Molecular Characterization of the Bacterial Communities in the Different Compartments of a Full-Scale Reverse-Osmosis Water Purification Plant

Abstract

The origin, structure, and composition of biofilms in various compartments of an industrial full-scale reverse-osmosis (RO) membrane water purification plant were analyzed by molecular biological methods. Samples were taken when the RO installation suffered from a substantial pressure drop and decreased production. The bacterial community of the RO membrane biofilm was clearly different from the bacterial community present at other locations in the RO plant, indicating the development of a specialized bacterial community on the RO membranes. The typical freshwater phylotypes in the RO membrane biofilm (i.e., Proteobacteria, Cytophaga-Flexibacter-Bacteroides group, and Firmicutes) were also present in the water sample fed to the plant, suggesting a feed water origin. However, the relative abundances of the different species in the mature biofilm were different from those in the feed water, indicating that the biofilm was actively formed on the RO membrane sheets and was not the result of a concentration of bacteria present in the feed water. The majority of the microorganisms (59% of the total number of clones) in the biofilm were related to the class Proteobacteria, with a dominance of Sphingomonas spp. (27% of all clones). Members of the genus Sphingomonas seem to be responsible for the biofouling of the membranes in the RO installation.Membrane biofouling is an important problem for reverseosmosis (RO) systems, in particular for RO membranes (13,14,17). The attachment of bacteria to membrane surfaces and subsequent biofilm growth in the spiral-wound RO membrane elements strongly influence RO system performance and RO plant productivity. Problems are due primarily to an increase in the differential pressures of the RO modules, the long-term membrane flux reduction of the RO plant, and the deterioration of product water quality as a result of high levels of biomass accumulation on RO membrane surfaces (37,43,45). Once in progress, biofouling regularly and persistently hampers the RO water treatment process (13,15).Presently, adequate measures to prevent or reduce biofouling are lacking. The microbiological and physical processes associated with biofilm formation and biofouling in these dynamic and high-pressure environments are poorly understood. The conditions change from an oligotrophic environment in the beginning to a heterotrophic environment when the biofilm is mature. The first indications that a variety of different microorganisms participate in biofilm development on RO membranes were obtained by traditional dissections of fouled RO membrane elements (autopsies) and the subsequent analysis of the membrane surface-fouling layers. The conventional plating and colony isolation methods showed the presence of a wide variety of species on the feed and permeative surfaces of biofouled cellulose acetate, polyetherurea thin-film composite, or polyamide thin-film-composite membranes (4,9,17,19,28,38,39). However, by cultivation-dependent methods, information about only 0.01 to 3% of the population in natural envi...

The role of cell-surface interactions in bacterial initial adhesion and consequent biofilm formation on nanofiltration/reverse osmosis membranes

“…In terms of microbial species, the work of Bereschenko et al found that members of the genus Sphingomonas played a very important role in the initial formation and subsequent maturation of biofilms on RO membrane [27,28]. Because they are facultative oligotrophs, they are metabolically well adapted to a low-carbon environment and can proliferate under conditions of limited substrates.…”

Development of Fourier transform mid-infrared calibrations to predict acetone, β-hydroxybutyrate, and citrate contents in bovine milk through a European dairy network

“…Once in process, biofouling continually and intensively hinders the RO filtration process. Additionally, the construction of "spiral-wound" membrane units, spacers between the membranes, additional inner surfaces, roughness of the membrane surface, and processing conditions also make these membranes susceptible to microbial attachment, leading to the formation of biofilm layers (Bereschenko et al, 2008(Bereschenko et al, , 2010.…”

Membrane Fouling and Chemical Cleaning in Three Full-Scale Reverse Osmosis Plants Producing Demineralized Water

“…An inorganic precipitation or scaling layer in contrast would reveal a sandpaper-like structure on the membrane surface. Furthermore, at location III, biofouling was reported in earlier studies and several biofouling key studies were performed at this location [20][21][22][23]. To differentiate between organic fouling and biological fouling, TOC, polysaccharides, proteins, and CFU measurements ( Figure 5) and SEM were performed.…”

“…At locations II and III, the low pH cleaning is performed with a commercial mixed acid detergent, intended to improve foulant solubility. At location III, which has been extensively studied for its biofouling problems [20][21][22][23], sodium bisulfite is used during the high pH cleaning in order to achieve anoxic conditions and improved microbial inactivation. The volumetric flow rate during cleaning at all locations is 9 m 3 h −1 for each membrane vessel in the first stage.…”

“…Biofouling is a major type of fouling at this location, which was confirmed by SEM observations (data not shown) showing microorganisms embedded in a polymeric matrix. Location III, very frequently associated with biofouling problems [20][21][22][23], showed no CFU plate counts and ATP concentrations were very low ( Figure 5). However, 20 days prior to membrane autopsy, an emergency CIP (Table 1 and Figure 3) with oxalic acid had to be performed due to a leak in the UF system (Supplementary Figure S1.3), which possibly explains the very low biomass parameters.…”