Operation Procedures for MICRODYN AQUADYN® UA860 Modules
22 | 37
Form-No: TM-WW002 // Revision: A // Date: Oct. 10, 17
The permeate water flows to the product/back flush tank where it is stored until the water is re-
quired downstream for further treatment or consumption via back flush. In case that there is a
back flush tank there must always be water inside this tank.
The flux rate shall be constant, hence it is advisable to install the feed pump with a frequency
inverter or a feed flow control valve controlled by means of flow output with safety interlocks
against over-pressurizing.
Depending on the quality of feed water and flux rate, a filtration time of between 30-60 minutes
(filtration cycle) between hydraulic cleaning cycles can be expected.
During dead-end filtration the rejected particulate matter will accumulate during the filtration
time. This accumulation will result in a gradual increase of transmembrane pressure (TMP) af-
ter each filtration and hydraulic cleaning cycle.
After reaching a pre-set quantity of filtration-hydraulic cleaning cycles or if the TMP reaches the
maximum allowed pressure the membrane module must be chemically cleaned via EBF or CIP.
Excessive buildup over prolonged periods will affect performance and recoverability of the
membrane module and must be removed regularly through regeneration methods which will be
covered in the next section. Figure shows an example of the operating mode during filtration.
Figure 9: Filtration Mode
6.2.2 Operation of Hydraulic Cleaning
Two steps are normally involved in the hydraulic cleaning cycle.
Air Scouring (AS)
Back flush
= Manual, automatic or non-return valve
Feed/CIP return/WW
Feed
Product
Pre-strainer
BF/CEB inlet
BF / CEB / CIP w aste w ater
Waste w ater
Air supply for Air Scouring
Air supply / CIP feed
Blow er
UF permeate
Feed tank
UF permeate tank
Chem 1
Chem 2
BF / CEB
Back flush
pump
pump
Feed/CIP
Chemical
dosing sets
CIP return & BF/CEB discharge
UA860
Perm.
CIP / WW tank
membrane
Operation Procedures for MICRODYN AQUADYN® UA860 Modules
23 | 37
Form-No: TM-WW002 // Revision: A // Date: Oct. 10, 17
The sequence of these steps can be altered in order to improve the hydraulic cleaning efficien-
cy.
Air Scouring (AS)
Air Scouring is essential as this agitates and dislodges the accumulated particles on the exteri-
or of the membrane fibers. The air is delivered via the air blower or pressurized airline to the in-
let located at the top side of the membrane module. The air connection is at the top side of the
module, but escape into the membrane module at the bottom side via the perforated center
pipe down. Ensure that the inlet air pressure is above the feed pressure and that the back flush
outlet valve is opened. As the air bubbles rise, turbulence is created which is sufficient to dis-
lodge the foulants from the membrane surface without damaging the fibers. The timer to be set
is approximately 30-60 seconds per air scouring.
Figure 10: Air scouring step during regeneration cycle
Back flush
Back flush is used to remove the remaining suspended particles from the membrane modules.
During back flush the permeate water is drawn from the product/back flush tank and forced
through the module from the filtrate side (lumen of the fibers) towards the feed side (shell side)
using the back flush pump. Hence, the flow direction is opposite to filtration flow direction.
The back flush water with loosen suspended particles are then forced out through the feed port
located at the top of the membrane module into the feed header and then directed into the
drain. The back flush must be conducted at a flux rate of 80 to 100 LMH.
Effective back flush duration is typically at least 30-60 seconds discounting the time taken for
the pump to ramp up and down. The duration and frequency can be altered depending on the
size of installation and the quality of the feed water.
= Manual, automatic or non-return valve
Feed/CIP return/WW
Feed
Product
Pre-strainer
BF/CEB inlet
BF / CEB / CIP w aste w ater
Waste w ater
Air supply for Air Scouring
Air supply / CIP feed
Blow er
UF permeate
Feed tank
UF permeate tank
CIP return & BF/CEB discharge
BF / CEB
Feed/CIP
Back flush
pump
pump
Chemical
dosing sets
UA860
Perm.
CIP / WW tank
membrane
Chem 1
Chem 2
Operation Procedures for MICRODYN AQUADYN® UA860 Modules
24 | 37
Form-No: TM-WW002 // Revision: A // Date: Oct. 10, 17
Figure 11: Back flush step during hydraulic cleaning cycle
It is highly recommended to ensure a reliable regeneration regime. A constant back flush flow
rate is adopted by using an inverter-controlled back flush pump. The pump should be controlled
such that the back flush flux is progressively ramped up to the desired back flush flow set-point
and ramped down at the end of the back flush without pressure spikes or water hammering ef-
fects.
Chemically Enhanced Backflush (EBF)
A Chemically Enhanced Back flush (EBF) cycle may also be included to optimize performance
and as a form of maintaining sustainability before CIP is carried out. Typical frequency for EBF
may be set at once every few hours or days of operation dependent on feed water characteris-
tics. A typical chemical that is used during EBF is sodium hypochlorite (NaOCl).
EBF is similar to a hydraulic cleaning cycle with the exception that chemicals are introduced in-
to the back flush water to enhance the cleaning effect of the membrane modules. Three addi-
tional steps are incorporated into the back flush cycle, namely dosing of chemical during back
flush, soaking, followed by additional back flush (rinsing out of chemicals).
Take note that whenever possible, always perform at least one back flush cycle prior to EBF to
ensure the larger suspended particles are removed as much as possible for increased effec-
tiveness of the EBF. Below is a description of the EBF:
1) Air Scouring to loosen the foulants on the membrane fibers and back flush as per usual hy-
draulic cleaning settings.
= Manual, automatic or non-return valve
Feed/CIP return/WW
Feed
Product
Pre-strainer
BF/CEB inlet
BF / CEB / CIP w aste w ater
Waste
Air supply for Air Scouring
Air supply / CIP feed
Blow er
UF permeate
Feed tank
UF permeate tank
CIP return & BF/CEB discharge
BF / CEB
Feed/CIP
Back flush
pump
pump
Chemical
dosing sets
UA860
Perm.
CIP tank
membrane
Chem 1
Chem 2
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