Regeneration Efficiency of Strong Acid Cation Exchange Resin using Low Concentration of NaCl from Synthetic RO Reject Water

Abstract

Groundwater resources are becoming an increasingly viable option for communities having limited access to fresh surface water supplies. About 90% of the groundwater is undesirable for consumption because of a water hardness and total dissolved solids (TDS), which need to be managed before being considered for drinking or other household applications. One of the foremost alternatives for resolving groundwater in the condition of hardness and total dissolved solids is the Reverse osmosis (RO) and ion exchange pretreatment which deal with the challenges in terms of large chemical usage for clean, membrane fouling, decreasing ion exchange efficiency with high TDS of raw water and wastewater management of high TDS. Which suggests having a certain operation model to predict their real-time utility. This work aims to prepare an operational model by investigating the effect of TDS on hardness removal and regeneration efficiency using low TDS wastewater from RO reject through a self-regeneration approach. The study found that the concentration of TDS directly affects the efficiency of hardness removal. With increasing the TDS from 0-7,500 mg/L, the ion exchange efficiency decreases from 100 to 48.31%, and so on. While studying the regeneration efficiency, it has been found that by increasing the concentration of brine solution from 5000 to 20000 mg/L, the Ca²⁺ recovery increases to achieve 100% recovery with a decrease in required bed volume of brine solution. Finally, considering the effect of TDS on the removal and regeneration efficiency of ion exchange, an operational model has been proposed which will help to predict the ion exchange efficiency and the real-time applicability of the RO-ion exchange process towards groundwater desalination.