Real-time fouling monitoring and membrane autopsy analysis in forward osmosis for wastewater reuse

Abstract

Forward osmosis process in emerging technology which can applicable in wastewater reuse and desalination simultaneously. In this study, the development of fouling on the FO membrane surface was monitored in real-time. The investigation of fouling layer physical and chemical characteristics was assessed by performance evaluation and in-depth analysis of fouling layer. Non-invasive visual monitoring and in-depth autopsy, combined with the performance and image analyses provided a better understanding of fouling phenomena. The relative roughness of the fouling layer was correlated with water flux decrease while the fouling layer thickness decreased rapidly when fouling was stabilized. From 66-day operation using the primary wastewater as the feed, membrane fouling development was classified into 4 phases: virgin performance, initial deposition, stabilization and aggregation. With the growing fouling layer and with aggregation, the removal rate of organic matter was reduced from 99 to 70%. Conversely, the removal rate of inorganic matter was maintained at a level higher than 90%. The fractionation of physical and chemical extraction had the following characteristics: TPI>HPI>HPO and HPI>TPI>HPO respectively. Also, low molecular weight and building blocks like organic matter were observed with a high composition ratio of fouling layer. Through the correlation between the process performance, real-time monitoring of fouling layer formation and deep-layer fouling analysis, it was possible to identify the major membrane contaminants and propose process optimization guidelines.