Pre-treatment with nanofiltration (NF) in seawater desalination-Preliminary integrated membrane tests in Urla, Turkey

In this study, the applicability of nanofiltration (NF) was investigated as a pre-treatment stage of reverse osmosis (RU) process for seawater desalination. The desalination performance of such integrated system was checked. Previously, NF (NF90 and NF270) and SWRO (SW30) membranes were used individually in the close-loop operation. Next, the NF permeate was collected using NF membrane by a continuous operation and then this permeate was used as a feed for a closed-loop SWRO system. The performances of single SWRO, NF and NF + RO integrated systems were compared in terms of permeate qualities and quantities. The results showed that permeate recovery of NF270 membrane was higher than that of NF90 membrane. However, the salt rejection of NF90 membrane was better than that of NF270. The single SW3O-RO membrane showed an average rejection of 98.2% for salinity, while the permeate recovery value was only 28% at 55 bar. Also the average permeate flux of single SW3O-RO membrane was 30.1 L/h m(2). For the integrated system experiments, the highest permeate flux was found with NF90 (30 bar) + SW3O-RO (40 bar) combination. Similar permeate flux values were obtained with single 5W30-RO and NF90 (30 bar) + SW3O-RO (30) bar combination. The lowest permeate flux was found with NF270 (30 bar) + SW3O-RO (40 bar) combination. Salinity was also highly rejected by all integrated system combinations. Permeate recovery values of integrated system combinations showed similar trend with permeate flux. Regarding permeate quality, it was seen that all integrated system combinations were better than single SW3O-RO membrane. It was obtained that the permeate quality with NF90 + SW3O-RO combination was better than that with NF270 + SW3O-RO combination. (C) 2015 Elsevier B.V. All rights reserved.