Removal of Organics with Ion-Exchange Resins (IEX) from Reverse Osmosis Concentrate

Reverse osmosis concentrate (ROC) produced as the by-product of the reverse osmosis process consists of a high load of organics (macro and micro) that potentially cause eco-toxicological effects in the environment. Previous studies focused on the removal of such compounds using oxidation, adsorption, and membrane-based treatments. However, these methods were not always efficient and formed toxic by-products. The impact of ion-exchange resin (IEX) (Purolite((R))A502PS) was studied in a micro-filtration-IEX hybrid system to remove organics from ROC for varying doses of Purolite((R)) A502PS (5-20 g/L) at a flux of 36 L/m(2)h. The purolite particles in the membrane reactor reduced membrane fouling, evidenced by the reduction of transmembrane pressure (TMP), by pre-adsorbing the organics, and by mechanically scouring the membrane. The dissolved organic carbon was reduced by 45-60%, out of which 48-81% of the hydrophilics were removed followed by the hydrophobics and low molecular weight compounds (LMWs). This was based on fluorescence excitation-emission matrix and liquid chromatography-organic carbon detection. Negatively charged and hydrophobic organic compounds were preferentially removed by resin. Long-term experiments with different daily replacements of resin are suggested to minimize the resin requirements and energy consumption.

Automated summary

This study focused on the treatment of organic compounds in reverse osmosis concentrate (ROC) using ion-exchange resin in a microfiltration-ion exchange hybrid system. It was found that the resin effectively removed organic compounds and reduced membrane fouling. Negatively charged and hydrophobic organic compounds were preferentially removed by the resin. Long-term experiments with different daily replacements of resin are suggested to minimize resin requirements and energy consumption.