desalination by membrane technology – state of the art and future trends

Experts in Chem-Feed and Water Treatment

Desalination by membrane technology –state of the art and future trends

Dr. Matthias Rothe and Oliver Hentschel

ProMinent GmbH Im Schuhmachergewann 5-11, D-69123 Heidelberg

Tel. +49 (6221) 842-0, Fax. +49 (6221) [email protected] www.prominent.com


Content

Dr. Rothe, Oliver Hentschel, 24.01.2014, SANEPAR 2

1. Basics and state of the art membrane filtration

2. Applications for desalination by membranes

3. Future trends for membrane desalination


1. Basics and state of the art membrane filtration


Membrane filtration: removal of particles and salts ensuring lowest operating costs

physical process using semi-permeable membranes

4 technologies depending on the size of the particles/molecules to be removed

Microfiltration

Ultrafiltration

Nanofiltration

Reverse Osmosis


Nanofiltration and Reverse Osmosis


Nanofiltration and Reverse Osmosis are the only membrane

technologies to remove ions/salts from water !

How does it work ?


Osmosis

dilutedsolution

concentratedsolution

semipermeable membrane

water columncorrespondingto osmotic pressure



Reverse Osmosis


pressure

dilutedsolution

concentratedsolution

semipermeable membrane


Development of Reverse Osmosis Membranes


cellulose acetate membranes

lifetime about 6 months

pH range: 4 - 8

salt rejection:up to 90-95%

polyamide hollow fibre modules

lifetime about 5 years

pH range: 4 - 11

salt rejection:up to 96-98%

less sensitive against bacteria

thin film composite membrane

lifetime about 10 years

pH range: 2 – 11, for cleaning: 1 - 12

salt rejection: up to 99.8%

stability up to 45°C

sanitary membr. 90°C

less sensitive against bacteria/biofilm

1960 1970 1980 - 2014


Thin film composite membrane


Polyamide ultrathin barrier layer (approx. 0.1-0.2µm)

Polysulfone micro-porous support (approx. 40µm)

Polyester non-woven web Carrier (approx. 120µm)


Crossflow membrane filtration



Thin film composite membrane module


http://www.youtube.com/watch?v=YlMGZWmh_Mw&feature=player_embedded


Water temperature influence on reverse osmosis


increased water temperature

reduction of water viscosity

increased permeate production

but:decreased salt rejection


Operation pressure influence on reverse osmosis


The salt rejection will be better, also

The higher the pressure the more permeate flow is produced


Recovery of membrane systems


R

K

P

25% drain to waste

75% permeate100% raw water

Recovery [%] = Output : Input = (Permeate flow / raw water flow) x 100

Typical recoveries: 70-80% for desalination of tap water35-45% for desalination of sea water


Typical reverse osmosis system


2 17

10

7/8

15

1913

13

20

13

2

11

12

13

1

2

3

54

1. particle filter2. pressure gauge3. solenoid valve incl. check valve4. pressure switch5. thermometer6. high-pressure pump7. pressure vessel8. membrane9. conductivity probe10. controller incl. conductivity measurement11. flow meter permeate12. 3-way valve

13. ball valve14. flow meter concentrate15. 3-way valve16. flow meter concentrate recycle17. sample valve18. cleaning tank19. cleaning pump20. check valve

616

9

11

18 10

16


Typical reverse osmosis system


11

22

33

44

5566

1 pressure vessels incl. membranes2 switch cabinet with RO control unit3 cleaning tank4 flow meter permeate + concentrate5 particle filter6 conductivity sensor permeate

1 pressure vessels incl. membranes2 switch cabinet with RO control unit3 cleaning tank4 flow meter permeate + concentrate5 particle filter6 conductivity sensor permeate


Overall design of a membrane system


Pre-treatment depending on the feed water‘s quality: filtration and chemical conditioning as a minimum

Pre-treatment depending on the feed water‘s quality: filtration and chemical conditioning as a minimum

Post-treatment depending on applicationPost-treatment depending on application


Applications for desalination by membranes


Tap water desalination(typically up to 1.000 mg/l of feed water salinity)

Brackish water desalination(typically 1.500 – 8.000 mg/l of feed water salinity)

Sea water desalination(typically more than 35.000 mg/l of feed water salinity)


Applications for Reverse Osmosis


industrial water desalination of tap water

• boiler water for steam production

• dilution water for juice- and softdrink production

• bottled water

• …

potable water production desalination of brackish and sea water reduction of nitrate reduction of fluoride reduction of arsenic


Desalination of tap water (installation example)


3x tap water desalination 1.200 m³/day, total 3.600 m³/day,process water for paintshop of KIA motors


Future trends for membrane desalination


nano-coating structures on the active membrane layer, advantages:

a. anti-fouling properties are improved




b. Increase in permeability

• less energy is needed at improved salt rejection rates

• first membranes with nano-coating are commercially available now

http://www.nanoh2o.com/technology/video




decreased energy consumption

• membrane desalination with renewable energies like solar power …




… or wind energy:




Combination of membrane technologies, e.g. Micro- and Ultrafiltration (MF/UF) as pre-treatment followed by reverse osmosis, advantages:

a. Smaller footprint of complete water treatment plant which leads to smaller buildings

b. Better quality water of pre-treatment e.g. in comparison to classical sand filters

c. Reverse osmosis after MF/UF can be designed much more aggressive because of higher filtrate quality. This saves investment and operation costs on the reverse osmosis downstream




Energy recovery on sea water desalination systems has moved from turbines to pressure exchangers. They reduce energy consumption of a sea water desalination units by 50-60% !


Cost considerations


Typical Pressure

Typical Recovery

Typical Energy Consumption for RO

PW 4 - 12 bar up to 80 % 0,4 – 0,75 kWh/m³

BW 10- 40 bar up to 60 % 1,2 – 2,00 kWh/m³

SW without ER

40 - 82 bar up to 30-50 % 4 – 8 kWh/m³

SW with PX 40 - 82 bar up to 30-50 % 1,8 – 3,5 kWh/m³

Energy consumption depend on: Salinity and permeate qualityRecovery RateFeed Water TemperatureMembrane Type and Aging (Fouling/Scaling)Pump Type and Configuration


Energy consumption of large SWTP


Source: Watereuse: Seawater desalination Power consumption


Typical Range of SWRO Facility Costs


Source: Watereuse: Seawater desalination Power consumption


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