Optimising thermal efficiency of direct contact membrane distillation by brine recycling for small-scale seawater desalination

Duong, Hung Cong; Cooper, Paul; Nelemans, Bart; Cath, Tzahi Y.; Nghiem, Long D.

doi:10.1016/j.desal.2015.07.009

Cited by 118 publications

(63 citation statements)

References 38 publications

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“…In this study, the mass transfer coefficient (K m ) of the DCMD, which was calculated based on the method described by Nghiem et al [49], ranged from 1.22 to 1.28 (×10 −3 ) L/m 2 h Pa. This value is in good agreement with that in previous studies [48,50]. Thus, this study shows both stable membrane hydraulic performance and improved enzymatic degradation of TrOCs following their complete retention by the MD membrane.…”

Section: Permeate Fluxsupporting

confidence: 80%

Degradation of Trace Organic Contaminants by a Membrane Distillation—Enzymatic Bioreactor

et al. 2017

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A high retention enzymatic bioreactor was developed by coupling membrane distillation with an enzymatic bioreactor (MD-EMBR) to investigate the degradation of 13 phenolic and 17 non-phenolic trace organic contaminants (TrOCs). TrOCs were effectively retained (90-99%) by the MD membrane. Furthermore, significant laccase-catalyzed degradation (80-99%) was achieved for 10 phenolic and 3 non-phenolic TrOCs that contain strong electron donating functional groups. For the remaining TrOCs, enzymatic degradation ranged from 40 to 65%. This is still higher than those reported for enzymatic bioreactors equipped with ultrafiltration membranes, which retained laccase but not the TrOCs. Addition of three redox-mediators, namely syringaldehyde (SA), violuric acid (VA) and 1-hydroxybenzotriazole (HBT), in the MD-EMBR significantly broadened the spectrum of efficiently degraded TrOCs. Among the tested redox-mediators, VA (0.5 mM) was the most efficient and versatile mediator for enhanced TrOC degradation. The final effluent (i.e., membrane permeate) toxicity was below the detection limit, although there was a mediator-specific increase in toxicity of the bioreactor media.

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Section: Permeate Fluxsupporting

confidence: 80%

Degradation of Trace Organic Contaminants by a Membrane Distillation—Enzymatic Bioreactor

et al. 2017

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“…Correspondingly, the GOR of the system decreased from 9.5 to 6.0. A similar influence of water circulation rate on thermal efficiency was also reported for DCMD with brine recycling [24] and when employing an external heat-exchanger [30,31].…”

Section: Influence Of Water Circulation Rate On the Performance Of Thmentioning

confidence: 59%

“…The observed improvement in thermal efficiency at high feed temperature can also be explained by the relationship between water vapour pressure and temperature according to the Antoine equation as noted above. The benefit of operating the process at a high feed temperature with regard to thermal efficiency has been reported for other MD configurations [23,24].…”

Section: Influence Of Evaporator Inlet Temperature On the Performancementioning

confidence: 99%

“…It is noteworthy that in the single-pass operation, the water recovery rate of the pilot AGMD system was noticeably low (i.e., 5%). Low water recovery rate together with a small concentration polarisation ensured that concentrations of potential scalants, such as CaCO3 and CaSO4 [24,32,33], at the membrane surface were well below their solubility limits. The stable distillate production rate (which indicates the absence of any membrane fouling) observed in this experiment can be also attributed to the low total organic carbon concentration of the seawater feed (i.e., 2 mg/L) and low operating permeate flux (i.e., 1.0 L/m 2 -h).…”

Section: Pilot Agmd Process Of Seawatermentioning

confidence: 99%

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Evaluating energy consumption of air gap membrane distillation for seawater desalination at pilot scale level

Duong

Cooper

Nelemans³

et al. 2016

Separation and Purification Technology

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166

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This study aimed to optimise an air gap membrane distillation (AGMD) system for seawater desalination with respect to distillate production as well as thermal and electrical energy consumption. Pilot evaluation data shows a notable influence of evaporator inlet temperature and water circulation rate on process performance. An increase in both distillate production rate and energy efficiency could be obtained by increasing the evaporator inlet temperature. On the other hand, there was a trade-off between the distillate production rate and energy efficiency when the water circulation rate varied. Increasing the water circulation rate resulted in an improvement in the distillate production rate, but also an increase in both specific thermal and electrical energy consumption. Given the small driving force used in the pilot AGMD, discernible impact of feed salinity on process performance could be observed, while the effects of temperature and concentration polarisation were small. At the optimum operating conditions identified in this study, a stable AGMD operation for seawater desalination could be achieved with specific thermal and electrical energy consumption of 90 and 0.13 kW h/m3, respectively. These values demonstrate the commercial viability of AGMD for smallscale and off-grid seawater desalination where solar thermal or low-grade heat sources are readily available. Abstract: This study aimed to optimise an air gap membrane distillation (AGMD) process for seawater desalination with respect to distillate production as well as thermal and electrical energy consumption. Pilot evaluation data shows a notable influence of evaporator inlet temperature and water circulation rate on process performance. An increase in both distillate production rate and energy efficiency could be obtained by increasing the evaporator inlet temperature. On the other hand, there was a trade-off between the distillate production rate and energy efficiency when the water circulation rate varied. Increasing the water circulation rate resulted in an improvement in the distillate production rate, but also an increase in both specific thermal and electrical energy consumption. Given the small driving force used in the pilot AGMD, discernible impact of feed salinity on process performance could be observed, while the effects of temperature and concentration polarisation were small. At the optimum operating conditions identified in this study, a stable AGMD operation for seawater desalination could be achieved with specific thermal and electrical energy consumption of 90 and 0.13 kWh/m 3 , respectively. These values demonstrate the commercial viability of AGMD for small-scale and off-grid seawater desalination where solar thermal or low-grade heat sources are readily available.

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“…The influence of feed salinity increase as a function of concentration factor on water flux could be simulated using a model previously described by Duong et al [28]. Salinity rejection by MD was assumed to be complete.…”

mentioning

confidence: 99%

Membrane distillation and membrane electrolysis of coal seam gas reverse osmosis brine for clean water extraction and NaOH production

et al. 2016

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Duke, M., Gray, S., Nelemans, B. & Nghiem, L. D. (2016). Membrane distillation and membrane electrolysis of coal seam gas reverse osmosis brine for clean water extraction and NaOH production. Desalination, Membrane distillation and membrane electrolysis of coal seam gas reverse osmosis brine for clean water extraction and NaOH production AbstractMembrane distillation (MD) and membrane electrolysis (ME) were evaluated for simultaneous fresh water extraction and NaOH production from a mixture of NaCl and NaHCO3 to simulate the composition of coal seam gas (CSG) reverse osmosis (RO) brine. Experimental results demonstrate the potential of MD for producing fresh water and simultaneously concentrating CSG RO brine prior to the ME process. MD water flux was slightly reduced by the increased feed salinity and the decomposition of bicarbonate to CO2 during the concentration of CSG RO brine. MD operation of CSG RO brine at a concentration factor of 10 (90% water recovery) was achieved with distillate conductivity as low as 18 μS/cm, and without any observable membrane scaling. Exceeding the concentration factor of 10 could lead to deterioration in both water flux and distillate quality due to the precipitation of NaCl, NaHCO3, and Na2CO3 on the membrane. With respect to ME, current density and water circulation rates exerted strong influences on the ME process performance. Combining ME with MD reduced the thermal energy requirement of ME by 3 MJ per kg of NaOH produced and the thermal energy consumption of MD by 22 MJ per m3 of clean water extracted. Abstract: Membrane distillation (MD) and membrane electrolysis (ME) were evaluated for simultaneous fresh water extraction and NaOH production from a mixture of NaCl and NaHCO3 to simulate the composition of coal seam gas (CSG) reverse osmosis (RO) brine. Experimental results demonstrate the potential of MD for producing fresh water and simultaneously concentrating CSG RO brine prior to the ME process. MD water flux was slightly reduced by the increased feed salinity and the decomposition of bicarbonate to CO2 during the concentration of CSG RO brine. MD operation of CSG RO brine at a concentration factor of 10 (90% water recovery) was achieved with distillate conductivity as low as 18 µS/cm, and without any observable membrane scaling. Exceeding the concentration factor of 10 could lead to deterioration in both water flux and distillate quality due to the precipitation of NaCl, NaHCO3, and Na2CO3 on the membrane. With respect to ME, current density and water circulation rates exerted strong influences on the ME process performance. Combining ME with MD reduced the thermal energy requirement of ME by 3 MJ per kg of NaOH produced and the thermal energy consumption of MD by 22 MJ per m 3 of clean water extracted.

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Optimising thermal efficiency of direct contact membrane distillation by brine recycling for small-scale seawater desalination

Cited by 118 publications

References 38 publications

Degradation of Trace Organic Contaminants by a Membrane Distillation—Enzymatic Bioreactor

Degradation of Trace Organic Contaminants by a Membrane Distillation—Enzymatic Bioreactor

Evaluating energy consumption of air gap membrane distillation for seawater desalination at pilot scale level

Membrane distillation and membrane electrolysis of coal seam gas reverse osmosis brine for clean water extraction and NaOH production

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