abdel-fatah2018.pdf

Nanofiltration systems and applications in wastewater treatment:
Review article
Mona A. Abdel-Fatah
Chemical Engineering and Pilot Plant Department, National Research Centre, Cairo, Egypt
a r t i c l e i n f o
Article history:
Received 31 January 2018
Revised 6 August 2018
Accepted 30 August 2018
Available online 9 November 2018
Keywords:
Membrane
Nanofiltration
NF applications
Wastewater treatment
a b s t r a c t
Nanofiltration membrane (NF) is one of the most important activities employed in wastewater treatment
field. It is a relatively recent development in membrane technology and it can be aqueous or non-
aqueous. Characteristics of NF fall between UF and RO, and functions by both pore-size flow (convective)
and the solution-diffusion mechanisms. Membrane charges play an important role in membrane function
and often NF membrane as have surface negative charges. NF technique is used in a variety of water and
wastewater treatment (WWT) in different industrial applications. The main job of NF is the selective
removal of ions and organic substances and it is used in some specified seawater desalination application.
The main objective of this review is to illustrate the main applications of NF process in water reuse, WWT
as tertiary treatment, water softening and desalination fields. Comparison of basic economic analyses
with other alternative processes in profitability is also performed.
Ó 2018 Ain Shams University. Production and hosting by Elsevier B.V. This is an open access article under
the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Existing situation of wastewater in Egypt
Egypt population has reached around 96 million according to
2017 census. Most of the inhabitants reside in the small area of
the Nile valley and delta. The available water resources are Nile
river 55 109
m3
/y, rainfall 1.3 109
m3
/y, fossil groundwater
extraction 2.2 109
m3
/y, desalination 0.2 109
m3
/y, extracting
groundwater from renewable resources 6.2 109
m3
/y, wastewa-
ter 3 109
m3
/y, and reuse of the drainage of agricultural water
13 109
m3
/y. Egypt, with around 670 m3
/year/capita in 2017, still
is a country under conditions of water stress (1000 m3
/year/capita)
[1].
Villages and rural areas suffer from low or almost disappear-
ance of effective wastewater management system, it is important
to expand the system of wastewater management throughout
Egypt especially in villages and rural areas. Different systems and
networks have been installed over the last decade throughout
Egypt, a comparison of the different networks used in Egypt are
shown in Tables 1–4 [2].
In Tables 1–4, a list of developed projects; the currently ongo-
ing projects is shown below. The following projects are funded by
international donations or funded by the Egyptian government
[3]:
To improve the access to clean water, wastewater management,
and health services for around 1 M Egyptians at the Nile delta,
the World Bank has funded a program to improve the life qual-
ity by a $550 M.
The Sinai Peninsula has attracted interest to find more water
resources through drilling wells; Arab Fund for Economic and
Social Development (AFESD) has funded this project, $200 M
has been given as a loan to the Egyptian Government.
Two projects are currently taking place in southern Egypt.
Two irrigation projects are funded by The OPEC Fund for
International Development (OFID) and a drinking water sani-
tation project is funded by the French Development Agency
(AFD).
Amount of $110 M is provided by the Islamic Development
Bank to improve the water and irrigation treatment in Egypt.
Upper Egypt drinking water and wastewater management are
under development by the support of Switzerland and German
development bank KFW through a $250 M grant which repre-
sents the second phase of an extended project.
https://doi.org/10.1016/j.asej.2018.08.001
2090-4479/Ó 2018 Ain Shams University. Production and hosting by Elsevier B.V.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
E-mail address: monamamin7@yahoo.com
Peer review under responsibility of Ain Shams University.
Production and hosting by Elsevier
Ain Shams Engineering Journal 9 (2018) 3077–3092
Contents lists available at ScienceDirect
Ain Shams Engineering Journal
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USAID funded a project to improve water infrastructure in
northern Sinai governorate in 2017 by $50 M.
Improving infrastructure throughout Egypt was funded by a
loan from Germany by $225 M; a $65.5 M is directed to Assuit
Barrage irrigation project.
Amount of $2 Billion projects is undergoing to improve sanita-
tion in rural areas funded in Egypt.
The NWRP project started in 1998 (Framework and Guideli-
nes Egypt State of the Water Reporting). The NWRP technique
applicable in Egypt, that is currently applicable, has a time-
frame till the end of 2017. This NP is employed as an outline for
the sectarian tactics and plans on resources and supply of water,
WWT and recycle, agricultural expansion, national growth, secu-
rity of the water supply etc. Regarding the national strategy for
water, the document for the ‘‘2050 National Strategy for the Devel-
opment and Management of Water Resources” has considered six
political pillars of this strategy [1]:
i. Development of water resources
ii. Water usage justification
iii. Pollution control of existing water resources
iv. Water irrigation and resource systems restoration
v. Weather changes adaptation
vi. Better management of water
Nomenclature
A membrane surface area, m2
AFD agency of French development
AFESD arab fund for economic and social development
AOX absorbable organic halides
B solute permeability coefficient
Cc the concentration in concentrate, mg/l
CF concentration factor
Cf feed solution concentration, mg/l
CFCR cross-flow with concentrate recycle
CIP clean-in-place
Cm mean salt concentration = [Cf + Cc]/2, mol/l
COD chemical oxygen demand
CP concentration polarization
Cp salt concentration in the permeate, mg/l
Cv volumetric concentration factor
Cwm water concentration in the membrane
DOC dissolved organic carbon
EDR electrodialysis reversal
IDB islamic development bank
IWRM integrated water resources management
IWWTP industrial wastewater treatment plant
Js salt flux, mol/m2
h
Jv permeated fluid volumetric flux, m s1
Jw permeate flux, L/m2
h
KFW Switzerland and German development bank
Kw solvent mass transfer coefficient, L/m2
h bar
M million
MED multiple-effect distillation
MF microfiltration
MSF multi-stage flash distillation
Mw molecular weight, kg/kmol
MWCO molecular weight cutoff
n number of moles
NDP net driving pressure
NF nanofiltration
NP national plan
NSDM national strategy for the development and management
NWRP national water resources plan
OFID OPEC fund for international development
PA polyamide
PAA polyacrylic acid
PAC powdered activated carbon
PAN poly-acrylonitrile
Pc concentrate pressure, bar
PDP pressure-driven process
PES polyethersulfone
PET polyester
Pew dimensionless permeate flux, [vwR/D]
Pf feed pressure, bar
Pm solvent permeability constant
Pm average pressure gradient, bar
Pp permeate pressure, bar
PPM parts per million
Ps membrane permeability with respect to dominant salt,
m/s
Pw water permeability’s and reflection coefficients
Q volumetric flow rate, m3
/s
Qc concentrate flow rate, L/h
Qf feed flow rate, L/h
Qp permeate flow rate, L/h
R system recovery, %
RBC rotating biological contactor
RO reverse osmosis
SBR sequential batch reactor
SDM solution-diffusion model
SEM scanning electron microscope
SP salt Passage, %
SPM semi-permeable membrane
SR salt rejection, %
SW spiral-wound
T temperature, K
TCF temperature correction factor
TDS total dissolved solids
TFM thin film membrane
THM total heavy metals
TOC total organic carbon
TMP trans-membrane pressure
UASB up-flow aerobic sludge blanket
UE upper Egypt
UF ultrafiltration
USAID American funded
VC vapor compression
VCF volumetric concentration factor
WB world bank
WR water resources
WWT wastewater treatment
y recovery fraction
a dimensionless parameter, [aC0Rr/DP]
b concentration polarization factor
d concentration boundary layer thickness, m
d film thickness
DC concentration gradient, mol/l
DCm solute concentration difference across the membrane
DP applied pressure difference across the membrane, bar
Dp osmotic pressure difference across membrane, bar
Dpm average osmotic pressure, bar
pc concentrate osmotic pressure, bar
pf feed osmotic pressure, bar
pm average osmotic pressure, bar
pp permeate osmotic pressure, bar
3078 M.A. Abdel-Fatah / Ain Shams Engineering Journal 9 (2018) 3077–3092

Pillars of I, iii and vi have a direct effect on the wastewater
reuse, considering the following important objectives:
Increasing water awareness through media and
communication
Controlling the main drains pollution source
Spreading the benefits of better water management
Water legalization and IWRM techniques enhancement
Developing national plans to be applied on governorate level
Imposing the industrial buildings to develop wastewater treat-
ment units
Spreading the units of water treatment in villages
Before membrane filtration process, wastewater was pretreated
by suitable techniques to remove most of the suspended or un-
dissolved ingredients like suspended solid, inorganic and organic
compounds to protect the membrane from damage due to its high
cost (recommendation all of the manufacturing membranes).
Residual contaminants are mainly dissolved heavy metals salts,
so in the treatment technique, we try to increase the molecular size
of the pollutants then selected the suitable membrane filtration
procedure for pollutants separation.
There are a plethora of very effective technologies available to
reduce the conc. of contaminants capable of fouling NF membrane.
They include filters, coagulation and precipitation processes, oil/
water separators, adsorbing resins and many others. Two relatively
new entrants in the field of pretreatment technologies are MF and
UF; MF designed for removal of suspended solids, while UF is
designed to remove dissolved macromolecules (organic). These
technologies are available in a wide variety of pore sizes and mate-
rials of construction, as described earlier [4].
The basic science of the membrane processes can be explained
by the heavy metals formation of cationic forms which are initially
complexes by a bonding agent which will increase the molecular
weight of the bonded cations and to increase the size of the mole-
cule to a size greater than the pores of the membrane which is used
for separation. The membrane filtration is distinguished by the fol-
lowing advantages compared to the other conventional separation
technologies: low-energy requirements, high selectivity of separa-
tion, and very fast reaction kinetics [3–7].
2. Overview of membrane separation technology
The membrane filtration has two aspects which discriminate
membrane filtration compared to other conventional filtration
techniques. The first aspect is, membranes are asymmetric and
the feed is faced by the pore small side which reduces the pressure
drop across the membrane and eliminates membrane plugging
tendency. The second aspect is, a strong cross flow over the mem-
brane surface is necessary to operate membrane systems. The
cross-flow eliminates the possibility of filter cake build-up. Usu-
ally, the filter cake or the concentration polarization in membranes
is limited to few microns [4].
2.1. Brief history of membrane filtration
At the beginning of the twentieth century, the recent membrane
filtration technology was considered, the membrane was fabri-
cated similarly to the artificial polymeric membrane which is well
known today, after the Second World War, the need for membrane
filtration has increased and played a crucial role in the drug indus-
try, medical applications, and microbiology field. Later on, the
reverse osmosis membrane has been developed and applied
through different stages: considered and produced initially in the
Table 1
Networks of Wastewater Management in Egypt, 2015. Source: Holding company for
water and wastewater in Egypt, 2015.
Year 2005 2015
Service region 12 governorates 27 governorates
Subsidiary companies 14 companies 25 companies
Water service coverage –
millions
2.5 No coverage
7.5 Rotation system
15 Unacceptable
Service
98%
Wastewater service coverage 40% 50%
85% Urban
10% Rural
Water production – annual
average
18 m m3
/day 27 million m3
/day
Water treatment plants 1005 plants 2845 plants
Wastewater treatment plants 149 plants 395 plants
Water distribution networks 74,000 km 167,000 km
Wastewater collection
networks
28,000 km 48,000 km
Table 3
WWTP classification and technologies.
Treatment technologies No
Activated sludge 99
Extended Aeration 122
Up-flow Aerobic Sludge Blanket (UASB) 5
Trickling filter 29
Rotating biological contactor (RBC) 24
Sequential batch reactor (SBR) 13
Oxidation ponds 85
Primary treatment 2
Tertiary treatment (by UF membrane) 4
Wetland 3
Aerated Lagoon 3
Others 12
Total 412
Table 4
Number and distribution of WWTP in each governorate.
Governorate No of WWTP Governorate No of WWTP
Assiut 5 Matrouh 2
Behira 24 Menufya 19
Cairo 12 Minia 19
Damietta 27 New Valley 8
Garbia 34 Port Said 6
Ismailia 6 Qalubiya 13
Alexandria 17 Qena 5
Aswan 15 Red Sea 1
Beni-Suef 15 Sharqya 29
Dakahelya 44 Sinai 12
Fayoum 25 Sohag 6
Giza 7 Suez 1
Kafr El-Sheikh 22 Luxor 5
Table 2
Basic figures of water/wastewater services in Egypt 2016.
Item Data
Current Population 92.5 million capita
No of WWTP 412
No of affiliated companies 25
Total produced water (million m3
/day) 24.9
Average water coverage % 97%
Average water capita/person/day 277 L
Total treated wastewater (million m3
/day) Design capacity :14.1
Actual discharge:10.5
Average Wastewater Coverage % in urban cities 83%
Average Wastewater Coverage % in rural villages 15%
Average Wastewater Coverage % 56%
M.A. Abdel-Fatah / Ain Shams Engineering Journal 9 (2018) 3077–3092 3079

1950s, research, and development in the 1960s, and finally, the RO
was used on a commercial level in the 1970s.
The RO was developed initially considering desalination of sea-
water and brackish water for a rural area to get drinking water.
After that, the UF has been established and industrialized to cover
the gap between reverse osmosis depending on salt rejection and
MF based on particle retaining and salt passing technique. To
approach an economical operating mode, the cross-flow mode
should be employed for RO and UF. The cross-flow mode may
results in a processing obligation in the certain operating situation;
however, the RO and UF technologies represent a major
improvement.
2.2. Types of membrane separation and scope of application
According to the pressure gradient across the membrane, mem-
brane techniques can be divided into MF, UF, NF, and RO. Both RO
and NF are classified under the main umbrella of membrane sepa-
ration by which treated water is pressurized and forced at the face
of the semi-permeable membrane. As a result desalted water pass
through membrane pores. Fig. 1 represents the filtration spectrum
for each type and the applicable range for each type. Correlation of
membrane features with ranges of separation is illustrated in
Table 5.
2.2.1. Nanofiltration: the up-and-coming membrane process
After the comparison mentioned in the above section, it was
found that NF has the special attraction in different applications
such as water reuse, industrial wastewater treatment, and drinking
water sectors. So the nanofiltration process through historical
development is shown in Table 6.
2.2.2. Why nanofiltration technology is needed?
RO membranes have been developed and a class of membranes
has been fabricated to be able for retaining all dissolved salt ions
and even the organic solutes with no charges. In addition, UF mem-
branes with special pore size can reject any molecular weight
higher than 10,000 gm-moles and can be used efficiently for
Fig. 1. Filtration spectrum.
Table 5
Correlation of membrane features with ranges of separation.
Types Reverse Osmosis Nanofiltration Ultrafiltration Microfiltration
Membrane Asymmetrical Asymmetrical Asymmetrical Asymmetrical
Asymmetrical
Thickness Surface film 150 mm
1 mm
150 mm
1 mm
150–250 mm
1 mm
10–150 mm
Pore Size 0.002 mm 0.002 mm 0.02 – 0.2 mm 0.2 – 5 mm
Rejects HMWC, LMWC, sodium
chloride,
glucose, amino acids, proteins
HMWC, mono, di – and oligo – saccharides,
polyvatent anions
Macromoie, cutes, proteins,
polysac – charides, viruses
Particulates, clay,
bacteria
Membrane material
(s)
CA: thin film CA: thin film Ceramic, PSO, CA, PVDF, thin
film
Ceramic, PP, PSO, PVDF
Membrane Module Tubular, spiral – wound,
plate and frame
Tubular, spiral – wound,
plate and frame
Tubular, hollow, fiber, spiral,
wound, plate and frame
Tubular, hollow fiber,
plate and frame
Pressure 15–150 bars 5–35 bars 1–10 bar 2 bars
*
CA-cellulose, acetate; PSO-polyaulfone; PVDF, polyvinylidene fluoride; PP-polypropylene; HMWC (high molecular weight compounds): 100.000–1 millions mole/g, LMWC
(low molecular-weight compounds): 1.000 – 100.000 mol/gm, macromolecules: 1 million mole/gm.

various industrial purposes. What is really needed to separate the
solute from the solution for molecular weight range from 500 to
10,000 gm-moles?
2.2.3. The start of new technology and membrane classification
Dr. Peter Eriksson named the new class of membranes in mar-
ket application NF membranes at 1984. The term NF is related to
the estimated pore size in a membrane characterized by MW
removal. The new membrane technology has initiated hat we can
call the fourth class of membranes operating under pressure driven
operation. NF is distinguished by the ability to separate small
solutes from solution by two mechanisms. The first mechanism,
which is well admitted in the science community, is separating
molecules based on their charge in water which is known ionic
separation of NF. The second mechanism is sieving according to
the molecular weight of uncharged solutes.
2.2.4. Current situation on nanofiltration
While RO and UF usage in water and wastewater treatment is
increasing gradually, NF applications are increasing exponentially
in water and wastewater treatment, other applications in the
industry like separation of solute or chemical from solution, pro-
ducing bio-materials, drug industry, and flavors. In addition to pro-
ducing different chemicals using NF, a recovery of fine chemicals
from outlet streams is widely used in industrial applications like
in medical applications and feed additives. With all such applica-
tions, NF is a major player in the separation technology in current
commercial applications. Also, NF membranes are used now to
replace RO in different applications like drinking water and
extracting fine and expensive materials to gain profits and reduce
energy expenses.
2.2.5. Future of nanofiltration
RO and UF have been used widely for different applications but
their applications are still limited and hard to be extended further,
NF applications are expanding and replacing other membrane fil-
tration techniques. NF membrane is composed of different materi-
als and its preparation is flexible either by employing RO
membrane polymers such as cellulose acetate and polyamide poly-
mers in addition to other chemically resistant polymers. Currently,
NF membranes are also made of ceramic materials to withstand
high temperature. The flexibility of preparation and the variety of
raw materials for NF preparation will increase and spread its appli-
cation in different processes. With such flexible raw material selec-
tion and easiness to be modified for different applications, NF will
be soon the major and most used membrane filtration technology
which requires that research community should focus more on NF
development.
2.3. Types of nanofiltration membrane
Types of the membrane are classified according to the mem-
brane structure and pore shape into isotropic micro-porous, non-
porous, dense, electrically charged, asymmetric, ceramic, and
liquid membranes [8–11].
2.3.1. Typical flow configurations
Usually, two flow configurations are distinguished in mem-
brane systems as shown in Fig. 2:
Cross-flow with concentrate recycle (CFCR); and
Flow system with a dead-end.
Cross-flow (also defined as tangential flow) filtration is con-
ducted by employing a high-pressure feed water flow across the
membrane. The solution is divided into two parts, a part passes
through the membrane or filtered which is called permeate and
Fig. 2. Membrane flow configurations.
Table 6
A general overview of historical development of nanofiltration membranes.
Membrane Persons/Manufacturer Year
Porous CA membranes (integrally
asymmetric)
Reid, Breton, Leob-
Sourirajan
1959
CA NF membranes (integrally asymmetric) Leob-Sourirajan, Cohen 1970
Composite RO membranes Rozelle, Cadotte, Riley 1970
Composite NF membranes Rozelle, Cadotte 1976
Polypiperazineamide NF membranes
(99% MgSO4 60% NaCl rejection)
Cadotte, Steuck,
Petersen
1981
Fully aromatic cross linked polyamide NF
membranes
Filmtec Co. 1985
Polyethyleneimine NF membranes Linder, Aviv, Perry,
Katraro
1988
Acid/base stable NF membranes Linder, Perry, Aviv 1988
Chlorine resistant NF membrane MeCray, Petersen 1989
NF membrane modified from RO
membranes
by acid, base, oxidant treatment
Strantz, Brehrn,
Cadotte
1989
Solvent resistant NF membrane Black, Shavit
Perry, Yacubowiez,
Linder
1990

the remaining just flow marginally with the membrane surface
without separation or filtration which is called the reject or con-
centrate. The concentrate composed of all rejected salts and it is
usually concentrated with all undesired materials.
The flow system that contains dead-end unit is operated by
accumulating reject until backwashing is required. The backwash-
ing process flushes and disposes of all the accumulated concentrate
using a washing liquid volume of 2–5% of the total inlet solution.
The cross-flow helps to preserve the uniform flow rate of permeate
and help to keep a longer membrane life by eliminating irre-
versible membrane fouling.
2.3.2. Nanofiltration membrane material and configurations
The NF membranes are characterized essentially by chemical
and physical compatibility with process liquors, pore size distribu-
tion, surface chemistry, porosity, and cost. The membrane func-
tionality depends on three layers: an active layer, porous
supporting layer, and macroporous structure underneath. The
active layer properties determine the permeability of a certain
component and hence the selectivity of a certain membrane for a
separation process. The supporting layer helps to modify the
mechanical properties. And the last layer is a macroporous layer
below the medium layer.
2.3.3. Configuration of nanofiltration membrane elements
The membrane surface working area per unit of membrane ele-
ment volume range for different membrane configuration, Table 7
Characteristics of the principal module designs [12,13]:
Plate and frame module [60–300 m2
/m3
];
Tubular membrane module [60–200 m2
/m3
];
Spiral wound module [300–800 m2
/m3
]; and
Hollow fiber membrane module [20 000–30 000 m2
/m3
].
2.3.3.1. Spirally wound membrane elements. Industrially the mem-
brane is used as spirally wound membrane element, each element
contains several spirally wound sections connected in series. The
inlet solution is introduced at one end of the spirally wound mem-
brane element, the feed will flow through the membrane gap and
permeate is produced by cross-flow through flow channels inside
the support material which is usually made of special fabrics.
The permeate then flows through the perforated tube at the central
part of the element. The concentrate enters through remaining
Table 7
Characteristics of the principal module designs.
Characteristics Spiral Wound Hollow Fiber Tubular Plate and Frame
Packing Density (m2
/m3
) 800 6000 70 500
Required Feed Flow (m3
/m2
-s) 0.25–0.50 0.005 1.0–5.0 0.25–0.50
Feed Pressure (psi) 43–85 1.4–4.3 28–43 43–85
Membrane Fouling Propensity High High Low Moderate
Ease of Cleaning Poor to good Poor Excellent Good
Feed Stream Filtration Requires 10–25 m
filtration
5–10 m
filtration
Not required 10–25 m
filtration
Fig. 3. Spirally wound membrane.
Fig. 4. Cross-section of a spiral-wound module.

membrane layers to undergo subsequent separation processes as
shown in Fig. 3 [14–16]. The design is shown in Fig. 3 is distin-
guished with a large surface area of membrane surface contained
in a small element volume, although the unused space might be
suspected to the formation of biological creatures.
Spirally wound elements are available in different element
diameter usually 5, 10, and 20 cm. A removal of suspended solids
is a necessary pretreatment step for the feed before filtration in
the spirally wound element. Spirally wound element is usually
employed in desalination of seawater and brackish water due to
a low price and compact nature. Fig. 4 explode view and cross-
section drawings of a spiral-wound module.
2.4. Nanofiltration process
NF is a process by which part of the feed passes through
semi-permeable membrane Fig. 5. The inlet stream is divided
into permeate which is the filtered portion of the stream and
the retentate or concentrate which is the rejected non-filtered
portion. NF has effectively shown efficient removal of organic
material. However, chlorine disinfection is important for
removal of microbial growth which has been reported in NF dis-
tribution systems. To reduce microbial growth, NF membranes
characterized by low inorganic material detention and high
removal of organic materials can produce water with an opti-
mum quality.
3. List of reverse osmosis and NF membrane manufactures
The membrane manufactures producing membranes for
domestic, industrial and desalination plant applications are shown
in Table 8.
3.1. Advantages and disadvantages
NF is distinguished with the removal of calcium and magne-
sium ions resulting in water softening, and no addition of sodium
ions during filtration [18–21] compared to ion exchange units.
NF does not require additional chemical treatment to reduce hard-
ness; so the water softening process is approached effectively
without realizing sodium resin in water which is the case for
50 years.
NF does not require heating or cooling of feed like distillation
for example which will reduce the cost of separation effectively.
In addition, no mechanical stirring is required which will maintain
gentle molecular separation. NF has the important benefit of han-
dling a high volume of feed in a continuous manner and a stable
flow rate of permeate.
However, NF has a limited application in the industry due to the
pore size of the membrane which is limited to nano-pore size. RO
and UF are preferred since they can cover the UF range effectively
without the cost limitation of NF due to high initial, operating and
maintenance cost [22]. Since replacement of NF membranes is a
Fig. 5. Principal of nanofiltration process.
Table 8
List of reverse osmosis NF membrane manufactures [17].
Vendor Telephone Vendor Telephone
A/G Technologies, MA 617-449-5786 New Logic, CA 510-655-7305
Advanced Recovery Systems, CA 818-764-6441 Osmonics, MN 404-892-3175
Amicon Corp., MA 617-777-4550 Pall Corporation, NY 800-289-7255
Cer-Wat Corp., TN 615-588-8342 Prosys Corp., MA 508-250-4940
CeraMem Separations, MA 617-899-0467 Pureflow, GA 404-939-7717
Dedert Corporation, IL 708-747-7000 Refractron Technologies, NY 315-331-6222
Desalination Systems, CA 619-746-4995 Rhone-Poulenc Inc., NJ 609-860-3580
Dupont Separation Systems, DE 302-695-5234 Rochem Separation Systems, CA 310-370-3160
DynatecInc, NJ 609-387-0330 Separation Technology, SC 803-366-5050
Epoc Filtration Systems, CA 209-291-8144 Separation System Technologies, CA 619-581-3765
Fluid Systems, CA 619-695-3840 Seprotech Systems Inc., Canada 613-523-1641
Fycon Technologies, NC 704-529-4370 Spin Tek, CA 714-848-3060
Gaston County Dye Machine, NC 704-263-6000 The Dow Chemical Company, MI 517-636-6786
Graver Separation Systems, SC 302-731-3539 US Filter, PA 512-772-1319
Graver Water Inc., NJ 908-964-2400 WL Gore Assoc., MA 410-392-3300
HC Warner Inc., NC 704-588-3388 Wheelabrator/Memtek, NJ 609-953-1788
Hoescht Celanese, NC 704-588-5310 Zenon Environmental, Canada 905-639-6320
Koch Membrane Systems, MA 508-657-4250 Zimpro Environmental, WI 608-838-6777
LCI Corporation, NC 704-394-8341 Millipore Corp., MA 617-275-9200
Membrex Corp., NJ 201-575-8388 National Environmental Tech., NC 704-529-5551

function of TDS, NF membranes are replaced in a shorter time com-
pared to the actual filter lifetime which increases the NF cost. List
of some commercially available nanofiltration membrane shown in
Table 9.
Using NF systems has increased the energy requirements for
water treatment 60–150%, low energy systems are an important
requirement. Green energy may act as an efficient way to reduce
energy requirement as suggested by Sombekke [23], however,
the green energy price is higher than conventional energy. One
way to reduce energy requirements of NF is to use of more perme-
able NF which will reduce pressure and energy requirements
which may affect membrane operation. So, a balance is required
to optimize energy requirements and optimum operation.
3.2. Design and operation
An efficient packing method is essential for commercializing
membrane application especially in industry, effective membrane
application requires large area; so the membrane is used commer-
cially after using an economically and effective housing/packing
[24]. A support is important to operate the membranes; the sup-
port should be porous and able to withstand the high pressure
inside the module. The components inside the module permit
appropriate flow conditions by providing flow channels reducing
concentration polarization. The design of an effective module
should consider the elimination of feed leakage to permeate using
O-rings or glue, reducing energy requirements by minimizing pres-
sure losses [25,26].
4. Nanofiltration membrane transport models
Mathematical presentation or models can be used to describe
the RO/NF membranes performance and operation, and to predict
the response of the membrane system under operating conditions.
These models are crucial for the design of RO/NF systems. Models
that can well predict the membrane performance will reduce the
experimental work required for exploring a particular system
[27–31].
4.1. RO/NF models can be categorized into 3model types
(i) Irreversible thermodynamics models;
(ii) Non-pores or homogeneous membrane model [solution-
diffusion model];
(iii) Pore models for membranes.
Models such as Donnan exclusion and extended Nernst-Planck
can be used to represent nanofiltration membranes. Nanofiltration
membranes are often negatively charged, so NF includes
electrostatic effects. The top layer of composite or asymmetric
Table 9
List of Some Commercially Nanofiltration Membranes [19].
Firm Membrane Material pH P
MPa
T
°C
R
%
Jp
L/m2
-h
Conditions °C, g/L;
Filmetc NF270 PA 3–10 4.1 40 40–60 CaCl2 97MgSO4 63
53
25;0.5;0.48
25;2;0.48
Filmetc NF90 PA 3–10 4.1 45 85–95 NaCl 97 MgSO4 32
41
25;2;0.48
Filmetc NF200 PA 3–10 4.1 45 35–50 CaCl2 97MgSO4 34
29
25;0.5;0.48
25;2;0.48
Koch SR2 n.s 4–9 2.4 45 10-30NaCL 97MgSO4 52 25;2;0.38
Koch SR3 n.s 4–10 3.45 50 30–50 NaCl 27 25;2;0.66
Koch MPS 36 n.s 1–13 3.5 70 10 NaCl 201 30;2;0.06
Koch MPS50 PPA 3–10 3.5 40 95 polymer in Butyl
acetate/xylene
n.s 30;5;3
Nitto NTR 7450 HG n.s 2–11 5 90 50 NaCl n.s 30;2;3
Nitto NTR 70 HG PVA 2–8 5 60 93 NaCl n.s 25;2;1
Nitto NTR 7430HG PVA 2–11 3 90 30 NaCl n.s 25;1.5;1
Nitto NTR7410 n.s 2–11 3 40 10 NaCl n.s 25;2;0.5
Nitto NTR7410HG n.s 2–11 5 90 10 NaCl n.s 25;2;0.5
Nitto LES90 n.s 2–10 2 40 95 NaCl n.s 25;2;1
Trisep XN45 PA-urea 3–11 4.1 45 95 MgSO4 n.s 25;2;1
Trisep TSS0 PA 4–11 4.1 45 99 MgSO4 42 25;2;0.67
Hydranauties ESNA PA 3–10 4.1 45 87 CaCl2 37 25;2;0.76
Nadir N30F PES 0–14 n.s 95 25–35 NaCl
85–95 NaSO4
40–70 25;0.5;0.52
Nadir NF PES 10 PES 0–14 n.s 95 5–15 NaCl
30–60 NaSO4
200–400 20;n.s;4
Toray SU 620 PA 3–8 4.1 45 55 NaCl 27 20;n.s;4
Sepro NF 1 PA 3–10 8.3 50 80 NaCl
90 MgSO4
110 25;0.5;0.35
Sepro NF 2 PA 3–10 83 50 55 NaCl
97 MgSO4
135 25;2;1.03
Sepro NF 3 PA 3–10 8.3 50 40 NaCl
98 MgSO4
42 25;2;1.03
Sepro NF 4 PA 3–10 8.3 50 35 NaCl
98 MgSO4
110 25;2;1.03
Osmonies Desal 5 (DK) PA 4–11 6.8 90 50 NaCl 38 25;1;0.7
Osmonies Desal G10 (GH) PA 4–11 6.8 90 30 NaCl 38 25;1;0.7
Osmonies HL n.s 3–9 3.1 50 98 MgSO4 46 25;2;0.69
Osmonies CK CA 5–6.5 3.1 30 97 MgSO4 38 n.s
Osmonies Durasliek n.s 5.5–7 4.1 50 98.6 MgSO4 48 25;2;0.69
Osmonies Seasoft n.s 2–11 4.1 50 98 MgSO4 38 n.s
Osmonies HR 2–11 4.1 50 98 MgSO4 35 n.s
PA = polymide, PVA = polyvinyl, CA = cellulose acetate, PES = polyethersulphone, n.s = not states, Manufacturer test results were based on spiral wound module except for
Nadir membranes, which were tested as flat samples.

membranes is the area studied in transport models since this layer
determine selectivity and flux. Models usually adopt equilibrium
condition or steady-state operation.
Also, most of the membrane models assume equilibrium [or
near equilibrium] or steady-state conditions in the membrane.
Below, a brief discussion of the solution-diffusion method is pre-
sented. The solution-diffusion method considers process variables
on membrane performance, concentration polarization, and water-
solute-membrane interactions.
4.2. Solution-diffusion model
The solution-diffusion model (SDM), this model is developed
assuming solute and solvent diffusion within the membrane. They
proposed a model with the following assumptions [27–33]:
(1) The membrane is composed of a surface layer that is non-
porous and homogenous;
(2) Solvent and solute dissolve in the surface layer;
(3) The chemical potential gradient controls the transportation
of matters; and
(4) The chemical potential gradients of solvent and solute are
affected by concentration and pressure differences across
the membrane.
4.3. Summary of equations of spiral-wound NF by SDM [27–33]
Concentration average; Cm ¼
Cf þ Cc
2

ð1Þ
Concentration polarization factor; b ¼ eky
¼ e0:7y
eky
¼ e0:7y
ð2Þ
Concentration gradient; DC ¼ bðCm CPÞ ð3Þ
Osmotic pressure; Dp ¼ p
pP ð4Þ
Net driving pressure ½NDP ¼ DP Dpm ð5Þ
Recovery; R% ¼
Qp
Qf
!
100 ð6Þ
Y; fraction recovery ¼
Qp
Qf
!
ð7Þ
Salt passage ½SP% ¼
Cp
Cf

100 ð8Þ
Salt rejection SR
½ ¼ 100 SP
½ % ð9Þ
Concentration factor CF
½ ¼
Cc
Cf

¼
1
1 y

ð10Þ
Permeate flux; Jw ¼
Qp
A

ð11Þ
Membrane permeability ½Kw ¼
Jw TCF
NDP

½FF ¼ 1newmembrane
ð12Þ
Salt flux; Js ¼
Qc
A

¼ Ks DC TCF ð13Þ
Mass transfer coefficient ½Ks ¼
Jc TCF
DC

ð14Þ
5. Applications of nanofiltration membranes [34]
Nanofiltration membranes are a relatively recent development,
filling a void between two well-established technologies: reverse
osmosis and ultrafiltration separation processes. One of the most
exciting characteristics of Nanofiltration membranes is their ability
to permeate mono-valent ions, such as sodium chloride, through
the membrane, while rejecting divalent and multivalent ions, such
as sodium sulfate. This flexibility opens up many possibilities in
the development of specialty process applications across multiple
industries. Filtration is primarily focused on process applications,
and so it was a natural fit to develop Nanofiltration membranes
to add to an already diverse product offering of ultrafiltration
and microfiltration membranes.
Nanofiltration membrane processes are commonly used by a
number of industrial processes, including Chemical industry, food,
textiles, metal finishing, pulp and paper, pharmaceutical and
biotechnology applications, and power generation. The reported
applications include mainly:
Application in the chemical industry,
Desalination of food industries [dairy, juice processing, soft
drinks, sugar industry, fish meal, beverage products, meat pro-
cessing, baker’s yeast, and olive processing],
Whey partial desalination,
Textile dyes desalination and brighteners of optical,
Removals of Metal, Nickel, and Chrome plating from metal fin-
ishing industries and leather industry,
Pharmaceutical and biotechnology applications, and
Purification spent clean-in-place (CIP) chemicals.
5.1. NF applications by industry
Food, Dairy, Beverage
and Plant Extracts
Concentration and demineraliza-
tion of lactose:
Nanofiltration membranes can
concentrate and demineralized
lactose at the same time, to vari-
ous degrees of purification as
required by the process
Maple syrup concentration:
As opposed to conventional boil-
ing reduction methods for thick
maple syrup, nanofiltration can
be employed to reduce both costs
and processing time
Gibberellins [plant/pharma]:
Gibberellins are plant hormones
used to promote plant growth
and other developmental pro-
cesses. Nanofiltration is a reliable
method to increase total product
yields by concentrating plant
hormones such as gibberellins
Textile and Dyes Dye desalting and concentration:
Dye desalting and concentration
using nanofiltration are an effec-
tive means of improving dye
strength, purity, and value. The
(continued on next page)

concentration capacity of nanofil-
tration membranes also plays an
important role in textile wastew-
ater treatment by increasing both
product recovery and reuse
Dye concentration: By allowing
salts and water to pass through
an NF membrane, nanofiltration
can be a practical alternative for
the concentration and desalina-
tion of dyes used in the textile
industry
Dye penetrate removal: Nanofil-
tration is widely applied in the
recovery of dye in order to meet
discharge regulations after pene-
trating testing with fluorescent
dyes
Optical brightening agent con-
centration and desalination: Opti-
cal brightening agents are able to
enhance colors appearance. To
reduce operating costs, nanofil-
tration can be employed to
increase the agent brightening
concentration to be reused
Industrial Processes
and Wastewater
Seawater sulfate removal:
Nanofiltration membranes have
the ability to selectively remove
sulfate found in seawater, impor-
tant in preventing scaling in oil-
field waterflood operations
Dissolved natural organic matter
removal from surface water: Nat-
ural organic matter [NOM] can be
removed from surface water
using nanofiltration to aid in the
production of NOM-enriched
water or for industrial process
water
Landfill leachate treatment: As a
lower energy alternative, nanofil-
tration can be used to treat
certain landfill Leachate by
removing pollutants, decreasing
TOC and COD levels, and lowering
turbidity
Brine recovery: NF membranes
can reject high amounts of sulfate
and allow sodium chloride ions to
pass through the membrane,
offering a viable solution for brine
recovery in industrial processes
Biotech/
Pharmaceutical
Antibiotics production: Nanofil-
tration membranes have been an
attractive separation process
technology employed in separa-
tion, concentration, and produc-
tion of hormones and antibiotics
Blood serum: Once blood serum
and blood plasma have been
separated, nanofiltration can be
used to capture fibrinogen and
other clotting compounds
5.2. Recent NF applications
5.2.1. Systems water softening
Hardness is caused by ions of Calcium [Ca2+
], Magnesium [Mg2+
]
and Bicarbonate [HCO3

]. The hardness ions or minerals cause scale
formation in pipes and equipment in potable water and systems
uses water process like the heat exchanger. Water can be purified
using softening units to remove scale-forming ions [35].
5.2.2. Municipal wastewater treatment
An advanced treatment combination for polishing municipal
wastewater with the purpose of a safe groundwater recharge was
investigated. The results indicated that NF is appropriate to treat
the tertiary effluent to reject DOC and AOX to a concentration less
than 2–3 mg/l and 20 lg/l. Bio-fouling on the NF membrane (Desal
DK5); the surface can be controlled by higher cross-flow velocity of
about 1 m/s. A suitable pretreatment like slow sand filtration is
required. Ozonation experiments with the concentrate to confirm
an enhanced bio-degradability of refractory DOC [36].
A combination of RO and NF with controlled crystallization was
implemented to treat landfill Leachate to reduce its volume of con-
centrate for further processing, by 75–80% [35]. Also, in another
study, NF was able to remove COD from refractory, permeate
shows a COD less than required for the discharge [37–39]. Table 10
shows the benefits of NF application in wastewater treatment.
5.2.3. Water treatment
Membrane Processing Technology is used widely in food indus-
try and treatment of food industry effluents. Fouling rate and
membrane layer rapid concentration are caused by wastewater
from the food industry especially when operating under high pres-
sure. Instead of RO/UF, a single NF stage can reduce the COD; for
example in whey production; a stream with COD of 100,000 mg
O2L-1 is filtered to reduce permeate with COD of 2787 mg O2L-1.
The rejected proteins stream is concentrated to around 88%
[40–43].
Table 10
The benefits of NF application in wastewater treatment.
Application Permeate Concentrate Benefits of NF
Whey/Whey
permeate
Salty
wastewater
Desalted whey
concentrate
Allows the recovery of
lactose and whey protein
concentrate with reduced
salt content
Textile Dyes Water, salts,
BOD, COD and
color
NF is used to desalt dyes
resulting in a higher
value product
Caustic cleaning
solutions
Caustic
cleaning
solution
BOD, COD,
suspended
solids, caustic
cleaner
Allows caustic cleaning
solution to be recycled
resulting in reduced
cleaning chemical costs
Recycle of acid
solutions
Acid
solution
BOD, COD,
calcium,
suspended
solids, acidic
water
Allows acid solution to be
recycled resulting in
reduced cleaning
chemical costs
Water Softened
water
Hard water Potable water
production. Softened
water reduces scaling on
equipment and heat
exchange surfaces
Antibiotics Salty waste
product
Desalted,
concentrated
Antibiotics
NF produces high value
pharmaceutical products
Pharmaceutical
Industry
Drug
Industry
Salty waste
product
Increases value of
pharmaceutical product

Small-scale food and beverages industrial units develop eco-
nomical processes to recover water from effluents due to the high
cost of water. One common process is to use a bioreactor in com-
bination with NF unit to fully disinfect and recover water. The
bioreactor reduces around 95% of wastewater COD. The produced
water has a quality similar to potable water according to German
Drinking Water. The recovered water can be used to cover a por-
tion of the industry needs [44].
In addition to water and wastewater treatment, NF can be
employed in water softening and low MW salt recovery. So, NF
can be employed in sulfate retention during seawater filtration
and treatment of petroleum products [45].
According to Song et al. [46], ‘‘the H2O2/UV oxidation of source
water prior to NF showed potential for the following: [i] mitigation
of flux decline due to membrane fouling, [ii] removal of the pesti-
cide and hydrogen sulfide, and [iii] improvement in membrane
clean-ability.” According to Wang et al. [47], membrane fouling is
mostly occurred through natural organic matter [NOM]. Several
problems arise during NF applications in wastewater treatment
and recovery of valuable materials; however, the most serious
problem for NF operation is the foulants accumulation.
5.2.4. Separation processes
NF can play a major role in separating valuable chemicals or
removal of a hazardous or undesirable substance from liquid
streams which can save cost and improve the environmental
impact of industry. NF can be used for solvent exchange [45]. pH
and concentration of substance are main parameters which may
affect the process efficiency. NF membrane systems [PES10,
N30F, and MPF36], produced using organic materials, are used to
recover the valuable lactic acid. Optimum results were achieved
using PES10 with a flow rate of 6.5 Lm2
h1
. NF can be employed
for separating different substance in the food industry; however,
further research is needed to improve efficiency and to overcome
expected problems [46].
Similar problems are encountered in gas/vapor separations, the
limitation of operating range and less diversity of membranes is a
major challenge. The membrane selectivity cannot be preserved
using such membrane fabricating materials. Tables 11 and 12 are
recent in NF application in industries and dye removals.
Dye industry is a series source for different pollutants before
discharge dye industry effluent should be treated to reduce the
negative effect on human and aquatic life. The conventional old
methods for dyes removal are oxidation, adsorption, biological
Table 11
Dye removal through ultrafiltration/nanofiltration.
Membrane Dyes Removal (%) Conditions
NF 200
NF270
Everzol Black
Everzol Blue
Everzol Red
90 Initial dye
Concentration: 600 mg/L, pressure: 3–12 bars
PMIA Eriochrome Black T 99 Initial dye
Concentration: 1 mg/L, pressure: 0.4 MPa, 1 g/L
Acrylic grafted
Poly sulfone
9 dyes of textile 86–99 Initial dye
Concentration: 50
CMC – Na/PP
Thin – film composite (700 Da)
Sunset Yellow
Methyl blue
Congo Red
82.2
99.7
99.9
Initial dye
Concentration: 100 mg/L, Ph: 6.8, pressure: 6.2 – 6.9 l/m2
h
Poly – sulfone polymide – thin film Reactive Black 5 60–97 Initial dye
Concentration: 0
0.4–2 g/L, pressure:
5–25 psi
CMC – Na/PP thin film composite (700 Da) Congo Red
Methyl blue
99.9 Initial dye
Concentration: 100 mg/L, pressure: 0.8 bar, flux; 6.2–6.9 l/m2
h
UV garfring on PPSU (1627–1674) Safranine O
Orang II
99.98, 86.76 Initial dye conc
50 mg/L, 30 min, pressure: 5 bars
Table 12
Recent NF Applications in Industries [48].
Industry Applications Future
Water Water softening
Removal of NOM from surface waters +
Removal of EDC/PPCPs from natural water and
wastewater
+
Removal of DOC and pesticides from surface water
and wastewater
+
Removal of nitrate ion from natural water +
Removal of heavy metals from industrial
wastewater
+
Sulphate removal
Seawater pre-treatment
Desalination by dual stage +
Partial demineralization of seawater to prepare
Personal body washing solution (salinity near 9 g/L)
+
Food Concentration and demineralization of whey/UF
whey
Treatment of vapor condensate in milk processing
Concentration of dairy matter
Recycle of process waters in dairy industry +
Recovery of cleaning agent from CIP discharge in
dairy industry
Purification of dextrose syrup
Decolonization of sugar solutions
Demineralization of colored brine from anion
exchange resin elution
Concentration of glycoside sweeteners from stevial
leaves
+
Concentration of xylose reaction liquor for
manufacturing xylitol sweetener
+
Beverage Grape juice concentration for win processing
Textile Removal of organics, color, turbidity in wastewater
Pulp and paper Treatment of effluences to reuse water
Leather Recovery and recycle of tannins in the leather
industry
Removal of sulphate and chromium from
wastewater
Pharmaceutical Recovery and concentration of antibiothics
Diverse Sulfate removal from brine feed to the electrolyzers
in chloralkali plants
Dewaxing organic solvent by solvent resistant NF
membranes
+
In production processes of organic acids +
Removal of caustic in aggressive wastewater
streams
+
Recovery of precious metals such as gold and silver +
Catalyst recovery by solvent resistant NF membrane +
In tissue engineering and orthopaedics +
DNA and protein separation +

treatment, and coagulation. The reverse micelle extraction is a rel-
atively new technique for dyes removal. However, old methods
have shown more effective removal. Combination of different
removal technologies should be employed to reach a reasonable
removal rate of dyes considering their negative impact on all spe-
cies. The research community is entitled to develop more effective
and economical removal methods to improve the quality of
wastewater and hence reduce the pollutant sources affecting water
resources on the planet.
6. Fouling of nanofiltration membranes
Membrane Fouling Phenomena: colloidal fouling, microbiologi-
cal fouling, and chemical fouling; Fig. 6 illustrates substance poten-
tially harmed to membranes.
Pretreatment is an essential and economical step to decrease
occurs in cleaning and extend membrane life. The following steps
represent effective methods for pretreatment [49–51]:
1. Pretreatment system monitoring.
2. Process technicians should be aware of how trace contami-
nants; e.g., trace oils and solvents can affect membranes.
3. The following parameters should be controlled to decrease
membrane fouling:
o pH of feed.
o The flow rate of permeate and concentrate.
o Feed temperature.
Organic and inorganic compounds, suspended particles, and
micro-organisms may cause membrane fouling; however organic
materials have shown the major role [52–55]. Such effect attribu-
ted to organic matter was found to vary depending on the applica-
tion. The findings of [56] showed that NF fouling and permeate flux
declination is mostly related to bio-fouling. Organic matter adsorp-
tion is affected by molecule nature and membrane properties. The
NOM molecule with a high MW causing NF membrane fouling
since the hydrophobic fractions of NOM adsorb on the membrane
[57–60] unfortunately hydrophilic NOM is important in many
application and cannot be removed [61].
6.1. Cleaning of nanofiltration membranes
Membrane proper selection and operating conditions may delay
the fouling process, a higher pressure can maintain a steady flux of
permeate but in some cases, cleaning is necessary to keep mem-
brane optimum performance. The cleaning process should be con-
ducted if: a permeate flux falls more than 10% or the salt content in
permeate increases by 10%, or when the NDP rises by 15% consid-
ering the optimum conditions. The cleaning intervals vary from
days to months depending on the application. However, it is rec-
ommended to clean the membrane on a regular basis even before
the above conditions are encountered [62].
Chemical cleaning is widely used but the process should be
effective in cleaning and also maintain membrane characteristics.
The membrane composition and thermal stability determine the
cleaning agent and conditions of cleaning process [63]. Tempera-
ture, concentration, and pH of the cleaning solution, pressure, flow
and cleaning time are an important factor in cleaning process
[64,65].
6.2. Cleaning agents
To remove bio-films and organic matters, alkaline cleaners are
recommended while acidic cleaners are recommended for inor-
ganic foulants [66,67]. Other cleaning agents such as detergents
and chelating agents may be used to reduce adsorption forces
and surface tension of foulants, in addition, to disturb metals and
calcium aggregates [68,69]. While for lipids and proteins, enzy-
matic cleaners should be used [70,71]. As shown in Table 13.
For complex layer, various chemicals are used. The composition
of cleaning solution and cleaning protocols change can achieve bet-
ter cleaning, a typical cleaning experiment is shown in Fig. 7. Mem-
brane cleaning is conducted by employing two processes namely,
rinsing and chemical cleaning. Clean water replaces the feed water
to reduce the deposited layer [66]. Then the cleaning agent is used.
After cleaning, clean water is used again to rinse the system. High-
quality water is supposed to be used during the rinsing process,
Fig. 6. Substances potentially harmed to membranes.
Table 13
Cleaning agents.
Type of foulant Cleaning agents
Mineral Deposits/Precip. Salts Acids
Organic Foulants Alkalis
Micro-organisms Enzymes
Oils, Fat and Grease Detergents
All Foulants in Tubular System Sponge Balls
Fig. 7. Flow diagram of chemical cleaning experiment.

since any contaminants entrained in cleaning water may result in
further blocking the membrane pores.
6.3. Membrane analyses
The membrane can be characterized using contact angle mea-
surement by the drop method [46]. Fourier Transform Infrared
(FTIR) spectroscopy can be used to determine membrane func-
tional groups. SEM can be used to study the surface appearance.
X-ray photoelectron spectroscopy (XPS) can be used for elemen-
tary composition.
6.4. Foulant analysis
NF fouled membranes is characterized by precipitates of alu-
minum, calcium, iron, sodium, magnesium, and silica and an
increase in the oxygen and CAO and CAN bonds which indicates
organic fouling existence. Silicates are believed to have a major
role in fouling, even if the feed with low silicates [47] since silicates
form a tightly adsorbed layer on the membrane surface. Formation
of a silicate and organic matter complex is another suggested
mechanism for fouling [48]. In addition to silicates, polysaccha-
rides and amides were found to cause fouling either for treating
river water and lake water. Other authors have also found similar
organic foulants on the NOM fouled membranes [50]. Fig. 8 Phases
of NF process treating coagulated surface water at shows.
7. Cost of Nanofiltration
Due to the high cost associated with NF operation, NF is not yet
commercially used in water treatment. Since there are no operat-
ing NF plants, cost data are collected based on studies conducted
over real operating plants [72,73], and on pilot-scale data with cal-
culated cost according to the experimental results [74–76].
Both Wiesner and Chellam [71] found that the cost of NF was
particularly sensitive to the flux, but the recovery had a relatively
small effect on the total cost of NF. However, in industrial plants,
other investment parameters have an effect on the total cost. The
proportion of the membrane-related investment costs has been
reported to be 20–30% of the total investment costs at smaller
plants (plant capacity 4000–8000 m3
/d), and the proportion
increases to near 50% as the plant size increases (plant capacity
53,000–125,000 m3
/d). To conclude, the membrane module cost
becomes a more important factor of cost and smaller economy of
scale is realized at larger plants [73].
Other important items of the cost are the operating and main-
tenance cost which include fixed cost like labor and general main-
tenance cost and viable cost like replacement costs, chemicals, and
energy [71]. Higher operation rate is important to reduce the cost
of membrane operation and maintenance. NF can compete well
with other treatment methods for low capacity water treatment
units [75]. The cost estimates for different NF units are presented
in Fig. 9. Since 42–61% of NF systems is attributed to energy and
materials especially membrane, changes in material cost, mem-
brane lifetime, and energy will have a remarkable effect on process
viability. So it is expected that the total cost would increase by 4–
6% if the electricity price has increased by 29% [73–80].
Membrane processes have increasingly attracted more applica-
tions in different life aspects. Due to the high demand for water, it
is expected that membrane applications will grow exponentially to
Fig. 8. Phases of NF process treating coagulated surface water.
Fig. 9. Distribution of operation and maintenance costs of NF process.

cover industrial and portable needs. A detailed market study is
shown in the Table 14 below [81–90]:
8. Conclusions
Membranes processes are among the best available techniques
for water and wastewater treatment [91–94]. Membrane technol-
ogy represents a viable alternative for conventional separation
technologies [95,96]. NF systems operated at a higher recovery rate
[83%] and had the advantages of lower cost operation and the least
environmental impact. The total and operation costs of NF can be
balanced to a minimum total cost at an optimum driving pressure
and the driving pressure has a direct linear relation with environ-
mental impact. The operating parameters reducing the NF cost
appeared to reduce the environmental impact of NF as well. Stud-
ies are mostly conducted on lab scale. Pilot scale studies will play a
better role in expecting the performance of industrial plants.
Fouling, low flux, instability, and poor durability are technical
barriers need to be overcome to ensure the viability of NF systems.
Different raw materials can be employed to produce membranes
for different application such as inorganic, organic and ceramic
membranes. Formation of large membrane modules is a major step
in improving economics and to incorporate the NF in different
industrial applications. Reducing energy consumption of NF sys-
tems is an important step to commercialize NF systems.
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Table 14
Detailed market study of 2017.
Global markets, title Subjects Ref.
Technologies for Water Recycling Reuse,
July 2017
Around $12.2 billion is the market of wastewater recycling around the globe in 2016. At 2021,
it is expected to reach $22.3 Billion with a compound annual growth rate of 13.1%
[81]
Major RO System Components for Water
Treatment: The Global Market, May 2017
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[82]
Membrane Technology for Liquid Gas
Separations, November 2016
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growth rate of 6.2%
[83]
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Global Markets, June 2016
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it is expected to reach $4.6 billion with a compound annual growth rate of 6.9%
[84]
Seawater Brackish Water Desalination,
March 2016
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it will reach $48.2 billion with a compound annual growth rate of 17.6%
[85]
Membrane Technology for Food Beverage
Processing: Global Markets, February 2016
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2015 and 2020, it will reach $4.2 and $5.8 billion respectively with a compound annual growth
rate of 6.7%
[86]
The Global Market for Membrane
Microfiltration, January 2016
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reach $2.6 billion with a compound annual growth rate of 6.7%
[87]
Membrane Bioreactors: Global Markets, June
2015
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[88]
Advanced Technologies for Municipal Water
Treatment, August 2014
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billion. At 2019, the market is expected to reach $3.2 billion with a compound annual growth
rate of 7.4%
[89]
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2013
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valued at $59.2 billion. At 2019, it is expected to reach $96.3 billion with a compound annual
growth rate of 10.2%
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Mona A. Abdel-Fatah. I am currently works at the
Department of Chemical Engineering and Pilot Plant,
National Research Centre, Egypt. My PhD in industrial
wastewater management titled ‘‘Study of Dye-house
Wastewater Treatment Using Nanofiltration Mem-
branes”. My work is concerned with the development of
new techniques for treatment of water and wastewater
from hazardous compounds and reused/recycled trea-
ted water. I have an excellent experience in this field
from 24 years ago; so I am a Consultant Engineer in the
field of ‘‘Management of Industrial and Domestic
Wastewater” - Consultant No. 241/5/2010.

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