Effects of feed solution pretreatment on pressure-retarded osmosis: changes in dissolved organic matter according to fluorescence excitation-emission matrix spectroscopy coupled with parallel factor analysis and liquid chromatography-organic carbon detection

Abstract

Pressure-retarded osmosis (PRO) is the next generation seawater desalination technology, and is considered an eco-friendly and economic renewable energy. As such, there have been studies on methods of efficient cleaning to restore degraded membrane performance due to the reversible membrane fouling that inevitably occurs after prolonged operation. Owing to the fact that fouling occurs differently in each type of pretreatment process involved in PRO, it is important to understand the type of organic matter that causes fouling in each of the PRO pretreatment processes. In this study, the composition of dissolved organic matter (DOM) was characterized and assessed among membrane bioreactor, ultrafiltration, activated carbon/sand filter, and low-pressure reverse osmosis PRO pretreatment processes. The characteristics of DOM that caused fouling in the PRO membrane was identified using fluorescence excitation-emission matrix spectroscopy (F-EEMs) coupled with parallel factor analysis (PARAFAC) and a liquid chromatography-organic carbon detector (LC-OCD) technique. The major components could be summarized as microbial humic-like fluorescence, humic and fulvic substances, terrestrial humic-like fluorescence in high nutrient and wastewater-influenced environments, and tryptophan-like substances. The foulants that affected the PRO membrane were found to be humic and fulvic substances as a result of the PARAFAC analysis and humic substances and building blocks as a result of the LC-OCD analysis.