This document discusses various desalination processes and their energy requirements and costs. It provides details on membrane-based processes like forward osmosis, reverse osmosis, and membrane distillation. Forward osmosis uses osmotic pressure to purify water and has potential applications in water treatment, energy production, and life sciences. The document outlines several pilot projects using forward osmosis and membrane distillation technologies and discusses the benefits and challenges of these innovative approaches to desalination.

1. Dainik Khant
Engineer Technology
Aquatech System Asia Pvt Ltd

2. New & Emerging Technologies for Water Desalination

3. Energy Requirement & Cost of various Desalination Processes
Process Total Energy
(kW-h/m3)
Capital Cost
($/m3/d)
Unit Water
($/m3)
MSF (Without waste heat) 55-57 - -
MSF (with waste heat) 10 - 16 1000 - 1500 0.8 -1.0
MED (without waste heat) 40-43 - -
MED (with waste heat) 6 - 9 900 - 1200 0.6-0.8
SWRO 3 - 6 800-1000 0.5-0.8
SWRO (with energy Recovery) 2 - 3 <800 0.45-.6
BWRO 0.5 – 2.5 <800 0.1-0.3
Innovative Technology/Hybridization < 2.0 * <800 <0.5

4. New Membrane Based Desalination :- Osmotic Membrane
Processes
Osmotic Membrane process classified in to three categorized
1. Forward osmosis (osmosis, manipulated osmosis, direct osmosis)
2. Reverse osmosis
3. Pressure retarded osmosis

5. Basic of Forward Osmosis & Reverse Osmosis
 Forward osmosis is an osmotic process that uses a semi
permeable membrane for effective separation of water from
dissolved solute.
 In the FO process, a net water movement occurs through a semi-
permeable membrane from a low concentration solution to a
high concentration solution.
 The driving force for water flux in forward osmosis is the
difference in osmotic pressure between two water solutions, the
saline water and the impaired water.
 Forward osmosis uses seawater or concentrated brackish water
as a draw solution to extract clean water from impaired water
streams(waste water).
 In Reverse Osmosis(RO), pressure is applied (greater than
osmotic pressure) on high concentrated solution side to produce
& recover fresh water from concentrated water.

6. 1. Forward Osmosis
 Uses natural osmosis to purify water
 When saline and pure water are separated by RO membrane, pure water flows
towards saline side.
 In FO, a solute is added to pure water side to reverse flow; Later it is withdrawn. The
temporarily high saline source is referred to as draw solution
 Key to the process is selection of draw solution and membrane system design

7. Forward Osmosis cont.…
 Desirable properties of ideal osmotic agent
 Non-toxic, inert, not fouling in nature, inexpensive
 High solubility
 High osmotic pressure on a mass or molar basis
 Easy to recover
 Osmotic agents considered
 Carbon dioxide/ammonia – recovered through use of low grade heat
 Sodium chloride
 Organic molecules (precipitate at higher temperatures)
 Mixtures (sugars and inorganic salts)
 Nanoparticles, magnetized particles
 Membrane:- RO-like membrane such as polyamide, cellulose acetate based membrane
but osmosis- is not pressure-driven
 Energy:- Required Low energy, low energy alternative to SWRO (energy saving)
 Feed: lower salinity or impaired quality source such as RO conc. or WW
 Draw: higher salinity solution such as Conc. DS or Seawater

8. Forward Osmosis Cont.……
 Draw Solution:- need high solubility, low cost, high osmotic pressure solution, easily
separable & reusable, non toxic & eco friendly.
 Post treatment:-
 Recovery of product water from diluted draw solution
 Recovery & recirculation of draw solution
 Concentrated feed treatment & environment impact.
 Challenges/Research Needs/Process Improvement:-
 New & better FO membrane (LPRO membrane, opened support layer, porosity etc)
 Minimize concentration polarization within support layer that decline flux.
 Minimize fouling & bio-fouling
 Novel draw solution (sea water vs synthetic solution)

9. Application of FO in field of water, energy & life science

10. FO based sea water treatment Pilot plant By Modern Water
1. Modern Water’s first full scale seawater plant (18 m3/day) was commissioned in Gibraltar in
September 2008 at an AquaGib site.
2. 100 m3/day located at the Public Authority for Electricity and Water’s site at Al Khaluf in Oman in
November 2009.
3. Modern Water was awarded a turnkey contract to build a 200 m3/day forward osmosis based
desalination plant at Al Najdah

11. Pipeline:- Al Najdah 200 m3/d FO desalination plant

12. Forward Osmosis By Oasys Water Inc.
 Oasys is developing this technology for high salinity desalination
 Draw solution: ammonia/carbon dioxide solution
 Solute recovered by application of heat
 Maturity –Details of removal of ammonia/carbon dioxide are not known
 Energy – for main process, only pumping. For withdrawal of draw solution, energy consumption is
not yet known for required level of removal .
 Oasys claim that its technology can produce desalinated water at less than half the cost and using
90 percent less energy than RO

13. Submerged Osmotic MBR for Waste water treatment By
Hydration Technology Innovation
Performance efficiency of HTI-OsMBR for Industrial Waste water application
% Removal
Parameter By FO By OsMBR ByOsMBR+RO
TOC (mg/l) >97 >99.7 >99.7
NH4-N >90 >97.5 >99.2
Component Conventional MBR
plus HQ water
reuse
HTI OsMBR plus HQ
water reuse
1 Mixer in
Anoxic tank
0.04kwh/m3 0.01kwh/m3(no
anoxic tank)
2 Membrane
Filtration
0.04kwh/m3 0.01kwh/m3 (
minimum flow-
osmotic circulation)
3 Submerged
recirculation
0.21 kwh/m3 0.01 kwh/m3
4 Blower for
Membrane
cleaning
0.49 kwh/m3 0.15 kwh/m3
5 Blower for air
diffuser
0.12 kwh/m3 0.12 kwh/m3
(minimum cleaning)
6 RO/NF for
polishing HQ
3.30 kwh/m3 2.5 kwh/m3
Total energy
estimate
4.20 kWh/m3 2.80 kWh/m3

14. Potential Benefits of FO in water treatment

15. 2. Pressure Retarded Osmosis
 When concentrated seawater and diluted fresh water (i.e. river water) are separated by a
semi permeable membrane, water will diffuse from the feed side into the draw solution side
(i.e. seawater side) that is pressurized.
 The pressurized and diluted seawater is then split into two streams: one going through a
hydro-turbine to generate power by depressurizing the diluted seawater, and the other one
passing through a pressure exchanger to assist in pressuring the seawater and thus
maintaining the circulation.

16. Pressure Retarded Osmosis cont…

17.  The world’s first osmotic power
plant with capacity of 4 kW ( enough
to heat a large electric kettle) nut by
2015 the target is 25 MW (same as a
small wind farm).
 Opened by Statkraft on 24
November 2009 in Tofte, Norway.
 This plant uses polyimide as a
membrane, and is able to produce
1W/m² of membrane.
Osmotic Power Plant by Statkrat.

18. MEMBRANE DISTILLATION
 Basic principle – transport of water vapor from a saline source through pores of a membrane .
 Membrane is the key – should be hydrophobic and allow only transport of vapor
 The temperature/vapor difference across the membrane provides driving force, that causes diffusion
of vapor through the membrane pores, producing distillate
 Driving force for transport of vapor through various means
 Condensing fluid, condensing surface with air gap, sweeping gas, or vacuum

19. Membrane distillation cont…
 Maturity – several studies at many universities; Companies – Memstill, Memsys;
 Recovery – High recovery possible; Up to 80% or higher, although tests are with simulated water
 Energy
 Electrical energy – primarily for conveyance of water while maintaining sufficient cross flow
velocity <1 kWh/m3
 Thermal energy – Needs low cost or waste thermal energy to raise water temperature to 40 to
80 deg C
 Materials – Plastic components, given the low operating temperature

20. MEMBRANE BASED PROCESS- VACCUUM MULTI EFFECT
MEMBRANE DISTILLATION (V-MEMD BY MEMSYS)
o Combination of multiple effect distillation and membrane distillation
o Essentially pressure is reduced across multiple stages
o Vacuum passing through membranes continues to evaporate water
o Maturity – Currently at 50 m3/day
o Energy – Electricity- very limited
o Thermal – needs low grade heat. 45 to 185 kWh/m3 depending on number of effects, and
energy recovery using vapor compression

21. MEMSTILL® is a new desalination technology based on membrane
distillation. developed by a consortium which includes TNO and Keppel
Integrated Engineering Ltd.
 The technology was first tested at bench scale and then with a 2m3/d pilot plant testing at
Senoko Refuse Incineration Plant from February 2006 to June 2007. This demonstrated the
principle of MEMSTILL® on a pilot scale, and sustainable operation of the M26 type MEMSTILL®
module. The up scaling of 3 m2 (membrane area) bench scale to 600 m2 proved that the integrity
of membrane modules remained well and no severe leakage was observed. The distillate quality
was superior throughout the pilot plant study period.
 A second MEMSTILL® pilot in the Netherlands (E.ON pilot) was carried out with improved
material and configurations, and was able to demonstrate up to 10X better results (e.g. flux,
intake flow, distillate flow, energy efficiency, heat input) than the Singapore pilot.
 A third pilot with further improvements is being tested out in AVR, the Netherlands. Keppel
Seghers intends to build a MEMSTILL® demonstration plant in Singapore to further develop and
commercialize the technology.

23. MMD Desalination Systems By Solar Spring Inc..
 MMD desalination systems (Modular Membrane Distillation) use solar energy to provide clean
water from saline water. Based on membrane distillation, MMD systems provide a secure and
reliable source of water for drinking or process applications. The self-contained systems are low
maintenance, robust and operate efficiently from brackish to highly saline well or seawater.
 MMD systems are even more cost effective when using available waste heat. Excess heat from
operations (cooling towers, cooling of diesel engines, etc.) can be used to recycle water for reuse in
the process.
 SolarSpring is a pioneer in membrane distillation systems driven by solar energy. The first field
system was deployed in the Canary Islands in 2004 and is still in operation today. Systems have now
been installed in countries from Mexico to the Middle East, Africa and Australia.
 Drinking water in Namibia:- A containerized and 100 % solar-driven MMD system was installed in
northern Namibia in 2010. This is one of the driest areas in the country and SolarSpring partnered
with Fraunhofer ISE to bring water to the region. The system includes thermal heat storage and
provides 5,000 liters of drinking water 24 hours a day.
 Process water in Pantelleria:- An MMD system using waste heat from a diesel generation station is
desalinating seawater for process use. The distilled water is used to make a urea solution for the
selective catalytic reduction of NOx exhaust gases. In addition to providing 5,000 liters of process
water, the MD process reduces the cooling load of the plant.

24. MMD System specification
Nominal Operating Parameters
 Raw water salinity 35,000 ppm seawater
 Production capacity (daily) 4 – 6 m3/day
 Production capacity (hourly) 167 – 250 l/hour
 Raw water feedrate 800 – 1200 l/hour
 Brine discharge rate 633 – 950 l/hour
 Operating temperature 80 °C, ambient pressure
 Specific thermal energy consumption 150 – 250 kWhth/m3
MMD desalination cont....

25. MD Potential Application & Challenges
Application :-
 The production of pure water:-
• Laboratories
• Semiconductor industries.
• Sea water desalination.
• concentration of aqueous solution
 Removal of compound organic volatiles (VOC´s)
• Contaminated surface water (benzene)
• Fermentation products and volatile bioproducts (ethanol,
butanol, acetone or aroma compounds).
Challenges/Research Need:-
• Improved MD membranes, increased flux
• Reduce temperature polarization
• Process modeling and scale-up

26. Microbial Fuel Cell (MFC)
Microbial Fuel Cell (MFC)
1. Covert chemical energy to electrical energy
(bioelectricity)
2. Two chambers, anode (oxygen starved
/anaerobic) and cathode (oxygen rich/aerobic)
3. Substrate (e.g., wastewater) introduced to
anaerobic chamber, oxidized and releases
electrons
4. Electrons migrate toward cathode, in aerobic
chamber

27. Microbial Desalination Cell (MDC)
Microbial Desalination Cell (MDC)
 Two Chambers, one with anode (oxygen starved /anaerobic)
and cathode (oxygen rich/aerobic) and third chamber with
seawater
 Wastewater introduced to anaerobic chamber, oxidized and
releases electrons
 Third chamber in between separated by ion-specific
membrane, allows either positive and negative charges to
pass though the membranes
 Electron migrates toward cathode in aerobic chamber and
produces energy and desalination simultaneously
 Third chamber, ions move from middle chamber to balance
charge, due to protons produced by bacteria at the anode,
protons removed at the cathode

28. MDC Status/Challenges
 Opportunity for low-energy desalination
 Batch vs. Continuous mode
 Possible fouling of membranes
 Presently limited to 90% TDS reduction with
single ED
 New, multiple stacks (Stacked MDC, SMDC) with
ion exchange membranes, up to 98% reduction
 Use of wastewater vs. simple substrate
(integrated desalination & WW treatment)
 MDC-RO Hybrids

29. Microbial Osmotic Fuel Cell
Technology Integration Energy Recovery + Wastewater Treatment + Water Reuse