Forward Osmosis for Ion Exchange Waste Brine Management
Miguel Arias‐Paić, Julie A. Korak
Abstract
For many water systems, ion exchange is the best available technology to meet nitrate, chromium, arsenic, and other inorganic removal requirements. The principal economic, environmental, and operational considerations relate to waste disposal. The salt saturator at ion exchange (IX) installations provides an untapped chemical energy source to reduce the IX waste brine volume that can be leveraged by integrating forward osmosis (FO) between the saturator and waste brine tank. The waste brine (FO feed solution) is concentrated by the salt saturator solution (FO draw solution) as water permeates across the FO membrane from the waste to the saturator. This study demonstrates waste reductions of 85% for chromium and 65% for nitrate IX waste brines. The augmented draw solution produced can be directly used in a subsequent IX regeneration, and waste solids can be recovered through precipitation. Due to the periodic generation of IX waste, high fluxes and single-pass efficiency are not required from the FO process. With the incorporation of FO into the IX process, significant operational flexibility to optimize the recovery of water from the waste brine exists, thereby decreasing the primary cost of IX operation.