Operation & Maintenance Manual for Cembrane SiC Ceramic

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Operation & Maintenance Manual for Cembrane SiC Ceramic Modules

Prepared by: Cembrane a/s, Nøglegårdsvej 10, 3540 Lynge

Revision date: 29th December, 2017 – Version 3.0

Notice

The data and information contained in this document are based upon technical

testing by Cembrane, and is to the best of our knowledge reliable. Cembrane

cannot control design and operating conditions, and consequently does not

assume any liability for results obtained or damage incurred through the

application of the information provided herein.

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Table of content 1 Introduction ......................................................................................................................................................................... 3

2 Technology overview ........................................................................................................................................................... 4

3 Silicon Carbide Ceramic Flat Sheet Membrane ................................................................................................................... 5

3.1 Membrane properties ................................................................................................................................................ 5

3.1.1 Zeta potential .................................................................................................................................................... 5

3.1.2 Chemical resistance ........................................................................................................................................... 6

3.2 Membrane module..................................................................................................................................................... 7

3.3 Module specifications ................................................................................................................................................ 9

3.3.1 SS316L module and related flat sheet membrane ............................................................................................ 9

3.3.2 PPO module and related flat sheet membrane ............................................................................................... 14

4 Handling............................................................................................................................................................................. 18

4.1 Receiving, Off-loading & storage .............................................................................................................................. 18

5 How to install ..................................................................................................................................................................... 19

5.1 Steel module: ........................................................................................................................................................... 19

5.1.1 Tower assembly .............................................................................................................................................. 19

5.1.2 Plate exchange guide ...................................................................................................................................... 21

5.2 Plastic (PPO) module ................................................................................................................................................ 22

5.2.1 Module assembly ............................................................................................................................................ 24

5.2.2 Module tower assembly .................................................................................................................................. 26

5.2.3 Disassembling of Towers ................................................................................................................................. 34

5.3 Preparation of filtration tank ................................................................................................................................... 34

5.3.1 Mounting the position holders and aeration .................................................................................................. 35

6 Commissioning & Operation guidelines ............................................................................................................................ 38

6.1 Operation guidelines ................................................................................................................................................ 38

6.2 Process steps ............................................................................................................................................................ 40

6.2.1 Low TSS applications ....................................................................................................................................... 41

6.2.2 High TSS applications ...................................................................................................................................... 42

6.3 Sludge filterability .................................................................................................................................................... 44

6.4 Integrity test / Leakage check .................................................................................................................................. 45

6.5 Clean water test (Permeability test) ......................................................................................................................... 46

6.6 Start-up Filtration ..................................................................................................................................................... 48

6.6.1 Critical flux test ............................................................................................................................................... 48

7 Maintenance ...................................................................................................................................................................... 50

7.1 Backwashing the modules ........................................................................................................................................ 50

7.2 Chemical cleaning ..................................................................................................................................................... 51

7.3 On-air sprinkler wash-down ..................................................................................................................................... 52

8 Trouble shooting................................................................................................................................................................ 53

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1 Introduction Thank you for selecting the ceramic SiC membrane module from Cembrane a/s. The following operation

and maintenance manual, describes how to handle, install, operate and maintain the Cembrane membrane

modules correctly. In this manual, two types of module frames are included; one in SS316L (SiCFM-line)

and one in PPO plastic (SiCPM-line). Since the membrane used for both types are identical, the operation

and performance is similar for the two types, only the installation guide differs. It is important to read this

manual carefully in order to handle the product safely and effectively.

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2 Technology overview A Cembrane membrane is a solid-liquid separation technology that can be used to filter various sources of

contaminated water and permeate high quality water. The Cembrane membrane modules are used in the

following applications:

MBR municipal and industrial wastewater

Sludge thickening of activated sludge

Drinking water from Ground- and surface water sources

Produced water treatment for re-injection of discharge

Scrubber wastewater for Marine scrubbers

Recovery of backwash wastewater from Sandfilters

Others

Incorporated into each Cembrane membrane module are multiple flat sheet membranes that acts as a

physical barrier to water bourn contaminants. With a membrane in the MF/UF range, it is able to repel:

Suspended solids

Bacteria

Oil & Grease

Micro-organisms

while allowing for free passage of filtered water. The modules are submerged directly into the water to be

treated, while a suction pump draws filtered water from outside-in. Below is shown a simplified flow

diagram of the submerged membrane modules in an installation:

Figure 1 Principle scheme (P&ID) of the CEMBRANE filtration towers

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3 Silicon Carbide Ceramic Flat Sheet Membrane A Cembrane flat sheet membrane as shown in below figure, is made of the ceramic material Silicon Carbide

(SiC). It is manufactured by mixing well-defined SiC particles in multiple sizes into a moldable substance,

which is then extruded and sintered at temperatures around 2.000o C. The membrane layer is applied with

even finer SiC particles on the outside of the extruded body in multiple layers and then undergo a final

sintering to around 1.700o-1.900o C.

3.1 Membrane properties The high resistance of SiC and the resulting cleaning possibilities generate a unique high performance

system. Depending on the medium and the operating conditions, mechanical, thermal and chemical

cleaning strategies it can be combined individually to achieve a stable and low maintenance long-term

operation.

3.1.1 Zeta potential The Silicon Carbide membrane is negatively charged above pH 2,7, which means it repels negatively

charged substances such as oil, bio-mass, bacteria and activated carbon. While positively charged

substances bond to the membranes, such as Cationic tensides. For that reason, avoid CATIONIC tensides

and polymers and a positive net charge of the media to be filtered, otherwise the membrane will tend to

foul rapidly. This only applies when the media has large amounts of organics, the fouling risk does not apply

for inorganic particles. See figure 2 below.

Figure 2 SiC ceramic flat sheet membrane

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Figure 3 Charge of the SiC and other ceramic materials at various pH levels

3.1.2 Chemical resistance The membrane material is based on Silicon Carbide, which is mostly an inert material to any chemicals.

Below is a list of chemical reactions between SiC and different chemicals.

The chemical limitations are in the material selected to bond and house the membranes. Below is a list of

tolerable amounts of chemical exposure to the complete module system at 20oC:

1. The module equipment is tolerant against the following chemicals (standard cleaning strategies

considered as CEB, CIP)

i. Citric acid

1. up to 2% for a maximum period of 24 hrs (maximum duration of one cleaning

period)

*Test time: 125 to 300 hours of submersive testing, continuously stirred. ** >1000 mg/cm yr - Completely destroyed within days. *** 100 to 999 mg/cm2 yr - Not recommended for service greater than a month. **** 50 to 100 mg/cm2 yr - Not recommended for service greater than one year. ***** 10 to 49 mg/cm2 yr - Caution recommended, based on the specific application. 0.3 to 9.9 mg/cm2 yr Recommended for long term service. ****** <.2 mg/cm2 yr - Recommended for long term service: no corrosion other than as a result of surface cleaning was evidenced.

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2. total maximum duration of cleaning periods per year: 500 hrs

ii. H2SO4

1. up to 0.5% for a maximum period of 24 hrs (maximum duration of one cleaning

period)


iii. NaOCl

1. up to 0.5% for a maximum period of 24 hrs (maximum duration of one cleaning

period)


iv. NaOH

1. up to 0,5% for a maximum period of 24 hrs (maximum duration of one cleaning

period)


2. The module equipment is tolerant against the following chemicals (extreme cleaning strategies

considered as CEB, CIP)

i. Citric acid


period)


ii. H2SO4


period)


iii. NaOCl


period)


iv. NaOH


period)

3.2 Membrane module The flat sheet membranes are then individually mounted in a module, in total comprising of 6 m2 of

membrane surface area. The modules are submersible and function as modular bricks that can be stacked

individually on top of each other up to 15 modules in total. The membrane surface area is the determining

factor for the capacity of the installation, the more surface area the more flow through the plant.

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Plastic module (PPO/PS)

No Steel parts

Integrated permeate line

SS316L module

PP external piping

Integrated permeate line

Single module 6 m2 Stack of modules

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3.3 Module specifications

3.3.1 SS316L module and related flat sheet membrane

Item code SiCFS-0151-DO-T-520

Membrane material Silicon Carbide (SiC)

O-ring material Viton/EPDM/NBR (NSF61)

Cap material Glass fiber/PPS (NSF61)

Active membrane surface 0,151 m2

Pore size 0,1 µm

pH range 1-14*

Overall dimensions L532xW150xT6/11mm

Fits into permeate manifold hole of Ø9,6mm H7

Maximum permeate flow 300 ltr/hour

Maximum suction pressure -700 mbar

Maximum backwash pressure 3 bar

Operating temperature 5-80o C

Cleaning methods Backwash/Ozone/High pressure jet/Chemical cleaning

Certifications NSF61 drinking water approval

Special features

Double side filtered water outlet

Double O-ring connection

Self-degassing due to filtered water outlet at the top of

the end-cap

*For more details, see Chemical resistance in section 3.1.2

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Item code SICFM-6040-DO-T-520

Module housing material SS316L

Available O-ring material Viton/EPDM/NBR (NSF61)

Pipe material Polypropylene

No. of single ceramic plates 40

Avg. distance between ceramic plates 5.7 mm

Active membrane surface 6.04 m²

Max. permeate flow 6.0 m³/hr

Max. filtration pressure -0.7 bar

Max. backwash pressure 3.0 bar

Temperature operating range 5 - 60 °C


Field of application Drinking water / waste water / industrial

Special features Multi ceramic plate configuration with exchangeable single

ceramic plates

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Length L 624 mm

Width W 648 mm

Height H 160 mm

Weight Approx. 35.5 kg (dry) / Approx 45.2 kg (wet)

Active area (open area between membrane plates) 0,14-0,15 m2

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Item code SICFM-6040-DO-T-520

No. of modules per single tower 1 – 15

Length L 715 mm

Width W 690 mm

Height H (with 1 module) 469 mm (369mm without extended legs)

Extra height per module 162 mm

Weight (with 1 module) Approx. 42.2 kg (dry) / Approx. 52.6 kg (wet)

Extra weight per module Approx. 35.5 kg (dry) / Approx. 45.2 kg (wet)

Displacement volume (with 1 module) 27.5 Liters (without vertical manifold)

Extra displacement volume per module 22.5 Liters*

Special features Maximum flexibility due to fully modular concept with free

selection of modules per tower and towers per rack

Allows for lift of individual module as well as an entire tower

Aeration unit is easily installed with a Ø50 hose

Vertical manifold is quickly attached to the tower by union joints

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3.3.2 PPO module and related flat sheet membrane

Item code SiCFS-0175-DO-T-599

Membrane material Silicon Carbide (SiC)

O-ring material Viton/EPDM/NBR (NSF61)

Cap material Glass fiber/PPS (NSF61)

Active membrane surface 0,1752 m2

Pore size 0,1 µm

pH range 1-14*

Overall dimensions L615xW150xT6/12mm

Maximum permeate flow 300 ltr/hour

Maximum suction pressure -700 mbar

Maximum backwash pressure 3 bar

Operating temperature 5-80o C


Special features

Double side filtered water outlet

Double O-ring connection

Self-degassing due to filtered water outlet at the top of

the end-cap

*For more on chemical resistance, see section 3.1.2

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Item code SICPM-6000-DO-T-606

Module housing material Reinforced fiberglass PPO/PS (NSF61)

Available O-ring material Viton/EPDM/NBR (NSF61)

No. of single ceramic plates 34

Avg. distance between ceramic plates 6.7 mm

Active membrane surface 6 m²

Max. permeate flow 9.0 m³/hr

Max. filtration pressure -0.7 bar

Max. backwash pressure 3.0 bar

Temperature operating range 5 - 60 °C


Field of application Drinking water / waste water / industrial

Special features Multi ceramic plate configuration with exchangeable single

ceramic plates

Internally filtered water piping - no additional external piping

required

Module housing fully made in plastic - free of any steel parts

suitable for harsh applications

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Length L 624 mm

Width W 648 mm

Height H 160 mm

Weight Approx. 35.5 kg (dry) / Approx 45.2 kg (wet)

Active area (open area between membrane plates) 0,14 m2

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No. of modules per single tower 1 – 15

Length L 700 mm

Width W 655 mm

Height H (with 1 module) 450 mm

Extra height per module 160 mm

Weight (with 1 module) Approx. 41.0 kg (dry) / Approx. 52.0 kg (wet)

Extra weight per module Approx. 35.7 kg (dry) / Approx. 47.0 kg (wet)

Displacement volume (with 1 module) 32 liters

Extra displacement volume per module 25 liters

Special features Maximum flexibility due to fully modular concept with free

selection of modules per tower and towers per rack

Lift or removal option for single towers (remaining towers stay in

operation)

Integrated double sprinkler line for enhanced cake layer removal

and chemical spray

Header system with option of direct injection of chemicals into

header collector or connection of additional instrumentation

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4 Handling

4.1 Receiving, Off-loading & storage 1. Stage the equipment (crane, hoist, or forklift) that will be used to offload the membrane shipment.

Refer to the technical specifications for exact weight of the units and always operate lifting

equipment per manufacturers recommendation.

2. Secondly, secure a storage facility for the membranes that live up to the following guidelines:

a. Temperature from 10-35oC – do not expose to frost

b. NOT in direct exposure to sunlight

c. Placed on a level surface

d. Kept away from heat or flame

e. Take extreme care to prevent membrane surface from damage, since membrane is

exposed to surroundings. If possible, maintain membrane modules in the wooden crates

they arrive in, until time of installation

f. Preferably store the membranes dry. If stored wet, there is a risk for biological growth on

and inside the membrane modules that will require expensive cleaning, for more see

section on cleaning and maintenance

3. Open the wooden crates they arrived in and remove the membrane modules individually. Lift the

modules in four corners by hand or with a lifting device and place on a level surface

NOTE: The membrane material is Silicon Carbide ceramic, which is an extremely hard but also a brittle

material. The membrane has a very thin layer placed on the outside, directly exposed to the surroundings.

Therefore, handle the product with care and it must not be in direct contact with hard and sharp objects

nor handled roughly. A good rule is to handle it similarly to porcelain.

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5 How to install

5.1 Steel module: Opening the wooden crates

1. Remove the parts from the wooden crates, this includes:

a. Modules

b. Vertical permeate pipe

c. Stud bolt / Steel rods

d. Lifting jig

e. Rack connectors

f. Aerator

5.1.1 Tower assembly

2. Assemble the tower in the following order:

a. Place the aerator on a flat surface outside the membrane tank

b. Place individually each module on top of each other on the aerator base

c. Mount the vertical permeate line

d. Insert the steel rods and lift the tower into the membrane tank. Make sure the tower is

fixed on the bottom to avoid movement of tower

e. The above steps can also be done inside the tank if the space allows for it

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Caution when lifting modules

NOTE: During installation, take caution not to drop heavy and hard objects on the ceramic membranes. This

can cause a chip damage on the membrane surface that might influence the filtration integrity. In the event

this happens, individual plates can be exchanges, or the chip can be repaired with a two-component

ceramic glue or an Epoxy. Cembrane recommends using Weicon repair stick Aqua ideal for ceramic

sealings:

Figure 4 Weicon repair stick Aqua for sealing chip damages on the ceramic membrane

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5.1.2 Plate exchange guide In the event a plate is broken and needs to be exchanged, follow the below guide:

Remember to grease the end-cap and manifold with Silicone grease for ease of sliding the flat sheet into

the manifold and to avoid wear and tear on the rubber o-rings. Cembrane recommends applying Molykote

Silicone with a brush, but similar products can also be used:

Figure 5 Silicone sliding agent for inserting end-caps into the manifold.

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5.2 Plastic (PPO) module

Opening the wooden crates

Remove the parts from the wooden crates, this typically includes:

a. Modules, closed bottom modules for the tower base and open modules for stacking on

top. See figure 7 below!

b. Gaskets, sealing between modules and to the header collector

c. Key locks, to lock the modules together

d. Base unit corner part, for the tower to stand on

e. Header collector

f. Sprinkler pipe

g. Filtered water outlet

h. Lifting jig

Figure 6 Single module exploded and assembled

Figure 7 Left: Closed bottom module. Right: Open module

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Figure 8 Single tower exploded and assembled

Figure 9 Tower lifting jig

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Caution

5.2.1 Module assembly The assembly of a membrane module can be done by one person only, but a third hand will be helpful.

Please follow the steps in the correct succession:

1. Take one front frame and mount the 4 O-Rings (36,2 x 2,6) on the left and right permeate channel.

2. Put sliding agent on the O-Rings and front frame and stick the front frame into both side frames.

3. Put the module frame on the table inside of the open rectangle with the open side in front of you.

4. Put slide agent into all small permeate channels in the front frame with a clean brush.

5. Put the first membrane sheet and slide it with its nipple into the right hole (left handed people start

left). For this, hold the membrane plate only on the plastic shoes. Hold with the left hand the distant

shoe in the middle of the shoe with the right hand same on the opposite side. Hold the plate exact

vertical and slide it parallel to the side frame into the permeate channel. Control the right vertical

position.

6. Put the rake under the front shoe of the first membrane plate.

7. Repeat point 5 for all remaining membrane plates until the module is fully loaded. If the space for

the left hand is too small hold the membrane on the top of the shoe. Avoid touching the membrane

surface.

Figure 10 DO NOT STEP ON THE MEMBRANES!

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Figure 11 White plastic is the membrane rake aligning each flat sheet membrane

8. If all membranes are ready insert and align the rake, so all shoes are standing on it. Take care that

the front and side frames are forming a rectangular.

9. Take the second front frame, mount the other 4 O-Rings and put slide agent on the O-Rings and on

the small permeate holes for the membrane shoes.

Figure 12 Appliance of silicone sliding agent

10. Put the front frame in front of you and hold it in the right position without pressure.

Figure 13 Putting front frame in correct position

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11. The second person puts now the 2 collets on the left and right position with low force.

12. Increase the force on the left and right collets until the big permeate channels of the front frame

starts to slide into the side frame.

13. Wobble on the top of the membrane shoes during increasing the force evenly on all collets until the

front frame and the side frame are together without a gap.

14. Put on all 4 corners the plastic bolt and nut and fix them without strong force. No tool for the nut is

necessary. Press the nut into the hexagon shape during turning the bolt with an Allen key (hexagon

socket screw key). Stop turning when the first “click” can be heard.

Remove the module from the table with two persons. Hold the module on the front frame. The fingers

must be beside the long nut.

5.2.2 Module tower assembly Please follow the steps in the correct succession:

1. Put one closed base module on the floor. Put it on the front frame and lift one side. Put 2 corner

feet in and fix it with 2 key locks. Lift the module in the same way on the other side and assemble

the other both feet inclusive key lock.

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2. For one tower two ropes are necessary. The ropes must have all the same and right length. Both ends

must be cut with a special hot rope cutter not with a knife or a scissors. The diameter of the rope

ends should not much wider than the rope itself otherwise it comes to problems during threading.

3. Thread one rope left and right into the holes on the lower side of the corner feet until it comes

out on the top of the first module. If it stops, try to drill the rope with the fingers under light

pressure. Do the same with the second rope on the other side. Finally, all 4 ends of the two ropes

are on the top of the first module.

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4. Put 4 asymmetric profile gaskets on the first module. Put the thicker side down. When all 4 gaskets

are in the right position coat only the outer side of the gasket with slide agent. Use a clean brush for

this work.

Thin side

Thick side down

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5. Put the second module on the top press it light and put the key lock into the holes and close it

with the ring spanner.

6. Thread the rope on every corner inside of the top module.

7. Repeat the instruction 4 to 6 until the right size of the tower is reached.

8. The completion of a tower is the header collector. Installation is the same as for a module (step 4

to 6).

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9. Prepare the lifting knots at every end of the ropes (see special chapter and video).

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10. Install the pipe clips for sprinkler system. Put the sprinkler pipes and turn until the top holes are

horizontal.

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11. Assemble the header adapter to the header collector

12. Insert the thimble and the shackles for lifting the tower

NOTE: During installation, take caution not to drop heavy and hard objects on the ceramic membranes. This

can cause a chip damage on the membrane surface that might influence the filtration integrity. In the event

this happens, individual plates can be exchanges, or the chip can be repaired with a two-component

ceramic glue or an Epoxy. Cembrane recommends using Weicon repair stick Aqua ideal for ceramic

sealings:

Figure 14 Weicon repair stick Aqua for sealing chip damages on the ceramic membrane

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5.2.3 Disassembling of Towers Lift the tower and put it on a flat floor. Remove the header by opening the 4 keys and tire on the header

parts. Put the header parts onto a clean floor.

For disassembling a tower, first must be opened all 4 knots of the ropes. Next step is to open all 4 keys of

the top module with a ring spanner. Lift the top module with 2 people. Repeat this procedure for the next

modules.

Take care by handling with the modules. Put them on a flat floor. Don’t put tools on the modules. If the

modules should store for longer time, cover the module, or put them into a box.

5.3 Preparation of filtration tank Normally the filtration tank should be as tight as possible to the module towers to reduce water loss during

discharge and cleaning operations. If a cross-flow during filtration – produced by continuous aeration

during the filtration process - is necessary, the area around each single tower should be at least the same as

the cross-section from the top view of a module tower. This is required for the downstream.

Most important for every process is a good working sludge removal during a backwash with emptying the

tank. For this, under every tower or tower row a ditch with a defined slope of at least 5° and a width of the

total inner width of the membrane tower is necessary (in general 520 mm). This applies for both module

types.

Figure 15: Example for a Tank design for a single tower with 3 modules height. By variation of the height and the length of the tank this design will work also for higher towers and more towers in parallel.

Inside of that ditch an aeration system must be installed. The aeration system contains perforated pipes

and pipe holders. The holes in the pipe should big enough to create a coarse aeration to achieve the

maximum cleaning effect.

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Figure 16: Example for a 2-row filtration tank with ready installed position holders (for 3 towers per row) and aeration system.

To put the membrane towers during assembling at the right position and keep them at this position a

position holder must be installed. This position holder is made from PP and must be fixed on the bottom of

the filtration tank.

Figure 17: Example for a multiple row filtration tank with ready installed position holder and aeration system.

Depending on the permeate connection type different collector pipes can be installed above the membrane

towers. Cembrane recommends using flexible hoses to absorb variations in dimensional tolerances from

the module tower to the header and to avoid putting the module tower under stress.

5.3.1 Mounting the position holders and aeration The correct position of every filtration tower inside of a filtration tank is very important. The tower must

stand exact leveled vertical. The distance between two towers is given by the holder itself.

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Position Holder

The position holder comes ready welded as can be seen in Figure below. The holder must be fixed on the

bottom of the tank with high quality stainless steel (V4A, 316L) screws the inner distance between two

opposite holders must be 520 mm.

Figure 18: Position Holder for filtration towers

The distance between two distance holders must be accurate because the size of the module gives it.

Figure 19: Mounting of the distance holder. The important dimension is 572 mm which is the size of the module feet distance.

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Aeration System

The aeration system contains the aeration pipes and the holders. The holders must be installed first inside

of the ditch. The holders should not be installed directly under a tower but between them. In practice this

means it is installed at the same position as the distance holder will be installed below figures.

Figure 20: Aeration holder

The pipes come in small parts with 1 m length and must be cut to fit in. The cut must be done in this way

that the holes are only inside of the membrane tower. After the cut to the right size all pipes must be glued

together by standard PVC glue. Take care during gluing, that all holes face exact left and right. It is

important to distribute the air equal over the whole cross-section of the tower

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6 Commissioning & Operation guidelines Before the membrane modules are seeded with feed water, the system should be function tested using clean

water to verify piping integrity, equipment operation, and membrane performance. However, before

performing a Clean Water Test, all system components and tankage must be thoroughly cleaned and inspected.

1. Rinse the tank walls with service water to remove debris, dust and other contaminants.

2. Remove the rinsed water.

3. Fill the tank with clean water to normal level above the membrane tower.

4. Turn on the aeration blowers and visually inspect each individual membrane tower for a uniform

bubble pattern. Notice the initial bubbles on the top of the tower to see if the entire membrane

surface is covered.

5. Function test all system input/output points to confirm logic. Remediate problems as required. Refer to

the system process and instrumentation diagrams (P&IDs) and control narrative to direct logic testing.

6. Calibrate all instrumentation, such as flow and pressure sensors, MLSS probe and Turbidity meter.

6.1 Operation guidelines In simple terms, to operate the membrane modules, please follow below instructions:

1. Pre-treat the wastewater with a minimum screen size of 3 mm

2. Always maintain at least 25 cm above the top membrane module

3. Always supply the minimum amount of cleaning air required per below tables. If necessary, extra air

can be added for process purposes or in some cases to increase the critical flux.

4. Always filter wastewater at or below the design flowrate

5. Periodically clean the diffusers

6. Clean the membranes when normal design permeability cannot be obtained

Parameter Recommended value Notes

Pre-treatment <3 mm

Oil & Grease <500 ppm

The membrane is not harmed by oil and hydrocarbons, but the flux rate is directly linked to the amount of oil in the water.

TSS organic <4,5%

The flux rate is directly correlated to the amount of solids in the filtration tank

TSS Inorganic (MLSS) <10%

The flux rate is directly correlated to the amount of solids in the filtration tank

Temperature 5-60oC Avoid sudden changes in temperature

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Sludge filterability in MBR 10 ml /5 ml See section on sludge filterability

pH range 1-11

The membrane is highly chemically resistant, but can deteriorate in strong chemicals known to dissolve SiO2

Flux rate 10-1.000 LMH

Depends on the application. Generally, the more organics in the feed water, the higher the fouling potential and hence the lower the flux rate. In ground water flux of 500-750 LMH can be achieved, whereas in MBR and sludge thickening, the flux rate can vary from 25-150 LMH

Backwash flow rate 100-1.000 LMH (<3 bar)

Generally, 2x the filtration flux in treatment of water with only inorganic TSS. 3-4x filtration flux in MBR, Sludge thickening and wastewater.

Sprinkler flow rate 4 m3/hour/module tower A sprinkler pump and unit can feed one filtration train at a time

Chemical sprinkler flow rate (CapClean) 4 m3/hour/module tower

Aeration rate 50-150 Nm3/hour/module tower

Continuous aeration is required in MBR and Sludge thickening and generally in water with TSS higher than 1.000 ppm. Aeration is only required during backwashing in water with TSS less than 1.000 ppm

Filtration pressure range 0 to -0,7 bar To avoid excessive fouling, maintain TMP below -0,7 bar

Pressure washing <10 bar minimum proximity 50 cm

Sludge accumulated inside the membrane tower can be removed with a pressure washer when modules are not submerged in water

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6.2 Process steps Cembrane recommends two process philosophies:

1. Low TSS with lower end fouling potential

a. TSS <1.000 ppm

b. TOC <30 ppm

c. Operation mode: Dead-end (no aeration and no recirculation of feed)

d. Applications:

i. Ground water

ii. Surface water

iii. Sand filter backwash water

iv. Precipitated metal or mineral removal

v. Polishing applications

2. High TSS and with high fouling potential

a. TSS >1.000 ppm

b. TOC >30 ppm

c. Operation mode: Cross-flow (aeration generates a cross-flow or shear force between

membranes)

d. Applications

i. MBR industrial & Municipal

ii. Sludge thickening & De-watering

iii. Filtering lime softened water (Clarifier replacement applications)

The below process steps are not limited to these modes of operation, the OEM can implement own operation

scheme as long as they adhere to the guidelines in this manual.

Figure 21 Generic Process flow diagram for low & high TSS applications.

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6.2.1 Low TSS applications Filtration process:

Filtration operates fully in dead-end mode. There is no aeration or recirculation of feed to generate a cross

flow.

Backwash process:

Backwash is initiated with time and/or when TMP reaches a certain level, typically 0,45-0,6 bar suction.

Chemical cleaning – CapClean through sprinkler:

Process Step Sequence Duration [sec] Flow Filtration Backwash Sprinkler Chemical dosage Aeration Drain Air-flushing Refill feed/seed De-gassing Note

Filt

rati

on

1 Filtration >2700 100-1.000 LMH ON

Filtration duration

varies from 45 min to

48 hours depending

on feed water. The

higher the TSS and

fouling potential, the

lower the filtration

duration.


1 Draining ON

Time depends on

speed of pump or

gravity

2 Backwash refil l 10 2x fi ltration flux ON

3 Sprinkler 50

20 m3/hour/tower &

Aeration >50

Nm3/hour/tower

ON ON ON

4 Refill tank ON ON

Time depends on

speed of pump or

gravity

Bac

kwas

h


1 Draining ON

Time depends on

speed of pump or

gravity

2 Air-flushing rotarary 30 3-15 Nm3/hour/tower ON

<2 bar pressure with

vane compressor. To

remove water from

the pores, in order

for chemicals to

easily be soaked in.

3 Sprinkler with chemical 1 20 4 m3/hour/tower ON ON

4 Soaking 60

5 Sprinkler with Chemical 2 10 4 m3/hour/tower ON ON

6 Soaking 60


8 Soaking 300

9 Backwash 10 2x fi ltration flux ON

10 Sprinkler 50 20 m3/hour/tower ON ON Till full tank

11 Drain tank ON ON

Time depends on

speed of pump or

gravity

12 Sprinkler 60 20 m3/hour/tower ON ON ON

13 Refil l tank ON ON

Cap

Cle

an (

Ch

em

ical

Cle

an t

hro

ugh

sp

rin

kle

r)

42

6.2.2 High TSS applications

Filtration process:

Filtration operates in cross flow mode. Where aeration generates a cross flow over the membrane, while the

feed is bled from the tank in a certain ratio, overflows, or is pumped back to pre-treatment, typically a

biological tank.

Backwash process:

Backwash is initiated with time and/or when TMP reaches a certain level, typically 0,4-0,6 bar suction.

Chemical cleaning – CapClean through sprinkler:

When backwash cannot recover the permeability fully, a CapClean is typically initiated. Alternatively, initiate a

conventional Chemical Enhanced Backwash (CEB) or Cleaning In Place (CIP).

6.2.2.1 Conventional recirculation mode vs. flow-through mode in MBR

Cembrane recommends that the tank design concept is based on a flow-through-concept (FTC) as opposed to a

conventional recirculation mode. Both options functions, but the FTC offers some technical advantages:

Flow-Through-Concept (FTC):

Instead of having space between each membrane tower to allow for sludge down-flow and recirculation inside the

membrane tank driven solely by aeration, whereas with the Flow Through Concept (FTC) the membrane towers are

packed densely together. The incoming sludge is directed under the module towers and up through the tower and

back into the biology (see illustration below) driven by the sludge return pump. This process creates an additional

cross flow, not only from the aeration, but from the return sludge pumping. See below illustration:

Process Step Sequence Duration [sec] Flow Filtration Backwash Sprinkler Chemical dosage Aeration Drain Air-flushing Refill feed/seed Recirculation De-gassing Note

Filt

rati

on

1 Filtration 540-1.140 30-150 LMH ON ON ONAeration flow:

>50Nm3/hour/tower


1 Relaxation 20-30 50 Nm3/hour/tower ON ON ON

2 Backwash 5-30 3-4x filtration flux ON ON ON ON

3 Relaxation 20-30 50 Nm3/hour/tower ON ON ONBac

kwas

h


1 Draining ONTime depends on speed of pump

or gravity

2 Air-flushing rotarary 30 3-15 Nm3/hour/tower ON<2 bar pressure with vane

compressor

3 Sprinkler with chemical 1 20 4 m3/hour/tower ON ON

4 Soaking 60


6 Soaking 60


8 Soaking 300

9 Backwash 10 2x fi ltration flux ON

10 Sprinkler 50 20 m3/hour/tower ON ON Till full tank

11 Drain tank ON ONTime depends on speed of pump

or gravity

12 Sprinkler 60 20 m3/hour/tower ON ON ON

13 Refil l tank ON ON ON

Cap

Cle

an (

Ch

em

ical

Cle

an t

hro

ugh

sp

rin

kle

r)

43

Figure 22 Flow-Through Concept (FTC)

The main benefits from this design are:

Complete discharge of sludge accumulations between membrane towers during backwash and relaxation mode

Free up space with around 40%, as circulating flow around the module towers is no longer required

Biology can be operated at higher MLSS due to onetime concentration inside filtration tower

Fast drainage of membrane tank, due to slim tank size, allowing for integrated wash-down cleaning of

membrane towers

Figure 23 3D design of MBR installation with FTC. Brown lines visualize the sludge flow path.

Conventional recirculation mode:

Designing the MBR with the conventional recirculation mode requires more space between the module towers,

which should be at least equal or greater than the active area inside the module towers. The active area is the

area between the membrane plates, which is roughly 0,15 m2. This would allow for minimum hindrance of the

sludge to flow down after exiting the top of the module towers. Tanks with several towers can result in

inhomogeneous MLSS concentration throughout the tank, as well as accumulation of sludge on the bottom of

the tank.

44

Figure 24 Conventional recirculation mode in MBR

6.3 Sludge filterability Unlike a conventional secondary or tertiary WWTP, the quality of MBR effluent is completely independent from

the quality of the activated sludge. In practical terms, this means that filamentous organisms cannot impact

effluent quality and, in fact, are often present in high concentrations. However, sludge quality can affect flux

rate and fouling rate and must therefore be monitored. The primary index used to measure sludge quality in a

MBR plant is referred to as filterability and is measured using the Paper Filtration Test (PFT).

PFT results can be used to troubleshoot membrane performance.

A PFT should be performed at least two times each week and, if possible, every day. For trouble shooting

purposes, the results of each test should be recorded and trended.

To conduct a PFT:

1. Gather the following items:

a. One piece of 5C filter paper as manufactured by the Toyo Roshi Company and distributed by

Advantec MFS, Inc.

b. Two 100 ml sample bottles

c. Two 50 ml graduated cylinders

d. One funnel (75 mm diameter)

e. One stop watch or clock

2. Collect a 100 ml sample of activated sludge from the MBR

3. Fill the other sample bottle with tap or distilled water.

4. Fold the filter paper into a cone shape as shown in Figure 12. The folded filter paper should have 16

equal partitions if folded correctly.

5. Set the folded filter paper into the funnel.

6. Set the funnel into a graduated cylinder.

7. Moisten the filter paper with a small amount of tap or distilled water, and wait until the water no

longer drips from the filter paper.

8. Drain the water used to moisten the filter paper and replace the funnel on top of the graduated

cylinder.

9. Fill the second graduated cylinder with 50 ml of activated sludge from the sample bottle.

10. Pour the sludge from graduated cylinder onto the filter paper in the funnel and start measuring the

filtration time.

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11. After 5 minutes of filtration, remove the filter paper and funnel from the graduated cylinder.

12. Measure the amount of collected filtrate and record the value.

13. The criterion by which the filterability of sludge is measured are as follows:

a. 5 ml, the sludge filterability is poor and must be improved

b. >5 ml but <10 ml, the test is inconclusive

c. 10 ml, the sludge filterability is considered good and should not impact flux rate

Figure 25 Filter paper test

6.4 Integrity test / Leakage check Before starting the filtration process the filtration towers have to be checked for any leakages. A leakage test is

a procedure to detect damages of a filtration tower which can result from manufacturing errors or damages

during transport or handling.

Leakages can be detected with a bubble-point test. For this, the filtered water header pipe is connected to an

air pipe with a suitable adapter/connector. The complete tower including header pipe has to be submerged in

clear water (filtration tank or separate tank).

While filling the tank larger leakages can already be identified.

If there are any larger leakages, the air inside of the filtration tower will exhaust and coarse bubbles will occur

in the water.

If no leakages are detected during filling, the filtered water pipe is afterwards charged with an over pressure.

The applied pressure depends on the actual submersion depth respective hydrostatic head above the filtration

tower. We recommend a submersion depth of about 3,0 m and thus a total over pressure of 550 mbar. Actual

over pressure is calculated as follows:

250 mbar + (fill level in m x 100 mbar / m)

Before charging full over pressure to the filtration tower, pressure is increased step by step as described in the

following:

46

Charging 50-100 mbar in order to detect leakages on the filtered water header and connected piping.

Holding time: 5 minutes.

Increasing pressure up to 100-150 mbar in order to detect leakages on the upper filtration modules

and piping. Holding time: 5 minutes.

Increasing pressure up to 200-250 mbar in order to detect leakages on the median filtration modules

and piping. Holding time: 5 minutes.

Increasing pressure to 550 mbar (depending on actual submersion depth, see above) in order to detect

leakages on the lower filtration modules and piping. Holding time: 10 minutes.

Intact filtration towers show an evenly distributed forming of fine bubbles only above the ceramic membranes.

If a filtration tower shows uneven distributed coarse bubbles, one or several membranes, sealings or frame

parts are possibly damaged. In that case, a detailed leak verification and fault correction has to be operated.

We recommend checking for leakages periodically, e.g. after every chemical cleaning.

6.5 Clean water test (Permeability test) After performing the integrity test and ensuring the system is leakage free, it is recommended to perform a

clean water test of the membranes.

1. Note down the water temperature

2. Start filtration at 50% the design flow rate and record the Trans Membrane Pressure (TMP)

3. Increase the permeate set-point in 10% increments until peak flow is attained. At each flowrate, note

the corresponding TMP, REMEMBER to adjust for the water height.

If the normalized corresponding flow rate divided by pressure is greater than 3.000 Liter/m2/hour/bar, the

system functions hydraulically.

Example:

Temperature: 20oC

Flow rate: 7.500 liter/hour

Membrane surface area: 18 m2

TMP: 0,1 bar

Flux rate: 7.500

18= 417 Liter/m2/hour

Permeability: 417

0,1= 4.170 Liter/m2/hour/bar [HYDRAULIC OK!]

The water flux typically increases by 3% for each degree oC temperature increase. In order to normalize the flux

rate to 20oC, use the below formula for reference:

J20 = JT ⋅ e [-0,032 ⋅ (T – 20)]

47

Where

J20 = normalized flux at 20°C (L/m2⋅h [gpd/sq ft]),

JT = actual flux at temperature T (L/m2⋅h [gpd/sq ft]),

T = Water temperature (oC)

48

6.6 Start-up Filtration During the start-up of the system, the functionality of all components like pumps, blowers, valves and sensors

is checked. Make sure that feed flow is available and the pre-treatment is working according to the design.

Check all hand valves for right position. The membranes have to be clean; with longer decommissioning period

a chemical cleaning of the membranes is recommended before starting the filtration process.

Only filtration towers which are faultlessly assembled and installed may be started. A successful leakage test of

the filtration towers is mandatory before start-up. All pipes and tanks should be rinsed and free from any

deposits (e.g. production residues, sludge). If tank filling was combined with leakage test the degassing valve

needs to be opened until all air is evacuated.

Once the preparation procedure is completed, sequence part can be put into operation:

1. After filling of the filtration tank, the filtration should be started first with a reduced flow of 25 % of

design flow rate and after trouble-free operation it can be increased in 25 % steps every hour. See

more details in next section “critical flux test”. Recommended operation time: 3 hours

2. Aeration system is started and functionality of blower and air pipes is checked. An even distribution of

air bubbles must be ensured. Recommended operation time: 5 minutes

3. Sprinkler system is started and functionality is checked. Recommended operation time: 5 minutes

4. Backwash (including aeration and sprinkler) is started as specified in the description of operation after

finishing 1 normal filtration step. Backwash pressure and flow as well as time for emptying and filling

the filtration tank should be recorded.

During the start-up time, the following parameters should be checked periodically, at least every hour:

Transmembrane pressure filtration/backwash

Flux

Permeability

Permeate quality: SDI, Turbidity, TSS

After three hours of operation the values of these parameters should be in accordance with the design

parameters. During the first 3 days of operation, permeate quality and all operation parameter (pressure, flow)

should be checked and recorded every two hours.

6.6.1 Critical flux test When starting up the plant as described above, in particular step 1 in start-up program, monitoring the critical

flux will allow the user to see under which conditions the membrane system operates at a maximum

production without applying unwanted strain to the membrane.

During the incremental increase in flow rate, the response Flux/TMP is monitored. While initially low flux and

stable operation will be observed, pronounced fouling will be seen when a certain flux rate is exceeded (fouling

is defined as a decrease in membrane permeability (ltr/m2/h/bar with time). Therefore during this test, identify

the highest possible flux at which no considerable fouling occurs.

49

See below example of a critical flux test:

Figure 26 Critical flux test during filtration. Values are for suction pressure, i.e. negative value!

50

7 Maintenance

7.1 Backwashing the modules Inside the filtration tank, the membranes separate the solids from the liquid, which accumulate on the

membrane surface (cake layer). This leads to an increase in filtration resistance and thus to a decrease in the

filtration performance of the membrane. If filtration performance is to be kept constant, this can only be

compensated by an increase in pressure or be contained by specific measures. For this purpose, periodic

backflushing is performed.

The key objective of this backflushing is to remove the cake layer and flush out the pores by reversing the

filtrate flow for a short period. Membrane backflushing is usually carried out by stopping the filtration pump

and starting the backwash pumps.

The picture below shows a typical flow diagram of a filtration process with periodical backwash and without

backwash.

If the decreased flow and/or increased transmembrane pressure reach a certain defined value a chemical

cleaning is required.

The chemical cleaning frequency depends on the characteristic of the inflow water (concentration of inorganic,

organic, and non-oxidized compounds). In general, a chemical cleaning mode is required after 1 – 3 months of

operation but depends on local effects.

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7.2 Chemical cleaning Due to the asymmetric membrane structure all potential macro fouling or blocking effects will be generated

only on the outside of the membrane. The results during all tests and running references had shown that only a

cake layer on the outside is formed and the membrane body itself is not affected on fouling or blocking and no

accumulations were detected.

Biological / colloidal fouling is the term used to describe the accumulation of colloidal dissolved substances on

the membrane surface whereby a slimy film is formed. This is generated by a bacterial growth caused by the

nutrients available in the feed water. This type of fouling occurs in all places where moistened surfaces are

prevalent and they are present in almost every technical system that does not operate on a sterile basis. This

type of deposit on the surface can reduce pore diameter, which result in a decrease in membrane flux.

Membrane blocking caused by fouling can be removed by cleaning with an oxidant. Generally, when

membranes are fouling, the following rule applies:

p(permeate) = p(backflush)

Scaling is the term used to describe salts that have formed on the membrane and in the pore structure caused

by inorganic precipitation. These generated by exceeding the solubility product on the membrane surface in

the form of sulphates, carbonates and phosphates. Since inorganic salts cannot degrade biologically and

solubility cannot be increased by raising the pH value for example, the only possible way to prevent this is to

avoid wastewater with high salt concentrations. In any case, salt concentration should be measured to detect

possible scaling. If scaling occurs, the deposits can generally be removed with acids. Generally, when

membranes are scaling, the following rule applies:

p(permeate) < p(backflush)

The inorganic micro-scaling is a typically long-term effect. The chemical cleaning frequency depends on the

characteristic of the inflow water (concentration of inorganic and non-oxidized compounds).

The following table introduces the possible chemical dosing volume of citric acid and sodium hypochlorite in

the cleaning solution.

Pollutant Type Chemical

Organic, colloidal, Silica removal Caustic

Hydroxides, carbonates and

phosphate

Organic film, bio-fouling

Oxidants,

Desinfectant

Hydrogen peroxide, sodium

hypochlorite and Ozone (gas).

Alkaline and anionic detergents with

low foaming.

52

Inorganic scale (salts, metals) Acids

Citric, Hydrochloric, Sulphuric, Oxalic

& Phosphoric

Calcium, Barium and Strontium Sulfate

scale Chelating agents EDTA, Citric Acid

The temperature of the cleaning solution shall be in the range of 10 - 45°C. For more information on chemical

dosage and limitations, see section 3.1.2 on chemical resistance.

7.3 On-air sprinkler wash-down The sprinkler wash-down system is an effective cleaning strategy to mechanically and/or chemically cleans the

membrane surface from the outside, while the modules are on-air. It can be used in three ways:

1. Spraying service water, RO concentrate or permeate water over the membranes at a pressure of 2-3

bars to remove membrane cake layer, hair and other debris.

2. Spraying hot water over the membrane modules.

3. Spraying a chemical solution on the membrane surface from the outside, allowing the capillary forces

in the membrane to absorb the chemicals into the body.

This function allows for efficient removal of buildup cake layer on the membrane as well as an integrated

cleaning of the tower to prevent clogging with debris, hair or other substances.

53

NOTE: When washing the modules when not submerged in water, do not exceed a working pressure of 10 bars

and a proximity closer than 50 cm.

8 Trouble shooting

Problem Possible cause Remedies

Aeration rate fails to meet specified values Damaged blower Repair or replace blower

Malfunctioning diffusers Repair the diffusors

Uneven aeration over the module tower Diffusor clogging Wash or clean the diffusors

Membrane diffusors are not level Level the diffusor

Clogging of the module tower Drain tank or remove module tower(s) and wash down the module tower with a pressure washer

High filtration pressure or too low flux rate Operational flux is higher than design flux

Lower the operational flux rate

Membrane surface is fouled/scaled

Clean the membrane

Poor sludge quality Improve feed quality or operate at lower flux rate.

Presence of cationic polymers and other polymers

Due to the strong negative charge of the membrane, avoid cationic polymers and polymers in the feed water. Or reduce the filtration flux to a stable level.

Fouling of ultrafine particles such as colloids.

Improve pre-treatment to enhance filterability of cake layer on membrane. This can be done by coagulation with an inorganic metal in combination with an oxidant.

54

Individual modules in one or more module towers are clogged unevenly.

Remove module tower(s) from the filtration tank and test backwash permeability of each module, if one is more fouled than the other, clean the module extensively and install.

Air in the permeate/backwash line preventing an effective backwashing.

Install a de-gassing valve to eject air.

The permeate quality is cloudy Leakage of membrane, module, hose or piping.

Perform an integrity test in water with air and repair the leakage accordingly.

The module towers are clogged with sludge or suspended solids.

Pre-treatment is not functioning and large solids accumulate in the module tower

Repair pre-treatment to avoid big solids accumulating in the modules. Utilize sprinkler wash-down of the module towers.

Solids have accumulated and grown inside the filtration tank and reached the module tower which has resulted in blockage

Perform frequent sprinkler wash-down and/or improve tank design to avoid sludge accumulation.

Documents

Operation & Maintenance Manual for Cembrane SiC Ceramic