AWWA ACE68650

This powerpoint presentation begins by providing a brief overview of the challenges of concentrate management, and the development of a hybrid approach. Overall project goals were to: examine the removal of the sparingly soluble salts (e.g., Ca, Mg, Ba, Sr, and silica) through intermediate precipitation after reverse osmosis (RO); examine the salt removal efficiency of two types of ED membranes; and, investigate the performance and cost of the hybrid RO-intermediate precipitation-ED/EDR system to improve water recovery of different types of brackish water. Research approach included the following: preliminary analysis using KMS ROPRO to calculate the water quality of RO concentrate (TFC-ULP); batch sequential operation of RO, intermediate precipitation and ED; water quality modeling to optimize operational parameters; and, economic-technical assessment. Presentation conclusions indicate that: ED/EDR is a viable technology to treat RO concentrate, in particular, with high silica concentration; at least 80% recovery can be achieved by ED treatment, increasing overall recovery to 94-97%; normal grade ion-exchange membranes exhibited higher salt removal than monovalent permselective membranes, however, intermediate precipitation is required to remove sparingly soluble salts; and, for ZLD with an evaporation pond, the RO-ED/EDR configuration would have a 25 to 42 percent cost advantage over conventional RO system. Includes tables, figures.