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Effects of ultrasonic cleaning on membrane-adherent biofilms derived from a laboratory-scale bioreactor

Rosi, Anton Nilo Warren
http://orcid.org/0000-0002-8226-3917
http://rave.ohiolink.edu/etdc/view?acc_num=osu1532073210664583

Abstract Details

2018, Master of Science, Ohio State University, Civil Engineering.
Membrane technology is a growing option for treatment of source and waste waters. As implementation of membrane treatment grows, however, the classical challenge of biofouling persists. Biofilm growth separates the membrane from well-mixed flow, leading to increased hydraulic resistance and ultimately higher costs. Despite best efforts by current technology to remove fouling layers, foulant build-up followed by membrane death is a matter of course. In highly fouling environments, a mechanism to de-foul the membranes in-situ would greatly improve treatment. Ultrasonic cleaning is known to provide a high level of cleaning via acoustic cavitation. Benefits of ultrasonic cleaning include high efficacy, synergy with chemical treatment, and potential to degrade recalcitrant compounds. Prior studies have demonstrated the ability of ultrasound to increase membrane flux and deter fouling. However, ultrasonic cleaning is usually investigated using model foulants. It is a stated problem that these model compounds do not exhibited the same fouling properties as biofilms, and indeed previous researchers have found that biofilm removal by ultrasonic cleaning is not always effective. In this study, membranes were biofouled using a laboratory-scale bioreactor. Membrane-adherent biofilms were then exposed to 0, 20, or 60 s of 205.5 kHz ultrasound at a power intensity of 6.38 W cm-2. Confocal laser scanning microscopy coupled with image analysis quantified biofilm thickness, biomolecular composition, and spatial autocorrelation of membrane-adherent biofoulant. 16S rRNA gene sequencing determined changes in biofilms’ microbial communities. Results demonstrated that 20 s of ultrasound – under the chemical, physical, and geometric conditions tested here – removed upper biofilm progressively, resulting in a biofilm population which exhibited a continuum of thicknesses ranging from 0 to 370 µm. Surface layers of biofilms sometimes retained some thickness after sonication, and exhibited depleted quantities of proteins or nucleic acids. On the other hand, 60 s of sonication consistently reduced membrane-adherent biomass to a thin, biopolymer-rich film. Complete removal was not observed, which emphasized that ultrasound may exhibit a modest effect on highly cohesive, viscoelastic structures such as basal biofilm strata. Analysis of microbial communities showed that differentiation between bioreactor and biofilm communities was apparent at the 17 hour mark. In particular, taxa from the genus Sediminibacterium were enriched in the biofilm phase. However, these taxa also exhibited the sharpest decreases following ultrasound, suggesting that Sediminibacterium may inhabit the upper strata of the biofilm. Conversely, Chryseobacterium spp. declined in proportion in biofilms; however, sonication increased its relative abundance in residual membrane-adherent biomass. This suggests that it was proportionately more prevalent in lower biofilm strata. If Chryseobacterium or similar taxa were viable following sonication, it would imply that they would play a role in driving the recolonization of the fouling layer. The properties of biofilm removal discussed herein provide insight into some of the possible morphologies and communities obtainable through ultrasonic cleaning. Conclusions drew attention to synergy between chemical cleaning and ultrasound, which have complementary strengths and weaknesses. Future work, such as research into acoustic membranes, should aim to take advantage of these findings knowledge and leverage them to create viable ultrasonic processes.
Linda Weavers, Dr. (Advisor)
Paula Mouser, Dr. (Advisor)
Hendrik Verweij, Dr. (Committee Member)
55 p.
Civil Engineering; Engineering; Environmental Economics; Environmental Engineering; Ethnic Studies; Microbiology
Biofilm, ultrasound, membrane, bioreactor, cleaning, acoustic, cavitation, variogram, fractal, microscopy, quantitative, image, analysis, 16S, community

Recommended Citations

Citations

  • Rosi, A. N. W. (2018). Effects of ultrasonic cleaning on membrane-adherent biofilms derived from a laboratory-scale bioreactor [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1532073210664583

    APA Style (7th edition)

  • Rosi, Anton. Effects of ultrasonic cleaning on membrane-adherent biofilms derived from a laboratory-scale bioreactor. 2018. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1532073210664583.

    MLA Style (8th edition)

  • Rosi, Anton. "Effects of ultrasonic cleaning on membrane-adherent biofilms derived from a laboratory-scale bioreactor." Master's thesis, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1532073210664583

    Chicago Manual of Style (17th edition)

osu1532073210664583
264
© 2018, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.