Project report based on Renewable and Sustainable form of energy resource. Team includes - Dhruvin Shah, Jinit Shah, Mandar Chalke, Manish Jain.

1. I
STUDY, ANALYSIS AND APPLICATION
OF REVERSE ELECTRODIALYSIS IN
A DESALINATION PLANT
Submitted in partial fulfillment of the
requirements of the degree of
Bachelor of Engineering in Mechanical
Engineering by
Project Guide: Prof. Shashikant Auti
Department of Mechanical Engineering
Dwarkadas J. Sanghvi College of Engineering
Dhruvin J. Shah 60005170039
Jinit U. Shah 60005170050
Mandar H. Chalke 60005170059
Manishkumar M. Jain 60005170061

2. II
CERTIFICATE
This is to certify that the project entitled “Study, analysis and application of
reverse electrodialysis in a desalination plant” is a bonafide work of “Dhruvin
J. Shah” (60005170039), “Jinit U. Shah” (60005170050), “Mandar H.
Chalke” (60005170059), & “Manishkumar M. Jain” (60005170061)
submitted to the University of Mumbai in partial fulfilment of the requirement
for the award of the degree of “Bachelor of Engineering” in “Mechanical
Engineering”.
Prof. Shashikant Auti
(Project Guide) (External Examiner)
Dr. K.N. Vijaya Kumar Dr. Hari Vasudevan
(Head of Department) (Principal)

3. III
Project Report Approval for B.E.
This project report entitled “Study, analysis and application of reverse
electrodialysis in a desalination plant” perspective by “Dhruvin J. Shah”
(60005170039), “Jinit U. Shah” (60005170050), “Mandar H. Chalke”
(60005170059), & “Manishkumar M. Jain” (60005170061) is approved for
the degree of Bachelor of Engineering in Mechanical Engineering.
Examiners
1.
2.
Date:
Place:

4. IV
Declaration
We declare that this written submission represents our ideas in our own words and
where others ideas or words have been included, we have adequately cited and
referenced the original sources. We also declare that we have adhered to all
principles of academic honesty and integrity and have not misrepresented or
fabricated or falsified any idea/data/fact/source in our submission. We understand
that any violation of the above will be cause for disciplinary action by the institute
and can also evoke penal action from the sources which have thus not been
properly cited or from whom proper permission has not been taken when needed.
Dhruvin J. Shah
60005170039
Jinit U. Shah
60005170050
Mandar H. Chalke
60005170059
Manishkumar M. Jain
60005170061
Date:

5. V
Acknowledgement
This project required a huge amount of hardwork, research and devotion. We
express our earnest gratitude towards the people who have helped us successfully
complete our project. We would like to demonstrate our most prominent
gratefulness to the very regarded and dedicated technical staff. We are thoroughly
obligated to each and every person who contributed towards the successful
completion of this study.
Above all, we are grateful to our supervisor, Prof. Ramesh Rajguru for his
expertise and technical support. We are also thankful to the Principal, Dr. Hari
Vasudevan and our Head of Department, Dr. Vijayakumar Kottur without whose
regulation the nature of results obtained would definitely have suffered.

6. VI
Abstract
There is a great need for new energy sources that are clean and sustainable without thermal or
chemical pollution and without emission of CO2. One of the potential sources is salinity
gradient power (SGP), the power that can be generated from the reversible mixing of river
water with sea water. A number of technologies have been proposed to convert SGP into
mechanical energy (pressure-retarded osmosis, PRO) or directly into electricity (namely,
reverse electrodialysis, RED, and capacitive mixing, CDLE). Among these, RED represents a
viable technology that might be brought to industrial implementation as soon as new
membranes will be available at competitive costs. This project focuses on the desalination
plants and the use of RED in desalination plants. Along with this it gives an insight to how
much power as well as other dependent parameters are generated in desalination plants on the
basis of various input variable parameters given by the user. It also focuses on the analysis of
the flow through the selectively permeable membranes and their conclusions bring drawn.
With such a technology developing day by day, India as a country with such a large coastline
cannot and must not stay abstained from its use. Keeping this fact in mind, a study
showcasing how it can be utilized in the Indian environment is also showcased with the help
of a case study.

7. VII
Table of Contents
Abstract
Table of Contents
List of Tables
List of Figures
Literature Review
1. Introduction
1.1. History
1.2. Introduction
1.2.1. Salinity Gradient Power
1.2.2. Principle of Reverse Electro-Dialysis
1.2.3. Membrane Development
1.2.4. Stack Design for Reverse Electro-Dialysis
1.2.5. Net Spacers and Profiled Membranes
1.2.6. Electrode Systems for RED
1.2.7. Pre-Treatment Strategies
1.3. The REAPower Project: RED Process with Concentrated Brine
1.3.1. Pilot Plant Description
2. Analysis
2.1. Simulation of Desalination Plant on Simulink
2.2. Analysis of Cell Unit on COMSOL MULTIPHYSICS
3. Case Study
3.1. Introduction
3.2. The Desalination Plant
3.2.1. History of the Plant
3.2.2. Some Facts About the Plant
3.2.3. Studies Undertaken for this Project
3.3. About Brine
3.4. About the Village
3.4.1. The Plan

8. VIII
3.4.2. Advantages of the location for RED process
3.4.3. Implementation
3.5.Outcome of Case Study
3.6.Ongoing Research
Conclusion
References

9. IX
List of Tables
Description Page
Table 2.1. Values assumed at the initial stages of the project for the sake of
simple calculations.
Table 2.2. Power output for different values of production capacity (Qp).
Table 2.3. Power output for different feed concentrations (Cf).
Table 2.4. Power output for different values of cell chamber thickness (d).
Table 2.5. Parameters for Unit Cell
Table 3.1. Cost

10. X
List of Figures
Description Page
Figure 1.1. Principle of the RED process.
Figure 1.2. Power density (expressed as W/m2 of membrane) .
Figure 1.3. Location of the REAPower pilot plant in Marsala (Trapani, Italy).
Figure 1.4. Simplified schematic diagram of the plant layout.
Figure 2.1. Screen clipping of our Simulink model showing all the above
.mentioned parameters.
Figure 2.2. Graph for Table 2.2.
Figure 2.3. Graph for Table 2.3.
Figure 2.4. Graph for Table 2.4.
Figure 2.5. Geometry of unit cell.
Figure 2.6. Electrolyte potential.
Figure 2.7. Electrolyte current density vector.
Figure 2.8. Concentration of Na+.
Figure 2.9. Concentration(for representation).
Figure 2.10. Graph of Electrolyte Potential.
Figure 2.11. Concentrations of Na+
& Cl-
.
Figure 2.12. Fluxes, Na.
Figure 2.13. Fluxes, Cl.
Figure 3.1. The image from the plant site.
Figure 3.2. Location of plant.
Figure 3.3. Booster pumps feeding the brine solution into the RO membranes.
Figure 3.4. Storage tanks.
Figure 3.5. The village Kattupalli.
Figure 3.6. Schematic diagram of the setup.
Figure 3.7. Illustration of Grapheme as Membrane.

11. XI
Literature Review
Multiple papers were reviewed and referred to for the selection of the project topic and the
various nuances involved in the project. The papers were chosen from various international
journals, conference proceedings and some reference books were also referred. The
relevant information collected from these sources is presented as follows:
M. Tedesco et.al. (2012) have done a lot of research in the field of reverse electrodialysis and
its utilization in desalination plants. Along with other renewable sources, they focus on salient
gradient power as a very upcoming and a clean source of energy. They used the concentration
difference to produce electricity. All this was done by the development of a model which was
based on mass balance and equations collected from various sources like scientific studies
which helped in refining the process. This model was then used for simulation of various real
life scenarios.
P. Mazzola et.al.(2014) while working along with Tedesco then carried out analysis and
simulation of the reverse electrodialysis technology with the help of RED unit deisgned by
them. They studied various factors which help in the performance of this RED stack. With the
help of process simulations, lab data and original small scale prototype data was verified. Study
regarding various concentration of the components as well as their flow rate was analysed. In
the end various parameters were proposed which could scale up the plant to a point where it
could generate 1 kw of power.
M. Tedesco et.al. (2016) tabulated and accounted all the results that were obtained from the
first full scale RED pilot plant. Here the plant was tested with natural as well as artificial brine
water solutions with varying molarity of NaCl. Also the effect of various factors such as
fouling on the performance of the plant was also tested.
Z. Zourmand et.al (2014) developed a mass transfer model with the help of COMSOL
Multiphysics for prediction of ion-transport through electrodialysis cell. Concentration
polarization phenomenon was studied and how it affects ion separation was studied. The well-
defined conditions were solved using the finite element analysis approach and various graphs
and results were plotted.
Reverse Electrodialysis design and optimization by modeling and experimentation, a book
by Jost Veerman gives detailed information on salinity gradient power and reverse

12. XII
electrodialysis. It also provides insights to various experiments performed throughout this
process. It even covers the performance of the plant with river as well as sea water.
Reverse electrodialysis advanced modelling and scale-up, a book by M. Tedesso is a
combination of the whole process carried out right from scratch for setting up of the prototype
of the RED unit in Italy. It includes various research articles on this very topic which help is
gaining best insights of the plant.

13. XIII
Chapter 1
Introduction
1.1. History
In 1972, the Club of Rome published Limits to Growth that created a public shock. The
report predicted that economic growth is limited by a finite amount of fossil fuels and ores.
Quickly after the publication, the oil crisis broke out and the public challenge about the
scarcity of natural resources become accelerated. In 1985 a convention on the “evaluation of
the role of Carbon Dioxide and other Greenhouse Gases in weather versions and associated
affects” turned into organized in Villach, Austria by means of UNEP/WMO/ICSU. The
realization changed into that greenhouse gases “are expected” to motive huge warming inside
the subsequent century and that a few warming is inevitable. In June 1988, James E. Hansen
said that human moves had already measurable effects on the global weather. The next
milestone was the Kyoto Protocol, adopted in 1997 and entered in force in 2005. The target of
the protocol was the reduction of the emission of four greenhouse gases (CO2, CH4, N2O, SF6)
and two groups of ozone attacking gases (hydrofluorocarbons and perfluorocarbons).
New renewable forms of energy are needed without thermal pollution, without emission
of environmental unwanted substances and without net emission of greenhouse gasses. Wind
power, hydropower, biofuel, solar power, geothermal power and ocean power are contributors
to an economy of renewable energy. Salinity gradient power (SGP) is an energy that can be
generated from reversible mixing of two kinds of water with different salt concentrations.
Pattle proposed this in 1954 and wrote: The osmotic pressure of sea-water is about 20
atmospheres, so that when a river mixes with the sea, free energy equal to that obtainable
from a waterfall 680 ft. high is lost. There thus exists an untapped source of power which has
(so far as I know) been unmentioned in the literature.
The potential of salinity gradient power (SGP) is the product of the energy density of river
water times the flow rate of the river water:
Potential power  Energy density * Flow rate
The average value of the energy content of river water can be used for estimating the
global power. The energy content is about 2.5*106
J/m3
when a large excess of sea water is
used. The total discharge of all rivers in the world gives an estimate value of 1.13*106
m3
/s.

14. XIV
As we can see the global potential power is 2.8 TeraWatt and that is a value near to the 2.6
TeraWatt, a value Wick and Schmitt estimated in 1977.
In 2008, the average world energy consumption was about 15 TW of which 5 TW was
used to generate 2 TW of electrical energy in coal fired power plants of most low efficiency.
Thus we can see that the potential of SGP is more than that of the current global electricity
consumption. The advantages of SGP are: limitless supply (if river and seawater are used), no
production of pollutants like NOx, no CO2 -exhaust, no thermal pollution, no radioactive
waste and no daily fluctuations in production due to variations in wind speed or sunshine. The
salinity gradient energy content of river water is however rather poor in comparison to other
fuels. Thereby, investment costs for a SGP plant may be rather high and transportation costs
of feed water to the plant and inside the plant is substantial.
1.2. RED
The increasing world energy demand during the last decades, together with sustainability
issues related to large use of fossil fuels, is leading to a growing interest towards new
alternative energy sources. Salinity Gradient Power (SGP) is a promising option amongst
several other which deals with the recovery of chemical energy associated with the
“controlled” mixing of two salt solutions with different concentrations. This kind of option
can be used in coastal areas, where river mouths reach the main reservoirs (seas and oceans).
The theoretically exploitable energy from natural salinity gradients is considerably high.
The SGP with a global power of 980 GigaWatt, is however estimated to be the second largest
marine-based energy source, and this energy will be potentially available for extraction.
Numerous technologies have been proposed to convert SGP, pressure-retarded osmosis
(PRO) can be used to gain mechanical energy or directly electricity can be gained by reverse
electrodialysis (RED). Among these options, RED represents a viable technology which
might be brought to industrial implementation as soon as new cheaper membranes will be
available.
Although the principle of RED technology is well known since 1950, the status of
development yet requires extensive R&D efforts for exploring the real potential of such
process. The overall performance of RED process depends on membranes properties, stack
design, and especially feed solution properties. Specifically, although most of the packages of
RED process have been to date restrained to river water and seawater, the usage of fresh water

15. XV
as dilute solution causes high electrical resistance within the stack, for this reason proscribing
the output strength. As a way to reduce the resistance of the dilute compartments, sea or
brackish water can be used as diluate, even as concentrated brine (e.g. from saltworks, salt
mines or other commercial activities) may be used as pay attention.
This idea has been at the core of the EU-funded REAPower project (Reverse
Electrodialysis Alternative Power), whose most important aim turned into to illustrate the
implementation of the RED technology for the case of concentrated brines.
Focus of this project has been a detailed study of the reverse electrodialysis (RED)
process, both through modelling and experimental activities. The research efforts, closely
related to the R&D of the REAPower project, eventually ended up with the construction and
testing of the first pilot plant operating with real brackish water and brine from a saltwork
located in Marsala (Italy).
The research was initially focused on the development of a new mathematical model for
the RED process powered by seawater (or brackish water) and brine. A multi-scale modelling
approach has been adopted for the purpose, since it is especially suitable for design and
optimisation of chemical processes of noteworthy complexity. In particular, the model has
been developed at two different scales of description: (i) a lower-scale model, describing the
physical phenomena in a single repeating unit of the system (cell pair); (ii) a higher-scale
model related to the whole equipment (stack), including all cell pairs and the relevant
interconnections. Finally, a model for the plant as a whole has been implemented in an
equation-based solver software (gPROMS), allowing the simulation of a number of stacks
interconnected with different layouts.
The model was validated against unique experimental records after which used to analyse
the influence of the principle working elements on energy output. An excellent matching
changed into observed between predictions and experiments for an extensive range of inlet
concentrations, drift rates and feed temperatures. The simulations finished on uneven stacks
and assuming special feed flow arrangements among purple modules ultimately supplied
symptoms for a scale-up of the process eventually.
The original data used for model validation were collected during a wide experimental
campaign performed on a laboratory RED unit at VITO (Flemish Institute for Technological
Research – Mol, Belgium). Two different sets of membranes were tested, analysing various

16. XVI
operating conditions in terms of feed concentration, temperature and flow rate. These tests
allowed to identify the optimal conditions for the investigated system and reached values of
power output among the highest reported to date in the literature.
As per the information collected from the laboratory investigations and modelling, a RED
pilot plant was designed and installed in Marsala (South of Italy) as final accomplishment of
the EU-funded REAPower project. A first prototype equipped with 125 cell pairs and 44*44
cm2
membrane area was installed and tested. The feed streams used were brackish water (0.03
mol/l NaCl) and saturated brine from saltworks (5 mol/l NaCl). The process performance was
monitored in terms of both pressure drops and power production over a period of five months
of operation.
The pilot plant has been later up-scaled through the installation of two larger prototypes,
each one equipped with 500 cell pairs. The plant, which has been tested over six months of
operation, is currently the first plant worldwide operating with real brine and brackish water.
The research activities carried out in a real environment suggest that the RED technology
can be considered as a reliable way to obtain sustainable electric energy in the near future.
Moreover, the improved knowledge in RED process can lead to novel applications, which
may not be confined to the use of natural streams.
To this end, the latest development of research activities carried out within the framework
of this project led to the conceptual analysis of a heat engine based on RED technology, in
which artificial salinity gradients are used to produce electricity. The discharged solutions
from the RED unit are then regenerated by low-grade heat through a suitable thermal
separation stage. Therefore, the RED process can be exploited as a viable alternative to
recover industrial waste heat and produce electricity in a sustainable way.
1.2.1. Salinity Gradient Power
Salinity Gradient Power (SGP) is a valuable renewable energy source based on the
controlled mixing of two solutions of different salinity. Reverse Electrodialysis (SGP-RE or
RED) is a promising technology that exploits this SGP energy source and is used to directly
generate electricity.
The aim of this chapter is to provide a brief review of the development of RED process,
understanding the main technological barriers still to overcome for a successful scale-up of
the process. In fact, although the principle of this technology has been well known for several

17. XVII
years, further R&D efforts are still necessary in order to explore the real potential of RED
process.
In particular, the use of seawater (or brackish water) and concentrated brine as feed
solutions can lead to a significant enhancement of the power output from a RED system. This
coined the idea of constructing the first pilot prototype plant in the minds of REAPower
which would demonstrate the potential of Reverse Electrodialysis technology.
Research activities on “water-related” renewable energy sources have seen an
increasing interest during last years. While hydroelectric processes already exploit 800 GW
worldwide, salinity gradient power (SGP) remains an untapped source of energy.
SGP can be seen as the chemical potential energy that can be exploited when two salt
streams with different salinity (e.g. river water and seawater) are mixed together. The amount
of energy theoretically exploited can be estimated as the Gibbs free energy of mixing.
According to this calculation, mixing one cubic meter of seawater (0.5 M) with the same
volume of fresh water (5 mM), about 0.5 kWh of energy can be theoretically produced, i.e.
equivalent to the hydroelectric power of 1 m3
of water flowing down a 175 m waterfall. The
available power from salinity gradients estimates to be between 1.4 and 2.6 TeraWatt
considering the average ocean salinity and the annual global discharge of rivers. Taken into
account technical issues related to actual energy conversion, about 980 GW of such energy
could be harvested, which still represents a notable amount of renewable energy.
Different technologies have been proposed to convert SGP into more exploitable
forms, i.e. mechanical energy or electricity. Pressure-Retarded Osmosis (PRO) and Reverse
Electrodialysis (RED) are two membrane-based processes that have been widely investigated.
These two processes can be seen as the opposite of the well-known desalination technologies
(reverse osmosis and electrodialysis, respectively), where the use of selective membranes
allow the passage of only solvent (PRO and RO) or ions (RED and ED).
Aside from PRO and RED, other salinity gradient power technologies have been
recently proposed, based on the use of capacitive electrodes, which can be also coupled with
ion exchange membranes. However, these technologies, whose main bottleneck is the
development of suitable electrode materials, are still in their very early research stage, and
will not described in this thesis.

18. XVIII
In pressure-retarded osmosis, two streams with different salinity are mixed together
through a semi-permeable membrane, which allows the flow of solvent (water), and retains
the solute (dissolved salts). As a result, water flows by osmosis through the membrane
towards the concentrated compartment. If a hydrostatic pressure is applied to the concentrate
compartment, the water flux results in a pressurisation of the concentrate. Such pressurised
solution can be sent to a hydroturbine to generate electricity.
In the reverse electrodialysis process, dilute and concentrated solutions are separated
by ion exchange membranes (IEMs), which are selective to the passage of either cations or
anions. Therefore, cation exchange membranes (CEMs) allow cations to flow through them
while anion exchange membranes (AEMs) allow anions to flow through them. As a result, the
salinity gradient creates an ionic current through the membranes; the ionic current is
eventually converted into electric current at the electrodes. As this technology has been the
focus of this thesis, a more detailed description of its principle is reported in the next
paragraph.
A comprehensive comparison between pressure-retarded osmosis and reverse
electrodialysis has been already presented by different authors, and it is beyond the scope of
this thesis. In particular, Post suggested that RED might be characterised by lower pre-
treatment requirements with respect to PRO, as electrodialysis membranes are generally less
sensible to biofouling than reverse osmosis membranes.
Both RED and PRO have experienced an increasing interest among the scientific
community during the last decade. In the case of PRO, a notable breakthrough for the
technology has been the use of pressure exchangers, firstly proposed by Loeb in 2002. On the
other hand, the main challenge of both technologies is the development of new membranes
with high performance (namely, high water permeability for PRO and low resistance for
RED) and relatively low cost (especially for RED, as ion exchange membranes are generally
more expensive than osmosis membranes).
Aside from the widely investigated PRO, RED and capacitive mixing processes,
researchers are currently focused on new systems for exploit salinity gradients, e.g. based on
swelling properties of hydrogels. Such growing interest in the development of new SGP
technology clearly demonstrates that salinity gradient power might change the overview on
renewable energy source in the near future.

19. XIX
1.2.2. Principle Of Reverse Electrodialysis
The principle of RED is sketched in Figure 1.1. The repeating unit of the system (cell
pair) consists of a Cation Exchange Membrane (CEM), a dilute (LOW) compartment, an
Anion Exchange Membrane (AEM) and a concentrate (HIGH) compartment. It is even
possible in electrodialysis for stacking upto several hundreds of cell pairs within a single unit
for practical applications. Inter-membranes distance is maintained and concentration
polarisation phenomena is reduced usually with the help of Polymeric Net Spacers. At the
ends of the stack, two external compartments contain the electrodes and an electrolyte
solution (electrode rinse solution) with a suitable redox couple (e.g. Fe2+
/ Fe3+
chloride).
Figure 1.1 Principle of the RED process. In this picture, seawater and brine are adopted as feed
solutions.
When two salt solutions with different salinity are fed to the stack, the concentration
gradient causes the transport of ions through the membranes. This ion flux is regulated by the
membrane permselectivity, i.e. the selectivity towards cation/anion transport through

20. XX
CEM/AEM, respectively. Ideally, only cations can flow through CEMs, and only anions flow
through AEMs (in the opposite direction). The ionic current which is generated through
membranes gets eventually converted into electric current by means of redox reactions at the
electrodes, and then it can be collected by an external load. The RED process has been
described as a reliable technology in the literature since 1954. Since then, a number of
researchers demonstrated by experiments the feasibility of the RED process (Figure 1.2).
Conventional electrodialysis (ED) stacks built with membranes and spacers, commonly used
for Electrodialysis, were initially exploited for this purpose.
Figure 1.2 Power density (expressed as W/m2 of membrane) experimentally obtained in RED system.
During the last years, Post, Dlugolecki, Veerman and Vermaas are few of the authors
who presented their investigations and made notable improvements in the RED process. With
this regard, Veerman et al. obtained a power of 0.93 Watts with a 50 cell pairs stack of 1 m2
of total membrane area, using river water and seawater as feed solutions.
The low conductivity of the solution (river water) causes high electric resistance
within the unit, limiting the output power achievable which makes the use of river water a
disadvantage. Thus, decreasing the compartments thickness a considerable reduction of the
stack resistance is obtained, thus enhancing the output power. For instance, Vermaas et al.

21. XXI
reported a power density of 2.2 W/m2
of membrane using spacers of 60μm thickness. Such
thin compartment thickness might be necessary to reduce the electric resistance in the river
water compartment. On the other hand, very thin channels cause high pressure drops,
increasing the risk of fouling. Another opportunity to keep away from excessive resistance
within the dilute compartment is the use of seawater (rather than river water) as dilute, and a
more focused solution as concentrate, consisting of focused brine from salt ponds, salt mines
or different industrial activities.
1.2.3. Membrane Development
The first studies on RED process were based on the use of commercial membranes for
electrodialysis. Audinos clearly suggested that the development of new IEMs is necessary to
suit the requirements of RED technology. In particular, the suitable IEMs should have:
 Low electrical resistance- Membranes with an electric resistance as low as possible are
required, especially when highly concentrated solutions are used as feed, when IEMs
resistance represent more than 70% of the overall stack resistance. Moreover, in the
case of fresh water – seawater conditions, it has been experimentally demonstrated
that membranes resistance increases significantly due to the low concentration of fresh
water.
 High permselectivity- The permselectivity of commercial membranes is generally
rather high (>96%) when diluted solutions are used (i.e. typical concentration of river
water and seawater). On the other hand, the permselectivity decreases sensibly when
highly concentrated solutions are used.
 Good mechanical stability- While the development of very thin membranes may
reduce significantly the overall resistance, a good mechanical stability should be
guaranteed for practical applications. Moreover, a low swelling degree increase the
mechanical stability of membranes.
 High chemical stability- The membrane should be stable in a wide range of pH. This is
particularly relevant when low pH is kept in the electrode compartments of some RED
systems.
 High thermal stability- High temperature has been proven to benefit the performance
of RED process. The development of IEMs stable at T > 60°C might be a further
enhancement of the technology.

22. XXII
Apart from the aforementioned properties, a significant reduction in the cost is necessary
to make RED technology economically feasible in the near future. Post assumed a cost of
installed membranes of 2 €/m2
(including end plates and electrodes) for an economic analysis
of a 200 kW RED module. In this way, a cost of electricity of 0.08 €/kWh is estimated, i.e.
comparable with the price of wind energy. More recently, Daniilidis suggested that a cost of
membranes below 4.3 €/m2
would be already acceptable for making RED technology
economically feasible. On the other hand, this more optimistic estimation may be achieved
assuming the use of brine instead of seawater as concentrated feed stream.
1.2.4. Stack Design For Reverse Electrodialysis
In principle, the stack design developed for commercial electrodialysis units can be
adopted for RED process. Co-current flow configuration is generally preferable in ED, in
order to avoid leakages due to local pressure difference across membranes. In fact, Veerman
demonstrated that a counter-current flow configuration does not improve appreciably the
overall performance, leading just to a 1% increase of the power output, yet increasing the risk
of internal leakages.
More recently, several patents have been reported on new stack design, based on
cross-flow arrangement for feed solutions. The aim of such new design is to ensure a more
homogeneous flow distribution within compartments, in order to reduce the internal resistance
of the stack. In particular, a crucial aspect in stack design is the development of a suitable
flow distribution system, i.e. able to reduce the concentrated pressure drops at inlet/outlet and
ensure a homogeneous flow distribution inside channels.
1.2.5. Net Spacers And Profiled Membranes
In a conventional electrodialysis unit, the membranes are separated and compartments
are created by using polymeric woven spacers. Both geometry and thickness of the spacer are
important parameters for reducing pressure drops, thus enhancing the net power output of the
system. In particular, the use of thinner spacers clearly reduces the electrical resistance of the
compartments, thus increasing the power output. For this reason, in general a lower
compartments thickness is preferable in reverse electrodialysis.
Vermaas analysed the influence of different types of spacers on power output, ranging
from 485 µm down to 60 µm thickness, observing that using very thin spacers allow to double

23. XXIII
the power density with respect to the case of thicker spacers. Such effect is remarkable when
fresh water is used as dilute, being the main ohmic loss in the overall stack resistance.
A sensible reduction of the overall stack resistance has been achieved by using
conductive spacers instead of common (uncharged) spacers. Długołecki et al. showed that the
power density can be increased 3 times when ion-conductive materials are used allowing to
halve the resistance when river water and seawater are used as feed. After these results, efforts
have been made on the construction of profiled membranes, where properly structured IEMs
substitute the spacers. In this way, a reduction of the overall resistance was detected, although
increasing the influence of concentration polarisation phenomena on the process. As a result,
only a slight increase in the power density was observed, essentially at high flow velocity.
Such first experimental results suggest that the use of profiled membranes can lead to a
reliable improvement in the stack design of RED process, though the current development
requires further investigation for identifying proper structure/geometry for the membranes.
1.2.6. Electrode Systems For RED
The electrode system required for a RED unit is constituted be two electrodes (anode
and cathode) placed in the outer compartments, plus two “outer” membranes (for separating
effectively the solution flowing in the electrode compartments from concentrate and diluate),
and an electrode rinse solution, which contains a suitable redox couple for electrochemical
reactions.
Stable performance of the RED process can be guaranteed by making the selection of
suitable conditions for the electrode system a priority. NaCl solution was used as electrode
rinse solution for the performing the first experiment on the RED process. However, this
determines the formation of chlorine and H2 as anodic and cathodic products, respectively. In
fact, the formation of gaseous species at the electrode surface causes also a significant
increase of the electric resistance in the compartments. Such phenomenon has been observed
also in RED system using ammonium bicarbonate as active species for the electrode rinse
solution. Sodium sulphate (Na2SO4) can be used to avoid chlorine formation, generating
oxygen at the anode.
A detailed investigation of suitable electrode systems for RED has been performed by
Veerman, who compared a number of electrode systems in terms of safety, health,
environment, technical feasibility and economics. Based on such investigation, the most

24. XXIV
suitable system proposed was the use of Fe2+
/ Fe3+
couple in a NaCl-HCl supporting
electrolyte, with Ru/Ir covered titanium electrodes. Apart from Fe+2
/ Fe+3
couple, also
hexacyanoferrate [Fe(CN)6]4-
/[Fe(CN)6]3-
is widely used as redox species in RED process; in
fact, this species is very stable in the process conditions, provided that the contact with
oxygen and light is avoided.
1.2.7. Pre-Treatment Strategies
Fouling and biofouling phenomena are relevant issues that affect the efficiency of any
membrane process. Although ion exchange membranes are less sensitive to fouling than
reverse osmosis membranes, some pre-treatment strategies of the feed solutions are still
required to guarantee long-term operation with natural streams. In particular, ion exchange
membranes are subject to fouling by electrically charged particles, such as polyelectrolytes,
humic acids, and surfactants. The electrical resistance could increase dramatically as IEMS
could also suffer the adsorption of natural organic matter.
The periodical switching of electrode polarity (i.e. Electrodialysis Reversal, EDR), in
electrodialysis applications, allowed to reduce the fouling caused by organic acids and
charged colloids. This method led to a significant less impact of fouling phenomena in ED,
and lead to long-term operation. The same principle has been proposed as possible strategy in
reverse electrodialysis, i.e. based on a reversal of feed waters. With this regard, Post showed
that a single reversal of feed streams is not effective to reduce pressure drops in RED stack
where biofilm formation occurred. On the other hand, in the first 15 days, a daily or hourly
switching was proved useful so as to retard biofouling phenomena.
Vermaas observed colloidal fouling while testing a RED stack with real seawater and
fresh water. The main reason was due to clay minerals and remnants of diatom shells. In
particular, when using a 20µm filter was used as only pre-treatment, the fouling rate was
unacceptable, causing a 50% reduction of power density in the first day of operation. The
methods suggested to reduce colloidal fouling has been periodic air sparging and switching of
feed streams
1.3. The Reapower Project: Red Process With Concentrated Brine
Power output achievable by the RED system is limited by the high electrical resistance
caused because of the use of fresh water as dilute stream. On the other hand, using seawater
(or brackish water) as diluate and brine as concentrate allows to reduce significantly the

25. XXV
internal electrical resistance, keeping a high salinity gradient as driving force for the RED
process. This concept was the basic idea of the EU-funded REAPower project (Reverse
Electrodialysis Alternative Power), whose main goal was to demonstrate the potential of RED
technology using sea/brackish water and brine as feed solutions. The installation of a pilot
plant in the South of Italy has certainly been the latest accomplishment of the REAPower
project. The saltwork area in Marsala (Tripani, Italy) proves to be an ideal location for a RED
plant as it provides a large amount of both solutions required for power production.
Figure 1.3. Location of the REAPower pilot plant in Marsala (Trapani, Italy). A picture of the
windmill hosting the RED pilot plant is shown on the right.
The highly concentrated solutions present inside the system strongly affect the
membrane properties, such as permselectivity and electric resistance. Therefore, significant
R&D efforts need to be taken to achieve high process performance. For this reason, the
following R&D activities have been identified and addressed within the REAPower project:
1. Development of new components (such as membranes, spacers, electrode rinse
solution, stack) tailored to the new process requirements;
2. Development and validation of a suitable process simulator, so as to provide a
predictive modelling tool for investigation on scaled-up units;
3. Experimental investigation of the developed RED system through laboratory-scale
testing;
4. Design, construction and testing of a RED pilot plant operating with natural solutions
in a real environment;
5. Economic analysis of the process, thus identifying the environmental impact and next
R&D activities necessary to develop further the RED technology.

26. XXVI
1.3.1. PILOT PLANT DESCRIPTION
Two intake lines of approximately 200 m long each have been connected to the pilot
plant in Italy. The first one is for the brackish water from a shoreline well and second one is
for the concentrated brine from saltworks basins. The concentrated brine gets procured from 4
dedicated basins that contain saturated brine which is normally adopted for NaCl
crystallisation. In addition, two storage tanks (2 m3
capacity each) were installed for testing
the system with artificial (NaCl) solutions.
The brackish water and brine are firstly sent to a filtration stage. Then they are moved
to a buffer tank of 125L capacity. In the end, for power generation, they are finally fed to the
RED unit. (a) a slightly diluted brine and (b) a slightly concentrated brackish water exit the
RED unit of which the former i.e.(a) can be recycled to the saltworks directly, where the sun
and wind evaporation will naturally restore its original concentration and the latter i.e.(b) is
discharged in a seawater channel which is close to the installation site. A simplified scheme
diagram of the plant layout is shown below.
Figure 1.4. Simplified schematic diagram of the plant layout

27. XXVII
Outputs From The Pilot Plant
 Area of a cell pair: 44*44 cm2
 As both sides of the cell will work hence net area =2*44*44 cm2
 Number of cell pairs= 125
 Net area available = 125*2*44*44 cm2
= 48.4 m2
 On using real brackish water and concentrated brine as feed solutions, an average
power output of 40 W was attained
 The same RED unit was tested also with artificial solutions, an average power output
of 65 W was attained.
 This pilot plant was scaled up to 500 cell pairs estimating about 400m2
of area and this
helped get more than 1 kW of energy after trying out various combinations.
As implemented on small scale, we found and calculated this power output which can be used
to power and electrify the rural coastal houses.

28. XXVIII
Chapter 2
Analysis
The process of Reverse electrodialysis is same as the process of electrodialysis in desalination
plants but the only major point of difference is that in reverse electrodialysis the polarity of
the electrodes is reversed periodically. But overall the flow process remains the same thus
helping us in analysing various things.
The design and operation of an Electrodialysis desalination process are based on a set of fixed
and variable parameters such as stack construction, feed and product concentration,
membrane properties, flow velocities, current density, recovery rates, etc. These parameters
are interrelated and may be rather different for different applications. For an efficient
operation of an electrodialysis desalination plant, the process has to be optimized in terms of
overall costs considering component properties and operating parameters. In this study the
design and optimization of an electrodialysis plant to be used for brackish water desalination
has been treated. User has to assign the following:
1-Productivity.
2-Recovery ratio.
3-Inlet feed concentration.
2.1. Simulation of Desalination Plant on Simulink
The following mentioned parameters were used in this simulation to find out various outputs
of the desalination plant :
1. Qp – Production capacity of the plant(m3
/day)
2. Cf – Concentration of feed inlet(ppm)
3. Cd – Concentration of dilute outlet (ppm)
4. RR – Recovery ratio
5. Alfa – Volume factor constant
6. Beta – Area factor/shadow effect constant
7. Gama – Equivalent conductance (S m2
/keq)
8. Zeta – Current utilization
9. d – Thickness of cell chamber(m)

29. XXIX
10. w – Effective width of cell(m)
11. Lst – Effective length of flow per stack(m)
12. u – Linear flow velocity(m2
/s)
13. a – Constant a (25000 A s b ml-b/keq)
14. b – Constant b
15. F – Faraday constant (9.65*108
As/keq)
16. Rawt – Total area resistance of the membrane (Ohm m2
)
17. SF – Safety factor
18. z – Electrochemical valency
Table 2.1. Values assumed at the initial stages of the project for the sake of simple calculations.
Thus when an input of all these 18 values is given, we get an output of 10 values which are:
1. Qf – Feed flow(m3
/day)
2. Cc – Concentration of concentrate outlet (keq/m3
)
3. Cfc – Concentration of concentrate inlet (keq/m3
)
4. Cs = Cf – Cd (keq/m3
)

30. XXX
5. Aprac – Practical area (m2
)
6. Lprac – Practical length (m)
7. At – Total plant area(m2
)
8. Nst – Number of stacks
9. Ncp – Total number of cell pairs
10. P – Plant power (kw)
11. SEC – Electrical power consumption(kWh/m3
)
12. It – Total current through stack(A)
13. Vt – Potential drop per stack(Volt)
Figure 2.1. Screen clipping of our Simulink model showing all the above mentioned parameters.
Behind this Simulink model there is a MATLAB function which helps us in calculating all the
outputs. The MATLAB function used is as follows :
function [Qf,Cc,Cfc,Cs,Aprac,Lprac,At,Nst,Ncp,Power,SEC,It,Vt]=
EMAT(Qp,Cf,Cd,RR,Alfa,Beta,Gama,Zeta,d,w,Lst,u,a,b,F,Rawt,SF,z)
%#codegen
%Total feed flow rate, m3
/day:
Qf= Qp./RR;
%Concentration concentrate Outlet, keq/m3
:
Cc=(Cf-(RR. *Cd)). /(1-RR);
%Concentration concentrate inlet, keq/m3
:
Cfc=((Cf.*(1-RR))./RR)+((Cc.*((2.*RR)-1))./RR);

31. XXXI
%concentration difference between feed solution and concentrate and
%dilute, keq/m3
:
Cs=Cf-Cd ;
%Empirical limiting current density, A/m2
:
ilim=a.*Cd.*(u.^b);
%Practical limiting current density, A/m2
:
iprac=SF.*ilim;
%Total length Of flow path,m:
Lprac=(((log((Cc.*Cf)./(Cfc.*Cd)))+((Gama.*Rawt.*(Cf-
Cd))./d)).*(z.*F.*Cd.*u.*d.*Alfa))./(((Cd./Cc)+1+(((Gama.*Cd)./d).*Rawt)).*(iprac.*Beta.*
Zeta));
%Number of stacks in series:
Nst=ceil(Lprac./Lst);
%Total number of cell pairs:
Ncp=ceil(Qp./(w.*d.*u.*24.*3600));
%PracticaI area, m2
:
Aprac=(Qp.*Lprac)./(24.*3600.*Ncp.*d.*u.*Alfa);
%Total plant area,m2
:
At=Aprac.*Ncp.*2;
It=(z.*F.*Qp.*Cs)./(24.*3600.*Zeta.*Ncp);
%direct current power, kWh:
Power=(((((Qp./(24.*3600)).^2).*(Cs.^2).*(z^2).*(F.^2))./(Ncp.*Aprac.*Zeta.^2)).*(((d.*log(
(Cc.*Cf)./(Cfc.*Cd)))./(Gama.*Cs))+Rawt))./1000 ;
%Specific energy consumption, kWh/m3
:
SEC=24.*Power./Qp ;
%Potential drop per stack, Volt:
Vt=(1000.*Power)./(0.75.*It);
Our major concern was the power output that was being generated from the plant as that was
something that we required for our further calculations and our case study. To study the actual
variation of power with various inlet factors, a number of iterations were done on this
Simulink model and they were plotted with the help of excel to get a rough idea as to how
exactly power varies and what all factors need to be taken into consideration.

32. XXXII
Table 2.2. Power output for different values of production capacity(Qp).
Here in the first case only Qp was changed for a set of 5 values while keeping all the other set
of parameters same as mentioned above. The following graph was obtained
Figure 2.2 Graph for Table 2.2.
From this graph it can be seen that on keeping all the other parameters constant and only
changing Qp i.e. Production capacity of the plant, the power varies linearly and increases
continuously.
Table 2.3.Power output for different feed concentrations(Cf).
1.493
2.24
2.987
3.733
4.48
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 50 100 150 200 250 300 350
POWER(KW)
Qp(m3/day)
Qp vs Power

33. XXXIII
Here in the second case, the production capacity of the plant was kept constant at 400 m3
/day
along with all other parameters and only Cf i.e. concentration of feed inlet was changed. Five
readings were taken according to the Simulink program and the following graph was plotted
Figure 2.3. Graph for Table 2.3.
Drawing a conclusion on the above graph, it is seen that in this case too power varies linearly
with the concentration of feed inlet. Hence more the inlet concentration, more will be the
power generated provided it is constrained under the above mentioned conditions.
Table 2.4. Power output for different values of cell chamber thickness(d).
In the third case, the production capacity of the plant was kept constant at 400 m3
/day like the
previous case. The addition here was that the concentration of feed inlet was also kept
constant at 3500 ppm and then d i.e. Thickness of cell chamber was changed. The following
graph was plotted
2.268
3.196
4.122
5.048
5.973
0
1
2
3
4
5
6
7
0 500 1000 1500 2000 2500 3000 3500 4000
POWER(KW)
Cf(ppm)
Cf vs POWER

34. XXXIV
Figure 2.4. Graph for Table 2.4.
From the graph it is clear that the thickness of the cell chamber is also directly related to the
power output and power also increases with increase in the thickness.
2.2. Analysis of Cell Unit on COMSOL MULTIPHYSICS
In the electrodialysis model of COMSOL MULTIPHYSICS, Nernst-Planck equations is used
for ion flux and charge transport by which the following equation describes the molar flux of
species i (which is either Cl or Na in this model), Ni, due to diffusion, migration and
convection
The first term is the diffusion flux, Di is the diffusion coefficient (SI unit: m2/s). The
migration term consists of the species charge number zi, the species mobility umob,i (SI unit:
s·mol/kg) and the electrolyte potential ( ). In the convection term, u denotes the fluid velocity
vector (SI unit: m/s).
The electrolyte current density is calculated using Faraday‟s law by summing up the
contributions from the molar fluxes, multiplied by the species charges, with the observation
that the convective term vanishes due to the electroneutrality condition:
4.679
5.11
5.542
5.973
6.405
0
1
2
3
4
5
6
7
0.0005 0.00055 0.0006 0.00065 0.0007
POWER(KW)
Thickness of cell chamber(m)
d vs POWER

35. XXXV
The conservation of current is then used to calculate the electrolyte potential.
This model uses Tertiary Current Distribution, Nernst-Planck interface when solving for the
electrolyte potential in the free electrolyte and ion-selective membrane domains
The analysis of flow was carried out in this software due to its usage of complex flow
equations and giving accurate results.
The following parameters were chosen in accordance to our previous values as well as certain
assumed values and further process was carried out.
Table 2.5. Parameters for Unit Cell
Name Expression Value Description
Vtot 1.5[V] 1.5 V Total potential drop over unit cell
DNa 2.5e-9[m2
/s] 2.5E−9 m²/s Diffusion coefficient, Na
DCl 2e-9[m2
/s] 2E−9 m²/s Diffusion coefficient, Cl
T 298.15[K] 298.15 K Temperature
cCl_0 0.098[mol/dm3
] 98 mol/m³ Inlet concentration, Cl
cMem 1[mol/dm3
] 1000 mol/m³ Membrane charge concentration
v_avg 0.075[m/s] 0.075 m/s Channel average flow velocity
L 1[m] 1 m Cell length
W_ch 209[mm] 0.209 m Channel width
W_m 0.65[mm] 6.5E−4 m Membrane width
The shown below diagram is the resultant geometry of the structure of the cell with one unit
which comprises of channels, selectively permeable membranes, inlets and outlets.

36. XXXVI
Geometry
Figure 2.5. Geometry of unit cell
Electrolyte Potential (tcd)
Figure 2.6. Electrolyte potential
Here it can be seen that the potential increases from left to right and thus creating a potential
difference which is utilized for the flow of charge.
INLETS
OUTLETS
CATION SELECTIVE MEMBRANE
ANION SELECTIVE MEMBRANE
DILUTATE DOMAIN

37. XXXVII
Electrolyte Current Density (tcd)
Figure 2.7. Electrolyte current density vector
This basically shows the flow of current from left to right.
Concentration, c1 (tcd)
Figure 2.8. Concentration of Na+

38. XXXVIII
Figure 2.9 Concentration (for representation)
The above figure shows the Na+
ion concentration in the cell for the membrane charge
concentration of 1000 mol/m3
. The concentration increases in the concentrate domains, and
decreases in the dilute domain. A boundary layer with high concentration gradients forms
close to the membrane surfaces.
Potential
Figure 2.10. Graph of Electrolyte Potential.
The above figure shows the electrolyte potential along a horizontal line placed at half the cell
height. The main part of the potential losses occurs in the membranes. The Donnan potential
discontinuity can be seen at the boundaries between the free electrolyte and membrane
domains.

39. XXXIX
What is DONNAN potential?
The Donnan potential is the name given to the interfacial potential difference that arises
when certain ionic solutes cannot cross the interface between two immiscible electrolyte
solutions while the remaining ions are free to move reversibly from one phase to the other.
Concentrations
Figure 2.11. Concentrations of Na+
& Cl-
The above figure shows the concentration of Na+
and Cl-
ions at half the cell height for the
membrane charge concentration, 1000 mol/m3
. The concentration of Na+
is significantly
lower than for Cl-
in the anion selective domain (and vice versa), but it is not zero.

40. XL
Fluxes, Na
Figure 2.12. Fluxes, Na
Fluxes, Cl
Figure 2.13. Fluxes, Cl
The above figures show a comparison between the migrative and diffusive fluxes in the free
electrolyte for Na+
and Cl-
, respectively. The diffusive fluxes get prominent close to the
membrane boundaries due to the high concentration gradients. The migrative fluxes govern in
the middle of the channels and have different signs for Na+
and Cl-
due to the different signs
of the ion charges.

41. XLI
Chapter 3
Case Study
3.1. Introduction
As explained in the study of reverse electro-dialysis we plan to implement the
electricity generated from this process to deploy in rural areas near the plant where electricity
process are more often due to load shedding and high concentration of power to the plant
itself. Here the plant is desalination plant. As in reverse electro-dialysis, when we treat the
brine water the waste product of desalination process with fresh or incoming sea water under
membrane setup it generates flow of ions that is Na+
and Cl-
. Because of this movement the
larger size ion Cl-
moves to one side of the setup and because of this flow of electrons
potential difference is developed and electricity is generated.
Using this study we plan to use this generated electricity by waste of desalination plant
i.e. brine water to be stored and transmitted to nearby coastal housing to fulfil their own
electricity requirements.
To fulfil this outcome we have researched and planned to implement this approach in
INDIA‟s only current desalination plant which produces tons of fresh drinking water from
reverse osmosis and desalination process. This plant is situated in Tamil Nadu, India.
3.2. The Desalination Plant
The Minjur Desalination Plant is a reverse osmosis water desalination plant located in
Katupalli village, a northern rural area of Chennai, India, on the Bay of Bengal coast, that
provides water to the city of Chennai. It is situated on a 60-acre plot of land. This is India's
largest desalination facility. At The Global Water Intelligence Conference in Barcelona,
Spain, the project was named one of the most commendable Desalination Deals of 2007.
This plant was designed, installed, and operated by our own 100 MLD desalination
plant, which was the first in the country and has been operating in Chennai for many years.
This plant is well positioned to take on the task of turning seawater into potable, fresh
drinking water for India's coastal areas.

42. XLII
Figure 3.1. The image from the plant site
3.2.1. History of this Plant
The demand for drinkable water is increasingly rapidly and many cities across the
world are struggling to meet the water requirements of their citizens. Chennai, on the other
hand, is a rapidly growing metropolis with an unmet need for clean drinking water,
necessitating a slew of projects. IVRCL came up with a prestigious project to commission a
desalination plant near Chennai that transforms sea water into safe potable water to solve the
issue.
Water is a necessary component of life and good health. In mostparts of our country and other
parts of the world, there is a scarcity of water to meet daily needs.
The problem is worsening globally as cities and populations expand, and household water de
mands rise. We all know that salt water makes up 99 percent of the world's water supply.
Issues-What better way to solve the problem than to convert?

43. XLIII
Desalination
It is the process of removing salt and
other impurities from water and rendering it
fit for human consumption. Seawater has a
high percentage of salt whereas pure
drinkable water should ideally contain less
than 10 ppm of salt.
Figure 3.2.illustrates the location and
coordinates of the plant. The red circular
mark is the Minjur plant.
3.2.2. Some Facts about the Plant Figure 3.2. Location of plant
Project Name: 100 Millions of Liters per Day Seawater Desalination Plant
Project Location: Kattupalli Village, Ponneri Taluk, Minjur
Project Cost: Rs. 550 Crores
Owner: M/s Chennai Water Desalination Ltd (CWDL).
A Special Purpose Vehicle formed by M/s IVRCL LTD.
Client: Chennai Metropolitan Water Supply & Sewerage Board (CMWSSB)
Project Type: Design Build Own Operate & Transfer basis (DBOOT)
Operation & Maintenance Period: 25 years from the date of Commerical Operations Date
(COD)
Process: According to IS 10500: 1991 and the BWPA between CMWSSB and CWDL,
seawater is desalinated using the reverse osmosis method to provide potable water. To
provide 100 MLD of potable water, about 237 MLD of seawater is drawn through HDPE
pipes by gravity intake from the Intake structures located around 589 metres from the shore at
a depth of 9 metres. The seawater is pre-treated with screening, coagulation and flocculation,
sand filters, anthracite filters, and chemical dosing to make it suitable for feeding to the
reverse osmosis system, and the treated water from the reverse osmosis system is post treated
with lime to meet the requirements of IS 10500:1991. The brine reject from the RO system

44. XLIV
Figure 3.3. Booster pumps feeding the brine solution into the RO membranes
be discharged via outfall pipes 650 metres from the shore. According to Ministry of
Environment and Forests regulations, the distance between the intake and outfall systems
must be held at 698 metres. The treated water will be metered before being delivered to the
plant's Product water tank, which is located within the plant's battery limits. The Energy
Recovery System recovers the energy from the brine in the reverse osmosis process and feeds
it back to the reverse osmosis membranes via booster pumps as shown in figure 3.3. This is
the primary benefit of our scheme, which significantly lowers the plant's energy costs.
3.2.3. Studies undertaken for this project:
CWDL has undertaken the following studies for the project.
1. Oceanographic studies.
2. Marine Environmental Impact Assessment studies.
3. Desalination of LTL and HTL and CRZ- Coastal Regulation Zone.
4. Marine geophysical investigations.
5. Mathematical Modelling study on the dispersion of saline reject disposed in the sea.
6. Water Quality Geotechnical Investigations studies to assess the properties of the soil.
Geotechnical investigations are experiments that are
conducted to determine the properties of the soil. On the
orders of the Ministry of Environment and Forests in
New Delhi, the Central Marine Fisheries Research
Institute in Kochi conducted a Rapid Impact
Assessment of high saline effluent from the proposed
Desalination plant at Minjur on Coastal marine life and
fishery. Figure 3.4. Storage tanks

45. XLV
Water projects are humbling experiences for this plant because they greatly contribute to
and affect the quality of life of our country's people, both directly and indirectly, and will
continue to do so in the future. Our engineering skills triumphed on the „sea water
desalination factory,' and we took pride in adding another jewel to India's crown.
 As mentioned above, this plant produces around 100 Million liters per day fresh
drinking water. This is carried out in large scale and huge land region is required to
setup the plants sections. As the plant uses Reverse Osmosis and Desalination as their
water purifying and treatment methods we get large amount of water which can be
treated according to their properties. The process involves extracting water from sea
treating them with desalination parameters and get fresh and pure drinking water.
 This process also gives out brine as a by-product along with water as sea water which
is salty in nature is treated, the water and salt both are separated to get the desired
output. This salt separated mixture is known as brine.
3.3. About Brine-
Brine a problem for coastal region - Brine is a salt (NaCl) solution with a high
concentration of water (H2O). In different circumstances, brine may refer to salt solutions
with concentrations ranging from about 3.5 percent (a standard concentration of seawater, on
the lower end of solutions used for brining foods) to about 26 percent (a typical saturated
solution, depending on temperature). Fresh water, brackish water, and other lower
concentration levels are referred to as fresh water, brackish water, and so on.
Its properties are- Brine naturally occurs on the Earth's surface, crust, and within brine
pools on ocean bottom. High-concentration brine lakes typically emerge due to evaporation of
ground saline water on high ambient temperatures. The corrosive and sediment-forming
effects of salts, as well as the toxicity of other chemicals diluted in it, can make wastewater
brine a major environmental threat. It must be disposed of properly, which can necessitate
permits and adherence to environmental regulations.
It is actually used in- Brine is used in a variety of technical methods, including food
processing and cooking (pickling and brining), de-icing of roads and other structures, and de-
icing of roads and other structures. It is also a by-product of many industrial processes, such
as desalination, and because of its corrosive and poisonous properties, it poses an

46. XLVI
environmental risk, necessitating wastewater treatment for proper disposal or further
processing.
Making use of this Brine as an input for Reverse Electro-Dialysis process.
 Desalination for human use and irrigation, power plant cooling towers, produced water
from oil and natural gas extraction, acid mine or acid rock drainage, reverse osmosis
reject, and chlor-alkali wastewater treatment are all examples of industrial processes
that generate brine, pulp and paper mill effluent, and waste streams from food and
beverage production.
 Returning unpolluted brine from desalination plants and cooling towers to the ocean is
the most straightforward way of disposing of it. It may be diluted with another stream
of water, such as a wastewater treatment system or a power plant's outfall, to reduce
the environmental effects.
 For handling polluted brine, membrane filtration processes such as reverse osmosis
and forward osmosis; ion exchange processes such as electrodialysis or weak acid
fulvic acids; and evaporation processes such as thermal brine concentrators and
crystallizers that use mechanical vapour recompression and steam are all choices.

47. XLVII
3.4. About the Village
Kattupalli is a medium-sized village in the Ponneri Taluka of the Thiruvallur district
of Tamil Nadu, with a population of 534 families. According to the 2011 Population Census,
the Kattupalli village has a population of 1911 people, with 1096 men and 815 women. The
energy layout and generation as explained can be used in this village and nearby areas
considering the population.
Going by the 2011 Census, the Voyalur panchayat, of which Urnambedu, Segenimedu
and five other villages are a part, has a population of 6,080. Over 3,400 residents of the
neighbouring village of Kattoor. Another 10 fishing villages along the coast, including
Kattupalli, are also likely to be moved out because of expansion of major business companies
but this will impact the overall population and reduce or will see a drop in energy requirement
for small scale purpose.
Figure 3.5. The village Kattupalli
The location being a business point in Tamil Nadu will help to only expand it‟s output and
its‟s efficiency in overall development. Major companies like. Adani Ports and L&T have
their huge plants in this region because of the advantage of large area of coastal line.

48. XLVIII
3.4.1. The Plan:
1. Village requirements of electricity is decreasing because of industrial shift but the
people residing because of this industrial change might use the electricity generated
using this process.
2. The a small part of whole system can be integrated with the reverse electro-dialysis
setup which will look like the below picture (figure 3.6.), where High concentration
and Low concentration solutions are kept in Container or a tank and have membranes
between them alternately placed which allows the process to take place.
3. The exact setup is an idea we have studied and analyzed for application of small scale
electricity generation.
4. As we have observed by having 100 m3
/d plant capacity as a unit of the setup for
calculations purpose, we get power outputs ranging from 2.5kW to 5kW by using
parametric values as per requirements and suitability.
3.4.2. Advantage of this location for RED process:
1. Proximity to sea.
2. Can be built in modules starting from as low as 2 MLD to as high as 200 MLD.
3. Better control over quality and quantity.
4. Dependence on external source for water is eliminated.
3.4.3. Implementation
Figure 3.6. Schematic diagram of the setup

49. XLIX
 The above diagram illustrates a basic setup where the ion movement takes place. This
is a systematic layout where negative charged ions i.e. Cl-
moves towards the left side
of the setup. This systematic arrangement of low concentration and high concentration
solutions which is low means the sea water which is directly extracted or used from
the sea and High concentration means the brine water which is a waste product of
desalination process.
 This movement allows the velocity movement and further this when studied and
analyzed with the existing RED plants gives us a rough idea about how much
electricity is generted in a particular setup when treated with ion exchange membrane.
The simulation done on MATLAB using the setup and standard values of a small scale plant
are used where we can clearly examine the outputs on different scales of input. As the blocks
mentioned in the above diagram the arrangement of membranes and Anode exchange
membrane and cathode exchange membrane placed alternatively creates ions flow.
The inputs for this particular setup and outputs revolved around cost initially required to run
the plant.
Table 3.1. Cost
If we use the current set of inputs as mentioned in the analysis selection, with specific alterations,
assumptions and consideration we can consider the approximate cost and basic costs calculations.
As we consider the operating hours of this plant to be 24 and assume it gives regulated outputs, and
consider the plant life cycle as 5 years.
Considering Load factor Lf = 0.9 constant throughout.
As, Membrane costs is huge and also one of main reasons on why this type of plant is not scaling
up widely in world. The estimated power output i.e. average 4.5kW requirement requires alternate
setting up of membrane.

50. L
Because of practical difficulties and current situations we consider membrane as a whole of process
and assumed total area.
The setup having flow and other flow related activities Electric costs are referred and assumed to be
around Rupee. 10 kW/h
 All the values after studying and reviewing are referred from the existing RED plant in
Italy and are iterated according to our requirement in India in Tamil Nadu.
 If plant capacity is increased we can get higher power output:
 Qp where it is assumed to be 100 m3
/d can be increased as per our
requirements upto 3500 m3
/d
 The other changes are subjected as per boundary conditions and availability of
resources.
3.5. OUTCOME OF CASE STUDY:
 Can fulfil the energy requirements on coastal households and provide electricity.
 Made to use the waste product of brine which is hazardous in nature.
 We can infer from the above calculations that value of power over particular set of
input values ranges from 2kW to 8kW. This is considered when under maximum
feasible boundary conditions.
 Clean and safe form of energy is used and electricity is generated.
 As we can observe the location has huge coastal line and large area covered with bay
of Bengal and water bodies, Endangered Marine life is saved from brine and marine
lifecycle balance is achieved.

51. LI
3.6. On-going Research
Recent developments and process on this working principle to give a general idea about
where this technology is heading towards.
Because of high costs of membrane and less availability in most of the regions, Reverse
electro-dialysis is being replaced by nano-technology in some regions where raw material is
available and application is possible. Membrane research - Graphene Sheet is added to
maintain composition and dimension. It has 97% efficient results in purification i.e. Covalent
bond of hydrogen with negative charged salt.
Figure 3.7 Illustration of Grapheme as Membrane.

52. LII
Conclusion
 Treated sea water is led back to the sea - Ions are freed and sea water is passed where
Hydrogen bond can easily break and pass within the dimension and pure water is
extracted.
 By using this process on a small part of system of desalination plant of Minjur and
integrating it with reverse electro-dialysis outcome, we can generate electricity and
provide it to the village of kattupalli and nearby coastal habitats. The volume of fresh
water production and plant outcomes is huge and to integrate the whole to Reverse
electro-dialysis is out of our study and is practically difficult considering the
vulnerabilities and errors involved for managing the whole plant.
 This also is financially difficult to achieve as the initial cost to setting up this plant is
high and might be replace by nano-technology in coming 15 years.
 The Technology evolving and growing as faster as ever opens up many possibilities
and areas which can be replaced or made efficient considering the urge of drinking
water requirement and electricity scarcity in various regions.

53. LIII
References
1. Musthafa O. Mavukkandya , Chahd M. Chabiba , Ibrahim Mustafa. Brine
management in desalination industry: From waste to resources generation.
Desalination. 2019.https://doi.org/10.1016/j.desal.2019.114187
2. C. Tristán, M. Fallanza, R. Ibáñez, I. Ortiz. Recovery of salinity gradient energy in
desalination plants by reverse electrodialysis. Desalination.
2020.https://doi.org/10.1016/j.desal.2020.114699
3. Argyris Panagopoulos,Katherine-Joanne Haralambous,Maria Loizidou. Desalination
brine disposal methods and treatment technologies - A review. Science of the total
environment.2019.https://doi.org/10.1016/j.scitotenv.2019.07.351
4. Michele Tedesco, Claudio Scalici, Davide Vaccari. Performance of the first Reverse
Electro-dialysis pilot plant for power production from saline waters and concentrated
brines. Journal of Membrane Science
.2015.https://doi.org/10.1016/j.memsci.2015.10.057
5. Michele Tedescoa , Paolo Mazzolaa , Alessandro Tamburini. Analysis and simulation
of scale-up potentials in reverse electrodialysis.Desalination and Water
Treatment.2014.https://doi.org/10.1080/19443994.2014.947781
6. Desalination plant of India: https://www.water-
technology.net/projects/minjurdesalination/
https://en.wikipedia.org/wiki/Minjur_Seawater_Desalination_Plant
7. Reverse Electrodialysis: Potential Reduction in Energy and Emissions of Desalination,
Department of Chemical and Biomolecular Engineering, University of Cantabria, Av.
Los Castros 46, 39005 Santander, Spain. https://doi.org/10.3390/app10207317