Sulfate removal from drinking water by commercially available nanofiltration membranes: a parametric study (original) (raw)

DESALINATION AND WATER TREATMENT

The efficacy of nanofiltration (NF) in removing sulfate from a high sulfate content (370-460 mg/L) surface water was investigated. NF tests were carried out using a laboratory-scale cross-flow NF module operated in total-recycle (full-recycle) mode. Membranes of varying characteristics; namely, DK-NF (Desal DK: GE Osmonics, USA), DL-NF (Desal DL: GE Osmonics, USA), and NF270 (Dow Filmtec Co., USA) were tested, and the effects of main operational parameters of cross-flow velocity, trans-membrane pressure, and pretreatment on permeate flux and sulfate removal were evaluated. The NF270 membrane exhibited the highest permeate flux and was found to be the best of the three membranes tested, with over 98% sulfate removal. The DK-NF membrane, which was poor in performance with a high flux decline, provided the lowest sulfate removal, lowest permeate flux, and highest fouling. Microfiltration (2.5-µm), as pretreatment, provided no considerable improvement in permeate flux. When the effects of operational parameters on NF performance using the DL-NF membrane were sought, it appeared that permeate flux, and sulfate removal efficiency did not change at all with trans-membrane pressure and cross-flow velocity. The study is expected to provide useful information about the NF of drinking water with high sulfate content in the future.