Improvement of drinking water quality and reduction of concentrate discharges using nanofiltration membranes

Abstract

Reverse Osmosis method is efficiently and widely used in drinking water production. Treatment of ground water faces three` main problems: scaling of membranes, concentrate handling and permeate ionic composition. A number of ionic pollutants (such as lithium, ammonia and boron) are poorly rejected by reverse osmosis membranes as compared to calcium and chloride ions. Thus, in cases when high lithium or ammonia concentrations are present in ground water, high rejection reverse osmosis membranes are usually used that provides a product water with low TDS and hardness values. Present article demonstrates results of research aimed at development of a new approach to change a ratio of monovalent and divalent ions in product water. An example of high boron water is discussed. A developed technique of ion separation is applied and experimental results are demonstrated, thus providing low boron concentration in product with increased TDS and calcium by 5 times as compared to the initial use of RO membranes. A flow diagram of the developed process is demonstrated based on experimentally obtained results.

Keywords

• reverse osmosis
• nanofiltration
• membrane rejection
• reduction of concentrate discharges
• evaluation of scaling rates