Kinetic Study of Seawater Reverse Osmosis Membrane Fouling Muhammad Tariq Khan, † Carmem-Lara de O. Manes, †,‡ Cyril Aubry, † Leonardo Gutierrez, § and Jean Philippe Croue* ,† † Water Desalination and Reuse Center, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi-Arabia ‡ Vale Institute of Technology (ITV), Rua Boaventura da Silva 955, Belem, Para, Brazil § Department of Civil and Environmental Engineering, Center of Advanced Materials for the Purification of Water with Systems, University of Illinois at Urbana-ChampaignUrbana, Illinois 61801, United States * S Supporting Information ABSTRACT: Reverse osmosis (RO) membrane fouling is not a static state but a dynamic phenomenon. The investigation of fouling kinetics and dynamics of change in the composition of the foulant mass is essential to elucidate the mechanism of fouling and foulant-foulant interactions. The aim of this work was to study at a lab scale the fouling process with an emphasis on the changes in the relative composition of foulant material as a function of operating time. Fouled membrane samples were collected at 8 h, and 1, 2, and 4 weeks on a lab-scale RO unit operated in recirculation mode. Foulant characterization was performed by CLSM, AFM, ATR-FTIR, pyrolysis GC-MS, and ICP-MS techniques. Moreover, measurement of active biomass and analysis of microbial diversity were performed by 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 changed over the age of the fouling layer. Microbial population in all the membrane samples was dominated by specific groups/species belonging to Proteobacteria and Actinobacteria phyla; however, similar to abiotic foulant, their relative abundance also changed with the biofilm age. 1. INTRODUCTION Seawater reverse osmosis (SWRO) process has played an essential role in producing fresh water for human con- sumption. 1,2 To improve this water treatment technique, a substantial amount of research has been conducted, i.e., development of new membranes and pretreatment strategies to benefit capital and operational costs. 3,4 Regardless of all the available state of the art technologies, fouling of desalination membranes remains as a problem which seriously impacts the performance and economic viability of this water treatment operation. 3,5,6 Membrane fouling is a complex and dynamic phenomenon as different phases are involved in the progressive development of a fouling layer. During organic, inorganic, and colloidal fouling the involved steps include foulant-membrane inter- actions (rapid initial step) and foulant-foulant interactions (gradual long-term step). 7 Similarly, different steps can be distinguished for microbiological fouling, i.e., conditioning film formation by glycoproteins and/or other organics, 8-10 cell attachment, cell growth, and cell dispersion. 11-13 Different phases taking place in the development of a fouling layer (i.e., kinetic aspect) can be tracked down through monitoring the changes in relative abundance and diversity of the fouling species over time. All previous fouling characterization studies were conducted using synthetic water as feedwater and/or focused on characterization of autopsied modules representing only a transitory state of a prevailing fouling scenario. Recently, Monruedee et al. 14 analyzed the changes in morphology and elemental composition of a SWRO membrane fouling layer through periodic samplings, i.e., 2-20 h. However, this system was fed with a synthetic solution and only ultrastructural fouling characterization techniques were used. Another kinetic fouling study (operation time 8 h to 24 days) was carried out by Ivnitsky et al. 15 with nanofiltration (NF) membranes used to treat wastewater. Biofouling is considered the main drawback of SWRO membranes, affecting approximately 70% of the seawater RO membrane systems. 16 Although biofilm formation phenomenon has been extensively investigated, a significant fraction of these studies have focused on systems rather than SWRO membranes. Moreover, there are only a few studies in the literature on microbial diversity or chemical composition of SWRO membrane biofilms, and no comprehensive study on the changes in microbial community and chemical composition of the biofilm matrix with operating time. Briefly, Manes et al. 17 studied changes in the profile of microbial diversity of full-scale SWRO membranes biofilm with operating times ranging from 10 to 330 days. Betaproteobacteria affiliated with the genus Ideonella were identified as potential primary colonizers. In the case of relatively mature biofilm, the majority of bacterial population belonged to phyla Alphaproteobacteria or Plancto- mycetes. However, since the membranes were subjected to chemical cleaning procedures, the biofouling profiles might Received: May 14, 2013 Revised: August 11, 2013 Accepted: August 28, 2013 Published: August 29, 2013 Article pubs.acs.org/est © 2013 American Chemical Society 10884 dx.doi.org/10.1021/es402138e | Environ. Sci. Technol. 2013, 47, 10884-10894