Lab scale study of SWRO membrane fouling dynamics

Abstract

Reverse Osmosis (RO) membrane fouling is not a static state but a dynamic phenomenon. Investigation of fouling kinetics and dynamics of change in composition of the foulant mass, is essential to probe the mechanism of fouling and foulant-foulant interactions. The aim of our work was to study at lab scale the fouling process with the emphasis on investigating the changes in the relative composition of foulant material as a function of running time. Two experiments were conducted for duration of 1 and 2 weeks on a lab scale RO unit operated on a recirculation mode. To complement this lab scale work, fouled modules harvested from a full-scale SWRO desalination plant was autopsied after 2 months of operation. Fouling characterization was performed by ATR-FTIR, Pyrolysis GC-MS, and ICP-MS techniques. Moreover, measurement of active biomass and analysis of microbial diversity were accomplished through HPC/ATP analysis and DNA extraction followed by pyro-sequencing respectively. A progressive increase in the abundance of almost all the foulant species was observed but their relative proportion was found changing over the age of the fouling layer. Microbial population in all the membranes was dominated by some specific groups/species belonging to Proteobacteria and Actinobacteria phyla, however, like abiotic foulants, their relative abundance was also found changing with the age of the biofilm. In spite of the difference in the pretreatment setup and level/mode of operation, this comparative analysis of fouled membranes operated on same source water helped in identifying the dynamics of the fouling. © 2012 American Water Works Association.