Removal of Hardness Ions by Nanofiltration and Reverse Osmosis for Water Softening

Abstract

In recent years, with increasing rate of industrialization and population growth, water resources have depleted and become polluted. Despite diminishing water resources, studies on development and generalization of water-saving models and use of recycled water are gaining speed to meet the rapidly growing water demand. Due to the legal arrangements for the protection of the environment and increasing water demand, the improvement of technologies for minimizing waste generation, water recovery and reuse of valuable materials come into prominence. Membrane processes can be used to remove water hardness in municipal or industrial systems. This study aims the removal of hardness ions from water for various feed hardness values and feed temperatures by using nanofiltration (NF) and reverse osmosis (RO) membranes. The experiments are carried out in an experimental set-up which involves circulation and reuse of the concentrate stream from the membrane unit. Commercially available polyamide thin film composite NF and RO membrane modules are tested and their performances are compared.