Abstract
Granule-base immobilization of biomass is a potential method for a decent quality granular sludge cultivation. In this study, 3D polyvinyl alcohol (PVA) gel beads were chemically cross-linked via a simple NaOH-titration method. The PVA gel beads’ porous morphology was characterized using scanning electron microscope (SEM) and Brunauer–Emmette–Teller (BET), and their mechanical properties were evaluated by swelling rate and compressive stress tests. When cross-linking time was 10 min, high quality gel beads (P10) were synthesized, which demonstrated a homogeneous porous structure, good swelling rate, and high compressive strength. A mechanism for synthesis of the gel beads was proposed based on the results of Fourier transform infrared (FTIR) and X-ray diffractometer (XRD) analysis. Briefly, the intermolecular hydrogen bonds of PVA were firstly broken by NaOH to generate active bond of O–Na, which easily reacted with B(OH)4− to produce the PVA-boric acid gel beads. P10 showed excellent biocompatibility for anaerobic ammonia oxidation (anammox) biomass’ immobilization. After incubation for three months, well granule-base immobilized sludge on P10 was developed in up-flow reactor. The sludge had high abundance of anammox biomass and was in balance with other functional bacteria. This work provides a simple method for the rapid preparation of 3D PVA gel beads and verifies their potential in granule-base immobilization of biomass.
Highlights
Carrier-assisted immobilization of biomass is a promising strategy for improving the performance of wastewater treatment bioreactors [1,2,3]
Zhang et al successfully immobilized Methanosarcina bacteria in the polyvinyl alcohol (PVA) gel beads that were prepared by freeze-thawing method, and the UASB (Up-flow anaerobic sludge bed) reactor consisting of these gel beads could achieve the biomass attachment of 0.93 g VSS/g [10]
The solution was stewed a moment at room temperature, which was followed by addition of 5% NaOH solution (1.5 g of NaOH dissolved in 30 mL deionized water) to the above PVA solution, obtaining alkali PVA solution
Summary
Carrier-assisted immobilization of biomass is a promising strategy for improving the performance of wastewater treatment bioreactors [1,2,3]. Zhang et al successfully immobilized Methanosarcina bacteria in the PVA gel beads that were prepared by freeze-thawing method, and the UASB (Up-flow anaerobic sludge bed) reactor consisting of these gel beads could achieve the biomass attachment of 0.93 g VSS/g [10]. Chemical cross-linking method is a promising economical method for preparation of PVA gel beads. Boric acid is used as a cross-linking reagent for synthesis of PVA gel. To the best of our knowledge, it is the first time that such a simple method for PVA gel beads quick preparation without any supporting materials is presented and their application in granule-base immobilization of anammox biomass assistance is discussed. The work would be beneficial for the development of 3D PVA gel beads synthesis and promote wastewater treatment upgrading
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