Characterization of microbial communities in water and biofilms along a large scale SWRO desalination facility: Site-specific prerequisite for biofouling treatments

Biofouling impacts seawater reverse osmosis (SWRO) desalination plants by hindering module performance, increasing energetic demands, and incurring further costs. Here we investigated the spatial–temporal dynamics of microbial communities along the feedwater, pretreatment, and reverse osmosis stages of a large-scale SWRO desalination facility. While the composition of water-based microbial communities varied seasonally, the composition of biofilm microbial communities clustered by locations. Proteobacteria dominated throughout the water and biofilm communities while other dominant phyla varied seasonally and spatially. The microbial community composition significantly differed along the pathway locations of feedwater, rapid sand filtration (RSF), cartridge filters (CF), and the reverse osmosis (RO) membranes. Biofilms on the RSF and CF were composed of more diverse microbial populations than RO biofilms as determined by the effective number of species. Biofilms that developed along the treatment pathway (CF) served as inocula enhancing biofouling downstream on the RO membranes. Subsequently, we believe that prior to the development of advanced antibiofouling treatments for the desalination industries, the site-specific microbial community of feedwater, pretreatment and RO biofouling should be characterized. Site specific identification of these communities will enable optimization of pretreatment and cleaning procedures and can ultimately reduce chemical usage and incurred costs. © 2015 Elsevier B.V. All rights reserved.

Large-scale desalination plant engineers have traditionally disregarded the complexities of the microbial populations along the desalination process treatment stages, and have thus designed generic pretreatment systems. Our study, which followed the spatial and temporal composition of microbial communities along the complete process pathway of a large scale SWRO desalination plant, clearly illustrates these complex dynamics within intake and pretreatment microbial communities. We also elucidate dramatic spatial differences between populations from intake-waters and biofilm communities and between biofilms formed at the pretreatment stages and on the RO membranes. Our study emphasizes the importance of site-specific monitoring in large-scale operational desalination plants, due to the variation in community composition between sites. Our results clarify the dynamic interactions between the ambient source planktonic bacteria, pretreatment biofilms, and the subsequent biofouling of RO membranes. We suggest that the monitoring of feedwater, pretreatment and RO biofilm microbial communities, together with additional water biological characteristics, should be taken into account as a prior stage in the development of advanced antibiofouling treatments for the desalination industries. Such a site specific approach can reveal the key bacterial species and their functional classifications, help to properly adjust and fine tune pretreatment procedures and perhaps ultimately reduce chemical usage and costs.