Mohammed Al-Abri Nanotechnology Research Center Sultan Qaboos - - PowerPoint PPT Presentation

Mohammed Al-Abri Nanotechnology Research Center Sultan Qaboos University

Small Desalination Units for Agriculture Sustainability: Challenges & Opportunities 5th March 2018

• Rainfall

• Groundwater

• Water shortage by Governorate

47.60% 1.10% 17.20% 0% 17.20% 1.90% 7.90% 7.10% Al Batinah Musandam Ad Dhahirah Al Wusta Ad Dakhiliya Ash Sharqiyah Dhofar Muscat

Musandam Al Batinah Ad Dhahirah Ad Dakhiliya Ash Sharqiyah Dhofar Muscat Al Wusta

• Water Use in Oman

88% 10% 2% Agriculture Domestic Industrial

http://www.fao.org

• Seawater Intrusion

(Oman Salinity Strategy. In Ministry Of Agriculture And Fisheries: Sultanate of Oman, 2012 )

• Al Batinah region accounts

for >50% of Oman’s agriculture production.

• Agriculture and livestock

use accounted for 97% of abstracted groundwater.

• Salinity increased due to

sea water intrusion

• To determine the suitable type of desalination process
• To determine the application of the product water
• To trouble shoot or predict operational problems

Concentration (mg/kg) Standard Seawater Mediterranea n Sea Arabian Gulf Mass %

Sodium, Na+ 10700 11800 13770 30.6 Magnesium, Mg2+ 1300 1423 1665 3.7 Calcium Ca2+ 421 463 540 1.2 Potassium, K+ 390 424 490 1.1 Strontium, Sr+ 13

• Chloride, Cl-

19250 21190 24802 55 Sulfate, SO4

2-

2700 2972 3465 7.7 Bicarbonate, HCO3 - 126 140 142

• Bromide, Br-

67 155 80

• Borate, BOH33-

26 28

• Fluoride, Fl-

1.3

• Silicate, SiO32-

2

• 1.5
• Others

3.7 5 44.5

• Total dissolved solids

35000 38600 45000

Biological Characteristics Physical Characteristics Chemical Characteristics

• Bacteria
• Viruses
• Fungi
• algae
• Turbidity
• Suspended solids
• Color
• Taste
• dor
• pH
• Conductivity
• Salinity
• Hardness
• Alkalinity
• Dissolved gases

RO ED Seawater Low Salinity & Brackish Water MEE Membrane Thermal Parallel Feed TVC MVC MSF

Desalination Processes

MVC SEE

Independent on

• salinity. Hardness is

main concern

Feed Concentrate brine Product water RO membrane module

Salinity Osmotic Pressure Hydraulic Pressure Operating Cost Brackish Water Seawater $0.25/ m3 $0.50/ m3 High pressure pump

• Capacity; 10 – 500,000 m3/day
• Recovery: ratio of produced water to feed water
• 30-40% seawater compared to 60-90% brackish water
• Feed quality; Salinity and hardness
• Pretreatment process
• Brine disposal
• Product quality; drinking or irrigation

• Precipitation of dissolved substances in water due to

concentration within an RO unit above saturation limit

• Scale potential is affected by:
• Presence of reactive species and other compounds
• Salt type and concentration
• Temperature
• Salinity
• pH

Na+ Ca++ Mg++ K+ Ba++ Sr++ Cl- 360 730 560 330 370 510 SO4

• 170

2 350 110 0.002 0.11 NO3

• 840

1220 740 300 90 70 CO3

• 190

0.013 1 1080 0.02 0.01 F- 45 0.016 0.076 930 1.6 0.1

Solubility of salts in pure water (g/L)

• Salts have

varying solubility in water

• Calcium carbonate is unusual in that its solubility decreases

with water temperature

• CO2 dissociation in water w.r.t. pH

• Solubility of CaCO3 in seawater is about 26 times higher than in

freshwater at the same temperature

• Calcium carbonate has low solubility in pure water (15 mg/L

at 25°C)

• May precipitate even below its saturation level in presence of

Al3+ & Fe3+

• Al3+ & Fe3+ must be very low in feed water to prevent scaling
• Fouling due to:
• Chemical reaction and precipitation (scale)
• Colloidal fouling with other particles in system

• Choice of desalination process is dependent on many factors
• Reverse Osmosis is currently the main brackish water

desalination process

• Hardness is limiting factor in brackish water desalination;

recovery

• Silica and other salts scale is important to identify
• New desalination technologies )ED, EDR, CDI, FO… etc.(

required

Thank You