APPLICATION OF NANOFILTRATION AND REVERSE OSMOSIS MEMBRANES TO THE SALTY AND POLLUTED SURFACE WATER

Abstract

Nanofiltration (NF) (TFC-S) and reverse osmosis (RO) (TFC-HR) membranes were evaluated for the treatment of salty and polluted Kucukcekmece Lake used as a drinking water reservoir for the Istanbul City. A thin film composite type of spiral wound membrane (2 m² area) was used. Experiments were conducted at different pressures, pH ranges and temperatures. Flowrate was about 300 l/h. The flux decreased with increasing pH. Highest rejections were obtained for all anionic and cationic ions in the pH range of 6.0–8.5. Several permeation runs were carried out for the pressure range of 6–12 bar for TFC-S and TFC-HR membranes. According to the Spiegler–Kedem model, the permeate flux (J_v) is linearly related to the applied hydraulic pressure (ΔP). L_p values were calculated by linear regression. Salt rejection was seen to increase with the increasing of operating pressure due to increase of solvent flux. Na⁺, Mg⁺², Ca⁺², Cl⁻ and SO₄ ⁻² rejections and z ₁ and z₂ constants have been determined and z values of cations were in the order of z _Mg > z_Ca > z_Na and similarly those of anions were in the order of z _SO4 > z_Cl. The Spiegler–Kedem model was able to correlate well the experimental data by fitting different best values of P and σ, respectively for all ions. Best fit values of P and σ were obtained by regression of the data according to the model.

Keywords:

• Anionic and cationic pollutants
• Nanofiltration
• Reverse osmosis
• Salt retention
• Spiegler–Kedem model

Acknowledgments