NEW & EMERGING WATER DESALINATION

TECHNOLOGIES – AN OVERVIEW

By

Dainik KhantEngineer Technology

Aquatech System Asia Pvt Ltd

New & Emerging Technologies for Water Desalination

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

New Membrane Based Desalination :- Osmotic Membrane Processes

Osmotic Membrane process classified in to three categorized1. Forward osmosis (osmosis, manipulated osmosis, direct osmosis)2. Reverse osmosis3. Pressure retarded osmosis

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.

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 In FO, a solute is added to pure water side to reverse flow; Later it is withdrawn.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

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

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)

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

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

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

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

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

Potential Benefits of FO in water treatment

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.

Pressure Retarded Osmosis cont…

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.

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

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

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

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.

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.

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....

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

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

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

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

Microbial Osmotic Fuel Cell

Technology Integration Energy Recovery + Wastewater Treatment + Water Reuse

Building a world of differences

Together

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