Training materials for students final r1-uf-ro. ULTRAFILTRATIONDURATION , REVERSE OSMOSIS

1. Sembcorp Water Technology Prize (SWTP)
2013
COMPETITION MANUAL FOR ULTRAFILTRATION + BACKWASHING + REVERSE
OSMOSIS ULTRAFILTRATION
DURATION: 1 HOUR 100
The objective for using the UF-RO filtration system for this competition is to collect as
much drinking water using the Reverse Osmosis filter. The water quality (TDS)
should also be below 100.
Equipment List (for each group)
a. 2 x 120 L water tank shared by 4 groups
b. 2 Pedrollo liquid pumps
c. Valves , fittings, M8 and M12 tubings
d. 1 UF-RO Setup ( w pressure gauges, hollow fibre UF housing, and RO membrane housing)
e. 1 Submersible pump
f. 1 RO permeate tank
g. 1 UF permeate tank
h. 1 To-drain pail
i. UF and RO membranes
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1.1. Methodology
A tank of dirty feed and a setup is supplied to each group of contestants. Contestants are
required to pump the dirty feed into the UF systems of the setup to obtain UF permeate,
before pumping it into the following RO systems to obtain clean RO permeates.
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2. UF membranes will be fouled by the particles during ultrafiltration process and thus UF
permeate produced will decrease over time. Backwashing the membranes with UF
permeate are able to recover the membrane performances. However, backwashing
process compromises the amount of UF permeates collected, which is used to produce
RO permeates later. Therefore, contestants have to decide their backwashing time in
order to maximize the recovery of the membrane performance with minimum amount
of UF permeate so to make sure that they can maximize the production of RO permeate
(Please refer to the attached Appendix A and Appendix B for detailed operating
procedures).
Appendix A
Objectives of running Ultrafiltration
1) To understand and operate the filtration process
2) To understand and operate the backwash process
3) To understand the effect of the timing of filtration and backwash process
Experimental Procedure for Filtration and Backwashing
[NOTE: Please use either your handphone or wrist watch for 2 stopwatches per group.]
PART I – Filtration and Backwashing
Filtration process
Refer to Appendix B Figure 3 for the schematic process.
1) Ensure the following are in “Off” position:
a. Feed Valve (connected to Feed Tank), Permeate Valve and RO Value (connected
to Permeate Tank).
b. UF Pump & RO Pump
c. V1 & V2, V3 & V4, V5 & V6 on the UR-RO System Module
2) Time for running UF process is 7 minutes.
3) Open Feed Valve and V-1 & V-2.
4) Switch on UF Pump to allow feed to be pumped through UF system.
5) Check to make sure UF Pressure Gauge is in the range of 1.8 bar to 2 bar by
tuning V-1.
6) Check constantly to ensure P1 is in the range of 1.8 bar to 2 bar by tuning V-1.
7) Switch off the UF Pump when the running time has ended.
8) Turn off the Feed Valve, V1 & V2.
Backwashing process (NOTE: Handle the UF module with care. Do not twist and
squeeze the fibers.) Refer to Appendix B Figure 2 for the schematic process.
9) Time for running backwashing process is 2 minutes.
10) Open Permeate Valve and V-3 & V-4.
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3. 11) Switch on UF Pump to allow permeate to be forced through UF system in opposite
direction to backwash the hollow fibres.
12) Stop the pump when the backwashing time has ended.
13) Empty the To-Drain Pail.
NOTE: YOU NOW HAVE SUFFICIENT UF PERMEATE STOCK TO START PRODUCING RO
PERMEATE.
Objective of Running Reverse Osmosis
1) To maximize the amount of RO permeate collected within a certain period by varying the
filtration and backwashing time and
2) To determine the best filtration and backwashing timing for maximum permeate
collected
Ensure that the permeate collected is clear (Clarity of the permeate will be taken into
consideration)
REVERSE OSMOSIS (RO) EXPERIMENT
Objective of the Reverse Osmosis Experiment
1) To understand and operate the RO system to produce drinking water
2) To calculate the total dissolved solids (TDS) removal percentage after the RO system
Experimental Procedure for Reverse Osmosis
[NOTE: Place only the Tip of the TDS meter into the water
for accurate results]
PART 11 – REVERSED OSMOSIS
Reverse osmosis process
Refer to Appendix B Figure 4 for the schematic process.
1) Ensure the following are in “Off” position:
a. Feed Valve (connected to Feed Tank), Permeate Valve
and RO Value (connected to Permeate Tank).
b. UF Pump & RO Pump
c. V1 & V2, V3 & V4, V5 & V6 on the UR-RO System Module
2) You have to watch the UF permeate tank level to ensure there is sufficient volume to run
the ROS system.
3) Check and record the conductivity of UF permeate by using the TDS meter provided.
4) Open RO Valve and V5 & V6.
5) Disconnect the inlet of RO system and switch on RO Pump to allow UF permeate to purge
the tubing until clear flow is seen through the tubing. Switch off RO Pump and reconnect
the inlet of RO system.
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4. 6) Switch on RO Pump to allow UF permeate to be pumped through RO system.
7) Constantly tune V-6 to make sure RO-P1 is at 3.8 bar.
8) Manually measure and record the RO permeate TDS with the tester.
[Note your water quality reading must be less than 100 to meet]
9) Switch off the RO Pump at your own time or when the UF Permeate Tank is depleted.
10) Repeat the ultrafiltration and backwashing processes described under PART I above
and reversed osmosis process here as many times as you wish until the 1 hours is up.
11) Our volunteer will come around and record the volume of RO permeate produced at the
end of 1 hour whose TDS reading MUST NOT EXCEED 100.
Appendix B
How ultrafiltration systems are maintained?
When hollow fibers are fouled, with foulant cake deposits on the surface, flux of permeate
drops as pressure of operation remained constant. The formula for the calculation of flux is as
followed:
ܲ݁‫ ݁ݐܽݎݓ݋݈ܨ ݁ݐܽ݁݉ݎ‬ሺ‫/ܮ‬ℎ‫ݎ‬ሻ
‫ ܬ ,ݔݑ݈ܨ‬ሺ‫݉/ܮ‬ଶ /ℎ‫ݎ‬ሻ = − − − ‫݊݋݅ݐܽݑݍܧ‬ሺ݅ሻ
‫ܽ݁ݎܣ ݁݊ܽݎܾ݉݁ܯ‬
Maintenance has to be done to recover the performance of the fibers, in order to maintained
the permeate flux and to extend the operation life. Backwashing is one of the easy and
efficient ways to restore the permeability of the fibers. It is done by pushing clean water,
usually the permeate produced, through the hollow fibers in an opposite direction of the
normal operation, forcing the particulates out of the membrane pores and away from the
surface of the membranes.
Normal operation
of ultrafiltration Backwash
Starting flux ends
Flux, J
Backwash
starts
Ending flux
Time, t
Figure 1 Flux recovery by backwashes
Operating a pilot UF system
For Sembcorp Water Technology Prize; a pilot UF-RO plant is built to treat model feed water.
The project is separated and carried out in two stages. The first stage comprises of a UF
system while the second stage consists of the UF-RO system.
Specifications:
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5. Ultrafiltration membrane : 9 ft2 (0.836 m2) hollow fibers cartridge
Configuration of UF system : “outside-in” filtration
Model feed water : 1g/L of Bentonite in UF water
Figure 2 and 3 shows the schematics of the filtration and backwash process. Figure 4 shows
the combined mode of operations.
Reverse Osmosis
Osmosis is the movement of solvent molecules through a selectively permeable membrane
into a region of higher solute ceoncentration, with the aim of equalizing the solute
concentrations on both sides (Refer to Figure 2(a). The solvent molecules passes through
the semi-permeable membrane from the filtered water to the unfiltered water due to the
difference in the osmostic pressure on both sides. The osmostic pressure is defined to be the
pressure required to maintain an equilibrium, with no net movement of solvent.
Reverse osmosis, on the other hand, force the solvent molecules from the unfiltered water to
move into the filtered water (Refer to Figure 2(b).
Figure 2(a) Osmosis Figure 2(b) Reverse Osmosis
Reverse Osmosis (RO) is a membrane-technology that removes large molecules and ions from
solution by applying pressure to the solution on the unfiltered water side of the selective
membrane. The solute will then be retained on the pressurized side of the membrane and the
pure solvent is allowed to pass through to the filtered water. The selective semipermeable
membrane allows only small molecules (such as solvent) to pass through while rejecting large
molecules and ions through the pores.
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6. Figure 3 Combined filtration and backwash model for UF system setup
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7. Figure 4 Combined filtration and backwash model for UF and RO system setup
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