Integrity of reverse osmosis membrane for removing bacteria: new insight into bacterial passage

Fujioka, Takahiro; Hoang, Anh T.; Ueyama, Tetsuro; Nghiem, Long D.

doi:10.1039/c8ew00910d

Cited by 13 publications

(13 citation statements)

References 20 publications

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“…Therefore, it cannot be excluded that the presence of prokaryotic cells and virus particles in the permeate was the result of the leakage of the membrane module and the imperfections of the membranes themselves. This was also noted in the case of reverse osmosis membranes [ 47 ]. Moreover, the possibility of secondary bacterial growth in water after membrane filtration cannot be rejected [ 31 , 46 ].…”

Section: Resultssupporting

confidence: 55%

“…If membrane techniques are used to disinfect treated wastewater discharged into the environment, this imperfection of membranes is not so significant as it is not necessary to obtain a full guarantee of retention of all microorganisms. An additional advantage of membrane techniques in this case is the possibility of improving the physico-chemical quality of the wastewater before it enters the environment [ 47 ].…”

Section: Introductionmentioning

confidence: 99%

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Ultrafiltration Process in Disinfection and Advanced Treatment of Tertiary Treated Wastewater

et al. 2021

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The paper presents the results of research on the use of ultrafiltration, using membranes of 200 and 400 kDa separation, for disinfection of municipal treated wastewater. The research was conducted on a fractional technical scale using real municipal treated wastewater from two large wastewater treatment plants treating most of the wastewater over the one-million polycentric Gdańsk agglomeration (1.2 million inhabitants). UF 200 kDa and UF 400 kDa processes enabled further improvement of the physical and chemical parameters of treated wastewater. Total phosphorus (to below 0.2 mg/L–UF 200 kDa, 0.13 mg/L–UF 400 kDa) and turbid substances (to below 0.2 mg/L, both membranes) were removed in the highest degree. COD was reduced efficiently (to below 25.6 mgO2/L–UF 200 kDa, 26.8 mgO2/L–UF 400 kDa), while total nitrogen was removed to a small extent (to 7.12 mg/L–UF 200 kDa and 5.7 mg/L–UF 400 kDa. Based on the reduction of indicator bacteria; fecal coliforms including E. coli (FC) and fecal enterococci (FE) it was found that the ultrafiltration is an effective method of disinfection. Not much indicator bacterial were observed in the permeate after processes (UF 200 kDa; FC—5 CFU/L; FE—1 CFU/L and UF 400 kDa; FC—70 CFU/L; FE—10 CFU/L. However, microscopic analysis of prokaryotic cells and virus particles showed their presence after the application of both membrane types; TCN 3.0 × 102 cells/mL–UF 200 kDa, 5.0 × 103 cells/mL–UF 400 kDa, VP 1.0 × 105/mL. The presence of potentially pathogenic, highly infectious virus particles means that ultrafiltration cannot be considered a sufficient disinfection method for treated wastewater diverted for reuse or discharged from high load wastewater treatment plants to recreational areas. For full microbiological safety it would be advisable to apply an additional disinfection method (e.g., ozonation).

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Section: Resultssupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Ultrafiltration Process in Disinfection and Advanced Treatment of Tertiary Treated Wastewater

et al. 2021

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“…By using intrinsic fluorescence, concentrations of bacteria in water can be monitored in real time without dyes for staining and detecting bacteria in water. Thus, online real time bacteriological counters may be more practical for physical treatment processes that provide continuous bacterial counts before and after treatment (Fujioka et al, 2019a;Fujioka et al, 2019b). This technology can be applied to sand filtration to monitor performance for bacterial removal and detect breakthrough of bacteria.…”

Section: Introductionmentioning

confidence: 99%

Online assessment of sand filter performance for bacterial removal in a full-scale drinking water treatment plant

et al. 2019

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Microbiological risks associated with drinking water can be minimized by providing enhanced 2 integrity monitoring of bacterial removal by water treatment processes. This study aimed to 3 evaluate the efficacy of real-time bacteriological counters for continuously assessing the 4 performance of a full-scale sand filter to remove bacteria. Over the course of an 8-day 5 evaluation, online counting of bacteria was successfully performed, providing continuous 6 bacterial counts in the sand filter influent and effluent over approximate ranges from 17×10 4 to 94×10 4 and from 0.2×10 4 to 1.3×10 4 counts/mL, respectively. Periodic variations were observed with online bacterial counts in the sand filter influent because of the changes in the performance of flocculation and sedimentation processes. Overall, online removal rates of bacteria determined during the full-scale test were 95.2-99.3% (i.e., 1.3-2.2-log), indicating that online bacterial counting can continuously demonstrate over 1.3-log removal in the sand filter. Real-time bacteriological counting technology can be a useful tool for assessing variability and detecting bacterial breakthrough. It can be integrated with other online water quality measurements to evaluate underlying trends and the performance of sand filters for bacterial removal, which can enhance the safety of drinking water.

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“…Nevertheless, some bacterial cells were still detected in the NF permeate. Other studies have shown that some bacterial cells are capable of passing through theoretically impenetrable RO membranes [ 21 ]. If left untreated, these bacterial cells can grow in the presence of nutrients and form problematic biofilms in the water distribution system.…”

Section: Resultsmentioning

confidence: 99%

Removal of Bacteria and Organic Carbon by an Integrated Ultrafiltration—Nanofiltration Desalination Pilot Plant

et al. 2020

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Fouling caused by organic matter and bacteria remains a significant challenge for the membrane-based desalination industry. Fouling decreases the permeate quality and membrane performance and also increases energy demands. Here, we quantified the amount of organic matter and bacteria at several stages along the water-treatment train of an integrated ultrafiltration–nanofiltration seawater treatment pilot plant. We quantified the organic matter, in terms of Total Organic Carbon (TOC) and Assimilable Organic Carbon (AOC), and evaluated its composition using Liquid Chromatography for Organic Carbon Detection (LC-OCD). The bacterial cells were counted using Bactiquant. We found that ultrafiltration (UF) was effective at removing bacterial cells (99.7%) but not TOC. By contrast, nanofiltration (NF) successfully removed both TOC (95%) and bacterial cells. However, the NF permeate showed higher amounts of AOC than seawater. LC-OCD analysis suggested that the AOC was mostly composed of low molecular weight neutral substances. Furthermore, we found that the cleaning of the UF membrane using chemically enhanced backwash reduced the amount of AOC released into the UF permeate. By implementing the cleaning-in-place of the NF membrane, the pressure drop was restored to the normal level. Our results show that the UF and NF membrane cleaning regimes investigated in this study improved membrane performance. However, AOC remained the hardest-to-treat fraction of organic carbon. AOC should, therefore, be monitored closely and regularly to mitigate biofouling in downstream processes.

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Integrity of reverse osmosis membrane for removing bacteria: new insight into bacterial passage

Abstract: Fluorescent microspheres (surrogates for bacteria) allowed identification of the fact that even an intact O-ring seal can allow for some bacterial passage through the reverse osmosis membrane element.

Cited by 13 publications

References 20 publications

Ultrafiltration Process in Disinfection and Advanced Treatment of Tertiary Treated Wastewater

Ultrafiltration Process in Disinfection and Advanced Treatment of Tertiary Treated Wastewater

Online assessment of sand filter performance for bacterial removal in a full-scale drinking water treatment plant

Removal of Bacteria and Organic Carbon by an Integrated Ultrafiltration—Nanofiltration Desalination Pilot Plant

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