Performance and cost estimation of nanofiltration for surface water treatment in drinking water production

This work addresses the evaluation of nanofiltration (NF) and the minimization of NF membrane fouling in the treatment of surface water for drinking water production. The fouling characteristics of the natural organic matter (NOM) present in the surface water are dependent on the feed water composition and on the NF operating parameters. NF experiments were carried out in a DSS Lab-unit M20 with a membrane surface area of 0.216 m2. Permeation experiments were performed both in total recirculation mode in order to optimize the operating conditions of pressure and recirculation flow rate and in concentration mode for design and optimization purposes. The concentration mode experiments were carried out at 15 bar and at a recirculation flow rate of 554 L/h. The water recovery rates (WRR) ranged up to 75%. A NF model was developed based on solute (NOM) and solvent differential mass balances and incorporating experimental data of the variation of permeation fluxes and total organic carbon (TOC) rejections with WRR. This model was used for the design of a NF plant with a permeate output of 100,000 m3/d. The NF treatment cost was estimated to be €0.214/m3.