Formation and ripening of alginate-like exopolymer gel layers during and after membrane filtration

WATER RESEARCH

卷:195

Article

Pfaff, N. -M.^1,3  Kleijn, J. Mieke²  van Loosdrecht, Mark C. M.¹  Kemperman, Antoine J. B.^3,4 

[1] Delft Univ Technol, TNW Appl Sci, Maasweg 9, NL-2629 HZ Delft, Netherlands

[2] Wageningen Univ, Phys Chem & Soft Matter, 124,Stippenweg 4, NL-6708 WE Wageningen, Netherlands

[3] European Ctr Excellence Sustainable Water Technol, Wetsus, Oostergoweg 9, NL-8911 MA Leeuwarden, Netherlands

[4] Univ Twente, Mesa Inst Nanotechnol, Fac Sci & Technol, Membrane Sci & Technol Cluster, POB 217, NL-7500 AE Enschede, Netherlands

关键词: Extracellular polymeric substances;    Calcium-binding;    Hydrogel;    Donnan potential;    Biofilm;   

DOI  :  10.1016/j.watres.2021.116959

来源: Elsevier

【 摘 要 】

The properties of biofilm EPS are determined by the multiple interactions between its constituents and the surrounding environment. Because of the high complexity of biofilm EPS, its constituents' characterisation is still far from thorough, and identification of these interactions cannot be done yet. Therefore, we use gels of bacterial alginate-like exopolysaccharides (ALEs) as a model component for biofilm EPS in this work. These gels have been examined for their cohesive properties as a function of CaCl2 and KCl concentration. Hereto, ALE gel layers were formed on membranes by dead-end filtration of ALE solutions. Accumulation of the cations Ca2+ and K+ in the gels could be well predicted from a Donnan equilibrium model based on the fixed negative charges in the ALE. This suggests that there is no specific binding of Ca2+ to the ALE and that on the time scale of the experiments, the Ca2+ ions can distribute freely over the gel and the surrounding solution. The concentration of fixed negative charges in the ALE was estimated around 1 mmol/g VSS (volatile suspended solids, organic mass) from the Donnan equilibrium. Moreover, an accumulation of H+ was predicted. Gels with more CaCl2 in the supernatant were more compact and bore a higher osmotic pressure than those with less CaCl2, revealing the role of Ca2+ ions in the network crosslinking. It is hypothesised that this mechanism later transitions into a rearrangement of the ALE molecules, which eventually leads to a fibrous network structure with large voids. (C) 2021 The Author(s). Published by Elsevier Ltd.

【 授权许可】

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