Composition and Variability of Biofouling Organisms in Seawater Reverse Osmosis Desalination Plants

Abstract

Seawater reverse osmosis (SWRO) membrane biofouling remains a common challenge in the desalination industry, but the marine bacterial community that causes membrane fouling is poorly understood. Microbial communities at different stages of treatment processes (intake, cartridge filtration, and SWRO) of a desalination pilot plant were examined by both culture-based and culture-independent approaches. Bacterial isolates were identified to match the genera Shewanella, Alteromonas, Vibrio, and Cellulophaga based on 16S rRNA gene sequencing analysis. The 16S rRNA gene clone library of the SWRO membrane biofilm showed that a filamentous bacterium, Leucothrix mucor, which belongs to the gammaproteobacteria, accounted for nearly 30% of the clone library, while the rest of the microorganisms (61.2% of the total clones) were related to the alphaproteobacteria. 16S rRNA gene terminal restriction fragment length polymorphism (T-RFLP) analysis indicated that bacteria colonizing the SWRO membrane represented a subportion of microbes in the source seawater; however, they were quite different from those colonizing the cartridge filter. The examination of five SWRO membranes from desalination plants located in different parts of the world showed that although the bacterial communities from the membranes were not identical to each other, some dominant bacteria were commonly observed. In contrast, bacterial communities in source seawater were significantly different based on location and season. Microbial profiles from 14 cartridge filters collected from different plants also revealed spatial trends.Technological advances in reverse osmosis (RO) membranes during the past decade have significantly reduced the energy cost of water production via desalination. Seawater desalination, at present, provides approximately 1% of the world's drinking water supply, and this percentage is increasing by the year (52). However, membrane fouling is one of the most important practical problems facing RO plant operators and membrane manufacturers. The phenomenon of the accumulation of marine organisms and their metabolic products (i.e., extracellular polysaccharides [EPS], proteins, and lipids) on the membrane surface is known as biofouling (10, 15, 16). Excessive membrane biofouling results in increased energy demand for salt separation and the deterioration of product water quality (1,3,17,45). Although research efforts have been devoted to prevent or alleviate biofouling by, for example, disinfection, chemical cleaning, and aeration (26, 50), these treatments yield temporary results. Advancements in membrane materials and the optimization of operational conditions have contributed to biofouling prevention (25,26,48,51); however, these changes cannot eliminate it. The accelerated growth of biofilm on RO membranes likely is due to the physiological response of the bacteria. Systematic and effective strategies for biofouling control have not been established.Investigations of the microbial community that causes RO membrane fouling have not progres...

Marine bacterial biofilm formation and its responses to periodic hyperosmotic stress on a flat sheet membrane for seawater desalination pretreatment

“…The model organism B2 used in the fouling study was isolated from a local desalination pilot plant and was identified as Alteromonas, which is one of the prevalent types of bacteria in the seawater intake and on the biofouled membrane [5,19,21]. The early characterization study indicated that this strain, B2, was a high biofilm producer and was relatively more resistant to hyperosmotic shocks.…”

“…Since B2 was relatively more resistant to the 30% NaCl shock and produced the most biofilm among the four bacterial isolates tested, it was chosen for the subsequent study to investigate the effectiveness of periodic hyperosmotic shocks to the recovery of membrane permeability. Additionally, the Alteromonas strain, B2, belongs to the class g-Proteobacteria, which is one of the dominant types of bacteria present in the seawater intake and on RO membranes in SWRO plants [5,19,21].…”

Analysis of raw and pre-treated seawater for potential biofouling precursors

“…Additional studies revealed that the seawater biofouling microorganisms were very different than those in the wastewater and freshwater environment, and that these bacteria may respond to different triggers in the environment [13][14][15][16]. The identification and study of biofouling microbial communities is a challenge as only a small portion of the marine bacterial community can be cultivated under laboratory conditions [17,18].…”

Dynamics of microbial communities in an integrated ultrafiltration–reverse osmosis desalination pilot plant located at the Arabian Gulf

“…High-throughput sequencing technology can be used to address all three questions by providing insights on the dynamics of microbial populations on the membranes and in the water samples collected along the desalination process. However, most of these studies were performed on seawater in other geographical locations which has water quality distinct from that in the Arabian Gulf [8,[10][11][12] and limited studies were conducted on the Arabian Gulf waters [13].…”