Water. desalination + reuse

RESEARCH 100000 5 10,000 4 1,000 Flux Brine conductive Feed conductive Distillate Cond 3 100 2 10 1 1 0 Conductivity uS/cm 1,000,000 6 Distillate flux, LMH 7 0 0 50 100 150 Time, hours 200 250 300 Figure 4. Performance of MD on brine from thermal plants (MD pilot A) Table 2. Water quality of MD operated on brine from thermal plants Parameter Unit Turbidity Conductivity TDS TOC Chloride Sodium Calcium Sulfate Bromide Magnesium Strontium Boron NTU mS/cm mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L Thermal brine 0.3 95,000 71,781 2 41,059 21,553 779 4,755 71 2,570 11 8.0 the MD process can fit into a thermal desalination plant. Figure 4 shows preliminary performance data of one of the MD technologies piloted using brine from the thermal plant. Stable performance (flux) was observed and the distillate water quality remained below 100 µS/cm while the feed/concentrate water quality was in excess of 100,000 µS/cm, indicating more than 99.9% salt rejection capabilities. Table 2 provides additional water quality data from the MD testing confirming the distillate quality of the product water. Additional data is currently being collected to optimize the MD process for this unique application, including pretreatment requirements. To our knowledge, this is the first time that MD technology has been benchmarked and tested to treat brines from thermal desalination plants, which means that there is no evidence of previous works on this topic that the results can be compared to. However, previous work published in the Distillate produced 0.1 24 2 <1 0.7 1.1 <1 0.2 <0.1 0.1 <0.2 <0.2 Rejected (%) >99.99 >99.99 >99.99 >99.99 >99.99 >99.99 >99.99 >99.99 >99.99 >99.99 >97.46 literature reported flux reduction with the MD process when treating salinities above 70,000 ppm TDS 4,5. CONCLUSIONS The results from Phase II-A indicate the viability of using MD in Qatar to treat brines from thermal desalination plants. This may contribute to augmenting the capacity of existing thermal desalination plants, significantly contributing to long-term water sustainability in Qatar. Phase II-A was carried out at QU on various solutions, including sodium chloride (NaCl) and brine from a local thermal desalination plant. The main results of Phase II-A are: Distillate was of high quality for all feed salinities tested (TDS <3 ppm). Up to NaCl 50,000 ppm, the flux was the same as with tap water. Up to NaCl 90,000 ppm, flux decreased ≈20% when compared with tap water. With thermal brine, flux was stable and good salt rejection was observed. | 42 | Desalination & Water Reuse | August-September 2013 Feed temperature and ∆T across the membrane are critical operating parameters. The tests to be performed in Phase II-B are currently ongoing and will provide a more comprehensive understanding of the real capabilities of the MD technology when treating brines under real field conditions and continuous operation in Qatar. If the above pilot-testing program proves successful, future plans may include a demonstration-scale unit to operate at a thermal desalination plant in Qatar. Ultimately, the projected outcomes of the project include: Sustainable augmentation of water production in Qatar Potential reduction of environmental impact Capacity building in Qatar System IP for novel technology & application ACKNOWLEDGEMENT The research team would like to thank Fahad Al Muhannadi, general manager of QEWC and Abdulsattar Al Rasheed, CEO of Ras Abu Fontas Desalination Plant, for their support of the overall testing program. The team would also like to thank Dr Farid Benyahia of Qatar University for facilitating and participating in the testing program, and to acknowledge their colleagues at the GWSC for conducting the water analysis on the seawater and brine samples. References 1. A Samer, A Janson, J Matar, R Dores, A Hussain, Sustainable Water Production By Membrane Distillation Using Low Grade Waste Heat, IDA World Congress, Perth, September 4-9, 2011. 2. A Samer, A Janson, J Matar, R Dores, A Hussain, Membrane Distillation using low grade waste heat, Singapore International Water Week, Singapore, July 1-5, 2012. 3. M S El-Bourawi, Z Ding, R Ma, M Khayet, A framework for better understanding membrane distillation separation process, Journal of Membrane Science, 285 (1-2) (2006) 4 - 29. 4. D Winter, J Koschikowski, M Wieghaus, Desalination using membrane distillation: Experimental studies on full scale spiral wound modules. Journal of Membrane Science, 375 (2011) 104-112. 5. Samer Adham, Altaf Hussain, Joel Minier Matar, Raul Dores, Arnold Janson, Application of Membrane Distillation for desalting brines from thermal desalination plants, Desalination, 314, (2013) 101-108

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