Control of the Ionic Composition of Nanofiltration Membrane Permeate to Improve Product Water Quality in Drinking Water Supply Applications

Reverse osmosis is efficiently used for producing drinking water from groundwater sources containing dissolved impurities, including fluoride, ammonia, lithium, strontium, boron, arsenic, etc. The principal problems of utilizing reverse include scaling on membrane surfaces, concentrate discharges, and low permeate TDS that often require conditioning. main goal this work was to demonstrate the viability a newly developed methodology relies low-rejection nanofiltration membranes improve product quality by increasing its calcium content, economic efficiency compared conventionally osmosis. Disadvantages employing production are attributed fact several pollutants (including boron) monovalent ions and, as such, poorly rejected calcium, sodium, sulfate, chloride ions. Thus, in cases which lithium or ammonia present high concentrations, rejection usually result water. This article presents results research aimed at developing new approach changing ratio divalent method described paper two-stage application enables us reduce impurities increase concentration values while leaving unchanged. achieved applying scheme with instead stage. treatment using same However, value concentrations appears be significantly higher measured feed groundwater. can different rejections these membranes. Therefore, (reduction volume) further dilution deionized produce associated an 2–4 times calcium. Treatment second stage produces drinking-quality required content increased concentration. We focus real-world example Yakutia, Russia, area where exceeds standards 24 times. technique ion separation demonstrates experimental provide removal value. resulting 2–5 lower than those obtained via conventional use A series experiments were conducted remove separation. Experimental flows each they without lithium. increases Calculations operational costs options (the osmosis, nanofiltration, approach) presented. These confirm advantage applications high-rejection facilitates reduction flow rate costs. comparison involved calculation number elements stage, carbonate rates, reagent consumption prevent scaling, amounts discharged into sewer. Experimentally confirmed feasibility level. Design characteristics calculate calculated sufficient (30–40%) utilization have propensities smaller payment discharge. single-stage provides multiple advantages improved quality, consumption, attributable Different case studies planned proposed techniques boron