Treatment of nanofiltration and reverse osmosis concentrates: Systematic study of coagulation, softening and anion exchange

摘要

Membrane processes are becoming more prevalent. However, disposal and treatment ofmembrane concentrate from nanofiltration (NF) and reverse osmosis (RO) are major challengesto implementing membrane treatment processes. Intermediate treatment of membraneconcentrate, between primary and secondary membrane stages, has the potential to increasesystem recovery rates and decrease the volume of concentrate produced. However, there is aneed to better understand physical-chemical treatment of membrane concentrate. This worksystematically evaluated lime softening, ferric sulfate coagulation, and ion exchange asindividual, intermediate treatment processes for membrane concentrate. Six membraneconcentrates with varying concentrations of calcium, dissolved organic matter (DOM) andsulfate were chosen for this study. Maximum removal of calcium, DOM and sulfate wasachieved by ion exchange. The results of this work show that physical-chemical treatment ofNF/RO concentrate is capable of producing treated concentrate with calcium and DOMconcentrations approximately equal to the initial source water.