sludge Deni

Nitri

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Kubota MBR Process • Development since the late 1980’s • First Plant Operation in 1991 • First Overseas Plant Operation in Feb.,1998 in UK (Porlock WwTW) • Now More Than 3,500 Plants in Operation and Under Construction

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Concept of Kubota MBR • • • • • •

Suitable for Wastewater Treatment Submersible Membrane in Tank Flat Sheet Membrane Easy Operation and Maintenance Small Footprint Stable and High Quality Treated Water

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Structure of Kubota SMU Manifold

Tube Membrane case Membrane cartridge

Diffuser case Diffuser

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Structure of Kubota SMU

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Kubota SMU Upper membrane case Lower membrane case

Membrane case Diffuser case

Single deck unit

Diffuser

Double deck unit 8

Installation Example

Double Deck

Single Deck

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2.Design of Membrane Tank

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System of Tank 1 oxic tank

Membrane

2 oxic tanks

One tank

additional

1 anoxic 1 oxic (for denitrification)

1 anoxic 2 oxic (for denitrification) additional 11

Layout of Units in Tank

×

Same type of units

○

× Same number of units in tanks

12

A

Height of membrane unit + 500 (min.)

650

1000

1000

650

B

C=(1000 to 1300) x n + 300  

Unit: mm A (Opening length)

B (Tank width)

C (Tank length)

FS50

1100 ～ B

More than1300

(1000~1300) n+300

ES75, FS75

1450 ～ B

More than 1800

(1000~1300) n+300

ES100

1800 ～ B

More than 2300

(1000~1300) n+300

ES125

2150 ～ B

More than 2800

(1000~1300) n+300

ES150, EK300

2500 ～ B

More than 3300

(1000~1300) n+300

ES200, EK400

3200 ～ B

More than 4300

(1000~1300) n+300

n = Nos.of Membrane Unit

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(mm)

Intermediate Case

3000 2000

Membrane Case

1000

1000

Membrane Case

Diffuser Case

Diffuser Case EK EK Model Model

Double Deck Unit

ES ES Model Model

FS FS Model Model

Single Deck Unit

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Min. Effective Sludge Level for Type of Units

Type

WL

≧500 HM

H

HM

H

EK

3,500

4,000

ES

2,000

2,500

FS

1,500

2,000

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Piping of Membrane Units Air Supply Inlet Header (Hi) Air Supply Inlet Side (Ai)

Permeate Header (Hw) Air Supply Outlet Header (Ho) Permeate Connection (W)

Air Supply Outlet Side (Ao)

Diffuser Connection (Ad)

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Design of Header Pipe Permeate header pipe Number of Units

ES150

ES200

EK300

EK400

2

φ65

φ80

φ65×2

φ80×2

3

φ80

φ100

φ80×2

φ100× 2

4

φ100

φ125

φ100× 2

φ125× 2

5

φ100

φ125

φ100× 2

φ125× 2

6

φ125

φ150

φ125× 2

φ150× 2

7

φ125

φ150

φ125× 2

φ150× 2

8

φ125

φ200

φ125× 2

φ200× 2

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Design of Header Pipe Air header pipe

Number of Units

ES150 ・ ES200 ・ EK300

EK400

Supply side

Diffuser cleaning

Supply side

Diffuser cleaning

2

φ80

φ65

φ80

φ80

3

φ100

φ80

φ100

φ100

4

φ125

φ100

φ125

φ125

5

φ125

φ100

φ125

φ125

6

φ150

φ125

φ150

φ150

7

φ150

φ125

φ150

φ150

8

φ200

φ125

φ200

φ200

9

φ200

φ150

φ200

φ200

10

φ200

φ150

φ200

φ200 18

Membrane Tank Section Reference Elbow

Diffuser cleaning valve Diffuser cleaning header

Diffuser cleaning header

Chemical cleaning port

Permeate header Air supply header

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3.Process Flow

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Example BOD Treating Flow

BOD 5mg/L pH 5.8 – 8.6

Flowrate 　 30m3/d BOD 300mg/L T-N 20mg/L T-P 3mg/L N-Hex 50mg/L pH 5.8 – 8.6

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Example High BOD Treating Flow

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4. Design Reference for Industrial wastewater Treatment BOD Treatment 　　

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Design Conditions ・ ・ ・ ・ ・

Type of wastewater 　 ： Food processing/Lunch box Flowrate ：　 300m3/d Influent duration ： 10 hours Treating time ： 24 hours Influent/Effluent water quality Item

Raw water

Treated water

Removal rate

BOD

≦1,000

≦10

99.0%

COD

≦300

(≦20)

(93.3%)

SS

≦800

≦3

99.6%

n-Hex

≦150

≦1

99.3%

pH

5.8-8.6

5.8-8.6

－

・ Suction filtration by pump ・ Recycle rate 　 200% （ 300%supply, 200%Return ） 24

Equalization Tank Required volume

＝

Equalized volume

+

Supernatant

・ Flowrate 　 300 m3/d 　　 ・ Inflow period 　 10 hours ・ Required volume 　 175m3 + supernatant 　　　　 [ = 300m3/d － (300m3/d÷24x10hours ） ] ・ Mixing required ・ Transfer pump ・ Constant transfer by measuring tank or timer control of transfer pump ・ Fine screen with 1mm opening 25

Biological tank 1. Tank volume

Required volume Aeration tank

= =

Influent BOD Pre-aeration tank

Treating rate

/ +

Membrane tank

・ Treating volume 　 300m3/d 　　 ・ Influent BOD 　 1,000mg/L ・ BOD load 　 300kg/d ・ Required volume 　 200m3 (Pre-aeration and membrane tanks)

　　　　　　　　　 [ = 300kg/d / 1.5kg/m3*d ] ・ Exclusive blower to be used for membrane units ・ Flowrate of blower for membrane units is specified for type of membrane units ・ Remaining required volume is supplied at pre-

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2 Calculation of number of cartridge ・ Filtration area per cartridge: 　 0.8 m2/pc ・ Flux ：　 0.4 m3/m2/d ・ Intermittent filtration ： 0.9 　 (OFF ： 1 min, ON ： 9 min ）

・ Required number of cartridge ： 　 1,042 pcs [ = 300m3/d / 0.8m2/pc / 0.4m/d / 0.9 ]

・ Type of unit: ES200 (200 pcs/unit) [ 6 units = 5.21 = 1,042 pcs / 200 pcs ]

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3 Design of tank ・ Type of units 　 ES200 x 6 units Tank size

・

[ 4.5mL x 3.5mW x 3.0mH x 2 = 94.5m3 ]

3,500

4,500

4,500

ES200

ES200

ES200

ES200

ES200

ES200

Membrane tank A

Membrane tank B

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4 Required Oxygen Volume Required oxygen volume

=

BOD oxidization

Coefficient for BOD oxidization ：

1.5 ）

+

Endogenous respiration

0.5 （ 0.45 -

Coefficient for endogenous respiration ：

0.1 （ 0.05

-0.15 ） ・ BOD load 　 300kg/d 　　 ・ BOD oxidization 　 150kg-O2/d 　　　　　　　　　 [ = 300kg/d x 0.5kgO2/kg-BOD ] ・ Endogenous respiration 178.1kg-O2/d 　 [ = （ 94.5 x 12 + 105.5 x 8 ） x 90% x 0.1 ] 　 ・ MLSS in Membrane tank 　 15,000mg/l MLSS in pre-aeration tank 10,000mg/l [ = 15,000 x 2/(2+1)] ・ MLVSS/MLSS 90% ・ Total required air volume 　 328.1kgO2/d 　　 29 　　　　 [ = 150kg-O2/d + 178.1kg-O2/d ]

5 Oxygen Supply from Membrane Units

Air volume Oxygen volume

= =

Number of cartridge Air volume

x

x

Specified air volume of cartridge

Oxygen transfer efficiency

x

α factor

・ Number of units 　 ES200 x 6 ・ 1,200 pcs x 10 l/min/pc = 12.0 m3/min ・ Oxygen transfer efficiency = 5% α = 0.6 ・ Oxygen supply from membrane units = 143.6 kg-O2/d

[ = 12.0m3/min x 0.277kg-O2/m3 x 5% x 0.8 x 1,440 min/d ] 30

Scouring Force - Stable Operation Biological Condition

Optimum Sludge Condition for Wastewater treatment Membrane operation

Hydraulic Condition Membrane Surface Cleaning by Air Scouring

Diffuser cleaning for uniform upflow Bubble

Air

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Cross Flow Filtration Membrane Cartridge

Membrane Cartridge

Air bubble Activated sludge

Upward flow velocity controls membrane biofilm. (Air scouring)

Higher upward flow velocity enhances flux rate. Permeate

Permeate

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Membrane Surface Cleaning Upward airflow among membranes

•

In the Kubota membrane system, we adopt cross-flow filtration to make the membrane surface clean and control bio-fouling on the membrane. This cross-flow aeration is enhanced with introduction of coarse bubble.

•

This coarse bubble aeration makes well vertical mixing flow.

•

Our diffuser system makes well distributed coarse bubble and disperse air in biomass.

•

This air is also used to transfer the oxygen into biomass.

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5-1 　 Specification or air volume for Cartridge Type of unit

Min air volume

Max air volume

ES Type

10 l/min/pc

15 l/min/pc

EK Type

7 l/min/pc

10 l/min/pc

FS type

12.5 l/min/pc

15 l/min/pc

Do not supply the air volume more than max air volume. This may make the usage period short.

The supplied air to membrane units is used also for biologically required oxygen. 34

5-2 　 Oxygen Transfer Coefficient from Membrane Unit & Alpha Factor 　　　　　　　　 Effective water depth

Coefficient

1.0m

2.0%

2.0m

3.5 ％

3.0m

5.0 ％

4.0m

6.0 ％

5.0m

7.0 ％

Oxygen transfer coefficient in sludge = Coefficient x α factor Alpha factor shall be discussed because there is no common guide line currently.

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6 Required Oxygen volume at Pre-aeration tank

Required oxygen volume at pre-aeration tank

=

Required oxygen volume

-

Oxygen volume from membrane units

・ Required oxygen volume = 328.1 kg-O2/d ・ Oxygen volume from membrane units = 143.6kg-O2/d ・ Oxygen volume at pre-aeration tank = 184.5kg-O2/d [ 328.1 - 143.6 ]

Fine bubble diffuser shall be selected according to specification of manufacturer locally available. 　　　　 　　　　　 36

7 Sludge Production ・ BOD load ： 　 300kg/d ・ MLSS ： 15,000mg/l ・ Sludge production rate ： 　 40% against BOD It depends on the conditions.

・ Sludge production ：　 120kg-ds/d [ =300kg/d x 40%] 8 ｍ 3/d (at MLSS=15,000mg/L) [120kg-ds/d / 15,000 x 1,000 ]

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Operation and Note for Equipment 1. Blower for pre-aeration tank 1. Possible for intermittent operation 24 hours continuous operation or intermittent operation with timer 2. Blower for membrane units 1. Exclusive blower for membrane units and tank 2. Capacity less than maximum air volume for membrane units 3. Continuous operation or intermittent operation with timer

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Operation and Note for Equipment 3. Fine screen Opening: 1 mm or less 24 hours continuous operation or connected to transfer pump operation 4. RAS recycle pump 　　 According to the recycle rate Minimum 2Q 24 hours continuous operation or control with water level 5. Suction pump 1. Self-priming pump, Suction level 5m or more 2. Pressure gauge (-100 - 100kPa) 3. Flow meter & Flow volumeter (Electromagnetic meter)

Pressure transmitter

Pressure sensor

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Operation of Suction Pump 1. Interlock to the connected membrane blower 2. Control with water level of pre-aeration tank or RAS tank 3. Stop of operation during diffuser cleaning valve open 4. Alarm and stop of operation with high TMP 5. Intermittent operation (off 1 min. / on 9 min. adjustable by timer) 6. Off start 　　

TMP is trans-membrane pressure which is not same as the pressure indicated by pressure gauge. It shall be adjusted according to water level and position of pressure gauge.

Emergency stop

-A kPa -(A + 5 ) kPa

5 kPa

TMP in operation Pressure increase

-20 kPa

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Operation of Diffuser Cleaning Valve 1. Operation with timer 2. Frequency: Once or twice a day Duration: 5 min. Frequency and duration is suitably adjustable. 3. Suction pump suspends with signal of "open of this valve" 4. Suction pump starts (off start) with signal of "close of this valve". 　

This operation prevent clogging of diffuser of membrane units.

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Low Load Operation Mode of exclusive Blower for Membrane units 1. Protection of membrane cartridge 2. Mixing of sludge to prevent settling • Lowest water level at equalization tank (LLWL) ⇒ Low load mode

• Intermittent operation for membrane blower Operation cycle 　　 Off: 55 min. On: 5 min. Membrane blower operation

Low load mode above LLWL

LLWL

Membrane blower stop

above LLWL

Empty equalization tank

55min 55min 55min 5min 5min

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Diffuser Cleaning Operation • Air and sludge makes the inside of diffuser pipe clean when the diffuser cleaning valve is open and membrane blower operates. Motor operated butterfly valve Air from blower

Cleaning valve

・ Frequency 　 1-2 time/day ・ Duration 　 each

Aeration

5 min.

Cleaning 43

In-Situ Chemical Cleaning Cleaning Interval Periodically (3 ～ 6 months) -Increase in Suction Pressure (5kPa) Chemicals -Sodium Hypochlorite (Cl: 0.5%) for Organic Fouling -Oxalic Acid (1.0%) for Inorganic Fouling Chemical volume: 3 l/Cartridge Cleaning Time: Pouring 5 - 15 min. + Cleaning 60 ～ 120 min.

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5. Case Study Operation Plant

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Porlock STW

Ariel view

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Porlock STW

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Porlock Treatment Building Permeate Pumps

4. 2.

Aeration Tanks 1-4

Crude Effluent inlet Fine Screens 3 mm

Final Effluent out

Tidal Storage

Anoxic recycle Tank

Blowers 1.

3.

Washing Tank

Membrane Units

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Porlock Treatment Building

Aeration tanks and 3 mm fine screens

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Porlock BOD Removal Feb 98 - Jan 03

BOD (mgO2/l) 700 600 500 400 300 200 100 0 0

1

2 3 Time in Years Raw Feed

4

5

Permeate

50

Process Performance Capability of removing coliform The average removal rate of bacteria reaches 6 Log ⇒ No need of disinfections Faec. Col. Raw feed 106/100 ml 1000 100 10 1 0.1 Sampling contamination 0.01 identified 0.001 0.0001 0.00001 0.000001 0 50 100 150 200

Permeate

250

300

350

400

Time in Days

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Thank you

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