In this study, two novel, highly-effective membrane materials were synthesized, characterized and evaluated for their performance in practical applications: PVAc-coated electrospun nylon 6/SiO2 composite MF membrane and electrospun nylon 6/SiO2 composite supported TFC FO
membrane with a polyamide/SiO2 composite active layer. A comprehensive study into the
selection of novel, highly-effective organic draw solutions for the desalination of fracking wastewater by FO process was also conducted for the first time. Finally, MF was tested for the first time as a pre-treatment process, using the fabricated MF membrane, along with FO, using the fabricated TFC membrane, as a post-treatment process for the desalination of highly saline fracking wastewaters. The identified organic draw solutions were used in the FO process for desalination of the fracking wastewaters. In the pre-treatment stage, ~ 98.5% turbidity and ~ 52% TOC were removed from the fracking wastewater by the MF process. Finally, treated water with TDS 23-44 mg/L was obtained from the pre-treated fracking wastewater by the combined process consisted of FO and MD.
From this work, four journal articles are expected with one already having been published in a well reputed journal in our field of research. The list of the articles (published, submitted, and in preparation) are provided below:
1. M. S. Islam, J. R. McCutcheon, M. S. Rahaman, A high flux polyvinyl acetate-coated electrospun nylon 6/SiO2 composite microfiltration membrane for the separation of oil-in-water
emulsion with improved antifouling performance, J. Membr. Sci. 537 (2017) 297–309 (Published).
2. M. S. Islam, M. S. Rahaman, Forward Osmosis Treatment of Fracking Wastewaters: Evaluation of Suitable Organic Draw Solutions (Submitted).
3. M. S. Islam, J. R. McCutcheon, M. S. Rahaman, Silica Nanoparticle Containing Novel Thin- Film Composite Forward Osmosis Membrane with High Flux and Antifouling Properties (In Preparation).
4. M. S. Islam, M. S. Rahaman, Performance of Combined MF-FO-MD processes for Fracking Wastewater Treatment (In Preparation).
Presentation has been made at scientific conferences to present the research work which was conducted during my Ph.D. studies. The list of all conferences is provided below:
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1. M. S. Islam, S. Sultana, M. S. Rahaman, “Renewable Energy Generation through Osmotic Heat Engine”, 12th International Conference on Mechanical Engineering, ICME 2017,
December 20-22, 2017, BUET, Dhaka, Bangladesh.
2. M. S. Islam, S. Sultana, M. S. Rahaman, “Highly Effective Microfiltration Membrane Based on Electrospun Nylon 6/SiO2 Composite”, Gordon Research Conference, July 31 - August 5,
2016, New London, NH, USA.
3. M. S. Islam, M. S. Rahaman,“Electrospun Nylon 6 Microfiltration Membrane for Treatment of Brewery Wastewater”, 11th International Conference on Mechanical Engineering, ICME
2015, December 18-20, 2015, BUET, Dhaka, Bangladesh.
4. M. S. Islam, M. Lemieux, M. S. Rahaman, “Effective organic draw solutes for engineered osmosis processes”, 250th ACS National Meeting and Exposition, August 16-20, 2015, Boston,
Massachusetts, USA.
5. M. S. Islam, M. S. Rahaman, “Highly porous superhydrophilic ultra-filtration membrane based on electrospun Nylon 6/SiO2 composite”, North American Membrane Society (NAMS)
annual conference, May 30-June 03, 2015, Boston, Massachusetts, USA.
6. M. S. Islam, M. S. Rahaman, “Preparation & characterization of polymer/CNT composite nanoparticles and nanofibers through electrospinning”. CSCE-2014 Annual Conference, Halifax, Nova Scotia.
7. A. Meikleham, M. S. Islam, M. S. Rahaman, Electorowicz, M., “Removal of Emerging Contaminants from Wastewater Effluents Using Nano-Composite Electrochemical Filters”. CSCE-2014 Annual Conference, Halifax, Nova Scotia.
7.2 Conclusions
Today, a huge quantity of highly saline wastewater (about 37 billion cubic feet/day)is released during the hydraulic fracturing process, a technology growing in use in a rapidly growing shale gas industry. The management of the released fracking wastewater is a serious challenge because of its harmful consequences to public health and to the environment at large. This highly saline fracking waster also contains sand and oil as suspended solids. In order to re-cycle the fracking wastewater, these suspended and dissolved solids can be removed by pre- and post-treatment of the fracking wastewater. Sand particles and oil can be removed from the fracking wastewater by microfiltration as a pre-treatment step. As a post-treatment process, FO, coupled with membrane distillation as downstream separator for draw solution recovery, can be
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used to desalinate the highly saline pre-treated fracking wastewater. Identification of effective draw solutions, the fabrication of a novel MF membrane with high water flux, high rejection and antifouling properties, and the fabrication of a novel FO membrane with high water flux, high rejection and antifouling properties were performed in order to optimize the FO process for successful treatment of fracking wastewater. In this research, seven potentially effective draw solutions were preselected for FO, with four of them demonstrated to be effective in treating the highly saline fracking wastewater. A high water flux polyvinyl acetate-coated electrospun nylon 6/SiO2 composite MF membrane was fabricated and its performance has
been tested in regards to water flux, oil rejection, and antifouling properties. This membrane exhibited better results than those seen with the commercially available MF membranes currently used for the same application. In the next step of this research, a high water-flux membrane with high rejection and antifouling properties was fabricated and characterized for use in FO. Finally, the fracking wastewaters were pre-treated using MF and then post-treated using FO coupled with membrane distillation using the membranes fabricated. This combined MF-FO-MD process yielded water with TDS 23-44 mg/L from the highly saline fracking wastewater. Literature demonstrates that the standard TDS values are 0 - 1000 mg/L for fresh water, 1000 - 10,000 mg/L for brackish water and ˃ 10,000 mg/L for saline water [201-202]. As it is demonstrated that TDS contents after treatment of fracking wastewaters by the combined MF/FO/MD process were in between 23 - 44 mg/L. This result revealed fresh water was obtained after treatment of highly saline fracking wastewaters. Most water used in hydraulic fracturing comes from surface water sources like lakes, rivers, aquifers, and municipal supplies [203]. Therefore, treated water coming from fracking wastewater can be reused for hydraulic fracturing as well as in utility sector. This treated water can also be reused for agricultural purpose in the areas very close to hydraulic fracturing industry.
The concentrated feed solution obtained from FO unit used in the combined MF/FO/MD process could be managed by disposing to evaporation pond. A geomembrane linear would be required to hinder seepage into ground in the pond. The area and depth of the pond should be designed by considering evaporation rate as compared to the volume of concentrated feed solution discharge. The salt residue after evaporation of water can be removed at regular time period to enlarge the pond’s life. The residue is mainly NaCl, which can be used as raw materials in chlor-alkali industry and soda-ash industry.
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