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

 Water Use in Oman 2% 10% Agriculture Domestic Industrial 88% http://www.fao.org

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

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

Concentration Standard Mediterranea Arabian Mass % (mg/kg) Seawater n Sea Gulf Sodium, Na + 10700 11800 13770 30.6 Magnesium, Mg 2+ 1300 1423 1665 3.7 Calcium Ca 2+ 421 463 540 1.2 1.1 Potassium, K + 390 424 490 - Strontium, Sr + 13 - - 55 Chloride, Cl - 19250 21190 24802 7.7 Sulfate, SO 4 2- 2700 2972 3465 - 126 140 142 Bicarbonate, HCO 3 - - Bromide, Br - 67 155 80 26 28 - - Borate, BOH3 3- Fluoride, Fl - 1.3 - - - Silicate, SiO3 2- 2 - 1.5 - - 3.7 5 44.5 Others Total dissolved solids 35000 38600 45000

Biological Chemical Physical Characteristics Characteristics Characteristics Bacteria Turbidity pH • • • Viruses Suspended solids • • Conductivity • Fungi Color • • Salinity • algae Taste Hardness • • • odor • Alkalinity • Dissolved gases •

Desalination Processes Membrane Thermal RO ED SEE MEE MSF MVC Parallel Feed Low Salinity & Seawater Brackish Water Independent on salinity. Hardness is main concern MVC TVC

RO membrane module High pressure pump Product water Feed Concentrate brine Osmotic Hydraulic Operating Salinity Pressure Pressure Cost Brackish Water Seawater $0.25/ m 3 $0.50/ m 3

 Capacity; 10 – 500,000 m 3 /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 Solubility of salts in pure water (g/L)  Salinity Na + Ca ++ Mg ++ K + Ba ++ Sr ++  pH Cl- 360 730 560 330 370 510 SO 4 -- 170 2 350 110 0.002 0.11 NO 3 - 840 1220 740 300 90 70 CO 3 190 0.013 1 1080 0.02 0.01 -- F - 45 0.016 0.076 930 1.6 0.1

 Salts have varying solubility in water

 Calcium carbonate is unusual in that its solubility decreases with water temperature

 CO 2 dissociation in water w.r.t. pH

 Calcium carbonate has low solubility in pure water (15 mg/L at 25 ° C)  Solubility of CaCO 3 in seawater is about 26 times higher than in freshwater at the same temperature

 May precipitate even below its saturation level in presence of Al 3+ & Fe 3+  Al 3+ & Fe 3+ 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