Water & Wastewater Asia September/October 2022

SINGAPORE FOCUS
MARICULTURE WATER RECYCLING
3E-NF membrane has been used for
seawater fish farm wastewater recycling,
laundry wastewater recycling, municipal
wastewater recycling for cooling tower
feed water, and more. In particular, the
membrane is suited for desalination pretreatment.
The 3E NF membrane module
Desalination plants generally use two types
of membranes: UF as a pre-treatment
to remove suspended particles, and RO
to remove the dissolved solids. The UF
membrane pre-treatment for the seawater
desalination is unable to remove hardness
and the majority of organic pollution, and
consequently the RO system is prone to
fouling and scaling. This leads to more
production downtime for the RO system
cleaning and maintenance as well. While
the water industry has been assessing
the removal of hardness through NF
membranes for a long time, no spiral-wound
NF membrane can replace the existing
UF membranes due to the space and flux
constraints.
On the other hand, HF NF membranes
improve desalination pre-treatment.
As they have the same configuration
as UF membranes and are capable of
removing hardness, they are a one-toone
replacement that will reduce the
overall capital and operating expense
of the desalination plants. With a wide
range of salt rejections to better suit
difficult feedwater qualities and permeate
standards, 3E NF membranes, can deliver
clean water with valuable ions preserved.
One of the company’s products was used in
a seawater fish farm to achieve low energy
water recycling in Singapore. Led by the
Singapore government and Singapore
Fish Culture Association, along with Ngee
Ann Polytechnic’s Environmental & Water
Technology Centre of Innovation, Aquarium
Iwarna, a marine ornamental fish import
and export company, cooperated with 3E
for the commissioning and installation of a
nanofiltration membrane wastewater reuse
system offering a 0.5m 3 /h capacity.
The system delivered the following
specifications:
• Feed: 38,000.0ppm
• Flux: 0.4±0.5 litres per hour
• Salt rejection: 20±0.3% (2000ppm
MgSO 2
)
• Operational pressure: 2.0 bar
With the 3E nanofiltration membrane, water
can be taken directly from the fish pond,
reducing equipment and overall operation
costs. More than that, the 3E-NF can
remove green algae via a variety of methods,
including backwashing, resulting in a more
stable system operation, in contrast to
conventional nanofiltration and reverse
osmosis membranes which are sensitive and
prone to the blooming of green algae in sea
water.
SUPPORTING WATER RECLAMATION
With up to 40LMH/bar flux, 3E-NF05
can also be used to achieve one-to-one
replacement of the traditional UF membrane
for the seawater desalination to reduce the
RO membrane fouling and scaling issue
without any footprint enlarge.
In another project, a 3E-NF05 HF
membrane system, with a 2,000m 3 per
day capacity NF-RO membrane system
design for cooling tower feed water, was
supplied, commissioned, and installed for
the Shangdong Kytoland Watertech. The
organisation had decided to use this system
in order to reduce demand of the Anqiu
thermal power plant for tap water, and to
preserve current drinking water resources.
After careful investigation, the 3E NF-RO
membrane was utilised in 2020 to treat
the reclaimed water, meeting discharge
standards; it was used for the cooling
tower’s water at the thermal power plant
after reaching the same standards as well.
With the NF-RO reclaimed water treatment
equipment, 3E thus attained its first
reclaimed water reuse project.
The system thus presented the following
parameters:
• Effective membrane area: 61.0m 2
• Water flow rate: 128±0.5 ton/day per bar
• Operation pressure: Maximum 3.0 bar
• Salt rejection: 2000ppm; MgSO 4
: 10±1%
• Maximum free-chloride resistance:
1000ppm
With the 3E-NF membranes, the overall
system will be able to run in a more stable
manner with a low maintenance cost. This
is due to the compact surface which is
not easily polluted, while also offering a
membrane flux that is close to ultrafiltration
membranes. In comparison, ultrafiltration
membranes offer a molecular weight
rejection rate of more than 5000da, which
cannot intercept the hardness of and organic
matter in water, resulting in the scaling and
pollution of the back RO membrane.
In addition, the 3E-NF membrane can
be used in a variety of ways, including
backwash to remove biological pollutants,
among others; its operating conditions
are also similar to those of ordinary
ultrafiltration membranes. Altogether, the
use of 3E-NF has supported a more reliable,
stable and feasible reuse of municipal
wastewater.
WATER & WASTEWATER ASIA | SEPTEMBER/OCTOBER 2022 13