Membrane distillation crystallization technology for zero liquid discharge and resource recovery: Opportunities, challenges and futuristic perspectives

Despite the tremendous success of the application of anion exchange resins (IX) in natural organic matter (NOM) removal over conventional removal methods, the considerable amount of brine spent during its regeneration cycle makes its sustainability questionable. This polluting saline stream can be challenging to manage and costly to discharge. Alternatively, and with the recent shift in perception of resource recovery, the produced spent brine can no longer be seen as a polluting waste but as an unconventional source of water, minerals and nutrients. In this research, for the first time, we evaluated the effectiveness of an integrated monovalent selective electrodialysis (MSED) and direct contact membrane distillation (DCMD) system in IX spent brine desalination and resource recovery. Of particular interest were the effects of operating time on the characteristics of the monovalent permselective ion exchange membranes, the impact of the DCMD stack configuration on minimizing heat loss to the ambient environment and the efficacy of the recovered NaCl in the regenerating cycle of the exhausted IXs. Our findings demonstrated that although the recovered NaCl from the stand-alone MSED can restore nearly 60% ion exchange capacity of the exhausted IXs, coupling MSED with DCMD led to minimizing the consumption of fresh NaCl (in the IX regeneration cycle) significantly, the potential application of NOM in agriculture and diminishing the risk of the IX spent brine disposal. In addition, the initial characteristics of the ion permselective membranes were maintained after 24 h of MSED and the transmembrane flux was increased when the feed/hot compartment (in the DCMD stack) was encapsulated on two outer ends with coolant/permeate compartments as a result of less heat loss to the ambient environment.

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Renewable Thermal Energy Driven Desalination Process for a Sustainable Management of Reverse Osmosis Reject Water

Sustainability ◽

10.3390/su131910860 ◽

2021 ◽

Vol 13 (19) ◽

pp. 10860

Author(s):

Kawtar Rahaoui ◽

Hamid Khayyam ◽

Quoc Linh Ve ◽

Aliakbar Akbarzadeh ◽

Abhijit Date

Keyword(s):

Reverse Osmosis ◽

Mass Flux ◽

Sustainable Management ◽

Membrane Distillation ◽

Water Volume ◽

Feed Water ◽

Crystal Formation ◽

Discharge System ◽

Reject Water ◽

Liquid Discharge

A sustainable circular economy involves designing and promoting products with the least environmental impact. This research presents an experimental performance investigation of direct contact membrane distillation with feed approaching supersaturation salinity, which can be useful for the sustainable management of reverse osmosis reject water. Traditionally, reject water from the reverse osmosis systems is discharged in the sea or in the source water body. The reinjection of high salinity reject water into the sea has the potential to put the local sea environment at risk. This paper presents a design of a solar membrane distillation system that can achieve close to zero liquid discharge. The theoretical and experimental analysis on the performance of the lab scale close to zero liquid discharge system that produces supersaturated brine is studied. The lab-based experiments were conducted at boundary conditions, which were close to the real-world conditions where feed water temperatures ranged between 40 °C and 85 °C and the permeate water temperatures ranged between 5 °C and 20 °C. The feed water was supplied at salinity between 70,000 ppm to 110,000 ppm, similar to reject from reverse osmosis. The experimental results show that the maximum flux of 17.03 kg/m2·h was achieved at a feed temperature of 80 °C, a feed salinity of 10,000 ppm, a permeate temperature of 5 °C and at constant feed and a permeate flow rate of 4 L/min. Whereas for the same conditions, the theoretical mass flux was 18.23 kg/m2·h. Crystal formation was observed in the feed tank as the feed water volume reduced and the salinity increased, reaching close to 308,000 ppm TDS. At this condition, the mass flux approached close to zero due to crystallisation on the membrane surface. This study provides advice on the practical limitations for the use of membrane distillation to achieve close to zero liquid discharge.

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Membrane Distillation Crystallization Hybrid Process for Zero Liquid Discharge in QAFCO Plant

10.29117/quarfe.2021.0010 ◽

2021 ◽

Author(s):

Mona Gulied ◽

Sifani Zavahir ◽

Tasneem Elmakki ◽

Hazim Qiblawey ◽

Bassim Hameed ◽

...

Keyword(s):

Research Work ◽

Membrane Distillation ◽

Economic Feasibility ◽

Operating Conditions ◽

Hybrid Process ◽

Optimum Operating ◽

Low Grade ◽

Water Recovery ◽

Ongoing Research ◽

Liquid Discharge

Qatar fertilizer company (QAFCO) is one of the world’s largest single site producer of ammonia and urea with production capacity of 12,900 metric tons per day. Currently, QAFCO faces major challenges in terms of water streams management that is generated from many processes such as wastewater from Harbor-Bosch process and brine solution from multi-stage flash (MSF) desalination process. To protect the environment; QAFCO has been making an effort to minimize the disposal of all types of water disposed into the sea. Here, this project proposes to develop a viable and economically effective process that can reach zero-liquid discharge (ZLD) of all processed water or wastewater from QAFCO facilities. The best method for ZLD is membrane distillation crystallization (MDC) hybrid process that concentrates and minimizes the volume of wastewater/brine streams to form solid through crystallizer. Membrane distillation (MD) is a thermally driven membrane process. It applies low-grade energy to create a thermal gradient across a microporous hydrophobic to vaporize water in the feed stream and condense the permeated vapor in the cold side. This research work aims to evaluate the performance of MDC for ZLD using commercial/fabricated electrospun nanofiber membrane (ENM) PVDF –base membranes at different type water streams. A general observation, higher water vapor flux and water recovery were exhibited at higher feed conductivity at 70°C. Moreover, the fabricated hydrophobic PVDF ENMs results confirmed the formation of nanofiber at the membrane surface using scanning electron microscopy (SEM). In addition, the water contact angle values of PVDF ENMs were greater than 100° and have stable mechanical and chemical properties. The ongoing research work will conduct a comparison between the optimum PVDF ENMs and the commercial MD membranes in terms of water recovery, salt rejection%, fouling/scaling, amount of collected solid and energy consumption at optimum operating conditions in MDC. In addition, it will perform a techno- economic feasibility assessment of the MDC hybrid process.

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