Comparing Biofouling Development in Membrane Fouling Simulators and Spiral-Wound Reverse Osmosis Elements Using River Water and Municipal Wastewater Gerard Massons-Gassol, † Guillem Gilabert-Oriol,* ,† Jon Johnson, ‡ and Tina Arrowood ‡ † Dow Water & Process Solutions, Dow Chemical Ibé rica S. L., Tarragona 43006, Spain ‡ Dow Water & Process Solutions, FilmTec Corporation, Edina, Minnesota 55439, United States * S Supporting Information ABSTRACT: Membrane fouling simulators (MFS) are flat cell units to simulate the biofouling development of spiral-wound reverse osmosis (RO) elements. MFS units and two RO testing systems were operated in parallel, using different water types. Differences in differential pressure increase and fouling distribution between the two pilot plants were evaluated. Several RO elements and MFS units were operated with the same conditions to assess the reliability of the testing systems. In a second study, the performance of different feed spacer types assembled in full-scale RO elements was compared to the same feed spacer types assembled in the MFS unit. These studies showed that the relative biofouling impact in the MFS units was equivalent to the performance of the RO elements. Additionally, the results from the second study provide indications that a prototype 28 mil feed spacer (28 T1) may provide more significant additional biofouling resistance than any of the other spacers evaluated. 1. INTRODUCTION Water scarcity is recognized as one of the main threats that mankind is facing globally. 1 Reverse osmosis (RO) membrane technology has developed as a promising, cost-effective technology to remove contaminants from nonpotable waters and provide fresh water supply to meet the growing demand. 2 RO elements, however, can suffer from progressive loss of performance when treating challenging waters due to fouling. 3 Of all fouling types, biofouling is one of the most complex to manage in RO water treatment systems. 4 It occurs when bacteria colonize and form biofilms in the feed channel of the RO elements, causing increased friction for water flow. This increases the feed-concentrate differential pressure (dP), 5 leading to hydraulic imbalance and, if not controlled, can damage the element. Additionally, biofilms can affect membrane transport properties, as the polymeric film formed on the membrane surface decreases the overall water permeability. 6 Each of these effects increases the energy of operation and leads to frequent system shutdowns for chemical cleanings to recover membrane performance. The high pH conditions needed to remove biofilms during cleaning can result in membrane hydrolysis and shorten the useful life of the element. Therefore, in total, system productivity, chemical usage, membrane life, and energy each contribute to a higher cost of water production when biofouling occurs. Mechanisms to control biofouling are needed to enable long-term performance when treating water with high contamination levels. 7 Studying biofouling in water treatment systems is complex due to the multiple variables that affect biofilm formation. 5 To accelerate research, screening tools which enable biofouling experiments to be conducted with different water types and capable to explore multiple parameters in parallel are needed. Membrane fouling simulators (MFS) have been described as a cost-effective tool to predict biofouling evolution in full-scale RO systems. 8 Differential pressure in the MFS models the increase of an RO system, since biofouling generally starts in the first centimeters of the feed-concentrate channel. 9,10 Thus, MFS units can be used to study biofilm formation and quickly screen new solutions without having to manufacture an entire RO element. 11 MFS units are especially suited for testing one of the key parameters influencing biofouling in spiral-wound RO elements, the feed spacer. 12 The main role of the feed spacer is to promote turbulence and improve mass transfer by distorting the laminar profile of the axial flow when operated in cross-flow configuration. 13 However, low shear stress zones from flow stagnation are created by the feed spacer, 14 and simulations suggest that these are the areas where biofilm develops more strongly. 15 Defining feed spacer design features (e.g., thickness, strand angle, spacing between filaments) to Received: August 3, 2017 Revised: September 19, 2017 Accepted: September 26, 2017 Published: September 26, 2017 Article pubs.acs.org/IECR © XXXX American Chemical Society A DOI: 10.1021/acs.iecr.7b03219 Ind. Eng. Chem. Res. XXXX, XXX, XXX-XXX