An investigation of desalination by nanofiltration, reverse osmosis and integrated (hybrid NF/RO) membranes employed in brackish water treatment

Abstract

BackgroundAs an appropriate tool, membrane process is used for desalination of brackish water, in the production of drinking water. The present study aims to investigate desalination processes of brackish water of Qom Province in Iran.MethodsThis study was carried out at the central laboratory of Water and Wastewater Company of the studied area. To this aim, membrane processes, including nanofiltration (NF) and reverse osmosis (RO), separately and also their hybrid process were applied. Moreover, water physical and chemical parameters, including salinity, total dissolved solids (TDS), electric conductivity (EC), Na+1 and Cl−1 were also measured. Afterward, the rejection percent of each parameter was investigated and compared using nanofiltration and reverse osmosis separately and also by their hybrid process. The treatment process was performed by Luna domestic desalination device, which its membrane was replaced by two NF90 and TW30 membranes for nanofiltration and reverse osmosis processes, respectively. All collected brackish water samples were fed through membranes NF90-2540, TW30-1821-100(RO) and Hybrid (NF/RO) which were installed on desalination household scale pilot (Luna water 100GPD). Then, to study the effects of pressure on permeable quality of membranes, the simulation software model ROSA was applied.ResultsResults showed that percent of the salinity rejection was recorded as 50.21%; 72.82 and 78.56% in NF, RO and hybrid processes, respectively. During the study, in order to simulate the performance of nanofiltartion, reverse osmosis and hybrid by pressure drive, reverse osmosis system analysis (ROSA) model was applied. The experiments were conducted at performance three methods of desalination to remove physic-chemical parameters as percentage of rejections in the pilot plant are: in the NF system the salinity 50.21, TDS 43.41, EC 43.62, Cl 21.1, Na 36.15, and in the RO membrane the salinity 72.02, TDS 60.26, EC 60.33, Cl 43.08, Na 54.41. Also in case of the rejection in hybrid system of those parameters and ions included salinity 78.65, TDS 76.52, EC 76.42, Cl 63.95, and Na 70.91.ConclusionsComparing rejection percent in three above-mentioned methods, it could be concluded that, in reverse osmosis process, ions and non-ion parameters rejection ability were rather better than nanofiltration process, and also better in hybrid compared to reverse osmosis process.The results reported in this paper indicate that the integration of membrane nanofiltration with reverse osmosis (hybrid NF/RO) can be completed by each other probably to remove salinity, TDS, EC, Cl, and Na.

Nanofiltration as a cost-saving desalination process

“…Results of this study agree to those of Silva et al [12] who reported that nanofiltration is equally effective as RO but lesser in energy consumption. Some other studies also support these findings [19,14,13].…”

“…The quality of RO and nanofiltration indicated that any one of these two waters can be used for various purposes like drinking, irrigation of plants, landscaping, and industry. Earlier studies in Iran [13] indicated a major part of salt rejection into brine water by using nanofiltration, reverse osmosis, and hybrid processes. In their research, Na removal was better than Cl in case of both membranes as well as the hybrid system.…”

“…Nanofiltration, a recently developed water purification process, is claimed just as effective as current methods but more energy efficient and potentially much less expensive [12]. Talaeipour et al [13] in their studies in Iran calculated the salt rejection of 50%; 70%, and 74%, respectively, using nanofiltration, reverse osmosis, and hybrid processes while Na removal proved better than Cl in both membranes and the hybrid system. However, fouling of membrane was reported after 4 months (2600 h), but after cleaning, the flux was recovered by 95% of pre-fouled condition [14].…”

Impact of independent and non-independent parameters on various elements’ rejection by nanofiltration employed in groundwater treatment

“…RO filters remove all salts dissolved in water, while NF filters, or nanofilters, create a selective mode of absorption of materials, giving us the right to choose the desired quality of water (Dach 2008). Several studies have proved that nanofiltration is even effective at low pressures; hence, it can be superior to reverse osmosis in similar conditions (Vaseghi et al 2016;Talaeipour et al 2017).…”

Status of hybrid membrane–ion-exchange systems for desalination: a comprehensive review

“…In order to enhance desalination performance, diverse efforts are being applied with time. For instance, the coupling of membrane filtration (MF) techniques such as nanofiltration and reverse osmosis (NF/RO) is largely important to optimize cost and produced water quality whereby ionexchange (IX)/MF coupling improved product quality and it is applied in the selective removal of particular pollutants (Ang et al 2015;Esfahani et al 2016;Talaeipour et al 2017;Zaib and Fath 2013).…”